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Commit bcc6525f authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Martin Schwidefsky
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[S390] s390: fix single stepping on svc0 



On s390 there are two ways of specifying the system call number for
the svc instruction. The standard way is to use the immediate field
in the instruction (or to use EXecute for values unknown during
assemble time). This can encode 256 system calls.
The kernel ABI also allows to put the system call number in r1 and
then execute svc 0 to enable system call numbers > 255.

It turns out that single stepping svc 0 is broken, since the PER
program check handler uses r1. We have to use a different register.

Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 8b94c1ed

arch/s390/kernel/entry.S

+4 −4
Original line number Diff line number Diff line
@@ -565,10 +565,10 @@ pgm_svcper: 
	lh	%r7,0x8a		# get svc number from lowcore

	l	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct

	TRACE_IRQS_OFF

	l	%r1,__TI_task(%r9)

	mvc	__THREAD_per+__PER_atmid(2,%r1),__LC_PER_ATMID

	mvc	__THREAD_per+__PER_address(4,%r1),__LC_PER_ADDRESS

	mvc	__THREAD_per+__PER_access_id(1,%r1),__LC_PER_ACCESS_ID

	l	%r8,__TI_task(%r9)

	mvc	__THREAD_per+__PER_atmid(2,%r8),__LC_PER_ATMID

	mvc	__THREAD_per+__PER_address(4,%r8),__LC_PER_ADDRESS

	mvc	__THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID

	oi	__TI_flags+3(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP

	TRACE_IRQS_ON

	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts

arch/s390/kernel/entry64.S

+4 −4
Original line number Diff line number Diff line
@@ -543,10 +543,10 @@ pgm_svcper: 
	mvc	__LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER

	llgh	%r7,__LC_SVC_INT_CODE	# get svc number from lowcore

	lg	%r9,__LC_THREAD_INFO	# load pointer to thread_info struct

	lg	%r1,__TI_task(%r9)

	mvc	__THREAD_per+__PER_atmid(2,%r1),__LC_PER_ATMID

	mvc	__THREAD_per+__PER_address(8,%r1),__LC_PER_ADDRESS

	mvc	__THREAD_per+__PER_access_id(1,%r1),__LC_PER_ACCESS_ID

	lg	%r8,__TI_task(%r9)

	mvc	__THREAD_per+__PER_atmid(2,%r8),__LC_PER_ATMID

	mvc	__THREAD_per+__PER_address(8,%r8),__LC_PER_ADDRESS

	mvc	__THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID

	oi	__TI_flags+7(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP

	TRACE_IRQS_ON

	stosm	__SF_EMPTY(%r15),0x03	# reenable interrupts