lkml.org 
[lkml]   [2001]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: How should nano_sleep be fixed (was: ptrace(), fork(), sleep(), exit(), SIGCHLD)
george anzinger wrote:
>
> 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?
>
How about something like:

In ../asm/signal.h (for i386)

#define PT_REGS_ENTRY(type,name,p1_type,p1, p2_type,p2) \
type name(p1_type p1,p2_typ p2)\
{ struct pt_regs *regs = (struct pt_regs *)&p1;
#define _do_signal() do_signal(regs, NULL)

in ../asm_arm/signal.h

#define PT_REGS_ENTRY(type,name,p1_type,p1, p2_type,p2) \
type name(p1_type p1,p2_typ p2, struct pt_regs *regs) \
{
#define _do_signal() do_signal(NULL,regs, NULL)

and other archs as needed.

in ../linux/signal.h (the default)

:
#include <asm/signal.h>

:
:
#ifndef PT_REGS_ENTRY
#define PT_REGS_ENTRY(type,name,p1_type,p1, p2_type,p2) \
type name(p1_type p1,p2_typ p2)\
{
#define _do_signal() 1
#endif
and finally in nano_sleep :

PT_REGS_ENTRY(asmlinkage long,sys_nanosleep,struct timespec
*,rqtp,struct timespec *,rmtp)

struct timespec t;
unsigned long expire;
:
: etc...

:
do {
current->state = TASK_INTERRUPTIBLE;
} while((expire = schedule_timeout(expire)) && !_do_signal());


The notion is that this could be used for other system calls, in
particular I want to implement clock_nanosleep() as part of the extended
POSIX standard.

Comments, flames,...

George
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:57    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site