Enhance bpftool to generate skeletons that properly handle global percpu variables. The generated skeleton now includes a dedicated structure for percpu data, allowing users to initialize and access percpu variables more efficiently. For global percpu variables, the skeleton now includes a nested structure, e.g.: struct test_global_percpu_data { struct bpf_object_skeleton *skeleton; struct bpf_object *obj; struct { struct bpf_map *percpu; } maps; // ... struct test_global_percpu_data__percpu { int data; char run; struct { char set; int i; int nums[7]; } struct_data; int nums[7]; } *percpu; // ... }; * The "struct test_global_percpu_data__percpu *percpu" points to initialized data, which is actually "maps.percpu->mmaped". * Before loading the skeleton, updating the "struct test_global_percpu_data__percpu *percpu" modifies the initial value of the corresponding global percpu variables. * After loading the skeleton, "maps.percpu->mmaped" has been marked as read-only in libbpf. If users want to update the global percpu variables, they have to update the "maps.percpu" map instead. * For lightweight skeleton, "lskel->percpu" will be protected by "mprotect(p, sz, PROT_READ)". * For subskeleton, those variables of global percpu data will be skipped. Acked-by: Quentin Monnet Assisted-by: Codex:gpt-5.5-xhigh Signed-off-by: Leon Hwang --- tools/bpf/bpftool/gen.c | 53 +++++++++++++++++++++++++++-------- tools/lib/bpf/skel_internal.h | 24 ++++++++++++++-- 2 files changed, 63 insertions(+), 14 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index a01d06d22d1a..a50540ef6521 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -101,6 +101,12 @@ static bool get_map_ident(const struct bpf_map *map, char *buf, size_t buf_sz) return true; } + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) { + snprintf(buf, buf_sz, "%s", name + 1); + sanitize_identifier(buf); + return true; + } + for (i = 0, n = ARRAY_SIZE(sfxs); i < n; i++) { const char *sfx = sfxs[i], *p; @@ -117,7 +123,7 @@ static bool get_map_ident(const struct bpf_map *map, char *buf, size_t buf_sz) static bool get_datasec_ident(const char *sec_name, char *buf, size_t buf_sz) { - static const char *pfxs[] = { ".data", ".rodata", ".bss", ".kconfig" }; + static const char *pfxs[] = { ".data", ".rodata", ".bss", ".percpu", ".kconfig" }; int i, n; /* recognize hard coded LLVM section name */ @@ -254,7 +260,7 @@ static const struct btf_type *find_type_for_map(struct btf *btf, const char *map return NULL; } -static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz) +static bool is_skel_data(const struct bpf_map *map, char *buf, size_t sz) { size_t tmp_sz; @@ -263,13 +269,24 @@ static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz) return true; } - if (!bpf_map__is_internal(map) || !(bpf_map__map_flags(map) & BPF_F_MMAPABLE)) + if (!bpf_map__is_internal(map)) return false; if (!get_map_ident(map, buf, sz)) return false; - return true; + if (bpf_map__map_flags(map) & BPF_F_MMAPABLE) + return true; + + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) + return bpf_map__btf_value_type_id(map) != 0; + + return false; +} + +static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz) +{ + return is_skel_data(map, buf, sz) && bpf_map__type(map) != BPF_MAP_TYPE_PERCPU_ARRAY; } static int codegen_datasecs(struct bpf_object *obj, const char *obj_name) @@ -287,7 +304,7 @@ static int codegen_datasecs(struct bpf_object *obj, const char *obj_name) bpf_object__for_each_map(map, obj) { /* only generate definitions for memory-mapped internal maps */ - if (!is_mmapable_map(map, map_ident, sizeof(map_ident))) + if (!is_skel_data(map, map_ident, sizeof(map_ident))) continue; sec = find_type_for_map(btf, map_ident); @@ -517,7 +534,7 @@ static void codegen_asserts(struct bpf_object *obj, const char *obj_name) ", obj_name); bpf_object__for_each_map(map, obj) { - if (!is_mmapable_map(map, map_ident, sizeof(map_ident))) + if (!is_skel_data(map, map_ident, sizeof(map_ident))) continue; sec = find_type_for_map(btf, map_ident); @@ -668,8 +685,7 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name) bpf_object__for_each_map(map, obj) { if (!get_map_ident(map, ident, sizeof(ident))) continue; - if (bpf_map__is_internal(map) && - (bpf_map__map_flags(map) & BPF_F_MMAPABLE)) + if (is_skel_data(map, ident, sizeof(ident))) printf("\tskel_free_map_data(skel->%1$s, skel->maps.%1$s.initial_value, %2$zu);\n", ident, bpf_map_mmap_sz(map)); codegen("\ @@ -741,7 +757,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h const void *mmap_data = NULL; size_t mmap_size = 0; - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!is_skel_data(map, ident, sizeof(ident))) continue; codegen("\ @@ -849,9 +865,23 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h bpf_object__for_each_map(map, obj) { const char *mmap_flags; - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!is_skel_data(map, ident, sizeof(ident))) continue; + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) { + codegen("\ + \n\ + err = skel_protect_map_data(skel->%1$s, &skel->maps.%1$s.initial_value, %2$zd);\n\ + if (err) \n\ + return err; \n\ + #ifdef __KERNEL__ \n\ + skel->%1$s = NULL; \n\ + #endif \n\ + ", + ident, bpf_map_mmap_sz(map)); + continue; + } + if (bpf_map__map_flags(map) & BPF_F_RDONLY_PROG) mmap_flags = "PROT_READ"; else @@ -955,8 +985,7 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t map_cnt, bool mmaped, bool map->map = &obj->maps.%s; \n\ ", i, bpf_map__name(map), ident); - /* memory-mapped internal maps */ - if (mmaped && is_mmapable_map(map, ident, sizeof(ident))) { + if (mmaped && is_skel_data(map, ident, sizeof(ident))) { printf("\tmap->mmaped = (void **)&obj->%s;\n", ident); } diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h index 53fee53d36d5..1f3f332dffbe 100644 --- a/tools/lib/bpf/skel_internal.h +++ b/tools/lib/bpf/skel_internal.h @@ -131,8 +131,10 @@ static inline void skel_free_map_data(void *p, __u64 addr, size_t sz) { if (addr != ~0ULL) kvfree(p); - /* When addr == ~0ULL the 'p' points to - * ((struct bpf_array *)map)->value. See skel_finalize_map_data. + /* + * When addr == ~0ULL the init buffer has already been released. + * For skel_finalize_map_data(), 'p' points to + * ((struct bpf_array *)map)->value. */ } @@ -170,6 +172,15 @@ static inline void *skel_finalize_map_data(__u64 *init_val, size_t mmap_sz, int return addr; } +static inline int skel_protect_map_data(void *p, __u64 *init_val, size_t sz) +{ + (void)sz; + + kvfree(p); + *init_val = ~0ULL; + return 0; +} + #else static inline void *skel_alloc(size_t size) @@ -208,6 +219,15 @@ static inline void *skel_finalize_map_data(__u64 *init_val, size_t mmap_sz, int return NULL; return addr; } + +static inline int skel_protect_map_data(void *p, __u64 *init_val, size_t sz) +{ + (void)init_val; + + if (mprotect(p, sz, PROT_READ)) + return -errno; + return 0; +} #endif static inline int skel_closenz(int fd) -- 2.55.0