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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: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2014-02-03 17:37:15 +01:00
parent d7736ff5be
commit 8d7f6690ce
1 changed files with 5 additions and 2 deletions
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7
arch/s390/kernel/head64.S
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@ -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)