From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (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 6AE2B3E3142 for ; Mon, 8 Jun 2026 14:52:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780930342; cv=none; b=rvHRdpzJdgQS9gnB5bdf3IJ1ilsn/d7w6/+fH+Ie4CkK18O6iPQxp96172KDz/j58ZaEpIH4OZARkvq4auwFSQbJ+rciLIf96XW08vFJhWkeiWnKfBryrElFcWVqPBf73M4pba/P8k0CfyLsv8RRCoIi2EEcZ8cJu4IxQOMn1Ok= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780930342; c=relaxed/simple; bh=wOdE8zdye6eYehDyzgVykZybe5+faY4jRhHsAjAthGY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ssxbQRfGFxSK+S0F1ow4xee5aCSi4zJqNLB1haSZN4UDBVj/gNSg5IGB2aCvu6pQ46a9beNt4PW0N2gZGbqRfsAEwRTKUku61/d3b83XS5ErC1xTszXwQyUMqfvaojVdq7MR30OFafFZ2AVvcyDT1kLDuf1YqfBXTUJvPU7RyKM= 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=gV/o4CVr; arc=none smtp.client-ip=95.215.58.183 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="gV/o4CVr" 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=1780930337; 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=8YP9wxQExZ/A+pdpZbBfKzHyR4j6PtbdgvLWu59Ku60=; b=gV/o4CVr04QNpEt9JtFmzwz9214cJt3obtZrmI3Hx/YbYfygYijqlhfJ71Q8yoNsm+67OE Clp36qm217UA1qeco+YHFyyLDWf2DXvI22DuNXxgoQCwktwWaBd+cYmoAmA3PMv7paVyYR Jvh/Mia2MDkEUxAu12MJIhtXiNPUBJk= From: Leon Hwang To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , John Fastabend , Quentin Monnet , Shuah Khan , Leon Hwang , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com Subject: [PATCH bpf-next v5 2/9] bpf: Introduce global percpu data Date: Mon, 8 Jun 2026 22:51:06 +0800 Message-ID: <20260608145113.65857-3-leon.hwang@linux.dev> In-Reply-To: <20260608145113.65857-1-leon.hwang@linux.dev> References: <20260608145113.65857-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Introduce global percpu data, inspired by the commit 6316f78306c1 ("Merge branch 'support-global-data'"). It enables the definition of global percpu variables in BPF, similar to the include/linux/percpu-defs.h::DEFINE_PER_CPU() macro. For example, in BPF, it is able to define a global percpu variable like: int data SEC(".percpu"); With this patch, tools like retsnoop [1] and bpfsnoop [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(".percpu.lbrs"); This eliminates the need to retrieve the CPU ID using the bpf_get_smp_processor_id() helper. Additionally, by reusing global percpu data map, sharing information between tail callers and callees or freplace callers and callees becomes simpler compared to reusing percpu_array maps. Links: [1] https://github.com/anakryiko/retsnoop [2] https://github.com/bpfsnoop/bpfsnoop Assisted-by: Codex:gpt-5.5-xhigh Signed-off-by: Leon Hwang --- kernel/bpf/arraymap.c | 39 +++++++++++++++++++++++++++++++++++++-- kernel/bpf/const_fold.c | 1 - kernel/bpf/fixups.c | 32 ++++++++++++++++++++++++++++++++ kernel/bpf/verifier.c | 14 ++++++++++++++ 4 files changed, 83 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index e6271a2bf6d6..e6b5d8e89723 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -259,6 +259,38 @@ 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) { @@ -551,9 +583,10 @@ static int array_map_check_btf(struct bpf_map *map, const struct btf_type *key_type, const struct btf_type *value_type) { - /* One exception for keyless BTF: .bss/.data/.rodata map */ + /* One exception for keyless BTF: .bss/.data/.rodata/.percpu 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; @@ -832,6 +865,8 @@ const struct bpf_map_ops percpu_array_map_ops = { .map_get_next_key = bpf_array_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/const_fold.c b/kernel/bpf/const_fold.c index b2a19acadb91..5787246bef30 100644 --- a/kernel/bpf/const_fold.c +++ b/kernel/bpf/const_fold.c @@ -182,7 +182,6 @@ static void const_reg_xfer(struct bpf_verifier_env *env, struct const_arg_info * u64 val = 0; if (!bpf_map_is_rdonly(map) || !map->ops->map_direct_value_addr || - map->map_type == BPF_MAP_TYPE_INSN_ARRAY || off < 0 || off + size > map->value_size || bpf_map_direct_read(map, off, size, &val, is_ldsx)) { *dst = unknown; diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c index 3cf2cc6e3ab6..4f84d087ca69 100644 --- a/kernel/bpf/fixups.c +++ b/kernel/bpf/fixups.c @@ -1819,6 +1819,38 @@ int bpf_do_misc_fixups(struct bpf_verifier_env *env) goto next_insn; } + if (env->prog->jit_requested && + bpf_jit_supports_percpu_insn() && + 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; + } + if (insn->code != (BPF_JMP | BPF_CALL)) goto next_insn; if (insn->src_reg == BPF_PSEUDO_CALL) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2690d063a240..eecd9ab82e91 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5556,6 +5556,8 @@ 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_INSN_ARRAY || map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) + return -EINVAL; err = map->ops->map_direct_value_addr(map, &addr, off); if (err) return err; @@ -8074,6 +8076,12 @@ static int check_arg_const_str(struct bpf_verifier_env *env, return -EACCES; } + if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) { + verbose(env, "%s points to percpu_array map which cannot be used as const string\n", + reg_arg_name(env, argno)); + return -EACCES; + } + if (!bpf_map_is_rdonly(map)) { verbose(env, "%s does not point to a readonly map'\n", reg_arg_name(env, argno)); return -EACCES; @@ -18143,6 +18151,12 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env) return -EINVAL; } + if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY && + !env->prog->jit_requested) { + verbose(env, "JIT is required to use global percpu data\n"); + return -EOPNOTSUPP; + } + err = map->ops->map_direct_value_addr(map, &addr, off); if (err) { verbose(env, "invalid access to map value pointer, value_size=%u off=%u\n", -- 2.54.0