From: Aneesh Kumar K.V aneesh.kumar@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.kumar@linux.ibm.com [mpe: Use IS_ENABLED(), massage change log] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20200524093822.423487-1-aneesh.kumar@linux.ibm.com Signed-off-by: Sasha Levin sashal@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);