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Commit 8d7f6690 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390: fix kernel crash due to linkage stack instructions 



The kernel currently crashes with a low-address-protection exception
if a user space process executes an instruction that tries to use the
linkage stack. Set the base-ASTE origin and the subspace-ASTE origin
of the dispatchable-unit-control-table to point to a dummy ASTE.
Set up control register 15 to point to an empty linkage stack with no
room left.

A user space process with a linkage stack instruction will still crash
but with a different exception which is correctly translated to a
segmentation fault instead of a kernel oops.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent d7736ff5

arch/s390/kernel/head64.S

+5 −2
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ ENTRY(startup_continue) 
	.quad	0			# cr12: tracing off

	.quad	0			# cr13: home space segment table

	.quad	0xc0000000		# cr14: machine check handling off

	.quad	0			# cr15: linkage stack operations

	.quad	.Llinkage_stack		# cr15: linkage stack operations

.Lpcmsk:.quad	0x0000000180000000

.L4malign:.quad 0xffffffffffc00000

.Lscan2g:.quad	0x80000000 + 0x20000 - 8	# 2GB + 128K - 8
@@ -67,12 +67,15 @@ ENTRY(startup_continue) 
.Lparmaddr:

	.quad	PARMAREA

	.align	64

.Lduct: .long	0,0,0,0,.Lduald,0,0,0

.Lduct: .long	0,.Laste,.Laste,0,.Lduald,0,0,0

	.long	0,0,0,0,0,0,0,0

.Laste:	.quad	0,0xffffffffffffffff,0,0,0,0,0,0

	.align	128

.Lduald:.rept	8

	.long	0x80000000,0,0,0	# invalid access-list entries

	.endr

.Llinkage_stack:

	.long	0,0,0x89000000,0,0,0,0x8a000000,0



ENTRY(_ehead)