| Seq | Timestamp | Type | Name | Duration |
|---|---|---|---|---|
| 0/0 | 2026/09/07 02:16 | flow | patch-triage |
0mArgs:null Results: {
"EnableConfigs": [
"DAMON",
"DAMON_VADDR",
"DAMON_PADDR",
"DAMON_SYSFS",
"TRANSPARENT_HUGEPAGE",
"HUGETLB_PAGE",
"MEMCG"
],
"FocusSymbols": [
"damon_ops_filter_match",
"damon_va_prep_probes",
"damon_va_apply_probes",
"damon_va_probe_pmd_entry",
"damon_va_probe_hugetlb_entry",
"damon_va_filter_match",
"damon_pa_filter_match"
],
"KMSANReasoning": "The patch introduces virtual address probe operations (prep and apply probes) and refactors common filter matching logic in the DAMON subsystem. \n\nEvaluating against KMSAN vs KASAN applicability:\n1. No uninitialized memory usage or info-leaks: All local variables (`matched`, `young`, `pass`, `i`), stack structures (`damon_va_probe_walk_private`, `mm_walk_ops`), and page table entry copies (`ptent`, `pmde`, `entry`) are explicitly initialized before use.\n2. No user-space copy mechanisms: The patch does not copy data to user space or manipulate uninitialized kernel buffers exposed to user space.\n3. Standard bug detectors are sufficient: Potential bugs in this code (such as array out-of-bounds on `probe_hits`, folio reference count mismatches, or page table locking issues) fall squarely within the purview of KASAN, UBSAN, and LOCKDEP.\n\nTherefore, there are no uninitialized memory risks that require a dedicated KMSAN fuzzing session.",
"NeedsKMSAN": false,
"Reasoning": "The patch introduces DAMON virtual address probe preparation and evaluation logic, including custom page table walking for normal, transparent huge pages, and hugetlb pages, alongside shared filter matching logic. These paths are executed by the DAMON kernel worker thread and are reachable via DAMON sysfs interfaces, making them relevant for fuzz testing.",
"WorthFuzzing": true
} |
| 1/1 | 2026/09/07 02:16 | action | read-patch-diff |
0mArgs:null Results: {
"PatchDiff": "commit 1726d66c1cd258bc56d6d0e0db5f7f6ca921ee8b\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Mon Sep 7 02:16:41 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c\nindex 7219c608b1952..cfcd4edee346a 100644\n--- a/mm/damon/ops-common.c\n+++ b/mm/damon/ops-common.c\n@@ -444,3 +444,35 @@ bool damos_ops_has_filter(struct damos *s)\n \t\treturn true;\n \treturn false;\n }\n+\n+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio)\n+{\n+\tbool matched = false;\n+\tstruct mem_cgroup *memcg;\n+\n+\tswitch (filter-\u003etype) {\n+\tcase DAMON_FILTER_TYPE_ANON:\n+\t\tif (!folio) {\n+\t\t\tmatched = false;\n+\t\t\tbreak;\n+\t\t}\n+\t\tmatched = folio_test_anon(folio);\n+\t\tbreak;\n+\tcase DAMON_FILTER_TYPE_MEMCG:\n+\t\tif (!folio) {\n+\t\t\tmatched = false;\n+\t\t\tbreak;\n+\t\t}\n+\t\trcu_read_lock();\n+\t\tmemcg = folio_memcg_check(folio);\n+\t\tif (!memcg)\n+\t\t\tmatched = false;\n+\t\telse\n+\t\t\tmatched = filter-\u003ememcg_id == mem_cgroup_id(memcg);\n+\t\trcu_read_unlock();\n+\t\tbreak;\n+\tdefault:\n+\t\tbreak;\n+\t}\n+\treturn matched == filter-\u003ematching;\n+}\ndiff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h\nindex 38d295488fa18..b832169b1cf8c 100644\n--- a/mm/damon/ops-common.h\n+++ b/mm/damon/ops-common.h\n@@ -21,3 +21,5 @@ bool damos_folio_filter_match(struct damos_filter *filter, struct folio *folio);\n unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid);\n \n bool damos_ops_has_filter(struct damos *s);\n+\n+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio);\ndiff --git a/mm/damon/paddr.c b/mm/damon/paddr.c\nindex c1e7d7a4f40df..ffde88ea7a13c 100644\n--- a/mm/damon/paddr.c\n+++ b/mm/damon/paddr.c\n@@ -143,29 +143,8 @@ static bool damon_pa_filter_match(struct damon_filter *filter,\n \t\tstruct folio *folio)\n {\n \tbool matched = false;\n-\tstruct mem_cgroup *memcg;\n \n \tswitch (filter-\u003etype) {\n-\tcase DAMON_FILTER_TYPE_ANON:\n-\t\tif (!folio) {\n-\t\t\tmatched = false;\n-\t\t\tbreak;\n-\t\t}\n-\t\tmatched = folio_test_anon(folio);\n-\t\tbreak;\n-\tcase DAMON_FILTER_TYPE_MEMCG:\n-\t\tif (!folio) {\n-\t\t\tmatched = false;\n-\t\t\tbreak;\n-\t\t}\n-\t\trcu_read_lock();\n-\t\tmemcg = folio_memcg_check(folio);\n-\t\tif (!memcg)\n-\t\t\tmatched = false;\n-\t\telse\n-\t\t\tmatched = filter-\u003ememcg_id == mem_cgroup_id(memcg);\n-\t\trcu_read_unlock();\n-\t\tbreak;\n \tcase DAMON_FILTER_TYPE_PGIDLE_UNSET:\n \t\tif (!folio)\n \t\t\tmatched = false;\n@@ -173,7 +152,7 @@ static bool damon_pa_filter_match(struct damon_filter *filter,\n \t\t\tmatched = damon_folio_young(folio);\n \t\tbreak;\n \tdefault:\n-\t\tbreak;\n+\t\treturn damon_ops_filter_match(filter, folio);\n \t}\n \treturn matched == filter-\u003ematching;\n }\ndiff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c\nindex f884d3f78f30a..090317191973b 100644\n--- a/mm/damon/vaddr.c\n+++ b/mm/damon/vaddr.c\n@@ -510,6 +510,236 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)\n \treturn max_nr_accesses;\n }\n \n+static void damon_va_prep_probe_region(struct damon_ctx *ctx,\n+\t\tstruct mm_struct *mm, struct damon_region *r,\n+\t\tstruct damon_probe *probe)\n+{\n+\tstruct damon_prep *p;\n+\n+\tdamon_for_each_prep(p, probe) {\n+\t\tswitch (p-\u003eaction) {\n+\t\tcase DAMON_PREP_SET_PGIDLE:\n+\t\t\tdamon_va_mkold(mm, r-\u003esampling_addr);\n+\t\t\tbreak;\n+\t\tdefault:\n+\t\t\tbreak;\n+\t\t}\n+\t}\n+}\n+\n+static void damon_va_prep_probes(struct damon_ctx *ctx, bool set_samples)\n+{\n+\tstruct damon_target *t;\n+\tstruct mm_struct *mm;\n+\tstruct damon_region *r;\n+\tstruct damon_probe *p;\n+\n+\tdamon_for_each_target(t, ctx) {\n+\t\tmm = damon_get_mm(t);\n+\t\tif (!mm)\n+\t\t\tcontinue;\n+\t\tdamon_for_each_region(r, t) {\n+\t\t\tif (set_samples)\n+\t\t\t\tr-\u003esampling_addr = damon_rand(ctx, r-\u003ear.start,\n+\t\t\t\t\t\tr-\u003ear.end);\n+\t\t\tdamon_for_each_probe(p, ctx)\n+\t\t\t\tdamon_va_prep_probe_region(ctx, mm, r, p);\n+\t\t}\n+\t\tmmput(mm);\n+\t}\n+}\n+\n+static bool damon_va_young_addr(struct folio *folio, pte_t *pte, pmd_t *pmd,\n+\t\tstruct mm_struct *mm, unsigned long addr)\n+{\n+\tbool young = false;\n+\n+\tif (pte)\n+\t\tyoung = pte_young(*pte);\n+\telse if (pmd)\n+\t\tyoung = pmd_young(*pmd);\n+\tyoung = young || !folio_test_idle(folio) ||\n+\t\tmmu_notifier_test_young(mm, addr);\n+\treturn young;\n+}\n+\n+static bool damon_va_filter_match(struct damon_filter *filter,\n+\t\tstruct folio *folio, pte_t *pte, pmd_t *pmd,\n+\t\tstruct mm_struct *mm, unsigned long addr)\n+{\n+\tbool matched = false;\n+\n+\tswitch (filter-\u003etype) {\n+\tcase DAMON_FILTER_TYPE_PGIDLE_UNSET:\n+\t\tif (!folio)\n+\t\t\tmatched = false;\n+\t\telse\n+\t\t\tmatched = damon_va_young_addr(folio, pte, pmd, mm,\n+\t\t\t\t\taddr);\n+\t\tbreak;\n+\tdefault:\n+\t\treturn damon_ops_filter_match(filter, folio);\n+\t}\n+\treturn matched == filter-\u003ematching;\n+}\n+\n+static bool damon_va_filter_pass(struct folio *folio, struct damon_probe *p,\n+\t\tpte_t *pte, pmd_t *pmd, struct mm_struct *mm,\n+\t\tunsigned long addr)\n+{\n+\tstruct damon_filter *f;\n+\tbool pass = true;\n+\n+\tdamon_for_each_filter(f, p) {\n+\t\tif (damon_va_filter_match(f, folio, pte, pmd, mm, addr)) {\n+\t\t\tpass = f-\u003eallow;\n+\t\t\tbreak;\n+\t\t}\n+\t\tpass = !f-\u003eallow;\n+\t}\n+\treturn pass;\n+}\n+\n+struct damon_va_probe_walk_private {\n+\tstruct damon_ctx *ctx;\n+\tstruct damon_region *r;\n+};\n+\n+static void damon_va_probe_folio(struct damon_ctx *ctx,\n+\t\tstruct damon_region *r, struct folio *folio,\n+\t\tpte_t *pte, pmd_t *pmd, struct mm_struct *mm)\n+{\n+\tstruct damon_probe *probe;\n+\tint i = 0;\n+\n+\tdamon_for_each_probe(probe, ctx) {\n+\t\tif (damon_va_filter_pass(folio, probe, pte, pmd, mm,\n+\t\t\t\t\tr-\u003esampling_addr))\n+\t\t\tr-\u003eprobe_hits[i]++;\n+\t\ti++;\n+\t}\n+}\n+\n+static int damon_va_probe_pmd_entry(pmd_t *pmd, unsigned long addr,\n+\t\tunsigned long next, struct mm_walk *walk)\n+{\n+\tpte_t *pte;\n+\tpte_t ptent;\n+\tspinlock_t *ptl;\n+\tstruct folio *folio;\n+\tstruct damon_va_probe_walk_private *priv = walk-\u003eprivate;\n+\n+#ifdef CONFIG_TRANSPARENT_HUGEPAGE\n+\tptl = pmd_trans_huge_lock(pmd, walk-\u003evma);\n+\tif (ptl) {\n+\t\tpmd_t pmde = pmdp_get(pmd);\n+\n+\t\tif (!pmd_present(pmde))\n+\t\t\tgoto huge_out;\n+\t\tfolio = vm_normal_folio_pmd(walk-\u003evma, addr, pmde);\n+\t\tif (!folio)\n+\t\t\tgoto huge_out;\n+\t\tdamon_va_probe_folio(priv-\u003ectx, priv-\u003er, folio, NULL, \u0026pmde,\n+\t\t\t\twalk-\u003evma-\u003evm_mm);\n+\n+huge_out:\n+\t\tspin_unlock(ptl);\n+\t\treturn 0;\n+\t}\n+#endif\t/* CONFIG_TRANSPARENT_HUGEPAGE */\n+\n+\tpte = pte_offset_map_lock(walk-\u003emm, pmd, addr, \u0026ptl);\n+\tif (!pte)\n+\t\treturn 0;\n+\tptent = ptep_get(pte);\n+\tif (!pte_present(ptent))\n+\t\tgoto out;\n+\tfolio = vm_normal_folio(walk-\u003evma, addr, ptent);\n+\tif (!folio)\n+\t\tgoto out;\n+\tdamon_va_probe_folio(priv-\u003ectx, priv-\u003er, folio, \u0026ptent, NULL,\n+\t\t\twalk-\u003evma-\u003evm_mm);\n+\n+out:\n+\tpte_unmap_unlock(pte, ptl);\n+\treturn 0;\n+}\n+\n+#ifdef CONFIG_HUGETLB_PAGE\n+static int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,\n+\t\tunsigned long addr, unsigned long end, struct mm_walk *walk)\n+{\n+\tstruct damon_va_probe_walk_private *priv = walk-\u003eprivate;\n+\tstruct hstate *h = hstate_vma(walk-\u003evma);\n+\tstruct folio *folio;\n+\tspinlock_t *ptl;\n+\tpte_t entry;\n+\n+\tptl = huge_pte_lock(h, walk-\u003emm, pte);\n+\tentry = huge_ptep_get(walk-\u003emm, addr, pte);\n+\tif (!pte_present(entry))\n+\t\tgoto out;\n+\n+\tfolio = pfn_folio(pte_pfn(entry));\n+\tfolio_get(folio);\n+\tdamon_va_probe_folio(priv-\u003ectx, priv-\u003er, folio, \u0026entry, NULL,\n+\t\t\twalk-\u003evma-\u003evm_mm);\n+\tfolio_put(folio);\n+\n+out:\n+\tspin_unlock(ptl);\n+\treturn 0;\n+}\n+#else\n+#define damon_va_probe_hugetlb_entry NULL\n+#endif /* CONFIG_HUGETLB_PAGE */\n+\n+static void __damon_va_apply_probes(struct damon_ctx *ctx,\n+\t\tstruct mm_struct *mm, struct damon_region *r)\n+{\n+\tstruct damon_va_probe_walk_private arg = {\n+\t\t.ctx = ctx,\n+\t\t.r = r,\n+\t};\n+\tstruct mm_walk_ops damon_probe_walk_ops = {\n+\t\t.pmd_entry = damon_va_probe_pmd_entry,\n+\t\t.hugetlb_entry = damon_va_probe_hugetlb_entry,\n+\t};\n+\tunsigned long addr = r-\u003esampling_addr;\n+\n+\tif (!mm)\n+\t\treturn;\n+\n+\tdamon_va_walk_page_range(mm, addr, addr + 1, \u0026damon_probe_walk_ops,\n+\t\t\t\u0026arg);\n+}\n+\n+static unsigned int damon_va_apply_probes(struct damon_ctx *ctx,\n+\t\tbool set_samples, bool return_max_wsum)\n+{\n+\tstruct damon_target *t;\n+\tstruct mm_struct *mm;\n+\tstruct damon_region *r;\n+\tunsigned int max_wsum = 0;\n+\n+\tdamon_for_each_target(t, ctx) {\n+\t\tmm = damon_get_mm(t);\n+\t\tdamon_for_each_region(r, t) {\n+\t\t\tif (set_samples)\n+\t\t\t\tr-\u003esampling_addr = damon_rand(ctx, r-\u003ear.start,\n+\t\t\t\t\t\tr-\u003ear.end);\n+\t\t\t__damon_va_apply_probes(ctx, mm, r);\n+\t\t\tif (return_max_wsum)\n+\t\t\t\tmax_wsum = max(damon_probe_hits_wsum(r, false,\n+\t\t\t\t\t\t\tctx), max_wsum);\n+\t\t}\n+\t\tif (mm)\n+\t\t\tmmput(mm);\n+\t}\n+\n+\treturn max_wsum;\n+}\n+\n static bool damos_va_filter_young_match(struct damos_filter *filter,\n \t\tstruct folio *folio, struct vm_area_struct *vma,\n \t\tunsigned long addr, pte_t *ptep, pmd_t *pmdp)\n@@ -938,6 +1168,8 @@ static int __init damon_va_initcall(void)\n \t\t.update = damon_va_update,\n \t\t.prepare_access_checks = damon_va_prepare_access_checks,\n \t\t.check_accesses = damon_va_check_accesses,\n+\t\t.prep_probes = damon_va_prep_probes,\n+\t\t.apply_probes = damon_va_apply_probes,\n \t\t.target_valid = damon_va_target_valid,\n \t\t.cleanup_target = damon_va_cleanup_target,\n \t\t.apply_scheme = damon_va_apply_scheme,\n"
