"%pB" is intended for return addresses, and actually resolves the
address - 1. So it should only be used for backtraces. Plain
instruction addresses should use "%pS", which resolves the given
address.
show_regs was using "%pB" to resolve the RIP symbol. This resolved the
wrong symbol if the first instruction after a symbol created the
OOPS/BUG. For example:
0000000000000049 <before>:
49: 90 nop
4a: 90 nop
4b: 90 nop
4c: 90 nop
000000000000004d <suicide>:
4d: ff 14 25 00 00 00 00 callq *0x0
54: c3 retq
Will produce a message saying it's "before" that crashed, not "suicide".
This problem only happens when the crash occurs in the first instruction
after a symbol. Therefore it's unlikely to occur on kernels with frame
pointers (CONFIG_FRAME_POINTER=y).
Signed-off-by: Marek Majkowski <ma...@cloudflare.com>
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index deb6421..4c90013 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -27,6 +27,12 @@ static int die_counter;
void printk_address(unsigned long address, int reliable)
{
+ pr_cont(" [<%p>] %s%pS\n",
+ (void *)address, reliable ? "" : "? ", (void *)address);
+}
+
+static void printk_trace_address(unsigned long address, int reliable)
+{
pr_cont(" [<%p>] %s%pB\n",
(void *)address, reliable ? "" : "? ", (void *)address);
}
@@ -151,7 +157,7 @@ static void print_trace_address(void *data, unsigned long
addr, int reliable)
{
touch_nmi_watchdog();
printk(data);
- printk_address(addr, reliable);
+ printk_trace_address(addr, reliable);
}
static const struct stacktrace_ops print_trace_ops = {
--
1.8.3.2
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