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bpf: Use NOP_ATOMIC5 instead of emit_nops(&prog, 5) for BPF_TRAMP_F_CALL_ORIG
author
Stanislav Fomichev
<sdf@google.com>
Sat, 20 Mar 2021 00:00:01 +0000
(17:00 -0700)
committer
Greg Kroah-Hartman
<gregkh@linuxfoundation.org>
Wed, 7 Apr 2021 13:00:14 +0000
(15:00 +0200)
commit
b9082970478009b778aa9b22d5561eef35b53b63
upstream.
__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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link:
https://lore.kernel.org/bpf/20210320000001.915366-1-sdf@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/x86/net/bpf_jit_comp.c
patch
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diff --git
a/arch/x86/net/bpf_jit_comp.c
b/arch/x86/net/bpf_jit_comp.c
index
652bd64
..
023ac12
100644
(file)
--- a/
arch/x86/net/bpf_jit_comp.c
+++ b/
arch/x86/net/bpf_jit_comp.c
@@
-1811,7
+1811,8
@@
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) {