Re: [PATCH bpf-next 12/13] bpf: arm64: add JIT support for multi-function programs
flat view
From: Alexei Starovoitov <hidden>
Date: 2017-12-18 17:56:00
Subsystem:
arm64 port (aarch64 architecture), bpf jit for arm64, bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Catalin Marinas, Will Deacon, Daniel Borkmann, Alexei Starovoitov, Puranjay Mohan, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
On 12/18/17 7:51 AM, Daniel Borkmann wrote:
On 12/18/2017 04:29 PM, Arnd Bergmann wrote:quoted
On Fri, Dec 15, 2017 at 2:55 AM, Alexei Starovoitov [off-list ref] wrote:quoted
+ if (jit_data->ctx.offset) { + ctx = jit_data->ctx; + image_ptr = jit_data->image; + header = jit_data->header; + extra_pass = true; + goto skip_init_ctx; + } memset(&ctx, 0, sizeof(ctx)); ctx.prog = prog;The 'goto' jumps over the 'image_size' initializationquoted
prog->bpf_func = (void *)ctx.image; prog->jited = 1; prog->jited_len = image_size;so we now get a warning here, starting with linux-next-20171218: arch/arm64/net/bpf_jit_comp.c: In function 'bpf_int_jit_compile': arch/arm64/net/bpf_jit_comp.c:982:18: error: 'image_size' may be used uninitialized in this function [-Werror=maybe-uninitialized] I could not figure out what the code should be doing instead, or if it is indeed safe and the warning is a false-positive.Good catch, it's buggy indeed. Fix like below is needed; I can submit it properly a bit later today:
good catch. My arm gcc 4.8.5 didn't warn about it. the following would be better fix:
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 396490cf7316..acaa935ed977 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c@@ -897,6 +897,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) image_ptr = jit_data->image; header = jit_data->header; extra_pass = true; + image_size = sizeof(u32) * ctx.idx; goto skip_init_ctx; } memset(&ctx, 0, sizeof(ctx));
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 396490c..a6fd585 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c@@ -855,6 +855,7 @@ static inline void bpf_flush_icache(void *start, void *end) struct arm64_jit_data { struct bpf_binary_header *header; u8 *image; + int image_size; struct jit_ctx ctx; };@@ -895,6 +896,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) if (jit_data->ctx.offset) { ctx = jit_data->ctx; image_ptr = jit_data->image; + image_size = jit_data->image_size; header = jit_data->header; extra_pass = true; goto skip_init_ctx;@@ -975,6 +977,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) } else { jit_data->ctx = ctx; jit_data->image = image_ptr; + jit_data->image_size = image_size; jit_data->header = header; } prog->bpf_func = (void *)ctx.image;