Messages in this thread | | | From | Alexei Starovoitov <> | Date | Fri, 29 Mar 2024 14:26:38 -0700 | Subject | Re: [PATCH RESEND bpf 1/2] x86/bpf: Fix IP after emitting call depth accounting |
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On Fri, Mar 29, 2024 at 2:49 AM Uros Bizjak <ubizjak@gmail.com> wrote: > > From: Joan Bruguera Micó <joanbrugueram@gmail.com> > > Adjust the IP passed to `emit_patch` so it calculates the correct offset > for the CALL instruction if `x86_call_depth_emit_accounting` emits code. > Otherwise we will skip some instructions and most likely crash. > > Fixes: b2e9dfe54be4 ("x86/bpf: Emit call depth accounting if required") > Link: https://lore.kernel.org/lkml/20230105214922.250473-1-joanbrugueram@gmail.com/ > Signed-off-by: Joan Bruguera Micó <joanbrugueram@gmail.com> > Cc: Alexei Starovoitov <ast@kernel.org> > Cc: Daniel Borkmann <daniel@iogearbox.net> > --- > arch/x86/net/bpf_jit_comp.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index a7ba8e178645..09f7dc9d4d65 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -479,9 +479,10 @@ static int emit_call(u8 **pprog, void *func, void *ip) > > static int emit_rsb_call(u8 **pprog, void *func, void *ip) > { > + void *adjusted_ip; > OPTIMIZER_HIDE_VAR(func); > - x86_call_depth_emit_accounting(pprog, func); > - return emit_patch(pprog, func, ip, 0xE8); > + adjusted_ip = ip + x86_call_depth_emit_accounting(pprog, func);
Why not just ip += x86_call_depth_emit_accounting(pprog, func);
?
> + return emit_patch(pprog, func, adjusted_ip, 0xE8); > } > > static int emit_jump(u8 **pprog, void *func, void *ip) > -- > 2.44.0 >
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