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powerpc: Fix kernel crash in show_instructions() w/DEBUG_VIRTUAL 

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: 4dd7554a64 ("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
This commit is contained in:
Aneesh Kumar K.V 2020-05-24 15:08:19 +05:30 committed by Michael Ellerman
parent b3a9e3b962
commit a6e2c226c3
1 changed files with 11 additions and 9 deletions
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20
arch/powerpc/kernel/process.c
View File

@ -1252,29 +1252,31 @@ struct task_struct *__switch_to(struct task_struct *prev,
static void show_instructions(struct pt_regs *regs) static void show_instructions(struct pt_regs *regs)
{ {
int i; int i;
unsigned long nip = regs->nip;
unsigned long pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int)); unsigned long pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int));
printk("Instruction dump:"); 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++) { for (i = 0; i < NR_INSN_TO_PRINT; i++) {
int instr; int instr;
if (!(i % 8)) if (!(i % 8))
pr_cont("\n"); 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) || if (!__kernel_text_address(pc) ||
probe_kernel_address((const void *)pc, instr)) { probe_kernel_address((const void *)pc, instr)) {
pr_cont("XXXXXXXX "); pr_cont("XXXXXXXX ");
} else { } else {
if (regs->nip == pc) if (nip == pc)
pr_cont("<%08x> ", instr); pr_cont("<%08x> ", instr);
else else
pr_cont("%08x ", instr); pr_cont("%08x ", instr);