| Message ID | 20170629115726.11060-1-bsingharora@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 1e2a516e89fc412a754327522ab271b42f99c6b4 |
| Headers | show |
On Thu, 2017-06-29 at 11:57:26 UTC, Balbir Singh wrote: > 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. > > This patch fixes > (3b10d00 powerpc/mm/radix: Prevent kernel execution of user space) > The commit above introduced 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. > > Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Signed-off-by: Balbir Singh <bsingharora@gmail.com> Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/1e2a516e89fc412a754327522ab271 cheers
diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S index c119044..8ac0bd2 100644 --- a/arch/powerpc/kernel/misc_64.S +++ b/arch/powerpc/kernel/misc_64.S @@ -614,6 +614,18 @@ _GLOBAL(kexec_sequence) li r0,0 std r0,16(r1) +BEGIN_FTR_SECTION + /* + * This is the best time to turn AMR/IAMR off. + * key 0 is used in radix for supervisor<->user + * protection, but on hash key 0 is reserved + * ideally we want to enter with a clean state. + * NOTE, we rely on r0 being 0 from above. + */ + mtspr SPRN_IAMR,r0 + mtspr SPRN_AMOR,r0 +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) + /* save regs for local vars on new stack. * yes, we won't go back, but ... */
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. This patch fixes (3b10d00 powerpc/mm/radix: Prevent kernel execution of user space) The commit above introduced 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. Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Balbir Singh <bsingharora@gmail.com> --- Changelog v2: - Put the code in a feature section for CPU_FTR_ARCH_300 arch/powerpc/kernel/misc_64.S | 12 ++++++++++++ 1 file changed, 12 insertions(+)