From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit 86807f348f418a84970eebb8f9912a7eea16b497 ]
The __diag260() inline asm temporarily changes the program check new psw to redirect a potential program check on the diag instruction. Restoring of the program check new psw is done in C code behind the inline asm.
This can be problematic, especially if the function is inlined, since the compiler can reorder instructions in such a way that a different instruction, which may result in a program check, might be executed before the program check new psw has been restored.
To avoid such a scenario move restoring into the inline asm. For consistency reasons move also saving of the original program check new psw into the inline asm.
Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/boot/mem_detect.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/s390/boot/mem_detect.c b/arch/s390/boot/mem_detect.c index 62e7c13ce85c..032d68165216 100644 --- a/arch/s390/boot/mem_detect.c +++ b/arch/s390/boot/mem_detect.c @@ -70,24 +70,27 @@ static int __diag260(unsigned long rx1, unsigned long rx2) register unsigned long _ry asm("4") = 0x10; /* storage configuration */ int rc = -1; /* fail */ unsigned long reg1, reg2; - psw_t old = S390_lowcore.program_new_psw; + psw_t old;
asm volatile( + " mvc 0(16,%[psw_old]),0(%[psw_pgm])\n" " epsw %0,%1\n" - " st %0,%[psw_pgm]\n" - " st %1,%[psw_pgm]+4\n" + " st %0,0(%[psw_pgm])\n" + " st %1,4(%[psw_pgm])\n" " larl %0,1f\n" - " stg %0,%[psw_pgm]+8\n" + " stg %0,8(%[psw_pgm])\n" " diag %[rx],%[ry],0x260\n" " ipm %[rc]\n" " srl %[rc],28\n" - "1:\n" + "1: mvc 0(16,%[psw_pgm]),0(%[psw_old])\n" : "=&d" (reg1), "=&a" (reg2), - [psw_pgm] "=Q" (S390_lowcore.program_new_psw), + "+Q" (S390_lowcore.program_new_psw), + "=Q" (old), [rc] "+&d" (rc), [ry] "+d" (_ry) - : [rx] "d" (_rx1), "d" (_rx2) + : [rx] "d" (_rx1), "d" (_rx2), + [psw_old] "a" (&old), + [psw_pgm] "a" (&S390_lowcore.program_new_psw) : "cc", "memory"); - S390_lowcore.program_new_psw = old; return rc == 0 ? _ry : -1; }