Re: next: s390 crash due to 's390: move sys_call_table and last_break from thread_info to thread_struct'

[Guenter Roeck]

On 11/25/2016 01:05 AM, Martin Schwidefsky wrote:
> Hi Guenter,
>
> On Thu, 24 Nov 2016 12:53:52 -0800
> Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> > > Thanks for the report. Builds for Z900 and Z990 are borked. This hunk
> > >
> > > @@ -287,7 +292,13 @@ ENTRY(system_call)
> > >         mvc     __PT_INT_CODE(4,%r11),__LC_SVC_ILC
> > >         stg     %r14,__PT_FLAGS(%r11)
> > >  .Lsysc_do_svc:
> > > -       lg      %r10,__TI_sysc_table(%r12)      # address of system call table
> > > +       # load address of system call table
> > > +#ifdef CONFIG_HAVE_MARCH_Z990_FEATURES
> > > +       lg      %r10,__TASK_thread+__THREAD_sysc_table(%r12)
> > > +#else
> > > +       lghi    %r10,__TASK_thread
> > > +       lg      %r10,__THREAD_sysc_table(%r10,%r12)
> > > +#endif
> > >         llgh    %r8,__PT_INT_CODE+2(%r11)
> > >         slag    %r8,%r8,2                       # shift and test for svc 0
> > >         jnz     .Lsysc_nr_ok
> > >
> > > makes ill use of %r10 in the #else part. Should be fixed now and tomorrows -next
> > > tree will have the fix. Thanks again.
> >
> > This is still crashing in -next with exactly the same message.
>
> Yes, it is (note to myself: don't do things in a hurry). The patch below
> gets linux-next booting again for CONFIG_MARCH_Z900=y on my test system.
> Sorry about the trouble.
No problem. Just trying to make sure it doesn't find its way into mainline.

> --
> From 2ec05f7c28963c12e9618e9f7f3b29edcec40482 Mon Sep 17 00:00:00 2001
> From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Date: Fri, 25 Nov 2016 09:53:42 +0100
> Subject: [PATCH] s390: fix kernel oops for CONFIG_MARCH_Z900=y builds
>
> The LAST_BREAK macro in entry.S uses a different instruction sequence
> for CONFIG_MARCH_Z900 builds. The branch target offset to skip the
> store of the last breaking event address needs to take the different
> length of the code block into account.
>
> Fixes: f8fc82b47149e344 ("s390: move sys_call_table and last_break from thread_info to thread_struct")
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Guenter

> ---
>  arch/s390/kernel/entry.S | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
> index 1cc4578..e2e47f7 100644
> --- a/arch/s390/kernel/entry.S
> +++ b/arch/s390/kernel/entry.S
> @@ -123,10 +123,11 @@ _PIF_WORK	= (_PIF_PER_TRAP)
>
>  	.macro	LAST_BREAK scratch
>  	srag	\scratch,%r10,23
> -	jz	.+10
>  #ifdef CONFIG_HAVE_MARCH_Z990_FEATURES
> +	jz	.+10
>  	stg	%r10,__TASK_thread+__THREAD_last_break(%r12)
>  #else
> +	jz	.+14
>  	lghi	\scratch,__TASK_thread
>  	stg	%r10,__THREAD_last_break(\scratch,%r12)
>  #endif