On 2/7/26 03:32, Andrii Nakryiko wrote: > On Wed, Jul 1, 2026 at 9:49 AM Quentin Monnet <[email protected]> wrote: >> >> 2026-06-29 23:24 UTC+0800 ~ Leon Hwang <[email protected]> [...] >>> @@ -254,6 +254,20 @@ static const struct btf_type *find_type_for_map(struct >>> btf *btf, const char *map >>> return NULL; >>> } >>> >>> +static bool bpf_map_is_skel_data(const struct bpf_map *map) >>> +{ >>> + if (!bpf_map__is_internal(map)) >>> + return false; >>> + >>> + if (bpf_map__map_flags(map) & BPF_F_MMAPABLE) >>> + return true; >>> + >>> + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) >>> + return true; >>> + >>> + return false; >>> +} >>> + >>> static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t >>> sz) >>> { >>> size_t tmp_sz; >>> @@ -263,7 +277,7 @@ 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_skel_data(map)) >>> return false; >>> >>> if (!get_map_ident(map, buf, sz)) >> >> >> Thanks! The bpftool patch looks good, with one reservation: after this >> patch, I believe "is_mmapable_map(map, ...)" will return true if map is >> a percpu map, although percpu maps aren't mmap-able, so we should >> probably update the name of that function to avoid any confusion? >> > > Great observation, Quentin! > > bpf_map_is_skel_data() I think was supposed to be exactly that generic > name. But it seems like Leon went half-way through with unification. > Unless there are some subtle situations where per-cpu array shouldn't > be handled where is_mmapable_map() is handled, we should rename > is_mmapable_map() and add BPF_MAP_TYPE_PERCPU_ARRAY check (assuming > it's internal map, of course) there. > > Leon, can you please check? > Aha, my bad.
Try to rename is_mmapable_map() to bpf_map_is_skel_data(). See below patch. Thanks, Leon --- >From 654306cd9091a175883dd61c7b251996c42e7cae Mon Sep 17 00:00:00 2001 From: Leon Hwang <[email protected]> Date: Mon, 29 Jun 2026 23:24:02 +0800 Subject: [PATCH bpf-next v9 5/9] bpftool: Generate skeleton for global percpu data 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. Assisted-by: Codex:gpt-5.5-xhigh Signed-off-by: Leon Hwang <[email protected]> --- tools/bpf/bpftool/gen.c | 72 ++++++++++++++++++++++++++--------- tools/lib/bpf/skel_internal.h | 24 +++++++++++- 2 files changed, 76 insertions(+), 20 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 6ae7262ebe0c..798a34366e08 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -92,7 +92,7 @@ static void get_header_guard(char *guard, const char *obj_name, const char *suff static bool get_map_ident(const struct bpf_map *map, char *buf, size_t buf_sz) { - static const char *sfxs[] = { ".data", ".rodata", ".bss", ".kconfig" }; + static const char *sfxs[] = { ".data", ".rodata", ".bss", ".percpu", ".kconfig" }; const char *name = bpf_map__name(map); int i, n; @@ -117,7 +117,7 @@ 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 +254,7 @@ 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 bpf_map_is_skel_data(const struct bpf_map *map, char *buf, size_t sz) { size_t tmp_sz; @@ -263,13 +263,19 @@ 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 true; + + return false; } static int codegen_datasecs(struct bpf_object *obj, const char *obj_name) @@ -286,8 +292,11 @@ static int codegen_datasecs(struct bpf_object *obj, const char *obj_name) return -errno; 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))) + /* + * Only generate definitions for internal maps that have + * mmapped data. + */ + if (!bpf_map_is_skel_data(map, map_ident, sizeof(map_ident))) continue; sec = find_type_for_map(btf, map_ident); @@ -339,8 +348,14 @@ static int codegen_subskel_datasecs(struct bpf_object *obj, const char *obj_name return -errno; 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))) + /* + * Only generate definitions for internal maps that have + * mmapped data. + */ + if (!bpf_map_is_skel_data(map, map_ident, sizeof(map_ident))) + continue; + + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) continue; sec = find_type_for_map(btf, map_ident); @@ -493,7 +508,10 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map) return map_sz; } -/* Emit type size asserts for all top-level fields in memory-mapped internal maps. */ +/* + * Emit type size asserts for all top-level fields in internal maps that + * have mmaped data. + */ static void codegen_asserts(struct bpf_object *obj, const char *obj_name) { struct btf *btf = bpf_object__btf(obj); @@ -517,7 +535,7 @@ 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 (!bpf_map_is_skel_data(map, map_ident, sizeof(map_ident))) continue; sec = find_type_for_map(btf, map_ident); @@ -669,7 +687,8 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name) if (!get_map_ident(map, ident, sizeof(ident))) continue; if (bpf_map__is_internal(map) && - (bpf_map__map_flags(map) & BPF_F_MMAPABLE)) + ((bpf_map__map_flags(map) & BPF_F_MMAPABLE) || + bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY)) printf("\tskel_free_map_data(skel->%1$s, skel->maps.%1$s.initial_value, %2$zu);\n", ident, bpf_map_mmap_sz(map)); codegen("\ @@ -741,7 +760,7 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h const void *mmap_data = NULL; size_t mmap_size = 0; - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!bpf_map_is_skel_data(map, ident, sizeof(ident))) continue; codegen("\ @@ -847,9 +866,23 @@ static int gen_trace(struct bpf_object *obj, const char *obj_name, const char *h bpf_object__for_each_map(map, obj) { const char *mmap_flags; - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!bpf_map_is_skel_data(map, ident, sizeof(ident))) continue; + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) { + codegen("\ + \n\ + err = skel_protect_map_data(skel->%1$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 @@ -953,8 +986,7 @@ 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 && bpf_map_is_skel_data(map, ident, sizeof(ident))) { printf("\tmap->mmaped = (void **)&obj->%s;\n", ident); } @@ -1738,7 +1770,9 @@ static int do_subskeleton(int argc, char **argv) /* Also count all maps that have a name */ map_cnt++; - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!bpf_map_is_skel_data(map, ident, sizeof(ident))) + continue; + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) continue; map_type_id = bpf_map__btf_value_type_id(map); @@ -1861,7 +1895,9 @@ static int do_subskeleton(int argc, char **argv) /* walk through each symbol and emit the runtime representation */ bpf_object__for_each_map(map, obj) { - if (!is_mmapable_map(map, ident, sizeof(ident))) + if (!bpf_map_is_skel_data(map, ident, sizeof(ident))) + continue; + if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) continue; map_type_id = bpf_map__btf_value_type_id(map); diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h index 74503d358bc8..485b0cd17017 100644 --- a/tools/lib/bpf/skel_internal.h +++ b/tools/lib/bpf/skel_internal.h @@ -135,8 +135,10 @@ 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. */ } @@ -174,6 +176,15 @@ 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) @@ -212,6 +223,15 @@ 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) -- 2.54.0
