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

From: Guenter Roeck
Date: Fri Nov 25 2016 - 11:20:40 EST

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)
- lg %r10,__TI_sysc_table(%r12) # address of system call table
+ # load address of system call table
+ lg %r10,__TASK_thread+__THREAD_sysc_table(%r12)
+ lghi %r10,__TASK_thread
+ lg %r10,__THREAD_sysc_table(%r10,%r12)
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>


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
+ jz .+10
stg %r10,__TASK_thread+__THREAD_last_break(%r12)
+ jz .+14
lghi \scratch,__TASK_thread
stg %r10,__THREAD_last_break(\scratch,%r12)