} |
| 2/1 | 2026/09/07 02:16 | agent | patch-evaluator |
0mModel:core Args: null Results: {
"EnableConfigs": [
"DAMON",
"DAMON_VADDR",
"DAMON_PADDR",
"DAMON_SYSFS",
"TRANSPARENT_HUGEPAGE",
"HUGETLB_PAGE",
"MEMCG"
],
"FocusSymbols": [
"damon_ops_filter_match",
"damon_va_prep_probes",
"damon_va_apply_probes",
"damon_va_probe_pmd_entry",
"damon_va_probe_hugetlb_entry",
"damon_va_filter_match",
"damon_pa_filter_match"
],
"Reasoning": "The patch introduces DAMON virtual address probe preparation and evaluation logic, including custom page table walking for normal, transparent huge pages, and hugetlb pages, alongside shared filter matching logic. These paths are executed by the DAMON kernel worker thread and are reachable via DAMON sysfs interfaces, making them relevant for fuzz testing.",
"WorthFuzzing": true
}Instruction: You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.
IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.
================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.
- REACHABILITY IS THE PRIMARY GATE:
Fuzzing can only discover bugs in code that can actually execute in standard virtualized
environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
regardless of whether it adds assertions or complex logic.
- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
Patch authors routinely label changes as "cleanups", "refactorings", or state
"No functional change intended". Do NOT take these claims at face value.
Code refactorings that rearrange logic, introduce helper functions, or alter state management
in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
If reachable executable code is modified or refactored, it MUST be fuzzed.
- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
Even if the author believes the invariant always holds, fuzzing is essential to verify whether
an unusual sequence of operations can violate it.
================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:
- Non-kernel and non-executable changes:
* Modifications to Documentation/, comments, or spelling fixes.
* User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
that do not affect the compiled kernel image (vmlinux) or kernel modules.
* Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
that do not alter control flow or data structures.
* Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
* Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
* Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
physical PCI hot-unplug or manual sysfs driver unbinding.
* Code paths exclusive to architectures other than the target architecture.
================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
* Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
* Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
* Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
* Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).
================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:
- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
Do NOT list generic, ubiquitous functions called by almost every program in the corpus
(including, but not limited to: general memory allocators and deallocators, page fault
and trap handlers, or core synchronization primitives; this is not an exhaustive list).
Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
which severely dilutes fuzzing effort away from the actual changes.
- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
List functions that specifically implement the logic being added or altered, or direct API entrypoints
for the subsystem feature under review.
- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).
================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 1726d66c1cd258bc56d6d0e0db5f7f6ca921ee8b
Author: syz-cluster <triage@syzkaller.com>
Date: Mon Sep 7 02:16:41 2026 +0000
syz-cluster: applied patch under review
diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index 7219c608b1952..cfcd4edee346a 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -444,3 +444,35 @@ bool damos_ops_has_filter(struct damos *s)
return true;
return false;
}
+
+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio)
+{
+ bool matched = false;
+ struct mem_cgroup *memcg;
+
+ switch (filter->type) {
+ case DAMON_FILTER_TYPE_ANON:
+ if (!folio) {
+ matched = false;
+ break;
+ }
+ matched = folio_test_anon(folio);
+ break;
+ case DAMON_FILTER_TYPE_MEMCG:
+ if (!folio) {
+ matched = false;
+ break;
+ }
+ rcu_read_lock();
+ memcg = folio_memcg_check(folio);
+ if (!memcg)
+ matched = false;
+ else
+ matched = filter->memcg_id == mem_cgroup_id(memcg);
+ rcu_read_unlock();
+ break;
+ default:
+ break;
+ }
+ return matched == filter->matching;
+}
diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
index 38d295488fa18..b832169b1cf8c 100644
--- a/mm/damon/ops-common.h
+++ b/mm/damon/ops-common.h
@@ -21,3 +21,5 @@ bool damos_folio_filter_match(struct damos_filter *filter, struct folio *folio);
unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid);
bool damos_ops_has_filter(struct damos *s);
+
+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio);
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index c1e7d7a4f40df..ffde88ea7a13c 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -143,29 +143,8 @@ static bool damon_pa_filter_match(struct damon_filter *filter,
struct folio *folio)
{
bool matched = false;
- struct mem_cgroup *memcg;
switch (filter->type) {
- case DAMON_FILTER_TYPE_ANON:
- if (!folio) {
- matched = false;
- break;
- }
- matched = folio_test_anon(folio);
- break;
- case DAMON_FILTER_TYPE_MEMCG:
- if (!folio) {
- matched = false;
- break;
- }
- rcu_read_lock();
- memcg = folio_memcg_check(folio);
- if (!memcg)
- matched = false;
- else
- matched = filter->memcg_id == mem_cgroup_id(memcg);
- rcu_read_unlock();
- break;
case DAMON_FILTER_TYPE_PGIDLE_UNSET:
if (!folio)
matched = false;
@@ -173,7 +152,7 @@ static bool damon_pa_filter_match(struct damon_filter *filter,
matched = damon_folio_young(folio);
break;
default:
- break;
+ return damon_ops_filter_match(filter, folio);
}
return matched == filter->matching;
}
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index f884d3f78f30a..090317191973b 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -510,6 +510,236 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
return max_nr_accesses;
}
+static void damon_va_prep_probe_region(struct damon_ctx *ctx,
+ struct mm_struct *mm, struct damon_region *r,
+ struct damon_probe *probe)
+{
+ struct damon_prep *p;
+
+ damon_for_each_prep(p, probe) {
+ switch (p->action) {
+ case DAMON_PREP_SET_PGIDLE:
+ damon_va_mkold(mm, r->sampling_addr);
+ break;
+ default:
+ break;
+ }
+ }
+}
+
+static void damon_va_prep_probes(struct damon_ctx *ctx, bool set_samples)
+{
+ struct damon_target *t;
+ struct mm_struct *mm;
+ struct damon_region *r;
+ struct damon_probe *p;
+
+ damon_for_each_target(t, ctx) {
+ mm = damon_get_mm(t);
+ if (!mm)
+ continue;
+ damon_for_each_region(r, t) {
+ if (set_samples)
+ r->sampling_addr = damon_rand(ctx, r->ar.start,
+ r->ar.end);
+ damon_for_each_probe(p, ctx)
+ damon_va_prep_probe_region(ctx, mm, r, p);
+ }
+ mmput(mm);
+ }
+}
+
+static bool damon_va_young_addr(struct folio *folio, pte_t *pte, pmd_t *pmd,
+ struct mm_struct *mm, unsigned long addr)
+{
+ bool young = false;
+
+ if (pte)
+ young = pte_young(*pte);
+ else if (pmd)
+ young = pmd_young(*pmd);
+ young = young || !folio_test_idle(folio) ||
+ mmu_notifier_test_young(mm, addr);
+ return young;
+}
+
+static bool damon_va_filter_match(struct damon_filter *filter,
+ struct folio *folio, pte_t *pte, pmd_t *pmd,
+ struct mm_struct *mm, unsigned long addr)
+{
+ bool matched = false;
+
+ switch (filter->type) {
+ case DAMON_FILTER_TYPE_PGIDLE_UNSET:
+ if (!folio)
+ matched = false;
+ else
+ matched = damon_va_young_addr(folio, pte, pmd, mm,
+ addr);
+ break;
+ default:
+ return damon_ops_filter_match(filter, folio);
+ }
+ return matched == filter->matching;
+}
+
+static bool damon_va_filter_pass(struct folio *folio, struct damon_probe *p,
+ pte_t *pte, pmd_t *pmd, struct mm_struct *mm,
+ unsigned long addr)
+{
+ struct damon_filter *f;
+ bool pass = true;
+
+ damon_for_each_filter(f, p) {
+ if (damon_va_filter_match(f, folio, pte, pmd, mm, addr)) {
+ pass = f->allow;
+ break;
+ }
+ pass = !f->allow;
+ }
+ return pass;
+}
+
+struct damon_va_probe_walk_private {
+ struct damon_ctx *ctx;
+ struct damon_region *r;
+};
+
+static void damon_va_probe_folio(struct damon_ctx *ctx,
+ struct damon_region *r, struct folio *folio,
+ pte_t *pte, pmd_t *pmd, struct mm_struct *mm)
+{
+ struct damon_probe *probe;
+ int i = 0;
