From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=115.124.30.100 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793786665; b=yIpVtUwlaN/qmrtudPoZwRgojyEksYrORHcPTLvSsFzCe2Z2PfnZ7SLAPjoDzrr/z5yG X5zjcduOjv9K0cnyFOw9uxavS9G5AkODJlVRZ60fTU/L0VAtdro+uYxJiN4su+a155/03 cnsS4Zxt3h1p9jsWOvyP2YmjZqSBko4gR5g22W2eUwSXK90X0VNRu2frf/C/T6ye7AH/c dH061XrgHebSdXg+qgj0psoSGD94yDAHwbZfGaNgAM9Q3qzNXX+JnJfG8XRQVLFkHGvsF fa1xnFS87o6e9ko8UfAVk92OmoY8osa9AGuWv/y36AAAR0qCbKGo0GCx85/FF/mUAgw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793786665; h=DMARC-Filter:DKIM-Signature:X-Alimail-AntiSpam:Received:From:To:Cc: Subject:Date:Message-ID:X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=El+HFS5rExaXpXDIDYVfuWdl9JJQDwNWbfTECGFZBOs=; b=SHtHowrlguVCX9G3XsZfYC+Fv2MhOSgxVmvAAfuOeRsHvRyk8VQ9fu09H9GM+NpBWNal 9FgXBYBBhY+DcOL16NiWI8fguf0YVKeOusnQ+J5uicBOZaV9+IzGQwSUBd/Fbt18w2Dpw PdmJ6XbhgHDxeWSCu852uxuYrCoAnnM2MlQQXxTQ98bChbIc21uoK4V6lW/SCTWs9KDLz f3GqSRhSE58i68Nioy4xWUGZYqRu7O3k3tRoPeMMC3mS2khKEyNhzX69a/GITaA4bjN5n 0YjyTytXXlEMUsX7g4SwxYSB9aXTwLPuR1Y9AVvEy+X70N9V1CdSr5OQW0eKZPmZU1Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b="l4/ma7aY"; arc=none smtp.remote-ip=115.124.30.100 Received: from out30-100.freemail.mail.aliyun.com (out30-100.freemail.mail.aliyun.com [115.124.30.100]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70C51606A32C; Wed, 4 Nov 2026 10:04:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 70C51606A32C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=l4/ma7aY DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1793786661; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=El+HFS5rExaXpXDIDYVfuWdl9JJQDwNWbfTECGFZBOs=; b=l4/ma7aYC7tNQ3Iy2BZS1YEWGvMRa/bTP9hmVOfvHReEpUbwXpdrYJEUgz6PcEpoqVDAJR7JGH0y3JM3vAaJ8e4NKuqvBjK7nFQTch+KEf4FQttRl0Mu4Gurn7hJOw3qSFm5P9oQFEAlMKdZarkFdKrxvSMJlDzvMLim6T4z2w8= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R691e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037033178;MF=cp0613@linux.alibaba.com;NM=1;PH=DS;RN=27;SR=0;TI=SMTPD_---0XE5SaZX_1793786658; Received: from DESKTOP-S9E58SO.localdomain(mailfrom:cp0613@linux.alibaba.com fp:SMTPD_---0XE5SaZX_1793786658 cluster:ay36) by smtp.aliyun-inc.com; Wed, 04 Nov 2026 18:04:19 +0800 From: Chen Pei To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, memxor@gmail.com, bjorn@kernel.org, puranjay@kernel.org Cc: eddyz87@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, pulehui@huawei.com, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, luke.r.nels@gmail.com, xi.wang@gmail.com, shuah@kernel.org, rgbi3307@gmail.com, guoren@kernel.org, bpf@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 bpf-next 1/3] riscv: bpf: Add BPF private stack support Date: Wed, 4 Nov 2026 18:04:09 +0800 Message-ID: <20261104100411.997-2-cp0613@linux.alibaba.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261104100411.997-1-cp0613@linux.alibaba.com> References: <20261104100411.997-1-cp0613@linux.alibaba.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A program on a private stack keeps its BPF frames in a per-CPU area of its own rather than on the kernel stack of whichever context entered it. bpf_enable_priv_stack() grants that mode only once the JIT reports bpf_jit_supports_private_stack(), which riscv64 did not: programs there always ran on the kernel stack, and a struct_ops program that requires one was rejected with -EACCES. Allocate a per-CPU area of the verifier calculated depth plus a 16 byte guard region at each end, and point BPF_REG_FP (S5) at the top of it while leaving SP on the kernel stack. Every BPF stack access already goes through S5, and S5 is callee-saved with each subprog deriving its own, so nothing else in the JIT has to know about the private stack. The outgoing stack argument area stays in the kernel frame: callers write it relative to SP, callees relative to RV_REG_FP, which the prologue sets to the caller's SP. The per-CPU lookup is emitted after the tail call entry point: a program using a private stack can