On Fri, 2009-12-04 at 17:08 +0100, Louis Rilling wrote:
> On 04/12/09 8:05 -0800, Dave Hansen wrote:
> > > syscall also destroys r11, so it should be added to the clobber list.
> >
> > Even though it is a ptregscall?
>
> The assembly instruction itself destroys r11 (same for rcx).
Thanks again for the help, Louis. How does this look?
int clone_with_pids(long flags_low, struct clone_args *clone_args, long args_size,
int *pids)
{
long retval;
__asm__ __volatile__(
"movq %5, %%r10\n\t" /* pids in r10*/
"syscall\n\t" /* Linux/x86_64 system call */
"testq %0,%0\n\t" /* check return value */
"jne 1f\n\t" /* jump if parent */
"popq %%rax\n\t" /* get subthread function */
"popq %%rdi\n\t" /* get the subthread function arg */
"call *%%rax\n\t" /* start subthread function */
"movq %6,%0\n\t"
"syscall\n" /* exit system call: exit subthread */
"1:\n\t"
:"=a" (retval)
:"0" (__NR_clone3),/* eax */
"D" (flags_low), /* rdi */
"S" (clone_args), /* rsi */
"d" (args_size), /* rdx */
"m" (pids), /* gets moved to r10 */
"i" (__NR_exit)
:"rcx", "r10", "r11", "cc"
);
/*
* glibc lists 'cc' as clobbered, so we might as
* well do it too. 'r11' and 'rcx' are clobbered
* by the 'syscall' instruction itself. 'r8' and
* 'r9' are clobbered by the clone, but that
* thread will exit before getting back out to C.
*/
if (retval < 0) {
errno = -retval;
retval = -1;
}
return retval;
}
> Thanks,
>
> Louis
>
-- Dave
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