From 5f01c98859073cb512b01d4fad74b5f4e047be0b Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Fri, 25 Oct 2013 15:06:58 +0200 Subject: x86/dumpstack: Fix printk_address for direct addresses Consider a kernel crash in a module, simulated the following way: static int my_init(void) { char *map = (void *)0x5; *map = 3; return 0; } module_init(my_init); When we turn off FRAME_POINTERs, the very first instruction in that function causes a BUG. The problem is that we print IP in the BUG report using %pB (from printk_address). And %pB decrements the pointer by one to fix printing addresses of functions with tail calls. This was added in commit 71f9e59800e5ad4 ("x86, dumpstack: Use %pB format specifier for stack trace") to fix the call stack printouts. So instead of correct output: BUG: unable to handle kernel NULL pointer dereference at 0000000000000005 IP: [] my_init+0x0/0x10 [pb173] We get: BUG: unable to handle kernel NULL pointer dereference at 0000000000000005 IP: [] 0xffffffffa0151fff To fix that, we use %pS only for stack addresses printouts (via newly added printk_stack_address) and %pB for regs->ip (via printk_address). I.e. we revert to the old behaviour for all except call stacks. And since from all those reliable is 1, we remove that parameter from printk_address. Signed-off-by: Jiri Slaby Cc: Namhyung Kim Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: joe@perches.com Cc: jirislaby@gmail.com Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@suse.cz Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 7a517bb41060..e7e1cac74e8d 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -596,7 +596,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, printk(KERN_CONT " at %p\n", (void *) address); printk(KERN_ALERT "IP:"); - printk_address(regs->ip, 1); + printk_address(regs->ip); dump_pagetable(address); } -- cgit v1.2.3