Re: Syscall restarted with the clobbered 5th argument

[Carl S. <sha...@gm...>]

Hi Kaz,

I've just fixed the same problem (in exactly the same way) in our
2.6.17 ST kernel!  It causes a failure in the glibc test tst-eintr1.

I found another minor problem as well - we are missing a test for
-ERESTART_RESTARTBLOCK in handle_signal().

i.e.

switch (regs->regs[0]) {
                        case -ERESTARTNOHAND:
                                regs->regs[0] = -EINTR;
                                break;

should be

switch (regs->regs[0]) {
                        case -ERESTART_RESTARTBLOCK:
                        case -ERESTARTNOHAND:
                                regs->regs[0] = -EINTR;
                                break;

(Apologies for lack of patch but it is only a one line change and I
don't have a copy of the latest git kernel handy).

This fixes the LTP test nanosleep03 - the current kernel causes
-ERESTART_RESTARTBLOCK to reach user space rather than the correct
-EINTR.

Slightly off-topic for the kernel mailing list, this work came about
because we are experiencing occasional problems with SH4 thread
unwinding after a pthread_cancel() and the ensuing signal.  I'll email
you more information off-list as well as some other SH glibc fixes we
have.

Carl

On 6/16/07, Kaz Kojima <kk...@rr...> wrote:
> Hi,
>
> I'm working on the latest GNU libc with the 2.6.22-rc4 kernel and
> I've found a few kernel problems.  This is the first one.
>
> We use R0 as the 5th argument of syscall.  When the syscall restarts
> after signal handling, we should restore the old value of R0.
> The attached patch does it.  Without this patch, I've experienced random
> failures in the situation which signals are issued frequently.
>
> Regards,
>         kaz
>
> Signed-off-by: Kaz Kojima <kk...@rr...>
>
> --- GIT/linux-2.6/arch/sh/kernel/signal.c       2007-06-09 07:33:58.000000000 +0900
> +++ linux-2.6.22-rc4/arch/sh/kernel/signal.c    2007-06-15 10:56:43.000000000 +0900
> @@ -481,7 +481,7 @@ give_sigsegv:
>
>  static int
>  handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
> -             sigset_t *oldset, struct pt_regs *regs)
> +             sigset_t *oldset, struct pt_regs *regs, unsigned int save_r0)
>  {
>         int ret;
>
> @@ -500,6 +500,7 @@ handle_signal(unsigned long sig, struct
>                                 }
>                         /* fallthrough */
>                         case -ERESTARTNOINTR:
> +                               regs->regs[0] = save_r0;
>                                 regs->pc -= instruction_size(
>                                                 ctrl_inw(regs->pc - 4));
>                                 break;
> @@ -583,7 +584,8 @@ static void do_signal(struct pt_regs *re
>         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
>         if (signr > 0) {
>                 /* Whee!  Actually deliver the signal.  */
> -               if (handle_signal(signr, &ka, &info, oldset, regs) == 0) {
> +               if (handle_signal(signr, &ka, &info, oldset, regs, save_r0)
> +                   == 0) {
>                         /* a signal was successfully delivered; the saved
>                          * sigmask will have been stored in the signal frame,
>                          * and will be restored by sigreturn, so we can simply
>
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