Add support for global percpu data in libbpf by adding a new ".percpu" section, similar to ".data". It enables efficient handling of percpu global variables in bpf programs.
When generating loader for lightweight skeleton, update the percpu_array map used for global percpu data using BPF_F_ALL_CPUS, in order to update values across all CPUs using one value slot. Unlike global data, the mmaped data for global percpu data will be marked as read-only after populating the percpu_array map. Thereafter, users can read those initialized percpu data after loading prog. If they want to update the percpu data after loading prog, they have to update the percpu_array map using key=0 instead. Signed-off-by: Leon Hwang <[email protected]> --- tools/lib/bpf/bpf_gen_internal.h | 3 +- tools/lib/bpf/gen_loader.c | 3 +- tools/lib/bpf/libbpf.c | 68 ++++++++++++++++++++++++++------ 3 files changed, 60 insertions(+), 14 deletions(-) diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h index 49af4260b8e6..5ea8383805d3 100644 --- a/tools/lib/bpf/bpf_gen_internal.h +++ b/tools/lib/bpf/bpf_gen_internal.h @@ -66,7 +66,8 @@ void bpf_gen__prog_load(struct bpf_gen *gen, enum bpf_prog_type prog_type, const char *prog_name, const char *license, struct bpf_insn *insns, size_t insn_cnt, struct bpf_prog_load_opts *load_attr, int prog_idx); -void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u32 value_size); +void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *value, __u32 value_size, + __u64 flags); void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx); void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *name, enum bpf_attach_type type); void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak, diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c index d79695f01c87..7ceb096f18ec 100644 --- a/tools/lib/bpf/gen_loader.c +++ b/tools/lib/bpf/gen_loader.c @@ -1190,7 +1190,7 @@ void bpf_gen__prog_load(struct bpf_gen *gen, } void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *pvalue, - __u32 value_size) + __u32 value_size, __u64 flags) { int attr_size = offsetofend(union bpf_attr, flags); int map_update_attr, value, key; @@ -1198,6 +1198,7 @@ void bpf_gen__map_update_elem(struct bpf_gen *gen, int map_idx, void *pvalue, int zero = 0; memset(&attr, 0, attr_size); + attr.flags = flags; value = add_data(gen, pvalue, value_size); key = add_data(gen, &zero, sizeof(zero)); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1368752aa13c..199d08d3cdcd 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -541,6 +541,7 @@ struct bpf_struct_ops { }; #define DATA_SEC ".data" +#define PERCPU_SEC ".percpu" #define BSS_SEC ".bss" #define RODATA_SEC ".rodata" #define KCONFIG_SEC ".kconfig" @@ -555,6 +556,7 @@ enum libbpf_map_type { LIBBPF_MAP_BSS, LIBBPF_MAP_RODATA, LIBBPF_MAP_KCONFIG, + LIBBPF_MAP_PERCPU, }; struct bpf_map_def { @@ -666,6 +668,7 @@ enum sec_type { SEC_DATA, SEC_RODATA, SEC_ST_OPS, + SEC_PERCPU, }; struct elf_sec_desc { @@ -1839,6 +1842,8 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map) switch (map->def.type) { case BPF_MAP_TYPE_ARRAY: return array_map_mmap_sz(map->def.value_size, map->def.max_entries); + case BPF_MAP_TYPE_PERCPU_ARRAY: + return map->def.value_size; case BPF_MAP_TYPE_ARENA: return page_sz * map->def.max_entries; default: @@ -1938,7 +1943,7 @@ static bool map_is_mmapable(struct bpf_object *obj, struct bpf_map *map) struct btf_var_secinfo *vsi; int i, n; - if (!map->btf_value_type_id) + if (!map->btf_value_type_id || map->libbpf_type == LIBBPF_MAP_PERCPU) return false; t = btf__type_by_id(obj->btf, map->btf_value_type_id); @@ -1962,6 +1967,7 @@ static int bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, const char *real_name, int sec_idx, void *data, size_t data_sz) { + bool is_percpu = type == LIBBPF_MAP_PERCPU; struct bpf_map_def *def; struct bpf_map *map; size_t mmap_sz; @@ -1983,7 +1989,7 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, } def = &map->def; - def->type = BPF_MAP_TYPE_ARRAY; + def->type = is_percpu ? BPF_MAP_TYPE_PERCPU_ARRAY : BPF_MAP_TYPE_ARRAY; def->key_size = sizeof(int); def->value_size = data_sz; def->max_entries = 1; @@ -1996,8 +2002,9 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, if (map_is_mmapable(obj, map)) def->map_flags |= BPF_F_MMAPABLE; - pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n", - map->name, map->sec_idx, map->sec_offset, def->map_flags); + pr_debug("map '%s' (global %sdata): at sec_idx %d, offset %zu, flags %x.