From: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
[ Upstream commit a6e2c226c3d51fd93636320e47cabc8a8f0824c5 ]
With CONFIG_DEBUG_VIRTUAL=y, we can hit a BUG() if we take a hard
lockup watchdog interrupt when in OPAL mode.
This happens in show_instructions() if the kernel takes the watchdog
NMI IPI, or any other interrupt, with MSR_IR == 0. show_instructions()
updates the variable pc in the loop and the second iteration will
result in BUG().
We hit the BUG_ON due the below check in __va()
#define __va(x)
({
VIRTUAL_BUG_ON((unsigned long)(x) >= PAGE_OFFSET);
(void *)(unsigned long)((phys_addr_t)(x) | PAGE_OFFSET);
})
Fix it by moving the check out of the loop. Also update nip so that
the nip == pc check still matches.
Fixes: 4dd7554a6456 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va and __pa
addresses")
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
[mpe: Use IS_ENABLED(), massage change log]
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Link:
https://lore.kernel.org/r/20200524093822.423487-1-aneesh.ku...@linux.ibm.com
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
arch/powerpc/kernel/process.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 639ceae7da9d8..bd0c258a1d5dd 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1218,29 +1218,31 @@ struct task_struct *__switch_to(struct task_struct
*prev,
static void show_instructions(struct pt_regs *regs)
{
int i;
+ unsigned long nip = regs->nip;
unsigned long pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int));
printk("Instruction dump:");
+ /*
+ * If we were executing with the MMU off for instructions, adjust pc
+ * rather than printing XXXXXXXX.
+ */
+ if (!IS_ENABLED(CONFIG_BOOKE) && !(regs->msr & MSR_IR)) {
+ pc = (unsigned long)phys_to_virt(pc);
+ nip = (unsigned long)phys_to_virt(regs->nip);
+ }
+
for (i = 0; i < NR_INSN_TO_PRINT; i++) {
int instr;
if (!(i % 8))
pr_cont("\n");
-#if !defined(CONFIG_BOOKE)
- /* If executing with the IMMU off, adjust pc rather
- * than print XXXXXXXX.
- */
- if (!(regs->msr & MSR_IR))
- pc = (unsigned long)phys_to_virt(pc);
-#endif
-
if (!__kernel_text_address(pc) ||
probe_kernel_address((const void *)pc, instr)) {
pr_cont("XXXXXXXX ");
} else {
- if (regs->nip == pc)
+ if (nip == pc)
pr_cont("<%08x> ", instr);
else
pr_cont("%08x ", instr);
--
2.25.1