still be entered as a tail call target, and RV_TAILCALL_OFFSET is a constant added to the target's bpf_func, so what is in front of it must be the same size in every program. The base is materialized with absolute moves, as on arm64, x86-64 and powerpc64: the vmalloc'd per-CPU area is beyond an auipc pair from the JIT region, and riscv64 has no register holding the per-CPU offset, so the address of __per_cpu_offset is loaded too. emit_imm() is a choice there, not a requirement; emit_addr() as used by insn_is_mov_percpu_addr() would need an extra_pass argument and an error return in bpf_jit_build_prologue(), touching bpf_jit_comp32.c too. Both constants are fixed before the offset convergence loop, so the prologue length is stable across passes. The guard value follows arm64, x86-64 and powerpc64, and the 16 byte two-copy region at each end follows arm64 and powerpc64, since x86-64 uses an 8 byte guard with a single copy. A jited program has them checked when it is freed, reporting the first corrupted CPU only; failure paths release the area unchecked since the image never ran, which also clears priv_stack_ptr for the later bpf_jit_free(). RV32 does not declare support and keeps the existing kernel stack behaviour. Signed-off-by: Chen Pei --- arch/riscv/net/bpf_jit.h | 1 + arch/riscv/net/bpf_jit_comp64.c | 42 +++++++++++++++-- arch/riscv/net/bpf_jit_core.c | 84 +++++++++++++++++++++++++++++---- 3 files changed, 115 insertions(+), 12 deletions(-) diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h index 21a190a6a6d9..efab2b6803e4 100644 --- a/arch/riscv/net/bpf_jit.h +++ b/arch/riscv/net/bpf_jit.h @@ -14,6 +14,7 @@ #define RV_MAX_REG_ARGS 8 #define RV_EXTRA_STK_ARGS (RV_MAX_REG_ARGS - MAX_BPF_FUNC_REG_ARGS) +#define PRIV_STACK_GUARD_SZ 16 /* verify runtime detection extension status */ #define rv_ext_enabled(ext) \ diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 371405598faa..a7a7d2f9da85 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -2134,12 +2134,34 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, return 0; } +static void emit_priv_stack_frame(struct rv_jit_context *ctx) +{ + u64 fp = (__force u64)ctx->prog->aux->priv_stack_ptr + PRIV_STACK_GUARD_SZ; + + fp += round_up(ctx->prog->aux->stack_depth, STACK_ALIGN); + emit_imm(RV_REG_S5, fp, ctx); +#ifdef CONFIG_SMP + emit_lw(RV_REG_T1, offsetof(struct thread_info, cpu), RV_REG_TP, ctx); + emit_imm(RV_REG_T2, (u64)__per_cpu_offset, ctx); + emit_sh3add(RV_REG_T1, RV_REG_T1, RV_REG_T2, ctx); + emit_ld(RV_REG_T1, 0, RV_REG_T1, ctx); + emit_add(RV_REG_S5, RV_REG_S5, RV_REG_T1, ctx); +#endif +} + void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog) { + bool priv_stack = ctx->prog->aux->priv_stack_ptr; int i, stack_adjust = 0, store_offset, bpf_stack_adjust = ctx->stack_arg_sz; - bpf_stack_adjust += round_up(ctx->prog->aux->stack_depth, STACK_ALIGN); - if (bpf_stack_adjust) + /* + * With a private stack only the outgoing stack argument area is left in + * this frame. It has to stay: the caller writes it relative to SP while + * the callee reads it relative to RV_REG_FP, the caller's SP set below. + */ + if (!priv_stack) + bpf_stack_adjust += round_up(ctx->prog->aux->stack_depth, STACK_ALIGN); + if (bpf_stack_adjust || priv_stack) mark_fp(ctx); if (seen_reg(RV_REG_RA, ctx)) @@ -2217,7 +2239,16 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx, bool is_subprog) emit_addi(RV_REG_FP, RV_REG_SP, stack_adjust, ctx); - if (bpf_stack_adjust) + /* + * Point BPF_REG_FP at the top of this CPU's private stack. A program + * with one can still be entered as a tail call target, at + * RV_TAILCALL_OFFSET, so this has to come after that entry point; the + * offset is a constant added to the target's bpf_func, so everything in + * front of it must also be the same size in every program. + */ + if (priv_stack) + emit_priv_stack_frame(ctx); + else if (bpf_stack_adjust) emit_addi(RV_REG_S5, RV_REG_SP, bpf_stack_adjust, ctx); ctx->stack_size = stack_adjust; @@ -2320,3 +2351,8 @@ bool bpf_jit_supports_hmul(void) { return true; } + +bool bpf_jit_supports_private_stack(void) +{ + return true; +} diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c index f2497ec7d378..f2021088e447 100644 --- a/arch/riscv/net/bpf_jit_core.c +++ b/arch/riscv/net/bpf_jit_core.