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Commit 56ea6a8b authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

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: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 6d2eea6f

arch/arm64/net/bpf_jit_comp.c

+13 −10
Original line number Diff line number Diff line
@@ -185,7 +185,7 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) 
/* Tail call offset to jump into */

#define PROLOGUE_OFFSET 7



static int build_prologue(struct jit_ctx *ctx)

static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)

{

	const struct bpf_prog *prog = ctx->prog;

	const u8 r6 = bpf2a64[BPF_REG_6];
@@ -232,6 +232,7 @@ static int build_prologue(struct jit_ctx *ctx) 
	/* Set up BPF prog stack base register */

	emit(A64_MOV(1, fp, A64_SP), ctx);



	if (!ebpf_from_cbpf) {

		/* Initialize tail_call_cnt */

		emit(A64_MOVZ(1, tcc, 0, 0), ctx);
@@ -241,6 +242,7 @@ static int build_prologue(struct jit_ctx *ctx) 
				    cur_offset, PROLOGUE_OFFSET);

			return -1;

		}

	}



	ctx->stack_size = STACK_ALIGN(prog->aux->stack_depth);
@@ -806,6 +808,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
	struct bpf_prog *tmp, *orig_prog = prog;

	struct bpf_binary_header *header;

	struct arm64_jit_data *jit_data;

	bool was_classic = bpf_prog_was_classic(prog);

	bool tmp_blinded = false;

	bool extra_pass = false;

	struct jit_ctx ctx;
@@ -860,7 +863,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
		goto out_off;

	}



	if (build_prologue(&ctx)) {

	if (build_prologue(&ctx, was_classic)) {

		prog = orig_prog;

		goto out_off;

	}
@@ -883,7 +886,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) 
skip_init_ctx:

	ctx.idx = 0;



	build_prologue(&ctx);

	build_prologue(&ctx, was_classic);



	if (build_body(&ctx)) {

		bpf_jit_binary_free(header);