Commit da905757 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

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



The tprot() 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: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 1b2f281f

arch/s390/boot/mem_detect.c

+17 −11
Original line number Diff line number Diff line
@@ -118,24 +118,30 @@ static int diag260(void) 


static int tprot(unsigned long addr)

{

	unsigned long pgm_addr;

	unsigned long reg1, reg2;

	int rc = -EFAULT;

	psw_t old = S390_lowcore.program_new_psw;

	psw_t old;



	S390_lowcore.program_new_psw.mask = __extract_psw();

	asm volatile(

		"	larl	%[pgm_addr],1f\n"

		"	stg	%[pgm_addr],%[psw_pgm_addr]\n"

		"	mvc	0(16,%[psw_old]),0(%[psw_pgm])\n"

		"	epsw	%[reg1],%[reg2]\n"

		"	st	%[reg1],0(%[psw_pgm])\n"

		"	st	%[reg2],4(%[psw_pgm])\n"

		"	larl	%[reg1],1f\n"

		"	stg	%[reg1],8(%[psw_pgm])\n"

		"	tprot	0(%[addr]),0\n"

		"	ipm	%[rc]\n"

		"	srl	%[rc],28\n"

		"1:\n"

		: [pgm_addr] "=&d"(pgm_addr),

		  [psw_pgm_addr] "=Q"(S390_lowcore.program_new_psw.addr),

		  [rc] "+&d"(rc)

		: [addr] "a"(addr)

		"1:	mvc	0(16,%[psw_pgm]),0(%[psw_old])\n"

		: [reg1] "=&d" (reg1),

		  [reg2] "=&a" (reg2),

		  [rc] "+&d" (rc),

		  "=Q" (S390_lowcore.program_new_psw.addr),

		  "=Q" (old)

		: [psw_old] "a" (&old),

		  [psw_pgm] "a" (&S390_lowcore.program_new_psw),

		  [addr] "a" (addr)

		: "cc", "memory");

	S390_lowcore.program_new_psw = old;

	return rc;

}