On 04/12/09 8:21 -0800, Dave Hansen wrote:
> 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?
Looks ok :)
Thanks,
Louis
>
> 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
>
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
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