From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 05BBF32E151 for ; Mon, 20 Apr 2026 15:36:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776699406; cv=none; b=q0B6gTIqK1fM1DvTF6FoRY0Ygr0jEtXXlOJaucLly27cGmPE8Wm/zErDC86e6p0UVO+ToPSPEsk819ZvWplEB5cDxr8HXD9g1SulaWHmZ0ESXLlYWvKQNrIhIGTo4hL0oITGIy5XQWCqIU0a2NgEXsqMnpb/+n6Cve012UiRPHQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776699406; c=relaxed/simple; bh=KYqn5yIucKslmNtiYcNKrZTl4JOQmWQhcGJiCKBzhfY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kEhiYXokIz22lQy1xMI17f/17vtAzY0oTEH5UEMc3XiieYcVGeRR+bsZyGvz/hHRKgqqx7Zqu79nY678pP/MLeh3HC0Ux560veQ8C9VuKysHYT4FB0gIhPYlYuSTbRIMCB4n9Gkvh98NYH4kynWzOKQCSTeVwJ0OPiIG9Szr8aw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=N8O8LaNx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="N8O8LaNx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54838C19425; Mon, 20 Apr 2026 15:36:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776699405; bh=KYqn5yIucKslmNtiYcNKrZTl4JOQmWQhcGJiCKBzhfY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N8O8LaNx20Bh0ubqDSRpK45CsKTghQ0uwPD/jz4zk42RMLBwpnZywXG4QAIXrS0A4 6m2dFv9upDMRjgg1wJCj3dWMxA7kRIAWUhhx6m0PQ43S8IpZsnAmKjU7ENMdXiU8Hs 9J+muvEgZ7N57pnsUHT252JUKAlmzDlkQfME0Wc2UC302iC0kcxZPXDNO/8FPGBEo2 KBVXxx14F1FLXJ+3MRXzl03hd42KlyswM+lIWGpFH6PPoegTslnfGvJak9AiuCEHel 2PNXupmp6wYEznk6tDv39GI9B9df1SQXSaV6SrncbuSXO5kI811Y4V3TqtAYoi1qJc XAw+ZsiPuXatQ== From: Puranjay Mohan To: bpf@vger.kernel.org Cc: Puranjay Mohan , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Yonghong Song" , "Xu Kuohai" , "Catalin Marinas" , "Will Deacon" , linux-arm-kernel@lists.infradead.org Subject: [PATCH bpf-next 2/3] bpf, arm64: Add JIT support for stack arguments Date: Mon, 20 Apr 2026 08:36:00 -0700 Message-ID: <20260420153603.4097618-3-puranjay@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260420153603.4097618-1-puranjay@kernel.org> References: <20260420153603.4097618-1-puranjay@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Implement stack argument passing for BPF-to-BPF and kfunc calls with more than 5 parameters on arm64, following the AAPCS64 calling convention. BPF R1-R5 already map to x0-x4. With BPF_REG_0 moved to x8 by the previous commit, x5-x7 are free for arguments 6-8. Arguments 9-12 spill onto the stack at [SP+0], [SP+8], ... and the callee reads them from [FP+16], [FP+24], ... (above the saved FP/LR pair). BPF convention uses fixed offsets from BPF_REG_PARAMS (r11): off=-8 is always arg 6, off=-16 arg 7, etc. The verifier invalidates all outgoing stack arg slots after each call, so the compiler must re-store before every call. This means x5-x7 don't need to be saved on stack. Signed-off-by: Puranjay Mohan --- arch/arm64/net/bpf_jit_comp.c | 87 +++++++++++++++++++++++++++++++++-- 1 file changed, 83 insertions(+), 4 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 085e650662e3..7adf2b0f4610 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -86,6 +86,7 @@ struct jit_ctx { __le32 *image; __le32 *ro_image; u32 stack_size; + u16 stack_arg_size; u64 user_vm_start; u64 arena_vm_start; bool fp_used; @@ -533,13 +534,19 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) * | | * +-----+ <= (BPF_FP - prog->aux->stack_depth) * |RSVD | padding - * current A64_SP => +-----+ <= (BPF_FP - ctx->stack_size) + * +-----+ <= (BPF_FP - ctx->stack_size) + * | | + * | ... | outgoing stack args (9+, if any) + * | | + * current A64_SP => +-----+ * | | * | ... | Function call stack * | | * +-----+ * low * + * Stack args 6-8 are passed in x5-x7, args 9+ at [SP]. + * Incoming args 9+ are at [FP + 16], [FP + 24], ... */ emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx); @@ -613,6 +620,9 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); + if (ctx->stack_arg_size) + emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + if (ctx->arena_vm_start) emit_a64_mov_i64(arena_vm_base, ctx->arena_vm_start, ctx); @@ -673,6 +683,9 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) /* Update tail_call_cnt if the slot is populated. */ emit(A64_STR64I(tcc, ptr, 0), ctx); + if (ctx->stack_arg_size) + emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + /* restore SP */ if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); @@ -1034,6 +1047,9 @@ static void build_epilogue(struct