linux-kernel - [PATCH bpf-next v2 3/3] bpf, arm64: Emit A64_{ADD,SUB}_I when possible in emit_{lse,ll_sc}

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <9ad3034a62361d91a99af24efa03f48c4c9e13ea.1735868489.git.yepeilin@google.com>
Date: Fri,  3 Jan 2025 02:04:18 +0000
From: Peilin Ye <yepeilin@...gle.com>
To: bpf@...r.kernel.org
Cc: Peilin Ye <yepeilin@...gle.com>, Xu Kuohai <xukuohai@...weicloud.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Puranjay Mohan <puranjay@...nel.org>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Josh Don <joshdon@...gle.com>, 
	Barret Rhoden <brho@...gle.com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 3/3] bpf, arm64: Emit A64_{ADD,SUB}_I when
 possible in emit_{lse,ll_sc}_atomic()

Currently in emit_{lse,ll_sc}_atomic(), if there is an offset, we add it
to the base address by doing e.g.:

  if (off) {
          emit_a64_mov_i(1, tmp, off, ctx);
          emit(A64_ADD(1, tmp, tmp, dst), ctx);
  ...

As pointed out by Xu, we can use emit_a64_add_i() (added in the previous
patch) instead, which tries to combine the above into a single A64_ADD_I
or A64_SUB_I when possible.

Suggested-by: Xu Kuohai <xukuohai@...weicloud.com>
Signed-off-by: Peilin Ye <yepeilin@...gle.com>
---
change in v2:
  * move the logic into a helper (added in v2 2/3) and use it (Xu)

v1: https://lore.kernel.org/bpf/953c7241e82496cb7a8b5a8724028ad646cd0896.1735342016.git.yepeilin@google.com/

 arch/arm64/net/bpf_jit_comp.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 8ee9528d8795..8446848edddb 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -662,8 +662,7 @@ static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	u8 reg = dst;
 
 	if (off) {
-		emit_a64_mov_i(1, tmp, off, ctx);
-		emit(A64_ADD(1, tmp, tmp, dst), ctx);
+		emit_a64_add_i(1, tmp, reg, tmp, off, ctx);
 		reg = tmp;
 	}
 	if (arena) {
@@ -734,7 +733,7 @@ static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	const s32 imm = insn->imm;
 	const s16 off = insn->off;
 	const bool isdw = BPF_SIZE(code) == BPF_DW;
-	u8 reg;
+	u8 reg = dst;
 	s32 jmp_offset;
 
 	if (BPF_MODE(code) == BPF_PROBE_ATOMIC) {
@@ -743,11 +742,8 @@ static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
 		return -EINVAL;
 	}
 
-	if (!off) {
-		reg = dst;
-	} else {
-		emit_a64_mov_i(1, tmp, off, ctx);
-		emit(A64_ADD(1, tmp, tmp, dst), ctx);
+	if (off) {
+		emit_a64_add_i(1, tmp, reg, tmp, off, ctx);
 		reg = tmp;
 	}
 
-- 
2.47.1.613.gc27f4b7a9f-goog