Re: [PATCH] compatibility syscall layer (lets try again)

[george anzinger <george@mvista.com>]

Stephen Rothwell wrote:
> 
> Hi Linus,
> 
> Below is the generic part of the start of the compatibility syscall layer.
> I think I have made it generic enough that each architecture can define
> what compatibility means.
> 
> To use this,an architecture must create asm/compat.h and provide typedefs
> for (currently) compat_time_t, compat_suseconds_t, struct compat_timespec.
> 
> Hopefully, this is what you had in mind - ohterwise back to the drawing
> board.
> 
> I will follow this posting with the architecture specific patches that I
> have done but not tested.

The standard for POSIX nano_sleep() says that it should not
return on a signal UNLESS the signal is delivered to the
user.  (I.e. not on SIGSTOP, SIGTRACE, etc. or any signal
that does not invoke a user handler.)  To do this sort of
thing the do_signal() function returns true in this case and
otherwise false.  The reason this is not in nano_sleep()
today seems to be that do_signal() requires &regs which
differs from arch to arch in how it is passed to a system
call handler.  The common code does not need or use regs
except to pass it to do_signal().

As a suggestion for a solution for this, is it true that
regs, on a system call, will ALWAYS be at the end of the
stack?  Lets assume, at least for nano_sleep, that it will
not be called from the kernel.  Even if it is, what should
signal behavior be in this case?  Should it not use the user
regs?

Here is a suggested function to get the regs:

struct pt_regs *get_task_registers(struct task_struct* task)
{
	return (struct pt_regs *)((unsigned char
*)task->thread.esp0 - 
				  sizeof(struct pt_regs));
}

comments?

