| Message ID | 1417595881-32218-1-git-send-email-zlim.lnx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Dec 3, 2014 at 12:38 AM, Zi Shen Lim <zlim.lnx@gmail.com> wrote: > 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") > Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com> yours is cleaner than my own attempt to fix it. Thanks! Acked-by: Alexei Starovoitov <ast@plumgrid.com>
On Wed, Dec 03, 2014 at 03:54:32PM +0000, Alexei Starovoitov wrote: > On Wed, Dec 3, 2014 at 12:38 AM, Zi Shen Lim <zlim.lnx@gmail.com> wrote: > > 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") > > Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com> > > yours is cleaner than my own attempt to fix it. > Thanks! > Acked-by: Alexei Starovoitov <ast@plumgrid.com> Cheers, I've applied this for 3.19. Will
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 41f1e3e..edba042 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;