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s390/mem_detect: fix diag260() program check new psw handling

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[ 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>
This commit is contained in:
Heiko Carstens
2021-06-14 21:40:43 +02:00
committed by Greg Kroah-Hartman
parent c25be19aa9
commit 7e1e0235b3
1 changed files with 11 additions and 8 deletions
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19
arch/s390/boot/mem_detect.c
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@@ -70,24 +70,27 @@ static int __diag260(unsigned long rx1, unsigned long rx2)
register unsigned long _ry asm("4") = 0x10; /* storage configuration */ register unsigned long _ry asm("4") = 0x10; /* storage configuration */
int rc = -1; /* fail */ int rc = -1; /* fail */
unsigned long reg1, reg2; unsigned long reg1, reg2;
psw_t old = S390_lowcore.program_new_psw; psw_t old;
asm volatile( asm volatile(
" mvc 0(16,%[psw_old]),0(%[psw_pgm])\n"
" epsw %0,%1\n" " epsw %0,%1\n"
" st %0,%[psw_pgm]\n" " st %0,0(%[psw_pgm])\n"
" st %1,%[psw_pgm]+4\n" " st %1,4(%[psw_pgm])\n"
" larl %0,1f\n" " larl %0,1f\n"
" stg %0,%[psw_pgm]+8\n" " stg %0,8(%[psw_pgm])\n"
" diag %[rx],%[ry],0x260\n" " diag %[rx],%[ry],0x260\n"
" ipm %[rc]\n" " ipm %[rc]\n"
" srl %[rc],28\n" " srl %[rc],28\n"
"1:\n" "1: mvc 0(16,%[psw_pgm]),0(%[psw_old])\n"
: "=&d" (reg1), "=&a" (reg2), : "=&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) [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"); : "cc", "memory");
S390_lowcore.program_new_psw = old;
return rc == 0 ? _ry : -1; return rc == 0 ? _ry : -1;
} }