> 
> --
> Cheers,
> Stephen Rothwell                    sfr@canb.auug.org.au
> http://www.canb.auug.org.au/~sfr/
> 
> diff -ruN 2.5.50-BK.2/fs/open.c 2.5.50-BK.2-32bit.1/fs/open.c
> --- 2.5.50-BK.2/fs/open.c       2002-12-04 12:07:36.000000000 +1100
> +++ 2.5.50-BK.2-32bit.1/fs/open.c       2002-12-04 12:01:36.000000000 +1100
> @@ -280,7 +280,7 @@
>   * must be owner or have write permission.
>   * Else, update from *times, must be owner or super user.
>   */
> -asmlinkage long sys_utimes(char * filename, struct timeval * utimes)
> +long do_utimes(char * filename, struct timeval * times)
>  {
>         int error;
>         struct nameidata nd;
> @@ -299,11 +299,7 @@
> 
>         /* Don't worry, the checks are done in inode_change_ok() */
>         newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
> -       if (utimes) {
> -               struct timeval times[2];
> -               error = -EFAULT;
> -               if (copy_from_user(&times, utimes, sizeof(times)))
> -                       goto dput_and_out;
> +       if (times) {
>                 newattrs.ia_atime.tv_sec = times[0].tv_sec;
>                 newattrs.ia_atime.tv_nsec = times[0].tv_usec * 1000;
>                 newattrs.ia_mtime.tv_sec = times[1].tv_sec;
> @@ -323,6 +319,16 @@
>         return error;
>  }
> 
> +asmlinkage long sys_utimes(char * filename, struct timeval * utimes)
> +{
> +       struct timeval times[2];
> +
> +       if (utimes && copy_from_user(&times, utimes, sizeof(times)))
> +               return -EFAULT;
> +       return do_utimes(filename, utimes ? times : NULL);
> +}
> +
> +
>  /*
>   * access() needs to use the real uid/gid, not the effective uid/gid.
>   * We do this by temporarily clearing all FS-related capabilities and
> diff -ruN 2.5.50-BK.2/include/linux/compat.h 2.5.50-BK.2-32bit.1/include/linux/compat.h
> --- 2.5.50-BK.2/include/linux/compat.h  1970-01-01 10:00:00.000000000 +1000
> +++ 2.5.50-BK.2-32bit.1/include/linux/compat.h  2002-12-04 15:42:36.000000000 +1100
> @@ -0,0 +1,29 @@
> +#ifndef _LINUX_COMPAT_H
> +#define _LINUX_COMPAT_H
> +/*
> + * These are the type definitions for the arhitecure sepcific
> + * compatibility layer.
> + */
> +#include <linux/config.h>
> +
> +#ifdef CONFIG_COMPAT
> +
> +#include <asm/compat.h>
> +
> +struct compat_timeval {
> +       compat_time_t           tv_sec;
> +       compat_suseconds_t      tv_usec;
> +};
> +
> +struct compat_utimbuf {
> +       compat_time_t           actime;
> +       compat_time_t           modtime;
> +};
> +
> +struct compat_itimerval {
> +       struct compat_timeval   it_interval;
> +       struct compat_timeval   it_value;
> +};
> +
> +#endif /* CONFIG_COMPAT */
> +#endif /* _LINUX_COMPAT_H */
> diff -ruN 2.5.50-BK.2/include/linux/time.h 2.5.50-BK.2-32bit.1/include/linux/time.h
> --- 2.5.50-BK.2/include/linux/time.h    2002-11-18 15:47:56.000000000 +1100
> +++ 2.5.50-BK.2-32bit.1/include/linux/time.h    2002-12-03 15:47:26.000000000 +1100
> @@ -138,6 +138,8 @@
>  #ifdef __KERNEL__
>  extern void do_gettimeofday(struct timeval *tv);
>  extern void do_settimeofday(struct timeval *tv);
> +extern long do_nanosleep(struct timespec *t);
> +extern long do_utimes(char * filename, struct timeval * times);
>  #endif
> 
>  #define FD_SETSIZE             __FD_SETSIZE
> diff -ruN 2.5.50-BK.2/kernel/Makefile 2.5.50-BK.2-32bit.1/kernel/Makefile
> --- 2.5.50-BK.2/kernel/Makefile 2002-11-28 10:34:59.000000000 +1100
> +++ 2.5.50-BK.2-32bit.1/kernel/Makefile 2002-12-03 15:42:28.000000000 +1100
> @@ -21,6 +21,7 @@
>  obj-$(CONFIG_CPU_FREQ) += cpufreq.o
>  obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
>  obj-$(CONFIG_SOFTWARE_SUSPEND) += suspend.o
> +obj-$(CONFIG_COMPAT) += compat.o
> 
>  ifneq ($(CONFIG_IA64),y)
>  # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
> diff -ruN 2.5.50-BK.2/kernel/compat.c 2.5.50-BK.2-32bit.1/kernel/compat.c
> --- 2.5.50-BK.2/kernel/compat.c 1970-01-01 10:00:00.000000000 +1000
> +++ 2.5.50-BK.2-32bit.1/kernel/compat.c 2002-12-04 17:40:08.000000000 +1100
> @@ -0,0 +1,114 @@
> +/*
> + *  linux/kernel/compat.c
> + *
> + *  Kernel compatibililty routines for e.g. 32 bit syscall support
> + *  on 64 bit kernels.
> + *
> + *  Copyright (C) 2002 Stephen Rothwell, IBM Corporation
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License version 2 as
> + *  published by the Free Software Foundation.
> + */
> +
> +#include <linux/linkage.h>
> +#include <linux/compat.h>
> +#include <linux/errno.h>
> +#include <linux/time.h>
> +
> +#include <asm/uaccess.h>
> +
> +asmlinkage long compat_sys_nanosleep(struct compat_timespec *rqtp,
> +               struct compat_timespec *rmtp)
> +{
> +       struct timespec t;
> +       struct compat_timespec ct;
> +       s32 ret;
> +
> +       if (copy_from_user(&ct, rqtp, sizeof(ct)))
> +               return -EFAULT;
> +       t.tv_sec = ct.tv_sec;
> +       t.tv_nsec = ct.tv_nsec;
> +       ret = do_nanosleep(&t);
> +       if (rmtp && (ret == -EINTR)) {
