From: Eric Dumazet <eric.dumazet@gmail.com>
To: Alexei Starovoitov <ast@kernel.org>, davem@davemloft.net
Cc: daniel@iogearbox.net, edumazet@google.com,
netdev@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH bpf] bpf: fix 32-bit divide by zero
Date: Thu, 18 Jan 2018 14:30:54 -0800 [thread overview]
Message-ID: <1516314654.3606.28.camel@gmail.com> (raw)
In-Reply-To: <20180113025952.3451758-1-ast@kernel.org>
On Fri, 2018-01-12 at 18:59 -0800, Alexei Starovoitov wrote:
> due to some JITs doing if (src_reg == 0) check in 64-bit mode
> for div/mod opreations mask upper 32-bits of src register
> before doing the check
>
Is the plan to fix JIT, and if they can all be fixed,
revert this patch ?
x86 patch would be something like :
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 87f214fbe66ec163d24b12b6defc7edab612ecc9..91e4ab69573e09f793eb1c1e29d1b5ffad1d5dc7 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -548,8 +548,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
if (BPF_SRC(insn->code) == BPF_X) {
/* if (src_reg == 0) return 0 */
- /* cmp r11, 0 */
- EMIT4(0x49, 0x83, 0xFB, 0x00);
+ if (BPF_CLASS(insn->code) == BPF_ALU64) {
+ /* cmp r11, 0 */
+ EMIT4(0x49, 0x83, 0xFB, 0x00);
+ } else {
+ /* cmp r11d, 0 */
+ EMIT4(0x41, 0x83, 0xFB, 0x00);
+ }
/* jne .+9 (skip over pop, pop, xor and jmp) */
EMIT2(X86_JNE, 1 + 1 + 2 + 5);
next prev parent reply other threads:[~2018-01-18 22:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-13 2:59 [PATCH bpf] bpf: fix 32-bit divide by zero Alexei Starovoitov
2018-01-13 16:45 ` Alexei Starovoitov
2018-01-14 22:06 ` Daniel Borkmann
2018-01-18 22:30 ` Eric Dumazet [this message]
2018-01-18 22:40 ` Alexei Starovoitov
2018-01-18 23:33 ` Daniel Borkmann
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