2020-04-17 12:02:26

by Christophe Leroy

Subject: [PATCH] powerpc/mm: Fix CONFIG_PPC_KUAP_DEBUG on PPC32

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: [email protected]
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/entry_32.S | 2 +-
arch/powerpc/platforms/Kconfig.cputype | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index a6371fb8f761..8420abd4ea1c 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -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
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 11412078e732..9fffe99b343d 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -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.
--
2.25.0

2020-04-25 23:53:07

by Michael Ellerman

Subject: Re: [PATCH] powerpc/mm: Fix CONFIG_PPC_KUAP_DEBUG on PPC32

On Fri, 2020-04-17 at 11:58:36 UTC, Christophe Leroy wrote:
> 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: [email protected]
> Signed-off-by: Christophe Leroy <[email protected]>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/feb8e960d780e170e992a70491eec9dd68f4dbf2

cheers