Re: Again: UML on s390 (31Bit)

[Bodo Stroesser]

Thank You!
That's what we need.

	Bodo


Martin Schwidefsky wrote:
> > > I've prepared and attached a small program that easily can reproduce
> > > the problem. I hope this will help to find a viable solution.
> >
> > Here is a slightly modified version of my testtool. The new version
> > covers the fact, that in certain situations UML must avoid syscall
> > restarting, even if PSWADDR is not modified.
>
>
> Ok, Uli convinced me that the original patch to clear regs->traps if
> the system call has been canceled on the first call to syscall_trace
> is the correct thing to do. If the tracer chooses to invalidate the
> system call of the traced process then the complete handling of the
> function executed for the system call is done in the tracer. That
> includes system call restarting in the case that another system call
> is involved to implement the function. The point is that the traced
> process did not execute a system call, ergo no system call restarting
> may take place.
> So after a long discussion I'll just use a slightly modified version
> of the original patch:
>
> Index: ptrace.c
> ===================================================================
> RCS file: /home/cvs/linux-2.5/arch/s390/kernel/ptrace.c,v
> retrieving revision 1.35
> diff -u -r1.35 ptrace.c
> --- ptrace.c      6 May 2005 18:59:13 -0000     1.35
> +++ ptrace.c      31 May 2005 16:50:50 -0000
> @@ -39,6 +39,7 @@
>  #include <asm/pgalloc.h>
>  #include <asm/system.h>
>  #include <asm/uaccess.h>
> +#include <asm/unistd.h>
>
>  #ifdef CONFIG_S390_SUPPORT
>  #include "compat_ptrace.h"
> @@ -762,6 +763,13 @@
>             return;
>       ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
>                          ? 0x80 : 0));
> +
> +     /*
> +      * If the debuffer has set an invalid system call number,
> +      * we prepare to skip the system call restart handling.
> +      */
> +     if (!entryexit && regs->gprs[2] >= NR_syscalls)
> +           regs->trap = -1;
>
>       /*
>        * this isn't the same as continuing with a signal, but it will do
>
> ===================================================================
>
> regs->trap should be reset for any invalid system call, not just for
> negative system call numbers.
>
> blue skies,
>    Martin
>
> Martin Schwidefsky
> Linux for zSeries Development & Services
> IBM Deutschland Entwicklung GmbH
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