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x86: bpf_jit: support negative offsets

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Commit a998d43423 claimed to introduce negative offset support to x86 jit,
but it couldn't be working, since at the time of the execution
of LD+ABS or LD+IND instructions via call into
bpf_internal_load_pointer_neg_helper() the %edx (3rd argument of this func)
had junk value instead of access size in bytes (1 or 2 or 4).

Store size into %edx instead of %ecx (what original commit intended to do)

Fixes: a998d43423 ("bpf jit: Let the x86 jit handle negative offsets")
Signed-off-by: Alexei Starovoitov <[email protected]>
Cc: Jan Seiffert <[email protected]>
Cc: Eric Dumazet <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Alexei Starovoitov authored and David S. Miller committed 2014-03-11 23:25:22 -04:00
1 parent 20a599bec9
commit fdfaf64e75
1 file changed
+1 -1
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arch/x86/net/bpf_jit.S
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@@ -140,7 +140,7 @@ bpf_slow_path_byte_msh:
push %r9; \
push SKBDATA; \
/* rsi already has offset */ \
mov $SIZE,%ecx; /* size */ \
mov $SIZE,%edx; /* size */ \
call bpf_internal_load_pointer_neg_helper; \
test %rax,%rax; \
pop SKBDATA; \