From: Stanislav Fomichev <sdf@google.com>
To: netdev@vger.kernel.org, bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net,
Stanislav Fomichev <sdf@google.com>
Subject: [PATCH bpf] bpf: use NOP_ATOMIC5 instead of emit_nops(&prog, 5) for BPF_TRAMP_F_CALL_ORIG
Date: Fri, 19 Mar 2021 17:00:01 -0700 [thread overview]
Message-ID: <20210320000001.915366-1-sdf@google.com> (raw)
__bpf_arch_text_poke does rewrite only for atomic nop5, emit_nops(xxx, 5)
emits non-atomic one which breaks fentry/fexit with k8 atomics:
P6_NOP5 == P6_NOP5_ATOMIC (0f1f440000 == 0f1f440000)
K8_NOP5 != K8_NOP5_ATOMIC (6666906690 != 6666666690)
Can be reproduced by doing "ideal_nops = k8_nops" in "arch_init_ideal_nops()
and running fexit_bpf2bpf selftest.
Fixes: e21aa341785c ("bpf: Fix fexit trampoline.")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
arch/x86/net/bpf_jit_comp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 72b5a57e9e31..b35fc8023884 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2012,7 +2012,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
/* remember return value in a stack for bpf prog to access */
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
im->ip_after_call = prog;
- emit_nops(&prog, 5);
+ memcpy(prog, ideal_nops[NOP_ATOMIC5], X86_PATCH_SIZE);
+ prog += X86_PATCH_SIZE;
}
if (fmod_ret->nr_progs) {
--
2.31.0.rc2.261.g7f71774620-goog
next reply other threads:[~2021-03-20 0:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-20 0:00 Stanislav Fomichev [this message]
2021-03-20 0:14 ` [PATCH bpf] bpf: use NOP_ATOMIC5 instead of emit_nops(&prog, 5) for BPF_TRAMP_F_CALL_ORIG Alexei Starovoitov
2021-03-20 0:25 ` Stanislav Fomichev
2021-03-20 0:33 ` Alexei Starovoitov
2021-03-20 1:40 ` Stanislav Fomichev
2021-03-20 2:31 ` Alexei Starovoitov
2021-03-20 2:40 ` patchwork-bot+netdevbpf
2021-03-22 6:39 ` Yauheni Kaliuta
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