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powerpc/kexec: Fix radix to hash kexec due to IAMR/AMOR
This patch fixes a crash seen while doing a kexec from radix mode to hash mode. Key 0 is special in hash and used in the RPN by default, we set the key values to 0 today. In radix mode key 0 is used to control supervisor<->user access. In hash key 0 is used by default, so the first instruction after the switch causes a crash on kexec. Commit3b10d0095a
("powerpc/mm/radix: Prevent kernel execution of user space") introduced the setting of IAMR and AMOR values to prevent execution of user mode instructions from supervisor mode. We need to clean up these SPR's on kexec. Fixes:3b10d0095a
("powerpc/mm/radix: Prevent kernel execution of user space") Cc: stable@vger.kernel.org # v4.10+ Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Balbir Singh <bsingharora@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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@ -614,6 +614,18 @@ _GLOBAL(kexec_sequence)
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li r0,0
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std r0,16(r1)
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BEGIN_FTR_SECTION
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/*
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* This is the best time to turn AMR/IAMR off.
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* key 0 is used in radix for supervisor<->user
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* protection, but on hash key 0 is reserved
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* ideally we want to enter with a clean state.
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* NOTE, we rely on r0 being 0 from above.
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*/
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mtspr SPRN_IAMR,r0
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mtspr SPRN_AMOR,r0
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END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
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/* save regs for local vars on new stack.
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* yes, we won't go back, but ...
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*/
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