Jamie Lokier wrote:
>
> No, your "real" code sequence is wrong.
>
> %ebx/%edi/%esi are preserved across sysenter/sysexit, whereas
> %ecx/%edx are call-clobbered registers in the i386 function call ABI.
>
> This is not a coincidence.
>
> So, getpid looks like this with the _smaller_ vsyscall code:
>
> getpid():
> movl $__NR_getpid,%eax
> call *%gs:0x18
> ret
... or just...
getpid:
movl $__NR_getpid, %eax
jmp *%gs:0x18
This doesn't mess up the call/return stack, even, because the ret in the
stub matches the call to getpid.
-hpa
-
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This archive was generated by hypermail 2b29 : Mon Dec 23 2002 - 22:00:28 EST