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s390/sclp: clear upper register halves in _sclp_print_early

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commit f9c87a6f46 upstream.

If the kernel is compiled with gcc 5.1 and the XZ compression option
the decompress_kernel function calls _sclp_print_early in 64-bit mode
while the content of the upper register half of %r6 is non-zero.
This causes a specification exception on the servc instruction in
_sclp_servc.

The _sclp_print_early function saves and restores the upper registers
halves but it fails to clear them for the 31-bit code of the mini sclp
driver.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Martin Schwidefsky
2015-07-06 17:58:19 +02:00
committed by Ben Hutchings
parent a62b33eed7
commit 436bd506ea
1 changed files with 4 additions and 0 deletions
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4
arch/s390/kernel/sclp.S
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@ -270,6 +270,8 @@ ENTRY(_sclp_print_early)
jno .Lesa2
ahi %r15,-80
stmh %r6,%r15,96(%r15) # store upper register halves
basr %r13,0
lmh %r0,%r15,.Lzeroes-.(%r13) # clear upper register halves
.Lesa2:
#endif
lr %r10,%r2 # save string pointer
@ -293,6 +295,8 @@ ENTRY(_sclp_print_early)
#endif
lm %r6,%r15,120(%r15) # restore registers
br %r14
.Lzeroes:
.fill 64,4,0
.LwritedataS4:
.long 0x00760005 # SCLP command for write data