On Thu, 2008-01-17 at 20:36 -0500, H. Peter Anvin wrote:
> Roland McGrath wrote:
> > It's indeed true that &pt_regs is truly the esp value for x86-32
> > kernel-mode trap frames. Because this nonobvious calculation is
> > only right for a kernel mode pt_regs and not for a user-mode one,
> > I think it would be better to use a name for the inline/macro that
> > makes this quite clear, rather than one so generic as "stack_addr".
>
> Indeed. This was certainly highly nonobvious in the current code.
>
What do you think of:
/*
* (unsigned long)regs looks strange, but it's correct for x86_32. x86_32 CPUs
* don't save the ss and esp registers if the CPU is already in kernel mode
* when it traps. So ®s happens to be esp. Valid only for kernel-mode
* pt_regs.
*/
static inline unsigned long stack_pointer(struct pt_regs *regs)
{
#ifdef CONFIG_X86_32
return (unsigned long)regs;
#else
return regs->sp;
#endif
}
Harvey
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