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powerpc/64s: Fix i-side SLB miss bad address handler saving nonvolatile GPRs 

commit 52396500f9 upstream.

The SLB bad address handler's trap number fixup does not preserve the
low bit that indicates nonvolatile GPRs have not been saved. This
leads save_nvgprs to skip saving them, and subsequent functions and
return from interrupt will think they are saved.

This causes kernel branch-to-garbage debugging to not have correct
registers, can also cause userspace to have its registers clobbered
after a segfault.

Fixes: f0f558b131 ("powerpc/mm: Preserve CFAR value on SLB miss caused by access to bogus address")
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Nicholas Piggin 2018-03-23 15:53:38 +10:00 committed by Greg Kroah-Hartman
parent 4c6d2518e1
commit 0726ba0491
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/kernel/exceptions-64s.S
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@ -704,7 +704,7 @@ EXC_COMMON_BEGIN(bad_addr_slb)
ld r3, PACA_EXSLB+EX_DAR(r13)
std r3, _DAR(r1)
beq cr6, 2f
li r10, 0x480 /* fix trap number for I-SLB miss */
li r10, 0x481 /* fix trap number for I-SLB miss */
std r10, _TRAP(r1)
2: bl save_nvgprs
addi r3, r1, STACK_FRAME_OVERHEAD