| From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 14/96] s390/boot/decompression: disable floating point in decompressor | Date | Fri, 13 Nov 2015 13:48:28 -0800 |
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3.13.11-ckt30 -stable review patch. If anyone has any objections, please let me know.
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From: Christian Borntraeger <borntraeger@de.ibm.com>
commit adc0b7fbf6fe9967505c0254d9535ec7288186ae upstream.
my gcc 5.1 used an ldgr instruction with a register != 0,2,4,6 for spilling/filling into a floating point register in our decompressor.
This will cause an AFP-register data exception as the decompressor did not setup the additional floating point registers via cr0. That causes a program check loop that looked like a hang with one "Uncompressing Linux... " message (directly booted via kvm) or a loop of "Uncompressing Linux... " messages (when booted via zipl boot loader).
The offending code in my build was
48e400: e3 c0 af ff ff 71 lay %r12,-1(%r10) -->48e406: b3 c1 00 1c ldgr %f1,%r12 48e40a: ec 6c 01 22 02 7f clij %r6,2,12,0x48e64e
but gcc could do spilling into an fpr at any function. We can simply disable floating point support at that early stage.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/s390/boot/compressed/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/s390/boot/compressed/Makefile b/arch/s390/boot/compressed/Makefile index f90d1fc..f70b232 100644 --- a/arch/s390/boot/compressed/Makefile +++ b/arch/s390/boot/compressed/Makefile @@ -12,7 +12,7 @@ targets += misc.o piggy.o sizes.h head$(BITS).o KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING -KBUILD_CFLAGS += $(cflags-y) -fno-delete-null-pointer-checks +KBUILD_CFLAGS += $(cflags-y) -fno-delete-null-pointer-checks -msoft-float KBUILD_CFLAGS += $(call cc-option,-mpacked-stack) KBUILD_CFLAGS += $(call cc-option,-ffreestanding) -- 1.9.1
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