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 626242EB10 for ; Mon, 27 Apr 2026 23:48:21 +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=1777333701; cv=none; b=U1jJjdZsBMyMmT+3ruJeHcPuc4XqLPdceKfjuhMXo3nhSu9aSEX4SFSJellQOJv7FkKtjjpuRRwg57h05sDlMzpYki3cCyaEcvfQveLB0nAsRr0LAJ7WtYW//EluX3mmPvcwWZ6OBir/kESbpm/og7ZRPTusWCp4f3fmEeriKVQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777333701; c=relaxed/simple; bh=vsvwuCoF2qRVwoN3GQCRv66dkn3pQGOzLIdgVu0E57s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=J3J+Zezo+o5o9NTXLNiFLJjoK6HibW4fUuktIg+qZt4gOJmcGVizjbnLovkGHDIxPsyy3UqQY9VW5+Uu6BQ6JSjxePuaSlqUIHnHy74IbtTruF1VY0HU9lcBLyCkC1+jvPEV8WzqAHOAjrzwUgpH+eOtWb1XDTvq/nTQL7waqNk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bVhWOkm8; 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="bVhWOkm8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7A77C19425; Mon, 27 Apr 2026 23:48:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777333701; bh=vsvwuCoF2qRVwoN3GQCRv66dkn3pQGOzLIdgVu0E57s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bVhWOkm8175KAHmeQMvKicDth5WgSaRvRKLDv4wzertQ8CM1FFHwtVeR0tqXgHdDN YUmCBq/zknAiILmvfvW6MENHDJVq7orBZDyTINfKY6i2f5TumOTzgNjlOzWtOibQD4 KXV0YGlqNEINrCShLANpMQZe0W4yB5xT4GFUEk+Vu25ghbavyuHCHKURJ5iLG5SG7V flPuRkJ/pllVPPNQuo8S6Q0XFINXC8o0xP7KHSVWuLu8cUabVIyheZjzAFmXeVb/aZ tcuwtoe3aGjiXQhSPhcL32ttKYv2mgyFeUUbl2YVuys4ZNbGuK1c5PVXwA9TXXOQ88 JwzDtgIVqul9A== From: Puranjay Mohan To: bpf@vger.kernel.org, "Yonghong Song" Cc: Puranjay Mohan , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Martin KaFai Lau" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Song Liu" , "Xu Kuohai" , "Catalin Marinas" , "Will Deacon" , linux-arm-kernel@lists.infradead.org Subject: [PATCH bpf-next v2 1/3] bpf, arm64: Map BPF_REG_0 to x8 instead of x7 Date: Mon, 27 Apr 2026 16:47:58 -0700 Message-ID: <20260427234801.2104511-2-puranjay@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260427234801.2104511-1-puranjay@kernel.org> References: <20260427234801.2104511-1-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 Move the BPF return value register from x7 to x8, freeing x7 for use as an argument register. AAPCS64 designates x8 as the indirect result location register; it is caller-saved and not used for argument passing, making it a suitable home for BPF_REG_0. This is a prerequisite for stack argument support, which needs x5-x7 to pass arguments 6-8 to native kfuncs following the AAPCS64 calling convention. Signed-off-by: Yonghong Song Signed-off-by: Puranjay Mohan --- arch/arm64/net/bpf_jit_comp.c | 4 ++-- arch/arm64/net/bpf_timed_may_goto.S | 8 ++++---- .../testing/selftests/bpf/progs/verifier_jit_inline.c | 2 +- tools/testing/selftests/bpf/progs/verifier_ldsx.c | 6 +++--- .../selftests/bpf/progs/verifier_private_stack.c | 10 +++++----- 5 files changed, 15 insertions(+), 15 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 0816c40fc7af..085e650662e3 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -47,7 +47,7 @@ /* Map BPF registers to A64 registers */ static const int bpf2a64[] = { /* return value from in-kernel function, and exit value from eBPF */ - [BPF_REG_0] = A64_R(7), + [BPF_REG_0] = A64_R(8), /* arguments from eBPF program to in-kernel function */ [BPF_REG_1] = A64_R(0), [BPF_REG_2] = A64_R(1), @@ -1048,7 +1048,7 @@ static void build_epilogue(struct jit_ctx *ctx, bool was_classic) /* Restore FP/LR registers */ emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx); - /* Move the return value from