+
+ damon_for_each_probe(probe, ctx) {
+ if (damon_va_filter_pass(folio, probe, pte, pmd, mm,
+ r->sampling_addr))
+ r->probe_hits[i]++;
+ i++;
+ }
+}
+
+static int damon_va_probe_pmd_entry(pmd_t *pmd, unsigned long addr,
+ unsigned long next, struct mm_walk *walk)
+{
+ pte_t *pte;
+ pte_t ptent;
+ spinlock_t *ptl;
+ struct folio *folio;
+ struct damon_va_probe_walk_private *priv = walk->private;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ ptl = pmd_trans_huge_lock(pmd, walk->vma);
+ if (ptl) {
+ pmd_t pmde = pmdp_get(pmd);
+
+ if (!pmd_present(pmde))
+ goto huge_out;
+ folio = vm_normal_folio_pmd(walk->vma, addr, pmde);
+ if (!folio)
+ goto huge_out;
+ damon_va_probe_folio(priv->ctx, priv->r, folio, NULL, &pmde,
+ walk->vma->vm_mm);
+
+huge_out:
+ spin_unlock(ptl);
+ return 0;
+ }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+ pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ if (!pte)
+ return 0;
+ ptent = ptep_get(pte);
+ if (!pte_present(ptent))
+ goto out;
+ folio = vm_normal_folio(walk->vma, addr, ptent);
+ if (!folio)
+ goto out;
+ damon_va_probe_folio(priv->ctx, priv->r, folio, &ptent, NULL,
+ walk->vma->vm_mm);
+
+out:
+ pte_unmap_unlock(pte, ptl);
+ return 0;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,
+ unsigned long addr, unsigned long end, struct mm_walk *walk)
+{
+ struct damon_va_probe_walk_private *priv = walk->private;
+ struct hstate *h = hstate_vma(walk->vma);
+ struct folio *folio;
+ spinlock_t *ptl;
+ pte_t entry;
+
+ ptl = huge_pte_lock(h, walk->mm, pte);
+ entry = huge_ptep_get(walk->mm, addr, pte);
+ if (!pte_present(entry))
+ goto out;
+
+ folio = pfn_folio(pte_pfn(entry));
+ folio_get(folio);
+ damon_va_probe_folio(priv->ctx, priv->r, folio, &entry, NULL,
+ walk->vma->vm_mm);
+ folio_put(folio);
+
+out:
+ spin_unlock(ptl);
+ return 0;
+}
+#else
+#define damon_va_probe_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static void __damon_va_apply_probes(struct damon_ctx *ctx,
+ struct mm_struct *mm, struct damon_region *r)
+{
+ struct damon_va_probe_walk_private arg = {
+ .ctx = ctx,
+ .r = r,
+ };
+ struct mm_walk_ops damon_probe_walk_ops = {
+ .pmd_entry = damon_va_probe_pmd_entry,
+ .hugetlb_entry = damon_va_probe_hugetlb_entry,
+ };
+ unsigned long addr = r->sampling_addr;
+
+ if (!mm)
+ return;
+
+ damon_va_walk_page_range(mm, addr, addr + 1, &damon_probe_walk_ops,
+ &arg);
+}
+
+static unsigned int damon_va_apply_probes(struct damon_ctx *ctx,
+ bool set_samples, bool return_max_wsum)
+{
+ struct damon_target *t;
+ struct mm_struct *mm;
+ struct damon_region *r;
+ unsigned int max_wsum = 0;
+
+ damon_for_each_target(t, ctx) {
+ mm = damon_get_mm(t);
+ damon_for_each_region(r, t) {
+ if (set_samples)
+ r->sampling_addr = damon_rand(ctx, r->ar.start,
+ r->ar.end);
+ __damon_va_apply_probes(ctx, mm, r);
+ if (return_max_wsum)
+ max_wsum = max(damon_probe_hits_wsum(r, false,
+ ctx), max_wsum);
+ }
+ if (mm)
+ mmput(mm);
+ }
+
+ return max_wsum;
+}
+
static bool damos_va_filter_young_match(struct damos_filter *filter,
struct folio *folio, struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep, pmd_t *pmdp)
@@ -938,6 +1168,8 @@ static int __init damon_va_initcall(void)
.update = damon_va_update,
.prepare_access_checks = damon_va_prepare_access_checks,
.check_accesses = damon_va_check_accesses,
+ .prep_probes = damon_va_prep_probes,
+ .apply_probes = damon_va_apply_probes,
.target_valid = damon_va_target_valid,
.cleanup_target = damon_va_cleanup_target,
.apply_scheme = damon_va_apply_scheme,
|
| 3/2 | 2026/09/07 02:16 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 6491 output: 27 thoughts: 359 Thoughts: **Fuzzing DAMON: Patch Analysis and Configuration Checklist** Okay, let's dive into this patch and figure out the fuzzing strategy. My initial thought is to determine if this change warrants fuzzing, and if so, how. The first step, as always, is to thoroughly understand what this patch is doing. Based on the file list, `mm/damon/ops-common.c`, `mm/damon/ops-common.h`, `mm/damon/paddr.c`, and `mm/damon/vaddr.c`, it's clearly a DAMON (Data Access MONitor) modification, which is immediately interesting. Specifically, it looks like `damon_ops_filter_match` is being introduced in `ops-common` and utilized in `paddr.c` and `vaddr.c`. This suggests some new filtering or matching mechanism within DAMON, possibly for selecting memory regions to monitor or influence. Looking deeper at `vaddr.c`, the functions added are particularly noteworthy: `damon_va_prep_probe_region`, `damon_va_prep_probes`, `damon_va_young_addr`, `damon_va_filter_match`, `damon_va_filter_pass`, `damon_va_probe_folio`, `damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`, `__damon_va_apply_probes`, and `damon_va_apply_probes`. The `.prep_probes` and `.apply_probes` hooks in `damon_va_initcall()` are key, especially if these replace functionality. These all point to virtual address space operations within DAMON. This suggests a new approach to memory access monitoring or manipulation within the virtual address space. This is a very interesting spot for fuzzing. Now, let's shift gears to the configuration side. I need to quickly determine the relevant Kconfig options and dependencies for this patch. I need to know which DAMON features, and specifically `DAMON_VADDR` or `DAMON_PADDR`, are needed to enable this functionality. I’ll need to run grepper or `read-file` on `mm/damon/Kconfig` to pin this down quickly. Any configuration issues are, obviously, a prime target for fuzzing. After that, I will need to look into any focus symbols that could impact it. |
| 4/2 | 2026/09/07 02:16 | tool | grepper |
0mArgs:{
"Expression": "config DAMON",
"PathPrefix": "mm/damon"
}Results: {
"Output": "mm/damon/Kconfig=3=menu \"Data Access Monitoring\"\nmm/damon/Kconfig-4-\nmm/damon/Kconfig:5:config DAMON\nmm/damon/Kconfig-6-\tbool \"DAMON: Data Access Monitoring Framework\"\n--\nmm/damon/Kconfig-14-\nmm/damon/Kconfig:15:config DAMON_DEBUG_SANITY\nmm/damon/Kconfig-16-\tbool \"Check sanity of DAMON code\"\n--\nmm/damon/Kconfig-25-\nmm/damon/Kconfig:26:config DAMON_KUNIT_TEST\nmm/damon/Kconfig-27-\tbool \"Test for damon\" if !KUNIT_ALL_TESTS\n--\nmm/damon/Kconfig-37-\nmm/damon/Kconfig:38:config DAMON_VADDR\nmm/damon/Kconfig-39-\tbool \"Data access monitoring operations for virtual address spaces\"\n--\nmm/damon/Kconfig-46-\nmm/damon/Kconfig:47:config DAMON_PADDR\nmm/damon/Kconfig-48-\tbool \"Data access monitoring operations for the physical address space\"\n--\nmm/damon/Kconfig-55-\nmm/damon/Kconfig:56:config DAMON_VADDR_KUNIT_TEST\nmm/damon/Kconfig-57-\tbool \"Test for DAMON operations\" if !KUNIT_ALL_TESTS\n--\nmm/damon/Kconfig-67-\nmm/damon/Kconfig:68:config DAMON_SYSFS\nmm/damon/Kconfig-69-\tbool \"DAMON sysfs interface\"\n--\nmm/damon/Kconfig-75-\nmm/damon/Kconfig:76:config DAMON_SYSFS_KUNIT_TEST\nmm/damon/Kconfig-77-\tbool \"Test for damon sysfs interface\" if !KUNIT_ALL_TESTS\n--\nmm/damon/Kconfig-87-\nmm/damon/Kconfig:88:config DAMON_RECLAIM\nmm/damon/Kconfig-89-\tbool \"Build DAMON-based reclaim (DAMON_RECLAIM)\"\n--\nmm/damon/Kconfig-99-\nmm/damon/Kconfig:100:config DAMON_LRU_SORT\nmm/damon/Kconfig-101-\tbool \"Build DAMON-based LRU-lists sorting (DAMON_LRU_SORT)\"\n--\nmm/damon/Kconfig-107-\nmm/damon/Kconfig:108:config DAMON_STAT\nmm/damon/Kconfig-109-\tbool \"Build data access monitoring stat (DAMON_STAT)\"\n--\nmm/damon/Kconfig-115-\nmm/damon/Kconfig:116:config DAMON_STAT_ENABLED_DEFAULT\nmm/damon/Kconfig-117-\tbool \"Enable DAMON_STAT by default\"\n"
} |
| 5/2 | 2026/09/07 02:16 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8156 output: 32 thoughts: 31 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: **Makefile Investigation for Ops-Common Compilation** Alright, time to dig into the build process. I need to understand how `ops-common.c`, `vaddr.c`, and `paddr.c` are being compiled. To do that efficiently, I'll go directly to the source of truth for the build: `/mm/damon/Makefile`. A quick scan of that `Makefile` should reveal the compilation flags, dependencies, and linking steps involved in generating the object files for those critical files. Knowing the build process will help me quickly understand and troubleshoot build errors, dependency problems, or inefficiencies in the generated code. Let's see what the makefile reveals. |
| 6/2 | 2026/09/07 02:16 | tool | read-file |
0mArgs:{
"File": "mm/damon/Makefile",
"FirstLine": 1,
"LineCount": 25
}Results: {
"Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0\n 2:\t\n 3:\tobj-y\t\t\t\t:= core.o\n 4:\tobj-$(CONFIG_DAMON_VADDR)\t+= ops-common.o vaddr.o\n 5:\tobj-$(CONFIG_DAMON_PADDR)\t+= ops-common.o paddr.o\n 6:\tobj-$(CONFIG_DAMON_SYSFS)\t+= sysfs-common.o sysfs-schemes.o sysfs.o\n 7:\tobj-$(CONFIG_DAMON_RECLAIM)\t+= modules-common.o reclaim.o\n 8:\tobj-$(CONFIG_DAMON_LRU_SORT)\t+= modules-common.o lru_sort.o\n 9:\tobj-$(CONFIG_DAMON_STAT)\t+= modules-common.o stat.o\n"
} |
| 7/2 | 2026/09/07 02:16 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8597 output: 33 thoughts: 41 Thoughts: Okay, let's dive into this. Here's how I'd approach that kernel configuration file check: **Kernel Configuration Dependencies Check** Alright, my first instinct is to zero in on the `mm/damon/Kconfig` file. I need to understand the dependencies for `DAMON`, `DAMON_VADDR`, `DAMON_PADDR`, and `DAMON_SYSFS`. I'm thinking I'll need to meticulously parse that Kconfig file. I'll be looking for things like `depends on`, `select`, and even `source` directives that might influence the availability or behavior of those DAMON features. The goal here is to get a complete picture of which other kernel components, features, or configurations are prerequisite for DAMON's core functionality. Knowing these dependencies is absolutely critical to avoid any potential configuration conflicts or runtime issues. I'll need to make sure I understand how these features interact and impact one another. |
| 8/2 | 2026/09/07 02:17 | tool | read-file |
0mArgs:{
"File": "mm/damon/Kconfig",
"FirstLine": 1,
"LineCount": 80
}Results: {
"Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\t\n 3:\tmenu \"Data Access Monitoring\"\n 4:\t\n 5:\tconfig DAMON\n 6:\t\tbool \"DAMON: Data Access Monitoring Framework\"\n 7:\t\thelp\n 8:\t\t This builds a framework that allows kernel subsystems to monitor\n 9:\t\t access frequency of each memory region. The information can be useful\n 10:\t\t for performance-centric DRAM level memory management.\n 11:\t\n 12:\t\t See https://www.kernel.org/doc/html/latest/mm/damon/index.html for\n 13:\t\t more information.\n 14:\t\n 15:\tconfig DAMON_DEBUG_SANITY\n 16:\t\tbool \"Check sanity of DAMON code\"\n 17:\t\tdepends on DAMON\n 18:\t\thelp\n 19:\t\t This enables additional DAMON debugging-purpose sanity checks in\n 20:\t\t DAMON code. This can be useful for finding bugs, but impose\n 21:\t\t additional overhead. This is therefore recommended to be enabled on\n 22:\t\t only development and test setups.\n 23:\t\n 24:\t\t If unsure, say N.\n 25:\t\n 26:\tconfig DAMON_KUNIT_TEST\n 27:\t\tbool \"Test for damon\" if !KUNIT_ALL_TESTS\n 28:\t\tdepends on DAMON \u0026\u0026 KUNIT=y\n 29:\t\tdefault KUNIT_ALL_TESTS\n 30:\t\thelp\n 31:\t\t This builds the DAMON Kunit test suite.\n 32:\t\n 33:\t\t For more information on KUnit and unit tests in general, please refer\n 34:\t\t to the KUnit documentation.\n 35:\t\n 36:\t\t If unsure, say N.\n 37:\t\n 38:\tconfig DAMON_VADDR\n 39:\t\tbool \"Data access monitoring operations for virtual address spaces\"\n 40:\t\tdepends on DAMON \u0026\u0026 MMU\n 41:\t\tselect PAGE_IDLE_FLAG\n 42:\t\tdefault DAMON\n 43:\t\thelp\n 44:\t\t This builds the default data access monitoring operations for DAMON\n 45:\t\t that work for virtual address spaces.\n 46:\t\n 47:\tconfig DAMON_PADDR\n 48:\t\tbool \"Data access monitoring operations for the physical address space\"\n 49:\t\tdepends on DAMON \u0026\u0026 MMU\n 50:\t\tselect PAGE_IDLE_FLAG\n 51:\t\tdefault DAMON\n 52:\t\thelp\n 53:\t\t This builds the default data access monitoring operations for DAMON\n 54:\t\t that works for the physical address space.\n 55:\t\n 56:\tconfig DAMON_VADDR_KUNIT_TEST\n 57:\t\tbool \"Test for DAMON operations\" if !KUNIT_ALL_TESTS\n 58:\t\tdepends on DAMON_VADDR \u0026\u0026 KUNIT=y\n 59:\t\tdefault KUNIT_ALL_TESTS\n 60:\t\thelp\n 61:\t\t This builds the DAMON virtual addresses operations Kunit test suite.\n 62:\t\n 63:\t\t For more information on KUnit and unit tests in general, please refer\n 64:\t\t to the KUnit documentation.\n 65:\t\n 66:\t\t If unsure, say N.\n 67:\t\n 68:\tconfig DAMON_SYSFS\n 69:\t\tbool \"DAMON sysfs interface\"\n 70:\t\tdepends on DAMON \u0026\u0026 SYSFS\n 71:\t\tdefault DAMON\n 72:\t\thelp\n 73:\t\t This builds the sysfs interface for DAMON. The user space can use\n 74:\t\t the interface for arbitrary data access monitoring.\n 75:\t\n 76:\tconfig DAMON_SYSFS_KUNIT_TEST\n 77:\t\tbool \"Test for damon sysfs interface\" if !KUNIT_ALL_TESTS\n 78:\t\tdepends on DAMON_SYSFS \u0026\u0026 KUNIT=y\n 79:\t\tdefault KUNIT_ALL_TESTS\n 80:\t\thelp\n"
} |
| 9/2 | 2026/09/07 02:17 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 9917 output: 28 thoughts: 242 Thoughts: **Analyzing the DAMON Patch for Fuzzing Potential** Okay, let's break this down. My initial assessment is focused on identifying the patch's changes, determining if they're reachable, and ultimately judging if fuzzing it is worthwhile. This is core MM subsystem code, DAMON, so it's inherently interesting from a security perspective. From what I see, the patch is implementing virtual address probes, specifically `damon_va_prep_probes` and `damon_va_apply_probes`. It looks like it also includes the necessary page table walks—`damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`—along with filter matching functions like `damon_va_filter_match` and `damon_ops_filter_match`. Finally, there's the usual sysfs/core DAMON integration. All standard stuff, really. The key thing here is that it's *fully* reachable from userspace, which is fantastic for fuzzing. We have the sysfs DAMON interface (`CONFIG_DAMON_SYSFS`, etc.) as a direct attack vector. I'm also going to check if there are any other DAMON control interfaces that might be relevant, like debugfs, but I'll focus on sysfs for now. It is likely the best path for fuzzer integration. I'm thinking I need to understand if the sysfs interface allows us to configure these probes or the DAMON contexts/targets. I should probably start by searching the codebase for calls to `prep_probes` or `apply_probes` to get a sense of how they're actually used. That's the next logical step. |
| 10/2 | 2026/09/07 02:17 | tool | grepper |
0mArgs:{
"Expression": "apply_probes",
"PathPrefix": "mm/damon"
}Results: {
"Output": "mm/damon/core.c=3893=static int kdamond_fn(void *data)\n--\nmm/damon/core.c-3945-\t\t\tmax_merge_score = ctx-\u003eops.check_accesses(ctx);\nmm/damon/core.c:3946:\t\tif (ctx-\u003eops.apply_probes) {\nmm/damon/core.c-3947-\t\t\tif (time_after_eq(ctx-\u003epassed_sample_intervals,\n--\nmm/damon/core.c-3952-\t\t\t\tget_max_wsum = false;\nmm/damon/core.c:3953:\t\t\tmax_wsum = ctx-\u003eops.apply_probes(ctx,\nmm/damon/core.c-3954-\t\t\t\t\taccess_check_disabled \u0026\u0026 !do_prep,\n--\nmm/damon/paddr.c=160=static bool damon_pa_filter_pass(phys_addr_t pa, struct folio *folio,\n--\nmm/damon/paddr.c-175-\nmm/damon/paddr.c:176:static unsigned int damon_pa_apply_probes(struct damon_ctx *ctx,\nmm/damon/paddr.c-177-\t\tbool set_samples, bool return_max_wsum)\n--\nmm/damon/paddr.c=456=static int __init damon_pa_initcall(void)\n--\nmm/damon/paddr.c-464-\t\t.prep_probes = damon_pa_prep_probes,\nmm/damon/paddr.c:465:\t\t.apply_probes = damon_pa_apply_probes,\nmm/damon/paddr.c-466-\t\t.target_valid = NULL,\n--\nmm/damon/vaddr.c=669=static int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,\n--\nmm/damon/vaddr.c-696-\nmm/damon/vaddr.c:697:static void __damon_va_apply_probes(struct damon_ctx *ctx,\nmm/damon/vaddr.c-698-\t\tstruct mm_struct *mm, struct damon_region *r)\n--\nmm/damon/vaddr.c-716-\nmm/damon/vaddr.c:717:static unsigned int damon_va_apply_probes(struct damon_ctx *ctx,\nmm/damon/vaddr.c-718-\t\tbool set_samples, bool return_max_wsum)\n--\nmm/damon/vaddr.c-730-\t\t\t\t\t\tr-\u003ear.end);\nmm/damon/vaddr.c:731:\t\t\t__damon_va_apply_probes(ctx, mm, r);\nmm/damon/vaddr.c-732-\t\t\tif (return_max_wsum)\n--\nmm/damon/vaddr.c=1163=static int __init damon_va_initcall(void)\n--\nmm/damon/vaddr.c-1171-\t\t.prep_probes = damon_va_prep_probes,\nmm/damon/vaddr.c:1172:\t\t.apply_probes = damon_va_apply_probes,\nmm/damon/vaddr.c-1173-\t\t.target_valid = damon_va_target_valid,\n"
} |
| 11/2 | 2026/09/07 02:17 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 11442 output: 28 thoughts: 22 Thoughts: Okay, here's my take on those thoughts, framed as my own: **Digging Deeper into `mm/damon/core.c`** Alright, I'm already thinking about DAMON and its internals, and I'm feeling that itch to really understand how this thing is operating. I've got my head around a few key areas, but I need to make sure I'm not missing anything crucial. Specifically, I'm now focusing in on `mm/damon/core.c` and realizing there's one specific thing that really needs a look at: `prep_probes`. I'm going to take a closer look at this and see how it interacts with the rest of the DAMON implementation. |
| 12/2 | 2026/09/07 02:17 | tool | grepper |
0mArgs:{
"Expression": "prep_probes",
"PathPrefix": "mm/damon"
}Results: {
"Output": "mm/damon/core.c=3893=static int kdamond_fn(void *data)\n--\nmm/damon/core.c-3933-\nmm/damon/core.c:3934:\t\tdo_prep = ctx-\u003eops.prep_probes \u0026\u0026 damon_has_prep(ctx);\nmm/damon/core.c-3935-\n--\nmm/damon/core.c-3938-\t\tif (do_prep)\nmm/damon/core.c:3939:\t\t\tctx-\u003eops.prep_probes(ctx, access_check_disabled);\nmm/damon/core.c-3940-\n--\nmm/damon/paddr.c=92=static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)\n--\nmm/damon/paddr.c-107-\nmm/damon/paddr.c:108:static void damon_pa_prep_probes_region(struct damon_region *r,\nmm/damon/paddr.c-109-\t\tstruct damon_probe *probe, struct damon_ctx *ctx)\n--\nmm/damon/paddr.c-124-\nmm/damon/paddr.c:125:static void damon_pa_prep_probes(struct damon_ctx *ctx, bool set_samples)\nmm/damon/paddr.c-126-{\n--\nmm/damon/paddr.c-136-\t\t\tdamon_for_each_probe(p, ctx)\nmm/damon/paddr.c:137:\t\t\t\tdamon_pa_prep_probes_region(r, p, ctx);\nmm/damon/paddr.c-138-\t\t}\n--\nmm/damon/paddr.c=456=static int __init damon_pa_initcall(void)\n--\nmm/damon/paddr.c-463-\t\t.check_accesses = damon_pa_check_accesses,\nmm/damon/paddr.c:464:\t\t.prep_probes = damon_pa_prep_probes,\nmm/damon/paddr.c-465-\t\t.apply_probes = damon_pa_apply_probes,\n--\nmm/damon/vaddr.c=513=static void damon_va_prep_probe_region(struct damon_ctx *ctx,\n--\nmm/damon/vaddr.c-529-\nmm/damon/vaddr.c:530:static void damon_va_prep_probes(struct damon_ctx *ctx, bool set_samples)\nmm/damon/vaddr.c-531-{\n--\nmm/damon/vaddr.c=1163=static int __init damon_va_initcall(void)\n--\nmm/damon/vaddr.c-1170-\t\t.check_accesses = damon_va_check_accesses,\nmm/damon/vaddr.c:1171:\t\t.prep_probes = damon_va_prep_probes,\nmm/damon/vaddr.c-1172-\t\t.apply_probes = damon_va_apply_probes,\n"
} |
