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    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
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