jit_ctx *ctx, bool was_classic) const u8 r0 = bpf2a64[BPF_REG_0]; const u8 ptr = bpf2a64[TCCNT_PTR]; + if (ctx->stack_arg_size) + emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + /* We're done with BPF stack */ if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); @@ -1191,6 +1207,41 @@ static int add_exception_handler(const struct bpf_insn *insn, return 0; } +static const u8 stack_arg_reg[] = { A64_R(5), A64_R(6), A64_R(7) }; + +#define NR_STACK_ARG_REGS ARRAY_SIZE(stack_arg_reg) + +static void emit_stack_arg_load(u8 dst, s16 bpf_off, struct jit_ctx *ctx) +{ + int idx = bpf_off / sizeof(u64) - 1; + + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, dst, stack_arg_reg[idx]), ctx); + else + emit(A64_LDR64I(dst, A64_FP, (idx - NR_STACK_ARG_REGS) * sizeof(u64) + 16), ctx); +} + +static void emit_stack_arg_store(u8 src_a64, s16 bpf_off, struct jit_ctx *ctx) +{ + int idx = -bpf_off / sizeof(u64) - 1; + + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, stack_arg_reg[idx], src_a64), ctx); + else + emit(A64_STR64I(src_a64, A64_SP, (idx - NR_STACK_ARG_REGS) * sizeof(u64)), ctx); +} + +static void emit_stack_arg_store_imm(s32 imm, s16 bpf_off, const u8 tmp, struct jit_ctx *ctx) +{ + int idx = -bpf_off / sizeof(u64) - 1; + + emit_a64_mov_i(1, tmp, imm, ctx); + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, stack_arg_reg[idx], tmp), ctx); + else + emit(A64_STR64I(tmp, A64_SP, (idx - NR_STACK_ARG_REGS) * sizeof(u64)), ctx); +} + /* JITs an eBPF instruction. * Returns: * 0 - successfully JITed an 8-byte eBPF instruction. @@ -1646,6 +1697,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_B: case BPF_LDX | BPF_MEM | BPF_DW: + if (insn->src_reg == BPF_REG_PARAMS) { + emit_stack_arg_load(dst, off, ctx); + break; + } + fallthrough; case BPF_LDX | BPF_PROBE_MEM | BPF_DW: case BPF_LDX | BPF_PROBE_MEM | BPF_W: case BPF_LDX | BPF_PROBE_MEM | BPF_H: @@ -1671,7 +1727,7 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn } if (src == fp) { src_adj = ctx->priv_sp_used ? priv_sp : A64_SP; - off_adj = off + ctx->stack_size; + off_adj = off + ctx->stack_size + ctx->stack_arg_size; } else { src_adj = src; off_adj = off; @@ -1752,6 +1808,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_ST | BPF_MEM | BPF_H: case BPF_ST | BPF_MEM | BPF_B: case BPF_ST | BPF_MEM | BPF_DW: + if (insn->dst_reg == BPF_REG_PARAMS) { + emit_stack_arg_store_imm(imm, off, tmp, ctx); + break; + } + fallthrough; case BPF_ST | BPF_PROBE_MEM32 | BPF_B: case BPF_ST | BPF_PROBE_MEM32 | BPF_H: case BPF_ST | BPF_PROBE_MEM32 | BPF_W: @@ -1762,7 +1823,7 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn } if (dst == fp) { dst_adj = ctx->priv_sp_used ? priv_sp : A64_SP; - off_adj = off + ctx->stack_size; + off_adj = off + ctx->stack_size + ctx->stack_arg_size; } else { dst_adj = dst; off_adj = off; @@ -1814,6 +1875,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_STX | BPF_MEM | BPF_H: case BPF_STX | BPF_MEM | BPF_B: case BPF_STX | BPF_MEM | BPF_DW: + if (insn->dst_reg == BPF_REG_PARAMS) { + emit_stack_arg_store(src, off, ctx); + break; + } + fallthrough; case BPF_STX | BPF_PROBE_MEM32 | BPF_B: case BPF_STX | BPF_PROBE_MEM32 | BPF_H: case BPF_STX | BPF_PROBE_MEM32 | BPF_W: @@ -1824,7 +1890,7 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn } if (dst == fp) { dst_adj = ctx->priv_sp_used ? priv_sp : A64_SP; - off_adj = off + ctx->stack_size; + off_adj = off + ctx->stack_size + ctx->stack_arg_size; } else { dst_adj = dst; off_adj = off; @@ -2065,6 +2131,14 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr ctx.user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena); ctx.arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena); + if (prog->aux->stack_arg_depth > prog->aux->incoming_stack_arg_depth) { + u16 outgoing = prog->aux->stack_arg_depth - prog->aux->incoming_stack_arg_depth; + int nr_on_stack = outgoing / sizeof(u64) - NR_STACK_ARG_REGS; + + if (nr_on_stack > 0) + ctx.stack_arg_size = round_up(nr_on_stack * sizeof(u64), 16); + } + if (priv_stack_ptr) ctx.priv_sp_used = true; @@ -2229,6 +2303,11 @@ bool bpf_jit_supports_kfunc_call(void) return true; } +bool bpf_jit_supports_stack_args(void) +{ + return true; +} + void *bpf_arch_text_copy(void *dst, void *src, size_t len) { if (!aarch64_insn_copy(dst, src, len)) -- 2.52.0