From a4c3f909b4d9bb9430bf42ad583661df6dfa86c6 Mon Sep 17 00:00:00 2001
From: Balbir Singh <bsingharora@gmail.com>
Date: Thu, 18 Feb 2016 13:48:01 +1100
Subject: [PATCH] powerpc: Fix BUG_ON() reporting in real mode
I ran into this issue while debugging an early boot problem. The system
hit a BUG_ON() but report bug failed to print the line number and file
name. The reason being that the system was running in real mode and
report_bug() searches for addresses in the PAGE_OFFSET+ region.
Suggested-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/kernel/traps.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index b6becc795bb5..4e5c11d4d19d 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1148,6 +1148,7 @@ void __kprobes program_check_exception(struct pt_regs *regs)
goto bail;
}
if (reason & REASON_TRAP) {
+ unsigned long bugaddr;
/* Debugger is first in line to stop recursive faults in
* rcu_lock, notify_die, or atomic_notifier_call_chain */
if (debugger_bpt(regs))
@@ -1158,8 +1159,15 @@ void __kprobes program_check_exception(struct pt_regs *regs)
== NOTIFY_STOP)
goto bail;
+ bugaddr = regs->nip;
+ /*
+ * Fixup bugaddr for BUG_ON() in real mode
+ */
+ if (!is_kernel_addr(bugaddr) && !(regs->msr & MSR_IR))
+ bugaddr += PAGE_OFFSET;
+
if (!(regs->msr & MSR_PR) && /* not user-mode */
- report_bug(regs->nip, regs) == BUG_TRAP_TYPE_WARN) {
+ report_bug(bugaddr, regs) == BUG_TRAP_TYPE_WARN) {
regs->nip += 4;
goto bail;
}