2026-06-29 23:24 UTC+0800 ~ Leon Hwang <[email protected]> > 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 | 49 +++++++++++++++++++++++++++++++---- > tools/lib/bpf/skel_internal.h | 24 +++++++++++++++-- > 2 files changed, 66 insertions(+), 7 deletions(-) > > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c > index 6ae7262ebe0c..2e60296358db 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 */ > @@ -254,6 +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? Quentin