bpf:r0 (aka x7) to x0 */ + /* Move the return value from bpf:r0 (aka x8) to x0 */ emit(A64_MOV(1, A64_R(0), r0), ctx); /* Authenticate lr */ diff --git a/arch/arm64/net/bpf_timed_may_goto.S b/arch/arm64/net/bpf_timed_may_goto.S index 894cfcd7b241..a9a802711a7f 100644 --- a/arch/arm64/net/bpf_timed_may_goto.S +++ b/arch/arm64/net/bpf_timed_may_goto.S @@ -8,8 +8,8 @@ SYM_FUNC_START(arch_bpf_timed_may_goto) stp x29, x30, [sp, #-64]! mov x29, sp - /* Save BPF registers R0 - R5 (x7, x0-x4)*/ - stp x7, x0, [sp, #16] + /* Save BPF registers R0 - R5 (x8, x0-x4)*/ + stp x8, x0, [sp, #16] stp x1, x2, [sp, #32] stp x3, x4, [sp, #48] @@ -28,8 +28,8 @@ SYM_FUNC_START(arch_bpf_timed_may_goto) /* BPF_REG_AX(x9) will be stored into count, so move return value to it. */ mov x9, x0 - /* Restore BPF registers R0 - R5 (x7, x0-x4) */ - ldp x7, x0, [sp, #16] + /* Restore BPF registers R0 - R5 (x8, x0-x4) */ + ldp x8, x0, [sp, #16] ldp x1, x2, [sp, #32] ldp x3, x4, [sp, #48] diff --git a/tools/testing/selftests/bpf/progs/verifier_jit_inline.c b/tools/testing/selftests/bpf/progs/verifier_jit_inline.c index 4ea254063646..885ff69a3a62 100644 --- a/tools/testing/selftests/bpf/progs/verifier_jit_inline.c +++ b/tools/testing/selftests/bpf/progs/verifier_jit_inline.c @@ -9,7 +9,7 @@ __success __retval(0) __arch_x86_64 __jited(" addq %gs:{{.*}}, %rax") __arch_arm64 -__jited(" mrs x7, SP_EL0") +__jited(" mrs x8, SP_EL0") int inline_bpf_get_current_task(void) { bpf_get_current_task(); diff --git a/tools/testing/selftests/bpf/progs/verifier_ldsx.c b/tools/testing/selftests/bpf/progs/verifier_ldsx.c index c8494b682c31..c814e82a7242 100644 --- a/tools/testing/selftests/bpf/progs/verifier_ldsx.c +++ b/tools/testing/selftests/bpf/progs/verifier_ldsx.c @@ -274,11 +274,11 @@ __jited("movslq 0x10(%rdi,%r12), %r15") __jited("movswq 0x18(%rdi,%r12), %r15") __jited("movsbq 0x20(%rdi,%r12), %r15") __arch_arm64 -__jited("add x11, x7, x28") +__jited("add x11, x8, x28") __jited("ldrsw x21, [x11, #0x10]") -__jited("add x11, x7, x28") +__jited("add x11, x8, x28") __jited("ldrsh x21, [x11, #0x18]") -__jited("add x11, x7, x28") +__jited("add x11, x8, x28") __jited("ldrsb x21, [x11, #0x20]") __jited("add x11, x0, x28") __jited("ldrsw x22, [x11, #0x10]") diff --git a/tools/testing/selftests/bpf/progs/verifier_private_stack.c b/tools/testing/selftests/bpf/progs/verifier_private_stack.c index 646e8ef82051..c5078face38d 100644 --- a/tools/testing/selftests/bpf/progs/verifier_private_stack.c +++ b/tools/testing/selftests/bpf/progs/verifier_private_stack.c @@ -170,12 +170,12 @@ __jited(" mrs x10, TPIDR_EL{{[0-1]}}") __jited(" add x27, x27, x10") __jited(" add x25, x27, {{.*}}") __jited(" bl 0x{{.*}}") -__jited(" mov x7, x0") +__jited(" mov x8, x0") __jited(" mov x0, #0x2a") __jited(" str x0, [x27]") __jited(" bl 0x{{.*}}") -__jited(" mov x7, x0") -__jited(" mov x7, #0x0") +__jited(" mov x8, x0") +__jited(" mov x8, #0x0") __jited(" ldp x25, x27, [sp], {{.*}}") __naked void private_stack_callback(void) { @@ -220,7 +220,7 @@ __jited(" mov x0, #0x2a") __jited(" str x0, [x27]") __jited(" mov x0, #0x0") __jited(" bl 0x{{.*}}") -__jited(" mov x7, x0") +__jited(" mov x8, x0") __jited(" ldp x27, x28, [sp], #0x10") int private_stack_exception_main_prog(void) { @@ -258,7 +258,7 @@ __jited(" add x25, x27, {{.*}}") __jited(" mov x0, #0x2a") __jited(" str x0, [x27]") __jited(" bl 0x{{.*}}") -__jited(" mov x7, x0") +__jited(" mov x8, x0") __jited(" ldp x27, x28, [sp], #0x10") int private_stack_exception_sub_prog(void) { -- 2.52.0