From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit 88c2510cecb7e2b518e3c4fdf3cf0e13ebe9377c ]
The __diag308() 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/ipl_parm.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/s390/boot/ipl_parm.c b/arch/s390/boot/ipl_parm.c index 24ef67eb1cef..75905b548f69 100644 --- a/arch/s390/boot/ipl_parm.c +++ b/arch/s390/boot/ipl_parm.c @@ -27,22 +27,25 @@ static inline int __diag308(unsigned long subcode, void *addr) register unsigned long _addr asm("0") = (unsigned long)addr; register unsigned long _rc asm("1") = 0; 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 %[addr],%[subcode],0x308\n" - "1: nopr %%r7\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), [addr] "+d" (_addr), "+d" (_rc) - : [subcode] "d" (subcode) + : [subcode] "d" (subcode), + [psw_old] "a" (&old), + [psw_pgm] "a" (&S390_lowcore.program_new_psw) : "cc", "memory"); - S390_lowcore.program_new_psw = old; return _rc; }