[RESEND][PATCH] Fix BUG_ON() reporting in real mode on PPC

Resending to remove whitespace issues created by email client

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 <redacted>
Signed-off-by: Balbir Singh <bsingharora@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

Hi Balbir,

[auto build test ERROR on powerpc/next]
[also build test ERROR on v4.5-rc4 next-20160217]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Balbir-Singh/Fix-BUG_ON-reporting-in-real-mode-on-PPC/20160218-082259
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-allnoconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=powerpc 

All errors (new ones prefixed by >>):

   arch/powerpc/kernel/traps.c: In function 'program_check_exception':

quoted

arch/powerpc/kernel/traps.c:1163:8: error: implicit declaration of function 'REGION_ID' [-Werror=implicit-function-declaration]

      if ((REGION_ID(bugaddr) == 0) && !(regs->msr & MSR_IR))
           ^
   cc1: all warnings being treated as errors

vim +/REGION_ID +1163 arch/powerpc/kernel/traps.c

  1157			/* trap exception */
  1158			if (notify_die(DIE_BPT, "breakpoint", regs, 5, 5, SIGTRAP)
  1159					== NOTIFY_STOP)
  1160				goto bail;
  1161	
  1162			bugaddr = regs->nip;

1163			if ((REGION_ID(bugaddr) == 0) && !(regs->msr & MSR_IR))

  1164				bugaddr += PAGE_OFFSET;
  1165	
  1166			if (!(regs->msr & MSR_PR) &&  /* not user-mode */

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation