powerpc/mm: Make NULL pointer deferences explicit on bad page faults.

[ Upstream commit 49a502ea23bf9dec47f8f3c3960909ff409cd1bb ] As several other arches including x86, this patch makes it explicit that a bad page fault is a NULL pointer dereference when the fault address is lower than PAGE_SIZE In the mean time, this page makes all bad_page_fault() messages shorter so that they remain on one single line. And it prefixes them by "BUG: " so that they get easily grepped. Signed-off-by: Christophe Leroy <[email protected]> [mpe: Avoid pr_cont()] Signed-off-by: Michael Ellerman <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
akeromi · Dec 5, 2019 · ba87ed0 · ba87ed0
1 parent d02f0fc
commit ba87ed0
Showing 1 changed file with 9 additions and 8 deletions.
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
@@ -633,21 +633,22 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 	switch (TRAP(regs)) {
 	case 0x300:
 	case 0x380:
-		printk(KERN_ALERT "Unable to handle kernel paging request for "
-			"data at address 0x%08lx\n", regs->dar);
+		pr_alert("BUG: %s at 0x%08lx\n",
+			 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
+			 "Unable to handle kernel data access", regs->dar);
 		break;
 	case 0x400:
 	case 0x480:
-		printk(KERN_ALERT "Unable to handle kernel paging request for "
-			"instruction fetch\n");
+		pr_alert("BUG: Unable to handle kernel instruction fetch%s",
+			 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
 		break;
 	case 0x600:
-		printk(KERN_ALERT "Unable to handle kernel paging request for "
-			"unaligned access at address 0x%08lx\n", regs->dar);
+		pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
+			 regs->dar);
 		break;
 	default:
-		printk(KERN_ALERT "Unable to handle kernel paging request for "
-			"unknown fault\n");
+		pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
+			 regs->dar);
 		break;
 	}
 	printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",