Commit d9698525 authored Jul 06, 2015 by Martin Schwidefsky Committed by Sasha Levin Aug 27, 2015

s390/sclp: clear upper register halves in _sclp_print_early



[ Upstream commit f9c87a6f46d508eae0d9ae640be98d50f237f827 ]

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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

parent 0d814959

arch/s390/kernel/sclp.S

+4 −0

Original line number	Diff line number	Diff line
		@@ -277,6 +277,8 @@ 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
		@@ -300,6 +302,8 @@ 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