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Message-Id: <20180514212234.2661-8-daniel@iogearbox.net>
Date: Mon, 14 May 2018 23:22:33 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: alexei.starovoitov@...il.com
Cc: netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf-next v2 7/8] 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@...earbox.net>
---
arch/arm64/net/bpf_jit_comp.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index c8a2620..a6fdaea 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -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];
@@ -232,14 +232,16 @@ static int build_prologue(struct jit_ctx *ctx)
/* Set up BPF prog stack base register */
emit(A64_MOV(1, fp, A64_SP), ctx);
- /* Initialize tail_call_cnt */
- emit(A64_MOVZ(1, tcc, 0, 0), ctx);
+ if (!ebpf_from_cbpf) {
+ /* Initialize tail_call_cnt */
+ emit(A64_MOVZ(1, tcc, 0, 0), ctx);
- cur_offset = ctx->idx - idx0;
- if (cur_offset != PROLOGUE_OFFSET) {
- pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
- cur_offset, PROLOGUE_OFFSET);
- return -1;
+ cur_offset = ctx->idx - idx0;
+ if (cur_offset != PROLOGUE_OFFSET) {
+ pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
+ 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);
--
2.9.5
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