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/kernel/dumpstack.c | 11 ++++++++--- arch/x86/kernel/process_64.c | 2 +- 2 files changed, 9 insertions(+), 4 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index deb6421c9e69..d9c12d3022a7 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -25,12 +25,17 @@ unsigned int code_bytes = 64; int kstack_depth_to_print = 3 * STACKSLOTS_PER_LINE; static int die_counter; -void printk_address(unsigned long address, int reliable) +static void printk_stack_address(unsigned long address, int reliable) { pr_cont(" [<%p>] %s%pB\n", (void *)address, reliable ? "" : "? ", (void *)address); } +void printk_address(unsigned long address) +{ + pr_cont(" [<%p>] %pS\n", (void *)address, (void *)address); +} + #ifdef CONFIG_FUNCTION_GRAPH_TRACER static void print_ftrace_graph_addr(unsigned long addr, void *data, @@ -151,7 +156,7 @@ static void print_trace_address(void *data, unsigned long addr, int reliable) { touch_nmi_watchdog(); printk(data); - printk_address(addr, reliable); + printk_stack_address(addr, reliable); } static const struct stacktrace_ops print_trace_ops = { @@ -281,7 +286,7 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err) #else /* Executive summary in case the oops scrolled away */ printk(KERN_ALERT "RIP "); - printk_address(regs->ip, 1); + printk_address(regs->ip); printk(" RSP <%016lx>\n", regs->sp); #endif return 0; diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 45ab4d6fc8a7..176ad94e1d57 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -63,7 +63,7 @@ void __show_regs(struct pt_regs *regs, int all) unsigned int ds, cs, es; printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip); - printk_address(regs->ip, 1); + printk_address(regs->ip); printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx\n", regs->ss, regs->sp, regs->flags); printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n", -- cgit v1.2.3