Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)

H. Peter Anvin
2011-08-23T01:19:11Z

On 08/22/2011 06:16 PM, Andrew Lutomirski wrote:
>
> I suspect that very few things care whether syscall arguments get
> clobbered. The only way it would matter is if gcc reuses the argument
> in the ecx slot after an inlined syscall later in the same function.
> Any code that does that is already wrong if the syscall restarts with
> changed ecx or if something like UML changes the syscall argument.
>

No, the glibc wrapper for the system call Al was looking at used %ecx to
hold a copy of the PIC pointer (normally %ebx)!

-hpa