bpf, arm64: save 4 bytes in prologue when ebpf insns came from cbpf
We can trivially save 4 bytes in prologue for cBPF since tail calls can never be used from there. The register push/pop is pairwise, here, x25 (fp) and x26 (tcc), so no point in changing that, only reset to zero is not needed. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -185,7 +185,7 @@ static inline int epilogue_offset(const struct jit_ctx *ctx)
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/* Tail call offset to jump into */
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#define PROLOGUE_OFFSET 7
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static int build_prologue(struct jit_ctx *ctx)
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static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)
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{
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const struct bpf_prog *prog = ctx->prog;
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const u8 r6 = bpf2a64[BPF_REG_6];
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@ -232,14 +232,16 @@ static int build_prologue(struct jit_ctx *ctx)
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/* Set up BPF prog stack base register */
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emit(A64_MOV(1, fp, A64_SP), ctx);
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/* Initialize tail_call_cnt */
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emit(A64_MOVZ(1, tcc, 0, 0), ctx);
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if (!ebpf_from_cbpf) {
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/* Initialize tail_call_cnt */
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emit(A64_MOVZ(1, tcc, 0, 0), ctx);
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cur_offset = ctx->idx - idx0;
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if (cur_offset != PROLOGUE_OFFSET) {
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pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
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cur_offset, PROLOGUE_OFFSET);
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return -1;
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cur_offset = ctx->idx - idx0;
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if (cur_offset != PROLOGUE_OFFSET) {
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pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
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cur_offset, PROLOGUE_OFFSET);
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return -1;
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}
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}
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ctx->stack_size = STACK_ALIGN(prog->aux->stack_depth);
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@ -806,6 +808,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
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struct bpf_prog *tmp, *orig_prog = prog;
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struct bpf_binary_header *header;
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struct arm64_jit_data *jit_data;
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bool was_classic = bpf_prog_was_classic(prog);
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bool tmp_blinded = false;
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bool extra_pass = false;
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struct jit_ctx ctx;
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@ -860,7 +863,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
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goto out_off;
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}
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if (build_prologue(&ctx)) {
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if (build_prologue(&ctx, was_classic)) {
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prog = orig_prog;
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goto out_off;
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}
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@ -883,7 +886,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
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skip_init_ctx:
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ctx.idx = 0;
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build_prologue(&ctx);
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build_prologue(&ctx, was_classic);
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if (build_body(&ctx)) {
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bpf_jit_binary_free(header);
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