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bpf, arm64: Emit A64_{ADD,SUB}_I when possible in emit_{lse,ll_sc}_atomic()

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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@huaweicloud.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/bpf/9ad3034a62361d91a99af24efa03f48c4c9e13ea.1735868489.git.yepeilin@google.com
This commit is contained in:
Peilin Ye 2025-01-03 02:04:18 +00:00 • committed by Daniel Borkmann
parent 66bb58ac06
commit 8c21f88407
1 changed files with 4 additions and 8 deletions
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12
arch/arm64/net/bpf_jit_comp.c
View file

@ -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;
}