From: Christophe Leroy <christophe.leroy@xxxxxx>
commit feb8e960d780e170e992a70491eec9dd68f4dbf2 upstream.
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: e2fb9f544431 ("powerpc/32: Prepare for Kernel Userspace Access Protection")
Cc: stable@xxxxxxxxxxxxxxx # v5.2+
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/540242f7d4573f7cdf1b3bf46bb35f743b2cd68f.1587124651.git.christophe.leroy@xxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/entry_32.S | 2 +-
arch/powerpc/platforms/Kconfig.cputype | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -705,7 +705,7 @@ 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
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -389,7 +389,7 @@ 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.
