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: [<ffffffffa01ac000>] my_init+0x0/0x10 [pb173]
We get:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
IP: [<ffffffffa0152000>] 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 <jslaby@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
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 <mingo@kernel.org>
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index deb6421..d9c12d3 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -25,12 +25,17 @@
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 @@
{
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 @@
#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;