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s390/sclp: clear upper register halves in _sclp_print_early

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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.

Cc: <stable@vger.kernel.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2015-07-06 17:58:19 +02:00
parent a215c8fbde
commit f9c87a6f46
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:
lr %r10,%r2 # save string pointer
lhi %r2,0
@ -291,6 +293,8 @@ ENTRY(_sclp_print_early)
.Lesa3:
lm %r6,%r15,120(%r15) # restore registers
br %r14
.Lzeroes:
.fill 64,4,0
.LwritedataS4:
.long 0x00760005 # SCLP command for write data