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include "bpf_jit.h" @@ -44,6 +45,62 @@ bool bpf_jit_needs_zext(void) return true; } +#define PRIV_STACK_GUARD_VAL 0xEB9F12345678eb9fULL + +static u32 priv_stack_size(struct bpf_prog *prog) +{ + return round_up(prog->aux->stack_depth, STACK_ALIGN) + + 2 * PRIV_STACK_GUARD_SZ; +} + +static int alloc_priv_stack(struct bpf_prog *prog) +{ + u32 size = priv_stack_size(prog); + u32 end = (size - PRIV_STACK_GUARD_SZ) / sizeof(u64); + void __percpu *ptr; + int cpu, i; + + ptr = __alloc_percpu_gfp(size, STACK_ALIGN, GFP_KERNEL); + if (!ptr) + return -ENOMEM; + + for_each_possible_cpu(cpu) { + u64 *stack = per_cpu_ptr(ptr, cpu); + + for (i = 0; i < PRIV_STACK_GUARD_SZ / sizeof(u64); i++) { + stack[i] = PRIV_STACK_GUARD_VAL; + stack[end + i] = PRIV_STACK_GUARD_VAL; + } + } + prog->aux->priv_stack_ptr = ptr; + return 0; +} + +static void priv_stack_check_guard(struct bpf_prog *prog) +{ + u32 end = (priv_stack_size(prog) - PRIV_STACK_GUARD_SZ) / sizeof(u64); + int cpu; + + for_each_possible_cpu(cpu) { + u64 *stack = per_cpu_ptr(prog->aux->priv_stack_ptr, cpu); + + if (stack[0] != PRIV_STACK_GUARD_VAL || + stack[1] != PRIV_STACK_GUARD_VAL || + stack[end] != PRIV_STACK_GUARD_VAL || + stack[end + 1] != PRIV_STACK_GUARD_VAL) { + pr_err("bpf-jit: private stack overflow/underflow guard of prog %s corrupted on CPU %d\n", + bpf_jit_get_prog_name(prog), cpu); + return; + } + } +} + +static void free_priv_stack(struct bpf_prog *prog) +{ + free_percpu(prog->aux->priv_stack_ptr); + prog->aux->priv_stack_ptr = NULL; +} + struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_prog *prog) { unsigned int prog_size = 0, extable_size = 0; @@ -84,12 +141,15 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr round_up((stack_arg_cnt - RV_EXTRA_STK_ARGS) * 8, STACK_ALIGN) : 0; ctx->prog = prog; + if (prog->aux->jits_use_priv_stack && alloc_priv_stack(prog)) + goto out_free_hdr; + ctx->offset = kvzalloc_objs(int, prog->len); if (!ctx->offset) - goto out_offset; + goto out_free_hdr; if (build_body(ctx, extra_pass, NULL)) - goto out_offset; + goto out_free_hdr; for (i = 0; i < prog->len; i++) { prev_ninsns += 32; @@ -104,7 +164,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr ctx->prologue_len = ctx->ninsns; if (build_body(ctx, extra_pass, ctx->offset)) - goto out_offset; + goto out_free_hdr; ctx->epilogue_offset = ctx->ninsns; bpf_jit_build_epilogue(ctx); @@ -124,7 +184,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr bpf_fill_ill_insns, bpf_prog_was_classic(prog)); if (!jit_data->ro_header) - goto out_offset; + goto out_free_hdr; /* * Use the image(RW) for writing the JITed instructions. But also save @@ -190,10 +250,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr ctx->offset[i] = ctx->offset[i - 1]; ctx->offset[0] = ninsns_rvoff(ctx->prologue_len); bpf_prog_update_insn_ptrs(prog, ctx->offset, jit_data->ro_image); -out_offset: - kvfree(ctx->offset); - kfree(jit_data); - prog->aux->jit_data = NULL; + goto out_free_ctx; } return prog; @@ -209,7 +266,12 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr sizeof(jit_data->header->size)); bpf_jit_binary_pack_free(jit_data->ro_header, jit_data->header); } - goto out_offset; + free_priv_stack(prog); +out_free_ctx: + kvfree(ctx->offset); + kfree(jit_data); + prog->aux->jit_data = NULL; + return prog; } u64 bpf_jit_alloc_exec_limit(void) @@ -261,6 +323,10 @@ void bpf_jit_free(struct bpf_prog *prog) prog->bpf_func = (void *)prog->bpf_func - cfi_get_offset(); hdr = bpf_jit_binary_pack_hdr(prog); bpf_jit_binary_pack_free(hdr, NULL); + if (prog->aux->priv_stack_ptr) { + priv_stack_check_guard(prog); + free_priv_stack(prog); + } WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); } -- 2.50.1