The BPF_MOV64_PERCPU_REG insn requires JIT to emit native code to for 'dst_reg = src_reg + '. However, the interpreter ignores the 'off' at its ALU64_MOV_X label. The 'off' indicates the insn is BPF_MOV64_PERCPU_REG insn. Then, when the interpreter loads memory from the register, it will hit a page fault. [ 2.545572] BUG: unable to handle page fault for address: ffffffffacaaf034 [ 2.546485] #PF: supervisor read access in kernel mode [ 2.547167] #PF: error_code(0x0000) - not-present page [ 2.547850] PGD 134e63067 P4D 134e63067 PUD 134e64063 PMD 10021c063 PTE 800ffffeca550062 [ 2.548912] Oops: Oops: 0000 [#1] SMP PTI Set jit_required as true in order to disallow interpreter fallback in core.c::__bpf_prog_select_runtime(), if any BPF_ADDR_PERCPU insn is patched to the prog. BTW, rename the helper bpf_map_supports_cpu_flags() to bpf_map_is_percpu_map(). Fixes: 7bdbf7446305 ("bpf: add special internal-only MOV instruction to resolve per-CPU addrs") Signed-off-by: Leon Hwang --- include/linux/bpf.h | 4 ++-- kernel/bpf/fixups.c | 5 +++++ 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 31181e0c2b80..d9542127dfdf 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -4163,7 +4163,7 @@ bpf_prog_update_insn_ptrs(struct bpf_prog *prog, u32 *offsets, void *image) } #endif -static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type) +static inline bool bpf_map_is_percpu_map(enum bpf_map_type map_type) { switch (map_type) { case BPF_MAP_TYPE_PERCPU_ARRAY: @@ -4190,7 +4190,7 @@ static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 all return -EINVAL; if (flags & (BPF_F_CPU | BPF_F_ALL_CPUS)) { - if (!bpf_map_supports_cpu_flags(map->map_type)) + if (!bpf_map_is_percpu_map(map->map_type)) return -EINVAL; if ((flags & BPF_F_CPU) && (flags & BPF_F_ALL_CPUS)) return -EINVAL; diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c index d3be972714b2..a0bddada7964 100644 --- a/kernel/bpf/fixups.c +++ b/kernel/bpf/fixups.c @@ -2008,6 +2008,9 @@ int bpf_do_misc_fixups(struct bpf_verifier_env *env) return -EFAULT; } + if (bpf_map_is_percpu_map(map_ptr->map_type)) + prog->jit_required = true; + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); if (!new_prog) @@ -2112,6 +2115,7 @@ int bpf_do_misc_fixups(struct bpf_verifier_env *env) * way, it's fine to back out this inlining logic */ #ifdef CONFIG_SMP + prog->jit_required = true; insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, (u32)(unsigned long)&cpu_number); insn_buf[1] = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0); insn_buf[2] = BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0); @@ -2133,6 +2137,7 @@ int bpf_do_misc_fixups(struct bpf_verifier_env *env) /* Implement bpf_get_current_task() and bpf_get_current_task_btf() inline. */ if ((insn->imm == BPF_FUNC_get_current_task || insn->imm == BPF_FUNC_get_current_task_btf) && bpf_verifier_inlines_helper_call(env, insn->imm)) { + prog->jit_required = true; insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, (u32)(unsigned long)¤t_task); insn_buf[1] = BPF_MOV64_PERCPU_REG(BPF_REG_0, BPF_REG_0); insn_buf[2] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); -- 2.55.0