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@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

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 8ee9528d87955c6334b5e8c2afe5b1ad94441edf..8446848edddb839b6d8dfdef66587326705789cb 100644 (file)
--- 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;
        }