> +               ct.tv_sec = t.tv_sec;
> +               ct.tv_nsec = t.tv_nsec;
> +               if (copy_to_user(rmtp, &ct, sizeof(ct)))
> +                       return -EFAULT;
> +       }
> +       return ret;
> +}
> +
> +/*
> + * Not all architectures have sys_utime, so implement this in terms
> + * of sys_utimes.
> + */
> +asmlinkage long compat_sys_utime(char *filename, struct compat_utimbuf *t)
> +{
> +       struct timeval tv[2];
> +
> +       if (t) {
> +               if (get_user(tv[0].tv_sec, &t->actime) ||
> +                   get_user(tv[1].tv_sec, &t->modtime))
> +                       return -EFAULT;
> +               tv[0].tv_usec = 0;
> +               tv[1].tv_usec = 0;
> +       }
> +       return do_utimes(filename, t ? tv : NULL);
> +}
> +
> +
> +static inline long get_compat_itimerval(struct itimerval *o,
> +               struct compat_itimerval *i)
> +{
> +       return (!access_ok(VERIFY_READ, i, sizeof(*i)) ||
> +               (__get_user(o->it_interval.tv_sec, &i->it_interval.tv_sec) |
> +                __get_user(o->it_interval.tv_usec, &i->it_interval.tv_usec) |
> +                __get_user(o->it_value.tv_sec, &i->it_value.tv_sec) |
> +                __get_user(o->it_value.tv_usec, &i->it_value.tv_usec)));
> +}
> +
> +static inline long put_compat_itimerval(struct compat_itimerval *o,
> +               struct itimerval *i)
> +{
> +       return (!access_ok(VERIFY_WRITE, o, sizeof(*o)) ||
> +               (__put_user(i->it_interval.tv_sec, &o->it_interval.tv_sec) |
> +                __put_user(i->it_interval.tv_usec, &o->it_interval.tv_usec) |
> +                __put_user(i->it_value.tv_sec, &o->it_value.tv_sec) |
> +                __put_user(i->it_value.tv_usec, &o->it_value.tv_usec)));
> +}
> +
> +extern int do_getitimer(int which, struct itimerval *value);
> +
> +asmlinkage long compat_sys_getitimer(int which, struct compat_itimerval *it)
> +{
> +       struct itimerval kit;
> +       int error;
> +
> +       error = do_getitimer(which, &kit);
> +       if (!error && put_compat_itimerval(it, &kit))
> +               error = -EFAULT;
> +       return error;
> +}
> +
> +extern int do_setitimer(int which, struct itimerval *, struct itimerval *);
> +
> +asmlinkage long compat_sys_setitimer(int which, struct compat_itimerval *in,
> +               struct compat_itimerval *out)
> +{
> +       struct itimerval kin, kout;
> +       int error;
> +
> +       if (in) {
> +               if (get_compat_itimerval(&kin, in))
> +                       return -EFAULT;
> +       } else
> +               memset(&kin, 0, sizeof(kin));
> +
> +       error = do_setitimer(which, &kin, out ? &kout : NULL);
> +       if (error || !out)
> +               return error;
> +       if (put_compat_itimerval(out, &kout))
> +               return -EFAULT;
> +       return 0;
> +}
> diff -ruN 2.5.50-BK.2/kernel/timer.c 2.5.50-BK.2-32bit.1/kernel/timer.c
> --- 2.5.50-BK.2/kernel/timer.c  2002-12-04 12:07:39.000000000 +1100
> +++ 2.5.50-BK.2-32bit.1/kernel/timer.c  2002-12-04 12:03:23.000000000 +1100
> @@ -1020,33 +1020,41 @@
>         return current->pid;
>  }
> 
> -asmlinkage long sys_nanosleep(struct timespec *rqtp, struct timespec *rmtp)
> +long do_nanosleep(struct timespec *t)
>  {
> -       struct timespec t;
>         unsigned long expire;
> 
> -       if(copy_from_user(&t, rqtp, sizeof(struct timespec)))
> -               return -EFAULT;
> -
> -       if (t.tv_nsec >= 1000000000L || t.tv_nsec < 0 || t.tv_sec < 0)
> +       if ((t->tv_nsec >= 1000000000L) || (t->tv_nsec < 0) || (t->tv_sec < 0))
>                 return -EINVAL;
> 
> -       expire = timespec_to_jiffies(&t) + (t.tv_sec || t.tv_nsec);
> +       expire = timespec_to_jiffies(t) + (t->tv_sec || t->tv_nsec);
> 
>         current->state = TASK_INTERRUPTIBLE;
>         expire = schedule_timeout(expire);
> 
>         if (expire) {
> -               if (rmtp) {
> -                       jiffies_to_timespec(expire, &t);
> -                       if (copy_to_user(rmtp, &t, sizeof(struct timespec)))
> -                               return -EFAULT;
> -               }
> +               jiffies_to_timespec(expire, t);
>                 return -EINTR;
>         }
>         return 0;
>  }
> 
> +asmlinkage long sys_nanosleep(struct timespec *rqtp, struct timespec *rmtp)
> +{
> +       struct timespec t;
> +       long ret;
> +
> +       if (copy_from_user(&t, rqtp, sizeof(t)))
> +               return -EFAULT;
> +
> +       ret = do_nanosleep(&t);
> +       if (rmtp && (ret == -EINTR)) {
> +               if (copy_to_user(rmtp, &t, sizeof(t)))
> +                       return -EFAULT;
> +       }
> +       return ret;
> +}
> +
>  /*
>   * sys_sysinfo - fill in sysinfo struct
>   */
> -
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-- 
George Anzinger   george@mvista.com
High-res-timers: 
http://sourceforge.net/projects/high-res-timers/
Preemption patch:
http://www.kernel.org/pub/linux/kernel/people/rml