Re: Fix BUG_ON() reporting in real mode on powerpc
From: Paul Mackerras <hidden>
Date: 2016-02-17 04:56:09
On Wed, Feb 17, 2016 at 03:43:11PM +1100, Balbir Singh wrote:
quoted hunk ↗ jump to hunk
From: Balbir Singh <bsingharora@gmail.com> 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 <redacted> Signed-off-by: Balbir Singh <bsingharora@gmail.com> --- arch/powerpc/kernel/traps.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index b6becc7..8f28120 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 +1159,13 @@ void __kprobes program_check_exception(struct pt_regs *regs)== NOTIFY_STOP) goto bail; + if (!(regs->msr & MSR_IR)) + bugaddr = regs->nip + PAGE_OFFSET; + else + bugaddr = regs->nip;
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. Paul.