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s390/traps: Fix test_monitor_call() inline assembly

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commit 5623bc23a1cb9f9a9470fa73b3a20321dc4c4870 upstream.

The test_monitor_call() inline assembly uses the xgr instruction, which
also modifies the condition code, to clear a register. However the clobber
list of the inline assembly does not specify that the condition code is
modified, which may lead to incorrect code generation.

Use the lhi instruction instead to clear the register without that the
condition code is modified. Furthermore this limits clearing to the lower
32 bits of val, since its type is int.

Fixes: 17248ea036 ("s390: fix __EMIT_BUG() macro")
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heiko Carstens 2025-02-25 10:53:10 +01:00 committed by Greg Kroah-Hartman
parent 469761d254
commit d09cf51421
1 changed files with 3 additions and 3 deletions
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4
arch/s390/kernel/traps.c
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@ -276,10 +276,10 @@ static void __init test_monitor_call(void)
return;
asm volatile(
" mc 0,0\n"
"0: xgr %0,%0\n"
"0: lhi %[val],0\n"
"1:\n"
EX_TABLE(0b, 1b)
: "+d" (val));
: [val] "+d" (val));
if (!val)
panic("Monitor call doesn't work!\n");
}