\n", + map->name, is_percpu ? "percpu " : "", map->sec_idx, + map->sec_offset, def->map_flags); mmap_sz = bpf_map_mmap_sz(map); map->mmaped = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE, @@ -2057,6 +2064,13 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj) NULL, sec_desc->data->d_size); break; + case SEC_PERCPU: + sec_name = elf_sec_name(obj, elf_sec_by_idx(obj, sec_idx)); + err = bpf_object__init_internal_map(obj, LIBBPF_MAP_PERCPU, + sec_name, sec_idx, + sec_desc->data->d_buf, + sec_desc->data->d_size); + break; default: /* skip */ break; @@ -4016,6 +4030,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj) sec_desc->sec_type = SEC_RODATA; sec_desc->shdr = sh; sec_desc->data = data; + } else if (strcmp(name, PERCPU_SEC) == 0 || + str_has_pfx(name, PERCPU_SEC ".")) { + sec_desc->sec_type = SEC_PERCPU; + sec_desc->shdr = sh; + sec_desc->data = data; } else if (strcmp(name, STRUCT_OPS_SEC) == 0 || strcmp(name, STRUCT_OPS_LINK_SEC) == 0 || strcmp(name, "?" STRUCT_OPS_SEC) == 0 || @@ -4544,6 +4563,7 @@ static bool bpf_object__shndx_is_data(const struct bpf_object *obj, case SEC_BSS: case SEC_DATA: case SEC_RODATA: + case SEC_PERCPU: return true; default: return false; @@ -4569,6 +4589,8 @@ bpf_object__section_to_libbpf_map_type(const struct bpf_object *obj, int shndx) return LIBBPF_MAP_DATA; case SEC_RODATA: return LIBBPF_MAP_RODATA; + case SEC_PERCPU: + return LIBBPF_MAP_PERCPU; default: return LIBBPF_MAP_UNSPEC; } @@ -4944,7 +4966,7 @@ static int map_fill_btf_type_info(struct bpf_object *obj, struct bpf_map *map) /* * LLVM annotates global data differently in BTF, that is, - * only as '.data', '.bss' or '.rodata'. + * only as '.data', '.bss', '.percpu' or '.rodata'. */ if (!bpf_map__is_internal(map)) return -ENOENT; @@ -5297,18 +5319,30 @@ static int bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map) { enum libbpf_map_type map_type = map->libbpf_type; + bool is_percpu = map_type == LIBBPF_MAP_PERCPU; + __u64 update_flags = 0; int err, zero = 0; size_t mmap_sz; + if (is_percpu) { + if (!obj->gen_loader && !kernel_supports(obj, FEAT_PERCPU_DATA)) { + pr_warn("map '%s': kernel does not support percpu data.\n", + bpf_map__name(map)); + return -EOPNOTSUPP; + } + + update_flags = BPF_F_ALL_CPUS; + } + if (obj->gen_loader) { bpf_gen__map_update_elem(obj->gen_loader, map - obj->maps, - map->mmaped, map->def.value_size); + map->mmaped, map->def.value_size, update_flags); if (map_type == LIBBPF_MAP_RODATA || map_type == LIBBPF_MAP_KCONFIG) bpf_gen__map_freeze(obj->gen_loader, map - obj->maps); return 0; } - err = bpf_map_update_elem(map->fd, &zero, map->mmaped, 0); + err = bpf_map_update_elem(map->fd, &zero, map->mmaped, update_flags); if (err) { err = -errno; pr_warn("map '%s': failed to set initial contents: %s\n", @@ -5353,6 +5387,13 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map) return err; } map->mmaped = mmaped; + } else if (is_percpu) { + if (mprotect(map->mmaped, mmap_sz, PROT_READ)) { + err = -errno; + pr_warn("map '%s': failed to mprotect() contents: %s\n", + bpf_map__name(map), errstr(err)); + return err; + } } else if (map->mmaped) { munmap(map->mmaped, mmap_sz); map->mmaped = NULL; @@ -10806,16 +10847,19 @@ int bpf_map__fd(const struct bpf_map *map) static bool map_uses_real_name(const struct bpf_map *map) { - /* Since libbpf started to support custom .data.* and .rodata.* maps, - * their user-visible name differs from kernel-visible name. Users see - * such map's corresponding ELF section name as a map name. - * This check distinguishes .data/.rodata from .data.* and .rodata.* - * maps to know which name has to be returned to the user. + /* + * Since libbpf started to support custom .data.*, .rodata.* and + * .percpu.* maps, their user-visible name differs from + * kernel-visible name. Users see such map's corresponding ELF section + * name as a map name. This check distinguishes plain .data/.rodata/.percpu + * from .data.*, .rodata.* and .percpu.* to choose which name to return. */ if (map->libbpf_type == LIBBPF_MAP_DATA && strcmp(map->real_name, DATA_SEC) != 0) return true; if (map->libbpf_type == LIBBPF_MAP_RODATA && strcmp(map->real_name, RODATA_SEC) != 0) return true; + if (map->libbpf_type == LIBBPF_MAP_PERCPU && strcmp(map->real_name, PERCPU_SEC) != 0) + return true; return false; } -- 2.54.0
