When a program check exception happens while MMU translation is
disabled, following Oops happens in kprobe_handler() in the following
test:
} else if (*addr != BREAKPOINT_INSTRUCTION) {
[ 33.098554] BUG: Unable to handle kernel data access on read at 0x0000e268
[ 33.105091] Faulting instruction address: 0xc000ec34
[ 33.110010] Oops: Kernel access of bad area, sig: 11 [#1]
[ 33.115348] BE PAGE_SIZE=16K PREEMPT CMPC885
[ 33.119540] Modules linked in:
[ 33.122591] CPU: 0 PID: 429 Comm: cat Not tainted
5.6.0-rc1-s3k-dev-00824-g84195dc6c58a #3267
[ 33.131005] NIP: c000ec34 LR: c000ecd8 CTR: c019cab8
[ 33.136002] REGS: ca4d3b58 TRAP: 0300 Not tainted
(5.6.0-rc1-s3k-dev-00824-g84195dc6c58a)
[ 33.144324] MSR: 00001032 <ME,IR,DR,RI> CR: 2a4d3c52 XER: 00000000
[ 33.150699] DAR: 0000e268 DSISR: c0000000
[ 33.150699] GPR00: c000b09c ca4d3c10 c66d0620 00000000 ca4d3c60 00000000
00009032 00000000
[ 33.150699] GPR08: 00020000 00000000 c087de44 c000afe0 c66d0ad0 100d3dd6
fffffff3 00000000
[ 33.150699] GPR16: 00000000 00000041 00000000 ca4d3d70 00000000 00000000
0000416d 00000000
[ 33.150699] GPR24: 00000004 c53b6128 00000000 0000e268 00000000 c07c0000
c07bb6fc ca4d3c60
[ 33.188015] NIP [c000ec34] kprobe_handler+0x128/0x290
[ 33.192989] LR [c000ecd8] kprobe_handler+0x1cc/0x290
[ 33.197854] Call Trace:
[ 33.200340] [ca4d3c30] [c000b09c] program_check_exception+0xbc/0x6fc
[ 33.206590] [ca4d3c50] [c000e43c] ret_from_except_full+0x0/0x4
[ 33.212392] --- interrupt: 700 at 0xe268
[ 33.270401] Instruction dump:
[ 33.273335] 913e0008 81220000 38600001 3929ffff 91220000 80010024 bb410008
7c0803a6
[ 33.280992] 38210020 4e800020 38600000 4e800020 <813b0000> 6d2a7fe0 2f8a0008
419e0154
[ 33.288841] ---[ end trace 5b9152d4cdadd06d ]---
Check MSR and convert regs->nip to virtual address if the trap
happened with MSR_IR cleared.
Reported-by: Larry Finger <larry.fin...@lwfinger.net>
Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly")
Cc: sta...@kernel.vger.org
Cc: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
The bug might have existed even before that commit from Naveen.
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
---
arch/powerpc/kernel/kprobes.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 2d27ec4feee4..f8b848aa65bd 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -23,6 +23,7 @@
#include <asm/cacheflush.h>
#include <asm/sstep.h>
#include <asm/sections.h>
+#include <asm/io.h>
#include <linux/uaccess.h>
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
@@ -264,6 +265,9 @@ int kprobe_handler(struct pt_regs *regs)
if (user_mode(regs))
return 0;
+ if (!(regs->msr & MSR_IR))
+ addr = phys_to_virt(regs->nip);
+
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
--
2.25.0