| 13/2 | 2026/09/07 02:17 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 12479 output: 37 thoughts: 1000 Thoughts: **DAMON Probe and Filter Logic Deep Dive** Okay, let's get right into this. I need to understand this new DAMON code that's been introduced. My initial focus is on the `kdamond_fn` function and how DAMON is managed. It's the core DAMON kernel thread, started when DAMON is enabled through sysfs using attributes like `kdamond_nr_schemes` and the "on" state in `/sys/kernel/mm/damon/admin/kdamonds/...`. I'm working under the assumption that this code is running when we're actively monitoring virtual addresses using probes or filters. The obvious question is whether this code is even reachable in standard setups, say in QEMU. The answer is yes, given standard memory management and sysfs functionality is the norm. Now, is this code worth fuzzing? Absolutely, without a doubt. We're looking at completely new probe execution logic, the mechanics of walking memory addresses (`damon_va_walk_page_range`), deep dives into the page tables (`damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`), THP (Transparent Huge Page) locking, huge page locking, folio handling, and filter checking – all core areas within the `mm/damon` subsystem. This is a fertile ground for discovery. Alright, let's meticulously go through all the relevant functions. What did the patch actually introduce or modify? Let's refresh our memory on the diff: 1. `damon_ops_filter_match` in `mm/damon/ops-common.c` 2. `damon_pa_filter_match` in `mm/damon/paddr.c` 3. `damon_va_prep_probe_region` in `mm/damon/vaddr.c` 4. `damon_va_prep_probes` in `mm/damon/vaddr.c` 5. `damon_va_young_addr` in `mm/damon/vaddr.c` 6. `damon_va_filter_match` in `mm/damon/vaddr.c` 7. `damon_va_filter_pass` in `mm/damon/vaddr.c` 8. `damon_va_probe_folio` in `mm/damon/vaddr.c` 9. `damon_va_probe_pmd_entry` in `mm/damon/vaddr.c` 10. `damon_va_probe_hugetlb_entry` in `mm/damon/vaddr.c` 11. `__damon_va_apply_probes` in `mm/damon/vaddr.c` 12. `damon_va_apply_probes` in `mm/damon/vaddr.c` Are these static or exported? Let's see: * `damon_ops_filter_match` is a non-static function defined in `mm/damon/ops-common.c`, and declared in `ops-common.h`. * `damon_pa_filter_match` is static in `mm/damon/paddr.c`. * `damon_va_prep_probes` and `damon_va_apply_probes` are operation callbacks in `damon_va_initcall` / `damon_operations`. * `damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`, `damon_va_filter_match`, etc. are static helpers within `vaddr.c`. Okay, let's select the key symbols for further review: * `damon_ops_filter_match` * `damon_va_prep_probes` * `damon_va_apply_probes` * `damon_va_probe_pmd_entry` * `damon_va_probe_hugetlb_entry` * `damon_va_filter_match` * `damon_pa_filter_match` What configurations are required? We need to make sure these are correctly set when we run: * `DAMON` * `DAMON_VADDR` * `DAMON_PADDR` * `DAMON_SYSFS` * `TRANSPARENT_HUGEPAGE` (for `#ifdef CONFIG_TRAN |
| 14/2 | 2026/09/07 02:17 | tool | read-file |
0mArgs:{
"File": "mm/damon/vaddr.c",
"FirstLine": 600,
"LineCount": 80
}Results: {
"Contents": " 600:\t\treturn pass;\n 601:\t}\n 602:\t\n 603:\tstruct damon_va_probe_walk_private {\n 604:\t\tstruct damon_ctx *ctx;\n 605:\t\tstruct damon_region *r;\n 606:\t};\n 607:\t\n 608:\tstatic void damon_va_probe_folio(struct damon_ctx *ctx,\n 609:\t\t\tstruct damon_region *r, struct folio *folio,\n 610:\t\t\tpte_t *pte, pmd_t *pmd, struct mm_struct *mm)\n 611:\t{\n 612:\t\tstruct damon_probe *probe;\n 613:\t\tint i = 0;\n 614:\t\n 615:\t\tdamon_for_each_probe(probe, ctx) {\n 616:\t\t\tif (damon_va_filter_pass(folio, probe, pte, pmd, mm,\n 617:\t\t\t\t\t\tr-\u003esampling_addr))\n 618:\t\t\t\tr-\u003eprobe_hits[i]++;\n 619:\t\t\ti++;\n 620:\t\t}\n 621:\t}\n 622:\t\n 623:\tstatic int damon_va_probe_pmd_entry(pmd_t *pmd, unsigned long addr,\n 624:\t\t\tunsigned long next, struct mm_walk *walk)\n 625:\t{\n 626:\t\tpte_t *pte;\n 627:\t\tpte_t ptent;\n 628:\t\tspinlock_t *ptl;\n 629:\t\tstruct folio *folio;\n 630:\t\tstruct damon_va_probe_walk_private *priv = walk-\u003eprivate;\n 631:\t\n 632:\t#ifdef CONFIG_TRANSPARENT_HUGEPAGE\n 633:\t\tptl = pmd_trans_huge_lock(pmd, walk-\u003evma);\n 634:\t\tif (ptl) {\n 635:\t\t\tpmd_t pmde = pmdp_get(pmd);\n 636:\t\n 637:\t\t\tif (!pmd_present(pmde))\n 638:\t\t\t\tgoto huge_out;\n 639:\t\t\tfolio = vm_normal_folio_pmd(walk-\u003evma, addr, pmde);\n 640:\t\t\tif (!folio)\n 641:\t\t\t\tgoto huge_out;\n 642:\t\t\tdamon_va_probe_folio(priv-\u003ectx, priv-\u003er, folio, NULL, \u0026pmde,\n 643:\t\t\t\t\twalk-\u003evma-\u003evm_mm);\n 644:\t\n 645:\thuge_out:\n 646:\t\t\tspin_unlock(ptl);\n 647:\t\t\treturn 0;\n 648:\t\t}\n 649:\t#endif\t/* CONFIG_TRANSPARENT_HUGEPAGE */\n 650:\t\n 651:\t\tpte = pte_offset_map_lock(walk-\u003emm, pmd, addr, \u0026ptl);\n 652:\t\tif (!pte)\n 653:\t\t\treturn 0;\n 654:\t\tptent = ptep_get(pte);\n 655:\t\tif (!pte_present(ptent))\n 656:\t\t\tgoto out;\n 657:\t\tfolio = vm_normal_folio(walk-\u003evma, addr, ptent);\n 658:\t\tif (!folio)\n 659:\t\t\tgoto out;\n 660:\t\tdamon_va_probe_folio(priv-\u003ectx, priv-\u003er, folio, \u0026ptent, NULL,\n 661:\t\t\t\twalk-\u003evma-\u003evm_mm);\n 662:\t\n 663:\tout:\n 664:\t\tpte_unmap_unlock(pte, ptl);\n 665:\t\treturn 0;\n 666:\t}\n 667:\t\n 668:\t#ifdef CONFIG_HUGETLB_PAGE\n 669:\tstatic int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,\n 670:\t\t\tunsigned long addr, unsigned long end, struct mm_walk *walk)\n 671:\t{\n 672:\t\tstruct damon_va_probe_walk_private *priv = walk-\u003eprivate;\n 673:\t\tstruct hstate *h = hstate_vma(walk-\u003evma);\n 674:\t\tstruct folio *folio;\n 675:\t\tspinlock_t *ptl;\n 676:\t\tpte_t entry;\n 677:\t\n 678:\t\tptl = huge_pte_lock(h, walk-\u003emm, pte);\n 679:\t\tentry = huge_ptep_get(walk-\u003emm, addr, pte);\n"
} |
| 15/2 | 2026/09/07 02:17 | llm | patch-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 15785 output: 233 thoughts: 316 Thoughts: **My Assessment of the DAMON Patch's Fuzzing Potential** Okay, so I'm looking at this new patch and I need to assess its fuzzing implications. My initial thought is to dive into `ops-common.c` and specifically examine `damon_ops_filter_match`. I see it uses `struct mem_cgroup`, and calls `folio_memcg_check(folio)` and `mem_cgroup_id(memcg)`. Now, the important thing here is that these functions are only active if `MEMCG` is enabled, so that's a key dependency. Let me make sure I understand the full context. I'm seeing that we've flagged this as `WorthFuzzing`, which aligns with my initial interest. The patch leverages a number of configurations including `DAMON`, `DAMON_VADDR`, `DAMON_PADDR`, `DAMON_SYSFS`, `TRANSPARENT_HUGEPAGE`, `HUGETLB_PAGE`, and crucially, `MEMCG`. All of those have been enabled. The patch seems to be introducing DAMON virtual address probe operations, including page table walking functions like `pmd_entry` and `hugetlb_entry`, plus filter matching, and probing callbacks. I'm particularly interested in the `FocusSymbols` list; `damon_ops_filter_match`, `damon_va_prep_probes`, `damon_va_apply_probes`, `damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`, `damon_va_filter_match`, and `damon_pa_filter_match`. These are the core functions that warrant my scrutiny during fuzz testing. The reasoning is clear: DAMON Sysfs/kdamond interfaces expose these functions. This patch looks ripe for fuzzing. The combination of page table walking, complex memory management interactions (via `MEMCG` and other configurations), and sysfs interfaces makes it a likely target. I should probably invoke `set-results` at this point. |
| 16/2 | 2026/09/07 02:17 | tool | set-results |
0mArgs:{
"EnableConfigs": [
"DAMON",
"DAMON_VADDR",
"DAMON_PADDR",
"DAMON_SYSFS",
"TRANSPARENT_HUGEPAGE",
"HUGETLB_PAGE",
"MEMCG"
],
"FocusSymbols": [
"damon_ops_filter_match",
"damon_va_prep_probes",
"damon_va_apply_probes",
"damon_va_probe_pmd_entry",
"damon_va_probe_hugetlb_entry",
"damon_va_filter_match",
"damon_pa_filter_match"
],
"Reasoning": "The patch introduces DAMON virtual address probe preparation and evaluation logic, including custom page table walking for normal, transparent huge pages, and hugetlb pages, alongside shared filter matching logic. These paths are executed by the DAMON kernel worker thread and are reachable via DAMON sysfs interfaces, making them relevant for fuzz testing.",
"WorthFuzzing": true
}Results: {
"EnableConfigs": [
"DAMON",
"DAMON_VADDR",
"DAMON_PADDR",
"DAMON_SYSFS",
"TRANSPARENT_HUGEPAGE",
"HUGETLB_PAGE",
"MEMCG"
],
"FocusSymbols": [
"damon_ops_filter_match",
"damon_va_prep_probes",
"damon_va_apply_probes",
"damon_va_probe_pmd_entry",
"damon_va_probe_hugetlb_entry",
"damon_va_filter_match",
"damon_pa_filter_match"
],
"Reasoning": "The patch introduces DAMON virtual address probe preparation and evaluation logic, including custom page table walking for normal, transparent huge pages, and hugetlb pages, alongside shared filter matching logic. These paths are executed by the DAMON kernel worker thread and are reachable via DAMON sysfs interfaces, making them relevant for fuzz testing.",
"WorthFuzzing": true
} |
| 17/1 | 2026/09/07 02:17 | action | If |
0mArgs:{
"WorthFuzzing": true
}Results: null |
| 18/2 | 2026/09/07 02:17 | agent | kmsan-evaluator |
0mModel:core Args: null Results: {
"KMSANReasoning": "The patch introduces virtual address probe operations (prep and apply probes) and refactors common filter matching logic in the DAMON subsystem. \n\nEvaluating against KMSAN vs KASAN applicability:\n1. No uninitialized memory usage or info-leaks: All local variables (`matched`, `young`, `pass`, `i`), stack structures (`damon_va_probe_walk_private`, `mm_walk_ops`), and page table entry copies (`ptent`, `pmde`, `entry`) are explicitly initialized before use.\n2. No user-space copy mechanisms: The patch does not copy data to user space or manipulate uninitialized kernel buffers exposed to user space.\n3. Standard bug detectors are sufficient: Potential bugs in this code (such as array out-of-bounds on `probe_hits`, folio reference count mismatches, or page table locking issues) fall squarely within the purview of KASAN, UBSAN, and LOCKDEP.\n\nTherefore, there are no uninitialized memory risks that require a dedicated KMSAN fuzzing session.",
"NeedsKMSAN": false
}Instruction: You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.
CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
a comprehensive suite of debugging tools and sanitizers, including KASAN
(out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
(locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
or page allocations) and kernel-to-user memory info-leaks.
Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.
Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.
Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
attributes, ioctl output arguments, socket options, or BPF buffers) where fields
or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
uninitialized bytes of existing buffers.
Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
dereferences, locking deadlocks, or use-after-free bugs (these are already caught
by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.
Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Target architecture: amd64
For your convenience, here is the diff of the changes:
commit 1726d66c1cd258bc56d6d0e0db5f7f6ca921ee8b
Author: syz-cluster <triage@syzkaller.com>
Date: Mon Sep 7 02:16:41 2026 +0000
syz-cluster: applied patch under review
diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index 7219c608b1952..cfcd4edee346a 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -444,3 +444,35 @@ bool damos_ops_has_filter(struct damos *s)
return true;
return false;
}
+
+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio)
+{
+ bool matched = false;
+ struct mem_cgroup *memcg;
+
+ switch (filter->type) {
+ case DAMON_FILTER_TYPE_ANON:
+ if (!folio) {
+ matched = false;
+ break;
+ }
+ matched = folio_test_anon(folio);
+ break;
+ case DAMON_FILTER_TYPE_MEMCG:
+ if (!folio) {
+ matched = false;
+ break;
+ }
+ rcu_read_lock();
+ memcg = folio_memcg_check(folio);
+ if (!memcg)
+ matched = false;
+ else
+ matched = filter->memcg_id == mem_cgroup_id(memcg);
+ rcu_read_unlock();
+ break;
+ default:
+ break;
+ }
+ return matched == filter->matching;
+}
diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
index 38d295488fa18..b832169b1cf8c 100644
--- a/mm/damon/ops-common.h
+++ b/mm/damon/ops-common.h
@@ -21,3 +21,5 @@ bool damos_folio_filter_match(struct damos_filter *filter, struct folio *folio);
unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid);
bool damos_ops_has_filter(struct damos *s);
+
+bool damon_ops_filter_match(struct damon_filter *filter, struct folio *folio);
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index c1e7d7a4f40df..ffde88ea7a13c 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -143,29 +143,8 @@ static bool damon_pa_filter_match(struct damon_filter *filter,
struct folio *folio)
{
bool matched = false;
- struct mem_cgroup *memcg;
switch (filter->type) {
- case DAMON_FILTER_TYPE_ANON:
- if (!folio) {
- matched = false;
- break;
- }
- matched = folio_test_anon(folio);
- break;
- case DAMON_FILTER_TYPE_MEMCG:
- if (!folio) {
- matched = false;
- break;
- }
- rcu_read_lock();
- memcg = folio_memcg_check(folio);
- if (!memcg)
- matched = false;
- else
- matched = filter->memcg_id == mem_cgroup_id(memcg);
- rcu_read_unlock();
- break;
case DAMON_FILTER_TYPE_PGIDLE_UNSET:
if (!folio)
matched = false;
@@ -173,7 +152,7 @@ static bool damon_pa_filter_match(struct damon_filter *filter,
matched = damon_folio_young(folio);
break;
default:
- break;
+ return damon_ops_filter_match(filter, folio);
}
return matched == filter->matching;
}
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index f884d3f78f30a..090317191973b 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -510,6 +510,236 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
return max_nr_accesses;
}
+static void damon_va_prep_probe_region(struct damon_ctx *ctx,
+ struct mm_struct *mm, struct damon_region *r,
+ struct damon_probe *probe)
+{
+ struct damon_prep *p;
+
+ damon_for_each_prep(p, probe) {
+ switch (p->action) {
+ case DAMON_PREP_SET_PGIDLE:
+ damon_va_mkold(mm, r->sampling_addr);
+ break;
+ default:
+ break;
+ }
+ }
+}
+
+static void damon_va_prep_probes(struct damon_ctx *ctx, bool set_samples)
+{
+ struct damon_target *t;
+ struct mm_struct *mm;
+ struct damon_region *r;
+ struct damon_probe *p;
+
+ damon_for_each_target(t, ctx) {
+ mm = damon_get_mm(t);
+ if (!mm)
+ continue;
+ damon_for_each_region(r, t) {
+ if (set_samples)
+ r->sampling_addr = damon_rand(ctx, r->ar.start,
+ r->ar.end);
+ damon_for_each_probe(p, ctx)
+ damon_va_prep_probe_region(ctx, mm, r, p);
+ }
+ mmput(mm);
+ }
+}
+
+static bool damon_va_young_addr(struct folio *folio, pte_t *pte, pmd_t *pmd,
+ struct mm_struct *mm, unsigned long addr)
+{
+ bool young = false;
+
+ if (pte)
+ young = pte_young(*pte);
+ else if (pmd)
+ young = pmd_young(*pmd);
+ young = young || !folio_test_idle(folio) ||
+ mmu_notifier_test_young(mm, addr);
+ return young;
+}
+
+static bool damon_va_filter_match(struct damon_filter *filter,
+ struct folio *folio, pte_t *pte, pmd_t *pmd,
+ struct mm_struct *mm, unsigned long addr)
+{
+ bool matched = false;
+
+ switch (filter->type) {
+ case DAMON_FILTER_TYPE_PGIDLE_UNSET:
+ if (!folio)
+ matched = false;
+ else
+ matched = damon_va_young_addr(folio, pte, pmd, mm,
+ addr);
+ break;
+ default:
+ return damon_ops_filter_match(filter, folio);
+ }
+ return matched == filter->matching;
+}
+
+static bool damon_va_filter_pass(struct folio *folio, struct damon_probe *p,
+ pte_t *pte, pmd_t *pmd, struct mm_struct *mm,
+ unsigned long addr)
+{
+ struct damon_filter *f;
+ bool pass = true;
+
+ damon_for_each_filter(f, p) {
+ if (damon_va_filter_match(f, folio, pte, pmd, mm, addr)) {
+ pass = f->allow;
+ break;
+ }
+ pass = !f->allow;
+ }
+ return pass;
+}
+
+struct damon_va_probe_walk_private {
+ struct damon_ctx *ctx;
+ struct damon_region *r;
+};
+
+static void damon_va_probe_folio(struct damon_ctx *ctx,
+ struct damon_region *r, struct folio *folio,
+ pte_t *pte, pmd_t *pmd, struct mm_struct *mm)
+{
+ struct damon_probe *probe;
+ int i = 0;
+
+ damon_for_each_probe(probe, ctx) {
+ if (damon_va_filter_pass(folio, probe, pte, pmd, mm,
+ r->sampling_addr))
+ r->probe_hits[i]++;
+ i++;
+ }
+}
+
+static int damon_va_probe_pmd_entry(pmd_t *pmd, unsigned long addr,
+ unsigned long next, struct mm_walk *walk)
+{
+ pte_t *pte;
+ pte_t ptent;
+ spinlock_t *ptl;
+ struct folio *folio;
+ struct damon_va_probe_walk_private *priv = walk->private;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ ptl = pmd_trans_huge_lock(pmd, walk->vma);
+ if (ptl) {
+ pmd_t pmde = pmdp_get(pmd);
+
+ if (!pmd_present(pmde))
+ goto huge_out;
+ folio = vm_normal_folio_pmd(walk->vma, addr, pmde);
+ if (!folio)
+ goto huge_out;
+ damon_va_probe_folio(priv->ctx, priv->r, folio, NULL, &pmde,
+ walk->vma->vm_mm);
+
+huge_out:
+ spin_unlock(ptl);
+ return 0;
+ }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+ pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ if (!pte)
+ return 0;
+ ptent = ptep_get(pte);
+ if (!pte_present(ptent))
+ goto out;
+ folio = vm_normal_folio(walk->vma, addr, ptent);
+ if (!folio)
+ goto out;
+ damon_va_probe_folio(priv->ctx, priv->r, folio, &ptent, NULL,
+ walk->vma->vm_mm);
+
+out:
+ pte_unmap_unlock(pte, ptl);
+ return 0;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,
+ unsigned long addr, unsigned long end, struct mm_walk *walk)
+{
+ struct damon_va_probe_walk_private *priv = walk->private;
+ struct hstate *h = hstate_vma(walk->vma);
+ struct folio *folio;
+ spinlock_t *ptl;
+ pte_t entry;
+
+ ptl = huge_pte_lock(h, walk->mm, pte);
+ entry = huge_ptep_get(walk->mm, addr, pte);
+ if (!pte_present(entry))
+ goto out;
+
+ folio = pfn_folio(pte_pfn(entry));
+ folio_get(folio);
+ damon_va_probe_folio(priv->ctx, priv->r, folio, &entry, NULL,
+ walk->vma->vm_mm);
+ folio_put(folio);
+
+out:
+ spin_unlock(ptl);
+ return 0;
+}
+#else
+#define damon_va_probe_hugetlb_entry NULL
+#endif /* CONFIG_HUGETLB_PAGE */
+
+static void __damon_va_apply_probes(struct damon_ctx *ctx,
+ struct mm_struct *mm, struct damon_region *r)
+{
+ struct damon_va_probe_walk_private arg = {
+ .ctx = ctx,
+ .r = r,
+ };
+ struct mm_walk_ops damon_probe_walk_ops = {
+ .pmd_entry = damon_va_probe_pmd_entry,
+ .hugetlb_entry = damon_va_probe_hugetlb_entry,
+ };
+ unsigned long addr = r->sampling_addr;
+
+ if (!mm)
+ return;
+
+ damon_va_walk_page_range(mm, addr, addr + 1, &damon_probe_walk_ops,
+ &arg);
+}
+
+static unsigned int damon_va_apply_probes(struct damon_ctx *ctx,
+ bool set_samples, bool return_max_wsum)
+{
+ struct damon_target *t;
+ struct mm_struct *mm;
+ struct damon_region *r;
+ unsigned int max_wsum = 0;
+
+ damon_for_each_target(t, ctx) {
+ mm = damon_get_mm(t);
+ damon_for_each_region(r, t) {
+ if (set_samples)
+ r->sampling_addr = damon_rand(ctx, r->ar.start,
+ r->ar.end);
+ __damon_va_apply_probes(ctx, mm, r);
+ if (return_max_wsum)
+ max_wsum = max(damon_probe_hits_wsum(r, false,
+ ctx), max_wsum);
+ }
+ if (mm)
+ mmput(mm);
+ }
+
+ return max_wsum;
+}
+
static bool damos_va_filter_young_match(struct damos_filter *filter,
struct folio *folio, struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep, pmd_t *pmdp)
@@ -938,6 +1168,8 @@ static int __init damon_va_initcall(void)
.update = damon_va_update,
.prepare_access_checks = damon_va_prepare_access_checks,
.check_accesses = damon_va_check_accesses,
+ .prep_probes = damon_va_prep_probes,
+ .apply_probes = damon_va_apply_probes,
.target_valid = damon_va_target_valid,
.cleanup_target = damon_va_cleanup_target,
.apply_scheme = damon_va_apply_scheme,
|
| 19/3 | 2026/09/07 02:17 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 5703 output: 32 thoughts: 308 Thoughts: **My DAMON Refactoring and Virtual Address Probing Analysis** Okay, so this patch is clearly making some significant changes within DAMON, specifically focusing on its interaction with virtual addresses. It's touching `mm/damon/ops-common.c`, `mm/damon/ops-common.h`, `mm/damon/paddr.c`, and `mm/damon/vaddr.c`, so I need to understand how the existing data access monitoring framework is evolving. First, it looks like `damon_ops_filter_match` is being abstracted into `ops-common.c`. That's a good sign; refactoring common functionality like that usually signals an intent to streamline the core DAMON operations and reduce code duplication. I'll need to see how that impacts the filter logic downstream. Now, the meat of the patch seems to be in `mm/damon/vaddr.c`. It's introducing a whole suite of new functions designed to support probing virtual addresses directly. I see functions like `damon_va_prep_probe_region`, `damon_va_prep_probes`, `damon_va_young_addr`, `damon_va_filter_match`, `damon_va_filter_pass`, and then functions for probing at the folio, pmd, and hugetlb levels: `damon_va_probe_folio`, `damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry`. Finally, the patch adds `__damon_va_apply_probes` and `damon_va_apply_probes` to implement the probe application process. The registration of `prep_probes` and `apply_probes` callbacks within `damon_va_initcall` confirms that these new functions are being integrated into the initialization sequence. This seems like a complete rewrite for virtual address handling within DAMON. I need to dive into the code more thoroughly. I’ll need to utilize `grepper` or `read-file` to fully grasp the data structures involved, and how these virtual address probing functions interface with the existing physical address monitoring. I'll focus particularly on how this is managing the interaction between virtual and physical address spaces, and how it handles different page table levels. It also will be important to understand if there is a way to configure the virtual address monitoring, and how this will work in conjunction with other DAMON modules. This seems like a pretty significant capability being added to DAMON. |
