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s390: fix system call single stepping

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When single stepping an svc instruction on s390, the kernel is entered
with a PER program check interruption. The program check handler than
jumps to the system call handler by reloading the PSW. The code didn't
set GPR13 to the thread pointer in struct task_struct. This made the
kernel access invalid memory while trying to fetch the syscall function
address. Fix this by always assigned GPR13 after .Lsysc_per.

Fixes: 0b0ed657fe ("s390: remove critical section cleanup from entry.S")
Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Sven Schnelle 2020-06-17 17:30:28 +02:00 committed by Heiko Carstens
parent 48778464bb
commit e64a1618af
1 changed files with 1 additions and 1 deletions
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2
arch/s390/kernel/entry.S
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@ -378,9 +378,9 @@ ENTRY(system_call)
stmg %r8,%r15,__LC_SAVE_AREA_SYNC
BPOFF
lg %r12,__LC_CURRENT
lghi %r13,__TASK_thread
lghi %r14,_PIF_SYSCALL
.Lsysc_per:
lghi %r13,__TASK_thread
lg %r15,__LC_KERNEL_STACK
la %r11,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs
UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER