Re: How should nano_sleep be fixed (was: ptrace(), fork(), sleep(), exit(), SIGCHLD)

[george anzinger <george@mvista.com>]

Russell King wrote:
> 
> On Thu, Aug 16, 2001 at 06:00:10PM +0200, christophe barbé wrote:
> > Le jeu, 16 aoû 2001 12:29:05, Russell King a écrit :
> > > Note also that this is bogus as an architecture invariant.
> > >
> > > On ARM, we have to pass a pt_regs pointer into any function that requires
> > > it.
> >
> > I'm not sure to understand your point.
> 
> Its quite simple:
> 
> int sys_foo(struct pt_regs regs)
> {
> }
> 
> does not reveal the user space registers on ARM.  It instead reveals crap.
> Why?  The ARM procedure call standard specifies that the first 4 words
> of "regs" in this case are in 4 processor registers.  The other words
> are on the stack immediately above the frame created by foo.  This is
> not how the stack is layed out on ARM on entry to a sys_* function
> due to the requirement for these to be restartable.
> 
> Instead, we must pass a pointer thusly:
> 
> int sys_foo(struct pt_regs *regs)
> {
> }
> 
> and the pointer is specifically setup and passed in by a very small
> assembler wrapper.
> 
> > The first sentence tell me that the "struct pt_regs ..." line is x86
> > specific and this was the reason behind my proposition to not add a _signal
> > macro but a  _sys_nanosleep macro to include this too.
> 
> Correct.  But the act of getting "struct pt_regs" on entry to the function
> is also architecture specific.
> 
> > The second sentence seem's to indicate that this is a classic problem for
> > the ARM port. So if this is correct what is the best way to solve it ?
> 
> It used to be with such functions as sys_execve.  Then, sys_execve
> became an architecture specific wrapper around do_execve (not by my
> hand), so I guess that its not an ARM specific problem.
> 
> --
So, it seems we need an arch. specific wrapper for nano_sleep.  Now, how
to do it so it is a smooth transition?

George