| 20/3 | 2026/09/07 02:17 | tool | grepper |
0mArgs:{
"Expression": "damon_for_each_probe",
"PathPrefix": "mm/damon"
}Results: {
"Output": "mm/damon/core.c=159=static bool damon_has_prep(struct damon_ctx *c)\n--\nmm/damon/core.c-163-\nmm/damon/core.c:164:\tdamon_for_each_probe(probe, c) {\nmm/damon/core.c-165-\t\tdamon_for_each_prep(prep, probe)\n--\nmm/damon/core.c=261=static struct damon_probe *damon_nth_probe(int n, struct damon_ctx *ctx)\n--\nmm/damon/core.c-265-\nmm/damon/core.c:266:\tdamon_for_each_probe(p, ctx) {\nmm/damon/core.c-267-\t\tif (i++ == n)\n--\nmm/damon/core.c=273=static bool damon_has_probe_weights(struct damon_ctx *c)\n--\nmm/damon/core.c-276-\nmm/damon/core.c:277:\tdamon_for_each_probe(p, c) {\nmm/damon/core.c-278-\t\tif (p-\u003eweight)\n--\nmm/damon/core.c=476=unsigned int damon_probe_hits_wsum(struct damon_region *r, bool last,\n--\nmm/damon/core.c-482-\nmm/damon/core.c:483:\tdamon_for_each_probe(probe, ctx) {\nmm/damon/core.c-484-\t\tif (last)\n--\nmm/damon/core.c=950=void damon_destroy_ctx(struct damon_ctx *ctx)\n--\nmm/damon/core.c-959-\nmm/damon/core.c:960:\tdamon_for_each_probe_safe(p, next_p, ctx)\nmm/damon/core.c-961-\t\tdamon_destroy_probe(p);\n--\nmm/damon/core.c=1010=static void damon_update_probe_hits(struct damon_region *r,\n--\nmm/damon/core.c-1016-\nmm/damon/core.c:1017:\tdamon_for_each_probe(p, ctx) {\nmm/damon/core.c-1018-\t\tr-\u003elast_probe_hits[i] = damon_nr_samples_for_new_attrs(\n--\nmm/damon/core.c=1427=static bool damon_valid_probe_params(struct damon_ctx *ctx)\n--\nmm/damon/core.c-1435-\tnr_probes = 0;\nmm/damon/core.c:1436:\tdamon_for_each_probe(probe, ctx)\nmm/damon/core.c-1437-\t\tnr_probes++;\n--\nmm/damon/core.c-1450-\twsum = 0;\nmm/damon/core.c:1451:\tdamon_for_each_probe(probe, ctx) {\nmm/damon/core.c-1452-\t\tif (probe-\u003eweight \u003e UINT_MAX / max_probe_hits)\n--\nmm/damon/core.c=1840=static int damon_commit_probes(struct damon_ctx *dst, struct damon_ctx *src)\n--\nmm/damon/core.c-1844-\nmm/damon/core.c:1845:\tdamon_for_each_probe_safe(dst_probe, next, dst) {\nmm/damon/core.c-1846-\t\tsrc_probe = damon_nth_probe(i++, src);\n--\nmm/damon/core.c-1859-\nmm/damon/core.c:1860:\tdamon_for_each_probe_safe(src_probe, next, src) {\nmm/damon/core.c-1861-\t\tif (j++ \u003c i)\n--\nmm/damon/core.c=2293=static void kdamond_reset_aggregated(struct damon_ctx *c)\n--\nmm/damon/core.c-2300-\tif (trace_damon_region_aggregated_enabled()) {\nmm/damon/core.c:2301:\t\tdamon_for_each_probe(probe, c)\nmm/damon/core.c-2302-\t\t\tnr_probes++;\n--\nmm/damon/paddr.c=125=static void damon_pa_prep_probes(struct damon_ctx *ctx, bool set_samples)\n--\nmm/damon/paddr.c-135-\t\t\t\t\t\tr-\u003ear.end);\nmm/damon/paddr.c:136:\t\t\tdamon_for_each_probe(p, ctx)\nmm/damon/paddr.c-137-\t\t\t\tdamon_pa_prep_probes_region(r, p, ctx);\n--\nmm/damon/paddr.c=176=static unsigned int damon_pa_apply_probes(struct damon_ctx *ctx,\n--\nmm/damon/paddr.c-195-\t\t\tfolio = damon_get_folio(PHYS_PFN(pa));\nmm/damon/paddr.c:196:\t\t\tdamon_for_each_probe(p, ctx) {\nmm/damon/paddr.c-197-\t\t\t\tif (damon_pa_filter_pass(pa, folio, p))\n--\nmm/damon/sysfs-schemes.c=90=static int damos_sysfs_probes_add_dirs(struct damos_sysfs_probes *probes,\n--\nmm/damon/sysfs-schemes.c-96-\nmm/damon/sysfs-schemes.c:97:\tdamon_for_each_probe(probe, ctx)\nmm/damon/sysfs-schemes.c-98-\t\ti++;\n--\nmm/damon/sysfs-schemes.c-108-\ti = 0;\nmm/damon/sysfs-schemes.c:109:\tdamon_for_each_probe(probe, ctx) {\nmm/damon/sysfs-schemes.c-110-\t\tstruct damos_sysfs_probe *sys_probe;\n--\nmm/damon/tests/core-kunit.h=1428=static void damon_test_commit_probes_for(struct kunit *test,\n--\nmm/damon/tests/core-kunit.h-1449-\tnr_dst_probes = 0;\nmm/damon/tests/core-kunit.h:1450:\tdamon_for_each_probe(dst_probe, dst)\nmm/damon/tests/core-kunit.h-1451-\t\tnr_dst_probes++;\nmm/damon/tests/core-kunit.h-1452-\tnr_src_probes = 0;\nmm/damon/tests/core-kunit.h:1453:\tdamon_for_each_probe(src_probe, src)\nmm/damon/tests/core-kunit.h-1454-\t\tnr_src_probes++;\n--\nmm/damon/tests/core-kunit.h-1458-\tnr_dst_probes = 0;\nmm/damon/tests/core-kunit.h:1459:\tdamon_for_each_probe(dst_probe, dst) {\nmm/damon/tests/core-kunit.h-1460-\t\tsrc_probe = damon_nth_probe(nr_dst_probes, src);\n--\nmm/damon/vaddr.c=530=static void damon_va_prep_probes(struct damon_ctx *ctx, bool set_samples)\n--\nmm/damon/vaddr.c-544-\t\t\t\t\t\tr-\u003ear.end);\nmm/damon/vaddr.c:545:\t\t\tdamon_for_each_probe(p, ctx)\nmm/damon/vaddr.c-546-\t\t\t\tdamon_va_prep_probe_region(ctx, mm, r, p);\n--\nmm/damon/vaddr.c=608=static void damon_va_probe_folio(struct damon_ctx *ctx,\n--\nmm/damon/vaddr.c-614-\nmm/damon/vaddr.c:615:\tdamon_for_each_probe(probe, ctx) {\nmm/damon/vaddr.c-616-\t\tif (damon_va_filter_pass(folio, probe, pte, pmd, mm,\n"
} |
| 21/3 | 2026/09/07 02:17 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 8826 output: 27 thoughts: 21 Thoughts: Here's a summary of my immediate thought process: **Allocation and Initialization Check** Okay, time to drill down on these variables. I need to make absolutely sure that `damon_region` and `probe_hits` are being allocated and initialized correctly. Given my experience, I've seen countless issues stem from improper memory management in low-level code like this. I have to verify that the memory is being requested with the appropriate flags and alignment, and that the data structures are being set up with their initial values that is appropriate for our algorithm, likely zeroed. I need to confirm the size calculations are correct. Any slip-up here could lead to crashes, memory corruption, or subtle bugs that are incredibly difficult to debug later on, so let's make sure this is rock solid before moving on. I’m thinking I’ll start by reviewing the allocation calls, look at the sizes being passed, and trace the initialization paths. No stone unturned. |
| 22/3 | 2026/09/07 02:17 | tool | grepper |
0mArgs:{
"Expression": "probe_hits",
"PathPrefix": "mm/damon"
}Results: {
"Output": "mm/damon/core.c=325=unsigned int damon_nr_accesses_mvsum(struct damon_region *r,\n--\nmm/damon/core.c-348-\nmm/damon/core.c:349:unsigned char damon_probe_hits_mvsum(int probe_idx, struct damon_region *r,\nmm/damon/core.c-350-\t\tstruct damon_ctx *ctx)\n--\nmm/damon/core.c-366-\tif (left_window_bp == 10000)\nmm/damon/core.c:367:\t\treturn r-\u003elast_probe_hits[probe_idx];\nmm/damon/core.c-368-\nmm/damon/core.c:369:\treturn damon_mvsum(r-\u003eprobe_hits[probe_idx],\nmm/damon/core.c:370:\t\t\tr-\u003elast_probe_hits[probe_idx], left_window_bp);\nmm/damon/core.c-371-}\n--\nmm/damon/core.c=389=struct damon_region *damon_new_region(unsigned long start, unsigned long end)\n--\nmm/damon/core.c-402-\tfor (i = 0; i \u003c DAMON_MAX_PROBES; i++) {\nmm/damon/core.c:403:\t\tregion-\u003eprobe_hits[i] = 0;\nmm/damon/core.c:404:\t\tregion-\u003elast_probe_hits[i] = 0;\nmm/damon/core.c-405-\t}\n--\nmm/damon/core.c=462=static bool damon_is_last_region(struct damon_region *r,\n--\nmm/damon/core.c-468-/**\nmm/damon/core.c:469: * damon_probe_hits_wsum() - Returns probe hits weighted sum of a region.\nmm/damon/core.c-470- * @r:\t\tregion to get the weighted sum of.\n--\nmm/damon/core.c-475- */\nmm/damon/core.c:476:unsigned int damon_probe_hits_wsum(struct damon_region *r, bool last,\nmm/damon/core.c-477-\t\tstruct damon_ctx *ctx)\n--\nmm/damon/core.c-484-\t\tif (last)\nmm/damon/core.c:485:\t\t\tsum += r-\u003elast_probe_hits[i++] * probe-\u003eweight;\nmm/damon/core.c-486-\t\telse\nmm/damon/core.c:487:\t\t\tsum += r-\u003eprobe_hits[i++] * probe-\u003eweight;\nmm/damon/core.c-488-\t}\n--\nmm/damon/core.c=1003=static unsigned int damon_nr_samples_for_new_attrs(unsigned int nr,\n--\nmm/damon/core.c-1009-\nmm/damon/core.c:1010:static void damon_update_probe_hits(struct damon_region *r,\nmm/damon/core.c-1011-\t\tstruct damon_attrs *old_attrs, struct damon_attrs *new_attrs,\n--\nmm/damon/core.c-1017-\tdamon_for_each_probe(p, ctx) {\nmm/damon/core.c:1018:\t\tr-\u003elast_probe_hits[i] = damon_nr_samples_for_new_attrs(\nmm/damon/core.c:1019:\t\t\t\tr-\u003elast_probe_hits[i], old_attrs, new_attrs);\nmm/damon/core.c-1020-\t\tif (!aggregating)\nmm/damon/core.c:1021:\t\t\tr-\u003eprobe_hits[i] = damon_nr_samples_for_new_attrs(\nmm/damon/core.c:1022:\t\t\t\t\tr-\u003eprobe_hits[i], old_attrs,\nmm/damon/core.c-1023-\t\t\t\t\tnew_attrs);\nmm/damon/core.c-1024-\t\telse\nmm/damon/core.c:1025:\t\t\tr-\u003eprobe_hits[i] = 0;\nmm/damon/core.c-1026-\t\ti++;\n--\nmm/damon/core.c=1030=static void damon_update_monitoring_result(struct damon_region *r,\n--\nmm/damon/core.c-1033-{\nmm/damon/core.c:1034:\tdamon_update_probe_hits(r, old_attrs, new_attrs, aggregating, ctx);\nmm/damon/core.c-1035-\n--\nmm/damon/core.c=1427=static bool damon_valid_probe_params(struct damon_ctx *ctx)\n--\nmm/damon/core.c-1429-\tunsigned long sample_interval;\nmm/damon/core.c:1430:\tunsigned char max_probe_hits;\nmm/damon/core.c-1431-\tstruct damon_probe *probe;\n--\nmm/damon/core.c-1448-\t/* invalid if probe hits weighted sum can overflow */\nmm/damon/core.c:1449:\tmax_probe_hits = damon_nr_samples_per_aggr(\u0026ctx-\u003eattrs);\nmm/damon/core.c-1450-\twsum = 0;\nmm/damon/core.c-1451-\tdamon_for_each_probe(probe, ctx) {\nmm/damon/core.c:1452:\t\tif (probe-\u003eweight \u003e UINT_MAX / max_probe_hits)\nmm/damon/core.c-1453-\t\t\treturn false;\nmm/damon/core.c:1454:\t\twsum_to_add = probe-\u003eweight * max_probe_hits;\nmm/damon/core.c-1455-\t\tif (UINT_MAX - wsum \u003c wsum_to_add)\n--\nmm/damon/core.c=2293=static void kdamond_reset_aggregated(struct damon_ctx *c)\n--\nmm/damon/core.c-2316-\t\t\tfor (i = 0; i \u003c DAMON_MAX_PROBES; i++) {\nmm/damon/core.c:2317:\t\t\t\tr-\u003elast_probe_hits[i] = r-\u003eprobe_hits[i];\nmm/damon/core.c:2318:\t\t\t\tr-\u003eprobe_hits[i] = 0;\nmm/damon/core.c-2319-\t\t\t}\n--\nmm/damon/core.c=3426=static void damon_merge_two_regions(struct damon_target *t,\n--\nmm/damon/core.c-3437-\tfor (i = 0; i \u003c DAMON_MAX_PROBES; i++)\nmm/damon/core.c:3438:\t\tl-\u003eprobe_hits[i] = (l-\u003eprobe_hits[i] * sz_l + r-\u003eprobe_hits[i]\nmm/damon/core.c-3439-\t\t\t\t* sz_r) / (sz_l + sz_r);\n--\nmm/damon/core.c=3444=static unsigned int damon_merge_score(struct damon_region *r, bool last,\nmm/damon/core.c:3445:\t\tstruct damon_ctx *ctx, bool use_probe_hits)\nmm/damon/core.c-3446-{\nmm/damon/core.c:3447:\tif (use_probe_hits)\nmm/damon/core.c:3448:\t\treturn damon_probe_hits_wsum(r, last, ctx);\nmm/damon/core.c-3449-\tif (last)\n--\nmm/damon/core.c=3461=static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,\n--\nmm/damon/core.c-3464-\tstruct damon_region *r, *prev = NULL, *next;\nmm/damon/core.c:3465:\tbool use_probe_hits = damon_has_probe_weights(ctx);\nmm/damon/core.c-3466-\n--\nmm/damon/core.c-3469-\nmm/damon/core.c:3470:\t\tscore = damon_merge_score(r, false, ctx, use_probe_hits);\nmm/damon/core.c:3471:\t\tlast_score = damon_merge_score(r, true, ctx, use_probe_hits);\nmm/damon/core.c-3472-\n--\nmm/damon/core.c-3486-\t\tdiff = abs_diff(score, damon_merge_score(prev, false, ctx,\nmm/damon/core.c:3487:\t\t\t\t\tuse_probe_hits));\nmm/damon/core.c-3488-\t\tif (diff \u003e thres)\n--\nmm/damon/core.c=3566=static int damon_split_region_at(struct damon_target *t,\n--\nmm/damon/core.c-3581-\t/* todo: do this for only installed probes */\nmm/damon/core.c:3582:\tmemcpy(new-\u003eprobe_hits, r-\u003eprobe_hits, sizeof(r-\u003eprobe_hits));\nmm/damon/core.c:3583:\tmemcpy(new-\u003elast_probe_hits, r-\u003elast_probe_hits,\nmm/damon/core.c:3584:\t\t\tsizeof(r-\u003elast_probe_hits));\nmm/damon/core.c-3585-\n--\nmm/damon/paddr.c=176=static unsigned int damon_pa_apply_probes(struct damon_ctx *ctx,\n--\nmm/damon/paddr.c-197-\t\t\t\tif (damon_pa_filter_pass(pa, folio, p))\nmm/damon/paddr.c:198:\t\t\t\t\tr-\u003eprobe_hits[i]++;\nmm/damon/paddr.c-199-\t\t\t\ti++;\n--\nmm/damon/paddr.c-203-\t\t\tif (return_max_wsum)\nmm/damon/paddr.c:204:\t\t\t\tmax_wsum = max(damon_probe_hits_wsum(r, false,\nmm/damon/paddr.c-205-\t\t\t\t\t\t\tctx), max_wsum);\n--\nmm/damon/sysfs-schemes.c=40=static void damos_sysfs_probe_release(struct kobject *kobj)\n--\nmm/damon/sysfs-schemes.c-47-\nmm/damon/sysfs-schemes.c:48:static struct kobj_attribute damos_sysfs_probe_hits_attr =\nmm/damon/sysfs-schemes.c-49-\t\t__ATTR_RO_MODE(hits, 0400);\n--\nmm/damon/sysfs-schemes.c=51=static struct attribute *damos_sysfs_probe_attrs[] = {\nmm/damon/sysfs-schemes.c:52:\t\u0026damos_sysfs_probe_hits_attr.attr,\nmm/damon/sysfs-schemes.c-53-\tNULL,\n--\nmm/damon/sysfs-schemes.c=90=static int damos_sysfs_probes_add_dirs(struct damos_sysfs_probes *probes,\n--\nmm/damon/sysfs-schemes.c-113-\t\tsys_probe = damos_sysfs_probe_alloc(\nmm/damon/sysfs-schemes.c:114:\t\t\t\tdamon_probe_hits_mvsum(i, region, ctx));\nmm/damon/sysfs-schemes.c-115-\t\tif (!sys_probe) {\n--\nmm/damon/tests/core-kunit.h=140=static void damon_test_split_at(struct kunit *test)\n--\nmm/damon/tests/core-kunit.h-154-\tr-\u003elast_nr_accesses = 15;\nmm/damon/tests/core-kunit.h:155:\tr-\u003eprobe_hits[0] = 7;\nmm/damon/tests/core-kunit.h:156:\tr-\u003elast_probe_hits[0] = 3;\nmm/damon/tests/core-kunit.h-157-\tr-\u003eage = 10;\n--\nmm/damon/tests/core-kunit.h-172-\tKUNIT_EXPECT_EQ(test, r-\u003elast_nr_accesses, r_new-\u003elast_nr_accesses);\nmm/damon/tests/core-kunit.h:173:\tKUNIT_EXPECT_EQ(test, r-\u003eprobe_hits[0], r_new-\u003eprobe_hits[0]);\nmm/damon/tests/core-kunit.h:174:\tKUNIT_EXPECT_EQ(test, r-\u003elast_probe_hits[0], r_new-\u003elast_probe_hits[0]);\nmm/damon/tests/core-kunit.h-175-\tKUNIT_EXPECT_EQ(test, r-\u003eage, r_new-\u003eage);\n--\nmm/damon/tests/core-kunit.h=181=static void damon_test_merge_two(struct kunit *test)\n--\nmm/damon/tests/core-kunit.h-195-\tr-\u003enr_accesses = 10;\nmm/damon/tests/core-kunit.h:196:\tr-\u003eprobe_hits[0] = 6;\nmm/damon/tests/core-kunit.h-197-\tr-\u003eage = 9;\n--\nmm/damon/tests/core-kunit.h-204-\tr2-\u003enr_accesses = 20;\nmm/damon/tests/core-kunit.h:205:\tr2-\u003eprobe_hits[0] = 14;\nmm/damon/tests/core-kunit.h-206-\tr2-\u003eage = 21;\n--\nmm/damon/tests/core-kunit.h-212-\tKUNIT_EXPECT_EQ(test, r-\u003enr_accesses, 16u);\nmm/damon/tests/core-kunit.h:213:\tKUNIT_EXPECT_EQ(test, r-\u003eprobe_hits[0], 11);\nmm/damon/tests/core-kunit.h-214-\tKUNIT_EXPECT_EQ(test, r-\u003eage, 17u);\n--\nmm/damon/tests/core-kunit.h=1514=static void damon_test_valid_probe_params(struct kunit *test)\n--\nmm/damon/tests/core-kunit.h-1538-\nmm/damon/tests/core-kunit.h:1539:\t/* More samples could overflow the probe_hits counters. */\nmm/damon/tests/core-kunit.h-1540-\tctx-\u003eattrs.aggr_interval = 256;\n--\nmm/damon/vaddr.c=608=static void damon_va_probe_folio(struct damon_ctx *ctx,\n--\nmm/damon/vaddr.c-617-\t\t\t\t\tr-\u003esampling_addr))\nmm/damon/vaddr.c:618:\t\t\tr-\u003eprobe_hits[i]++;\nmm/damon/vaddr.c-619-\t\ti++;\n--\nmm/damon/vaddr.c=717=static unsigned int damon_va_apply_probes(struct damon_ctx *ctx,\n--\nmm/damon/vaddr.c-732-\t\t\tif (return_max_wsum)\nmm/damon/vaddr.c:733:\t\t\t\tmax_wsum = max(damon_probe_hits_wsum(r, false,\nmm/damon/vaddr.c-734-\t\t\t\t\t\t\tctx), max_wsum);\n"
} |
| 23/3 | 2026/09/07 02:17 | llm | kmsan-evaluator |
0mModel:gemini-3.7-flash Args: null Results: null Tokens: input: 13227 output: 244 thoughts: 1653 Thoughts: **Patch Analysis: DAMON Virtual Address Probing and Filtering** Okay, let's break this patch down systematically. First, I see they've refactored the `damon_ops_filter_match` function, moving it to `ops-common.c`. That's a reasonable organizational change. Checking the `damon_ops_filter_match` code itself, I see it's properly handling different filter types (ANON, MEMCG), and all variables within are initialized before use, specifically `matched` and `memcg`. No immediate red flags there. The `rcu_read_lock` and `rcu_read_unlock` are appropriately paired within the MEMCG check. Next, I'm diving into the virtual address probing code in `vaddr.c`. The `damon_va_prep_probe_region` and `damon_va_prep_probes` functions look straightforward, setting up the probing process. Now, let's examine `damon_va_young_addr`. I want to be certain about the validity of `pte` and `pmd` dereferences here. Looking at where they're used, I see that within `damon_va_probe_folio`, either `pte` or `pmd` is passed. The initialization in `damon_va_probe_pmd_entry`, `damon_va_probe_hugetlb_entry` seems robust using `pmdp_get`, `ptep_get` and `huge_ptep_get` respectively, which are good. The `young` variable is also initialized before being used. The filter matching logic in `damon_va_filter_match` is simple and, if not, it defers to `damon_ops_filter_match` which we reviewed earlier. The `damon_va_filter_pass` function is similarly simple with a `pass` flag being initialized. The `damon_va_probe_folio`, `damon_va_probe_pmd_entry` and `damon_va_probe_hugetlb_entry`, which contain loops and walkers, are carefully handling probes and incrementing `r->probe_hits[i]++`, so it's a critical point to check, which seems okay. Structs in page walks, like `arg`, are using designated initializers, which is good practice. Now, let's step back and consider potential vulnerability areas. I'm not seeing any kernel structures being passed to user space via things like `copy_to_user`, ioctls, or netlink. No uninitialized memory is read or copied, which is good. Could we introduce any uninitialized memory risks? The answer is "no". However, I'm immediately thinking about: * **Locking/Reference Counting:** Potentially things like `folio_get`/`folio_put`, or locking in the page table walk (`pte_offset_map_lock`, `spin_unlock`) are a primary focus for standard detectors. KASAN and LOCKDEP will catch that. * **Out-of-Bounds Access:** While the patch introduces a loop that increments `r->probe_hits[i]`, checking `nr_probes > DAMON_MAX_PROBES` would be necessary. KASAN/UBSAN should flag any out-of-bounds access. * **Concurrency Issues:** Page table walks can be tricky. Page table walk concurrency / page state issues that could happen on any MM code, can be picked up by KASAN/kernel assertions. Therefore, for a KMSAN perspective, all of these memory errors are caught by standard KASAN/UBSAN detectors. I will double-check the 4 criteria for NeedsKMSAN: 1. **Kernel-to-User:** Nothing. 2. **Conditional Logic/Branching:** Explicit initialization. 3. **Complex Data Structures:** No allocation, or uninitialized read. 4. **Bounds Checks:** No surrounding code accessing uninitialized bytes. Based on this, **NeedsKMSAN should be false**. **KMSAN vs KASAN Reasoning:** The patch implements virtual address probing and filter matching within DAMON. All relevant local variables, flags, and walker structs are initialized. It does not touch kernel-to-user memory transfers. No new memory allocation is introduced. Issues like race conditions, bounds checks (probe\_hits), are detected by standard detectors like KASAN/UBSAN/LOCKDEP. Therefore, KMSAN is not warranted here. |
| 24/3 | 2026/09/07 02:17 | tool | set-results |
0mArgs:{
"KMSANReasoning": "The patch introduces virtual address probe operations (prep and apply probes) and refactors common filter matching logic in the DAMON subsystem. \n\nEvaluating against KMSAN vs KASAN applicability:\n1. No uninitialized memory usage or info-leaks: All local variables (`matched`, `young`, `pass`, `i`), stack structures (`damon_va_probe_walk_private`, `mm_walk_ops`), and page table entry copies (`ptent`, `pmde`, `entry`) are explicitly initialized before use.\n2. No user-space copy mechanisms: The patch does not copy data to user space or manipulate uninitialized kernel buffers exposed to user space.\n3. Standard bug detectors are sufficient: Potential bugs in this code (such as array out-of-bounds on `probe_hits`, folio reference count mismatches, or page table locking issues) fall squarely within the purview of KASAN, UBSAN, and LOCKDEP.\n\nTherefore, there are no uninitialized memory risks that require a dedicated KMSAN fuzzing session.",
"NeedsKMSAN": false
}Results: {
"KMSANReasoning": "The patch introduces virtual address probe operations (prep and apply probes) and refactors common filter matching logic in the DAMON subsystem. \n\nEvaluating against KMSAN vs KASAN applicability:\n1. No uninitialized memory usage or info-leaks: All local variables (`matched`, `young`, `pass`, `i`), stack structures (`damon_va_probe_walk_private`, `mm_walk_ops`), and page table entry copies (`ptent`, `pmde`, `entry`) are explicitly initialized before use.\n2. No user-space copy mechanisms: The patch does not copy data to user space or manipulate uninitialized kernel buffers exposed to user space.\n3. Standard bug detectors are sufficient: Potential bugs in this code (such as array out-of-bounds on `probe_hits`, folio reference count mismatches, or page table locking issues) fall squarely within the purview of KASAN, UBSAN, and LOCKDEP.\n\nTherefore, there are no uninitialized memory risks that require a dedicated KMSAN fuzzing session.",
"NeedsKMSAN": false
} |
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| Total Calls | Total Duration (Seconds) | Avg Duration (Seconds) |
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