Messages in this thread | | | Date | Thu, 7 Nov 2013 08:54:48 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] Wrong symbol resolved for RIP on OOPS/BUG |
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* Marek Majkowski <marek@cloudflare.com> wrote:
> "%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 = {
There's a recent commit from Jiri Slaby that I think tries to address the same problem:
8d4c812a3e5f x86/dumpstack: Fix printk_address for direct addresses
You can find it in the -tip tree:
git remote add tip git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
Thanks,
Ingo
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