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powerpc/mm: Fix CONFIG_PPC_KUAP_DEBUG on PPC32

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CONFIG_PPC_KUAP_DEBUG is not selectable because it depends on PPC_32
which doesn't exists.

Fixing it leads to a deadlock due to a vital register getting
clobbered in _switch().

Change dependency to PPC32 and use r0 instead of r4 in _switch()

Fixes: e2fb9f5444 ("powerpc/32: Prepare for Kernel Userspace Access Protection")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/540242f7d4573f7cdf1b3bf46bb35f743b2cd68f.1587124651.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy 2020-04-17 11:58:36 +00:00 committed by Michael Ellerman
parent b61c38baa9
commit feb8e960d7
2 changed files with 2 additions and 2 deletions
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2
arch/powerpc/kernel/entry_32.S
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@ -732,7 +732,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_SPE)
stw r10,_CCR(r1)
stw r1,KSP(r3) /* Set old stack pointer */
kuap_check r2, r4
kuap_check r2, r0
#ifdef CONFIG_SMP
/* We need a sync somewhere here to make sure that if the
* previous task gets rescheduled on another CPU, it sees all

2
arch/powerpc/platforms/Kconfig.cputype
View File

@ -397,7 +397,7 @@ config PPC_KUAP
config PPC_KUAP_DEBUG
bool "Extra debugging for Kernel Userspace Access Protection"
depends on PPC_KUAP && (PPC_RADIX_MMU || PPC_32)
depends on PPC_KUAP && (PPC_RADIX_MMU || PPC32)
help
Add extra debugging for Kernel Userspace Access Protection (KUAP)
If you're unsure, say N.