> It might be a little better to do this:
>
> bugaddr = regs->nip;
> if (REGION_ID(bugaddr) == 0 && !(regs->msr & MSR_IR))
> bugaddr += PAGE_OFFSET;
>
> It is possible to execute from addresses with the 0xc000... on top in
> real mode, because the CPU ignores the top 4 address bits in real
> mode.
Good catch! Thank you
Changelog:
Don't add PAGE_OFFSET blindly, check if REGION_ID is 0
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 <pau...@samba.org>
Signed-off-by: Balbir Singh <bsinghar...@gmail.com>
---
arch/powerpc/kernel/traps.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index b6becc7..4de4fe7 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 +1159,12 @@ void __kprobes program_check_exception(struct pt_regs
*regs)
== NOTIFY_STOP)
goto bail;
+ bugaddr = regs->nip;
+ if ((REGION_ID(bugaddr) == 0) && !(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;
}
--
2.5.0
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