[RFC][v6][PATCH 8/9]: Define clone_with_pids() syscall

Arnd Bergmann arnd at arndb.de
Fri Sep 11 03:31:29 PDT 2009


On Thursday 10 September 2009, Sukadev Bhattiprolu wrote:
> Since this is a variant of clone() and clone is listed as a PTREGSCALL(),
> I pass in the pt_regs.
> 
> arch/x86/kernel/entry_32.S lists clone() under this comment:
> 
> /*
>  * System calls that need a pt_regs pointer.
>  */
> 
> Is there a guideline on what system calls use/need pt_regs ?

You need pt_regs if you access any registers from the user task
other than the argument registers. In case of clone(), this is
the user stack pointer.

The user_stack_pointer() function is relatively new, before this
you couldn't get the stack pointer out of pt_regs in a generic
way.

	Arnd <><


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