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x86: fix messed up page fault BUG messages

PATCH In review Fengguang Wu 2 participants 2 messages Aug 13, 2014

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x86 x86 MM
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Fengguang Wu

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#0 lore raw

PATCH 1/1 x86: fix messed up page fault BUG messages

The 0day boot test robot hits messed up BUG lines like

[   25.732010] BUG: unable to handle kernel paging requestrun: /lkp/wfg/sr at 000000000000d908
[   24.986598] BUG: unable to handle kernel run: /lkp/wfg/srpaging request at 000000000000d908
[   24.914406] BUG: unable to handle kernel run: /lkp/wfg/srearly console in decompress_kernel

Which makes the generated bug ID not stable and hence not bisectable.

Fix it by printing the BUG message in one shot.

Signed-off-by Fengguang Wu <[email protected]>
---
 arch/x86/mm/fault.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
arch/x86/mm/fault.c +4 -4
index 3664279..f3e0e0a 100644
@@ -599,13 +599,13 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
 	}
 
-	printk(KERN_ALERT "BUG: unable to handle kernel ");
 	if (address < PAGE_SIZE)
-		printk(KERN_CONT "NULL pointer dereference");
+		printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer dereference at %p\n",
+		       (void *) address);
 	else
-		printk(KERN_CONT "paging request");
+		printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer paging request at %p\n",
+		       (void *) address);
 
-	printk(KERN_CONT " at %p\n", (void *) address);
 	printk(KERN_ALERT "IP:");
 	printk_address(regs->ip);
Signature · 1 line
2.1.0.rc1
Acked-by on v1 1/1
#1 lore raw
Quoted 27 lines · Fengguang Wu

The 0day boot test robot hits messed up BUG lines like

[   25.732010] BUG: unable to handle kernel paging requestrun: /lkp/wfg/sr at 000000000000d908
[   24.986598] BUG: unable to handle kernel run: /lkp/wfg/srpaging request at 000000000000d908
[   24.914406] BUG: unable to handle kernel run: /lkp/wfg/srearly console in decompress_kernel

Which makes the generated bug ID not stable and hence not bisectable.

Fix it by printing the BUG message in one shot.

Signed-off-by Fengguang Wu <[email protected]>
---
 arch/x86/mm/fault.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
arch/x86/mm/fault.c +1 -2
index 3664279..f3e0e0a 100644
@@ -599,13 +599,13 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
 	}
 
-	printk(KERN_ALERT "BUG: unable to handle kernel ");
 	if (address < PAGE_SIZE)
-		printk(KERN_CONT "NULL pointer dereference");
+		printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer dereference at %p\n",

arch/x86/mm/fault.c show_fault_oops(struct pt_regs *regs, unsigned long error_code, · line 611

Quoted 10 lines
arch/x86/mm/fault.c +3 -2
+		       (void *) address);
 	else
-		printk(KERN_CONT "paging request");
+		printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer paging request at %p\n",
+		       (void *) address);
 
-	printk(KERN_CONT " at %p\n", (void *) address);
 	printk(KERN_ALERT "IP:");
 	printk_address(regs->ip);

That's been around forever, but I trust that an automated boot testing robot would find it more troublesome than most, so I agree it needs to be fixed. One problem: it changes the message from

	BUG: unable to handle kernel paging request at %p

to

	BUG: unable to handle kernel NULL pointer paging request at %p

and the test for address < PAGE_SIZE is supposed to be the determining factor on whether it is a "NULL pointer" or not. When that's fixed:

Acked-by David Rientjes <[email protected]>