path: root/arch/s390
diff options
authorHeiko Carstens <heiko.carstens@de.ibm.com>2017-11-09 23:00:14 +0100
committerHeiko Carstens <heiko.carstens@de.ibm.com>2017-11-10 18:58:08 +0100
commitd0e810eeb3d326978f248b8f0233a2f30f58c72d (patch)
treee8ada4a3ddac2d0b5e0dfd57c345c0604ee50ac0 /arch/s390
parenta1c5befc1c24eb9c1ee83f711e0f21ee79cbb556 (diff)
s390/noexec: execute kexec datamover without DAT
Rebooting into a new kernel with kexec fails (system dies) if tried on a machine that has no-execute support. Reason for this is that the so called datamover code gets executed with DAT on (MMU is active) and the page that contains the datamover is marked as non-executable. Therefore when branching into the datamover an unexpected program check happens and afterwards the machine is dead. This can be simply avoided by disabling DAT, which also disables any no-execute checks, just before the datamover gets executed. In fact the first thing done by the datamover is to disable DAT. The code in the datamover that disables DAT can be removed as well. Thanks to Michael Holzheu and Gerald Schaefer for tracking this down. Reviewed-by: Michael Holzheu <holzheu@linux.vnet.ibm.com> Reviewed-by: Philipp Rudo <prudo@linux.vnet.ibm.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Fixes: 57d7f939e7bd ("s390: add no-execute support") Cc: <stable@vger.kernel.org> # v4.11+ Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Diffstat (limited to 'arch/s390')
2 files changed, 1 insertions, 3 deletions
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index c72e551e5951..4d91761f1177 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -265,6 +265,7 @@ static void __do_machine_kexec(void *data)
data_mover = (relocate_kernel_t) page_to_phys(image->control_code_page);
+ __arch_local_irq_stnsm(0xfb); /* disable DAT - avoid no-execute */
/* Call the moving routine */
(*data_mover)(&image->head, image->start);
diff --git a/arch/s390/kernel/relocate_kernel.S b/arch/s390/kernel/relocate_kernel.S
index 4bdc65636603..a613581fea67 100644
--- a/arch/s390/kernel/relocate_kernel.S
+++ b/arch/s390/kernel/relocate_kernel.S
@@ -28,7 +28,6 @@
basr %r13,0 # base address
- stnsm sys_msk-.base(%r13),0xfb # disable DAT
stctg %c0,%c15,ctlregs-.base(%r13)
stmg %r0,%r15,gprregs-.base(%r13)
lghi %r0,3
@@ -102,8 +101,6 @@ ENTRY(relocate_kernel)
.align 8
.long 0x00080000,0x80000000
- sys_msk:
- .quad 0
.rept 16
.quad 0

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