Messages in this thread Patch in this message | | | From | Marek Majkowski <> | Subject | [PATCH] Wrong symbol resolved for RIP on OOPS/BUG | Date | Wed, 6 Nov 2013 11:59:57 -0800 |
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"%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 <marek@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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