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Peter Zijlstra
1cd5f059d9
Paolo reported that the instruction sequence that is used to replace:
call __static_call_return0
namely:
66 66 48 31 c0 data16 data16 xor %rax,%rax
decodes to something else on i386, namely:
66 66 48 data16 dec %ax
31 c0 xor %eax,%eax
Which is a nonsensical sequence that happens to have the same outcome.
*However* an important distinction is that it consists of 2
instructions which is a problem when the thing needs to be overwriten
with a regular call instruction again.
As such, replace the instruction with something that decodes the same
on both i386 and x86_64.
Fixes: 3f2a8fc4b1 ("static_call/x86: Add __static_call_return0()")
Reported-by: Paolo Bonzini <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]