diff options
| author | Zi Shen Lim <zlim.lnx@gmail.com> | 2014-12-03 08:38:01 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2014-12-03 18:04:09 +0000 |
| commit | 51c9fbb1b146f3336a93d398c439b6fbfe5ab489 (patch) | |
| tree | 2928e70795aaf5fba8d0263ac06b9205d42364d7 /arch/arm64/net | |
| parent | e4f88d833bec29b8e6fadc1b2488f0c6370935e1 (diff) | |
| download | linux-51c9fbb1b146f3336a93d398c439b6fbfe5ab489.tar.bz2 | |
arm64: bpf: lift restriction on last instruction
Earlier implementation assumed last instruction is BPF_EXIT.
Since this is no longer a restriction in eBPF, we remove this
limitation.
Per Alexei Starovoitov [1]:
> classic BPF has a restriction that last insn is always BPF_RET.
> eBPF doesn't have BPF_RET instruction and this restriction.
> It has BPF_EXIT insn which can appear anywhere in the program
> one or more times and it doesn't have to be last insn.
[1] https://lkml.org/lkml/2014/11/27/2
Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/net')
| -rw-r--r-- | arch/arm64/net/bpf_jit_comp.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 41f1e3e2ea24..edba042b2325 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -60,7 +60,7 @@ struct jit_ctx { const struct bpf_prog *prog; int idx; int tmp_used; - int body_offset; + int epilogue_offset; int *offset; u32 *image; }; @@ -130,8 +130,8 @@ static void jit_fill_hole(void *area, unsigned int size) static inline int epilogue_offset(const struct jit_ctx *ctx) { - int to = ctx->offset[ctx->prog->len - 1]; - int from = ctx->idx - ctx->body_offset; + int to = ctx->epilogue_offset; + int from = ctx->idx; return to - from; } @@ -463,6 +463,8 @@ emit_cond_jmp: } /* function return */ case BPF_JMP | BPF_EXIT: + /* Optimization: when last instruction is EXIT, + simply fallthrough to epilogue. */ if (i == ctx->prog->len - 1) break; jmp_offset = epilogue_offset(ctx); @@ -685,11 +687,13 @@ void bpf_int_jit_compile(struct bpf_prog *prog) /* 1. Initial fake pass to compute ctx->idx. */ - /* Fake pass to fill in ctx->offset. */ + /* Fake pass to fill in ctx->offset and ctx->tmp_used. */ if (build_body(&ctx)) goto out; build_prologue(&ctx); + + ctx.epilogue_offset = ctx.idx; build_epilogue(&ctx); /* Now we know the actual image size. */ @@ -706,7 +710,6 @@ void bpf_int_jit_compile(struct bpf_prog *prog) build_prologue(&ctx); - ctx.body_offset = ctx.idx; if (build_body(&ctx)) { bpf_jit_binary_free(header); goto out; |