From patchwork Mon Jan 13 15:24:36 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leon Hwang X-Patchwork-Id: 13937638 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-171.mta1.migadu.com (out-171.mta1.migadu.com [95.215.58.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 717F024023F for ; Mon, 13 Jan 2025 15:25:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736781910; cv=none; b=AWOzQR1eUUYzuJWSR7VR6uycmfYMGTpmbaxzhPwPfMT+Cs1RgqhARsilJEHRrD2QOVgwbQKVONYrUDu91ur4vmJa2YSZHAZn00lL+l1ZuR9UpHWvxieS/+qDcP6b88cOX/VYiaEBEMiCL8UIbOGaQABrdmveR1eUlFtQQiBS3oc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736781910; c=relaxed/simple; bh=tig0w0UfcTNWzRaGJuWCFD6KvnTR9iuNAFSJds9vaNI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tQI/ikubp3TKWmKuDvoVHE3MQYFNCI5dvlh/Tefbcuckv3Sa3wbMreZVY6o+WVSOg+9Pd9dEHdAOITAJFyrvaBcDDOL8WIFJLno3PTnIEOxQILoezMUb+i7s6bpRn8ly7tmoWWTj8hGys9j4Z9C5zbnK8qnBgtelcqmY1hmyKkM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=CuT6Mzgy; arc=none smtp.client-ip=95.215.58.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="CuT6Mzgy" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1736781906; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=T9gvuSGsgt8dMr0ph+0u+xe2RXVlcr9fiKN2o0ANsH8=; b=CuT6MzgyvcoNyulgB4RgYHUm1Zx78oguFoj/7Up7I9OmllvRs8nz/YMozilWGgDpe1wOz4 nn8lKyq91QUPisSFrvLZaIWNgvhct6kuOgyPmotUeipwOWOYozS6Z1xz84tdiv5yuStNn+ McHfEDSCagotSAkwMACeeQfmfPEVe5Y= From: Leon Hwang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yonghong.song@linux.dev, song@kernel.org, eddyz87@gmail.com, leon.hwang@linux.dev, kernel-patches-bot@fb.com Subject: [RFC PATCH bpf-next 1/2] bpf: Introduce global percpu data Date: Mon, 13 Jan 2025 23:24:36 +0800 Message-ID: <20250113152437.67196-2-leon.hwang@linux.dev> In-Reply-To: <20250113152437.67196-1-leon.hwang@linux.dev> References: <20250113152437.67196-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net X-Patchwork-State: RFC This patch introduces global per-CPU data, inspired by commit 6316f78306c1 ("Merge branch 'support-global-data'"). It enables the definition of global per-CPU variables in BPF, similar to the DEFINE_PER_CPU() macro in the kernel[0]. For example, in BPF, it is able to define a global per-CPU variable like this: int percpu_data SEC(".data..percpu"); With this patch, tools like retsnoop[1] and bpflbr[2] can simplify their BPF code for handling LBRs. The code can be updated from static struct perf_branch_entry lbrs[1][MAX_LBR_ENTRIES] SEC(".data.lbrs"); to static struct perf_branch_entry lbrs[MAX_LBR_ENTRIES] SEC(".data..percpu.lbrs"); This eliminates the need to retrieve the CPU ID using the bpf_get_smp_processor_id() helper. Additionally, by reusing global per-CPU variables, sharing information between tail callers and callees or freplace callers and callees becomes simpler compared to using percpu_array maps. Links: [0] https://github.com/torvalds/linux/blob/fbfd64d25c7af3b8695201ebc85efe90be28c5a3/include/linux/percpu-defs.h#L114 [1] https://github.com/anakryiko/retsnoop [2] https://github.com/Asphaltt/bpflbr Signed-off-by: Leon Hwang --- kernel/bpf/arraymap.c | 39 +++++++++++++- kernel/bpf/verifier.c | 45 +++++++++++++++++ tools/lib/bpf/libbpf.c | 112 ++++++++++++++++++++++++++++++++--------- 3 files changed, 171 insertions(+), 25 deletions(-) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index eb28c0f219ee4..f8c60d8331975 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -249,6 +249,40 @@ static void *percpu_array_map_lookup_elem(struct bpf_map *map, void *key) return this_cpu_ptr(array->pptrs[index & array->index_mask]); } +static int percpu_array_map_direct_value_addr(const struct bpf_map *map, + u64 *imm, u32 off) +{ + struct bpf_array *array = container_of(map, struct bpf_array, map); + + if (map->max_entries != 1) + return -EOPNOTSUPP; + if (off >= map->value_size) + return -EINVAL; + if (!bpf_jit_supports_percpu_insn()) + return -EOPNOTSUPP; + + *imm = (u64) array->pptrs[0]; + return 0; +} + +static int percpu_array_map_direct_value_meta(const struct bpf_map *map, + u64 imm, u32 *off) +{ + struct bpf_array *array = container_of(map, struct bpf_array, map); + u64 base = (u64) array->pptrs[0]; + u64 range = array->elem_size; + + if (map->max_entries != 1) + return -EOPNOTSUPP; + if (imm < base || imm >= base + range) + return -ENOENT; + if (!bpf_jit_supports_percpu_insn()) + return -EOPNOTSUPP; + + *off = imm - base; + return 0; +} + /* emit BPF instructions equivalent to C code of percpu_array_map_lookup_elem() */ static int percpu_array_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf) { @@ -534,7 +568,8 @@ static int array_map_check_btf(const struct bpf_map *map, /* One exception for keyless BTF: .bss/.data/.rodata map */ if (btf_type_is_void(key_type)) { - if (map->map_type != BPF_MAP_TYPE_ARRAY || + if ((map->map_type != BPF_MAP_TYPE_ARRAY && + map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) || map->max_entries != 1) return -EINVAL; @@ -815,6 +850,8 @@ const struct bpf_map_ops percpu_array_map_ops = { .map_get_next_key = array_map_get_next_key, .map_lookup_elem = percpu_array_map_lookup_elem, .map_gen_lookup = percpu_array_map_gen_lookup, + .map_direct_value_addr = percpu_array_map_direct_value_addr, + .map_direct_value_meta = percpu_array_map_direct_value_meta, .map_update_elem = array_map_update_elem, .map_delete_elem = array_map_delete_elem, .map_lookup_percpu_elem = percpu_array_map_lookup_percpu_elem, diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b8ca227c78af1..94ce02a48ddc1 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6809,6 +6809,8 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val, u64 addr; int err; + if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) + return -EINVAL; err = map->ops->map_direct_value_addr(map, &addr, off); if (err) return err; @@ -7324,6 +7326,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn /* if map is read-only, track its contents as scalars */ if (tnum_is_const(reg->var_off) && bpf_map_is_rdonly(map) && + map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY && map->ops->map_direct_value_addr) { int map_off = off + reg->var_off.value; u64 val = 0; @@ -9140,6 +9143,11 @@ static int check_reg_const_str(struct bpf_verifier_env *env, return -EACCES; } + if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) { + verbose(env, "percpu_array map does not support direct string value access\n"); + return -EINVAL; + } + err = check_map_access(env, regno, reg->off, map->value_size - reg->off, false, ACCESS_HELPER); @@ -10751,6 +10759,11 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env, return -EINVAL; num_args = data_len_reg->var_off.value / 8; + if (fmt_map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) { + verbose(env, "percpu_array map does not support snprintf\n"); + return -EINVAL; + } + /* fmt being ARG_PTR_TO_CONST_STR guarantees that var_off is const * and map_direct_value_addr is set. */ @@ -21304,6 +21317,38 @@ static int do_misc_fixups(struct bpf_verifier_env *env) goto next_insn; } +#ifdef CONFIG_SMP + if (insn->code == (BPF_LD | BPF_IMM | BPF_DW) && + (insn->src_reg == BPF_PSEUDO_MAP_VALUE || + insn->src_reg == BPF_PSEUDO_MAP_IDX_VALUE)) { + struct bpf_map *map; + + aux = &env->insn_aux_data[i + delta]; + map = env->used_maps[aux->map_index]; + if (map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) + goto next_insn; + + /* Reuse the original ld_imm64 insn. And add one + * mov64_percpu_reg insn. + */ + + insn_buf[0] = insn[1]; + insn_buf[1] = BPF_MOV64_PERCPU_REG(insn->dst_reg, insn->dst_reg); + cnt = 2; + + i++; + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt); + if (!new_prog) + return -ENOMEM; + + delta += cnt - 1; + env->prog = prog = new_prog; + insn = new_prog->insnsi + i + delta; + + goto next_insn; + } +#endif + if (insn->code != (BPF_JMP | BPF_CALL)) goto next_insn; if (insn->src_reg == BPF_PSEUDO_CALL) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 6c262d0152f81..881174f4f90a4 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -516,6 +516,7 @@ struct bpf_struct_ops { }; #define DATA_SEC ".data" +#define PERCPU_DATA_SEC ".data..percpu" #define BSS_SEC ".bss" #define RODATA_SEC ".rodata" #define KCONFIG_SEC ".kconfig" @@ -562,6 +563,8 @@ struct bpf_map { __u32 btf_value_type_id; __u32 btf_vmlinux_value_type_id; enum libbpf_map_type libbpf_type; + int num_cpus; + void *data; void *mmaped; struct bpf_struct_ops *st_ops; struct bpf_map *inner_map; @@ -1923,11 +1926,35 @@ static bool map_is_mmapable(struct bpf_object *obj, struct bpf_map *map) return false; } +static bool map_is_percpu_data(struct bpf_map *map) +{ + return str_has_pfx(map->real_name, PERCPU_DATA_SEC); +} + +static void map_copy_data(struct bpf_map *map, const void *data) +{ + bool is_percpu_data = map_is_percpu_data(map); + size_t data_sz = map->def.value_size; + size_t elem_sz = roundup(data_sz, 8); + int i; + + if (!data) + return; + + if (!is_percpu_data) + memcpy(map->mmaped, data, data_sz); + else + for (i = 0; i < map->num_cpus; i++) + memcpy(map->data + i*elem_sz, data, data_sz); +} + 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_data = str_has_pfx(real_name, PERCPU_DATA_SEC); struct bpf_map_def *def; + const char *data_desc; struct bpf_map *map; size_t mmap_sz; int err; @@ -1948,7 +1975,8 @@ 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_data ? BPF_MAP_TYPE_PERCPU_ARRAY + : BPF_MAP_TYPE_ARRAY; def->key_size = sizeof(int); def->value_size = data_sz; def->max_entries = 1; @@ -1958,29 +1986,57 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type, /* failures are fine because of maps like .rodata.str1.1 */ (void) map_fill_btf_type_info(obj, map); - if (map_is_mmapable(obj, map)) - def->map_flags |= BPF_F_MMAPABLE; + data_desc = is_percpu_data ? "percpu " : ""; + pr_debug("map '%s' (global %sdata): at sec_idx %d, offset %zu, flags %x.\n", + map->name, data_desc, map->sec_idx, map->sec_offset, + def->map_flags); - 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); + if (is_percpu_data) { + map->num_cpus = libbpf_num_possible_cpus(); + if (map->num_cpus < 0) { + err = errno; + pr_warn("failed to get possible cpus\n"); + goto free_name; + } - mmap_sz = bpf_map_mmap_sz(map); - map->mmaped = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_ANONYMOUS, -1, 0); - if (map->mmaped == MAP_FAILED) { - err = -errno; - map->mmaped = NULL; - pr_warn("failed to alloc map '%s' content buffer: %s\n", map->name, errstr(err)); - zfree(&map->real_name); - zfree(&map->name); - return err; - } + map->data = calloc(map->num_cpus, roundup(data_sz, 8)); + if (!map->data) { + err = -ENOMEM; + pr_warn("failed to alloc percpu map '%s' content buffer: %s\n", + map->name, errstr(err)); + goto free_name; + } - if (data) - memcpy(map->mmaped, data, data_sz); + if (data) + map_copy_data(map, data); + else + memset(map->data, 0, map->num_cpus*roundup(data_sz, 8)); + } else { + if (map_is_mmapable(obj, map)) + def->map_flags |= BPF_F_MMAPABLE; + + mmap_sz = bpf_map_mmap_sz(map); + map->mmaped = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if (map->mmaped == MAP_FAILED) { + err = -errno; + map->mmaped = NULL; + pr_warn("failed to alloc map '%s' content buffer: %s\n", + map->name, errstr(err)); + goto free_name; + } + + if (data) + memcpy(map->mmaped, data, data_sz); + } pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name); return 0; + +free_name: + zfree(&map->real_name); + zfree(&map->name); + return err; } static int bpf_object__init_global_data_maps(struct bpf_object *obj) @@ -5127,16 +5183,21 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map) enum libbpf_map_type map_type = map->libbpf_type; int err, zero = 0; size_t mmap_sz; + size_t data_sz; + void *data; + data_sz = map_is_percpu_data(map) ? roundup(map->def.value_size, 8)*map->num_cpus + : map->def.value_size; + data = map_is_percpu_data(map) ? map->data : map->mmaped; if (obj->gen_loader) { bpf_gen__map_update_elem(obj->gen_loader, map - obj->maps, - map->mmaped, map->def.value_size); + data, data_sz); 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, data, 0); if (err) { err = -errno; pr_warn("map '%s': failed to set initial contents: %s\n", @@ -9041,6 +9102,8 @@ static void bpf_map__destroy(struct bpf_map *map) if (map->mmaped && map->mmaped != map->obj->arena_data) munmap(map->mmaped, bpf_map_mmap_sz(map)); map->mmaped = NULL; + if (map->data) + zfree(&map->data); if (map->st_ops) { zfree(&map->st_ops->data); @@ -10348,7 +10411,8 @@ int bpf_map__set_initial_value(struct bpf_map *map, if (map->obj->loaded || map->reused) return libbpf_err(-EBUSY); - if (!map->mmaped || map->libbpf_type == LIBBPF_MAP_KCONFIG) + if ((!map->mmaped && !map->data) || + map->libbpf_type == LIBBPF_MAP_KCONFIG) return libbpf_err(-EINVAL); if (map->def.type == BPF_MAP_TYPE_ARENA) @@ -10358,7 +10422,7 @@ int bpf_map__set_initial_value(struct bpf_map *map, if (size != actual_sz) return libbpf_err(-EINVAL); - memcpy(map->mmaped, data, size); + map_copy_data(map, data); return 0; } @@ -10370,7 +10434,7 @@ void *bpf_map__initial_value(const struct bpf_map *map, size_t *psize) return map->st_ops->data; } - if (!map->mmaped) + if ((!map->mmaped && !map->data)) return NULL; if (map->def.type == BPF_MAP_TYPE_ARENA) @@ -10378,7 +10442,7 @@ void *bpf_map__initial_value(const struct bpf_map *map, size_t *psize) else *psize = map->def.value_size; - return map->mmaped; + return map->def.type == BPF_MAP_TYPE_PERCPU_ARRAY ? map->data : map->mmaped; } bool bpf_map__is_internal(const struct bpf_map *map)