Re: [RFT PATCH -next ] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

(2014/05/26 20:25), Suzuki K. Poulose wrote:
> On 05/07/2014 05:25 PM, Masami Hiramatsu wrote:
>> On ia64 and ppc64, the function pointer does not point the
>> entry address of the function, but the address of function
>> discriptor (which contains the entry address and misc
>> data.) Since the kprobes passes the function pointer stored
>> by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
>> initalizing its blacklist, it fails and reports many errors
>> as below.
>>
>>   Failed to find blacklist 0001013168300000
>>   Failed to find blacklist 0001013000f0a000
>>   Failed to find blacklist 000101315f70a000
>>   Failed to find blacklist 000101324c80a000
>>   Failed to find blacklist 0001013063f0a000
>>   Failed to find blacklist 000101327800a000
>>   Failed to find blacklist 0001013277f0a000
>>   Failed to find blacklist 000101315a70a000
>>   Failed to find blacklist 0001013277e0a000
>>   Failed to find blacklist 000101305a20a000
>>   Failed to find blacklist 0001013277d0a000
>>   Failed to find blacklist 00010130bdc0a000
>>   Failed to find blacklist 00010130dc20a000
>>   Failed to find blacklist 000101309a00a000
>>   Failed to find blacklist 0001013277c0a000
>>   Failed to find blacklist 0001013277b0a000
>>   Failed to find blacklist 0001013277a0a000
>>   Failed to find blacklist 000101327790a000
>>   Failed to find blacklist 000101303140a000
>>   Failed to find blacklist 0001013a3280a000
>>
>> To fix this bug, this introduces function_entry() macro to
>> retrieve the entry address from the given function pointer,
>> and uses it in NOKPROBE_SYMBOL().
>>
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Reported-by: Tony Luck <tony.luck@gmail.com>
>> Cc: Tony Luck <tony.luck@intel.com>
>> Cc: Fenghua Yu <fenghua.yu@intel.com>
>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> Cc: Paul Mackerras <paulus@samba.org>
>> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>> Cc: Kevin Hao <haokexin@gmail.com>
>> Cc: linux-ia64@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Cc: linuxppc-dev@lists.ozlabs.org
>> ---
>>  arch/ia64/include/asm/types.h    |    2 ++
>>  arch/powerpc/include/asm/types.h |   11 +++++++++++
>>  include/linux/kprobes.h          |    3 ++-
>>  include/linux/types.h            |    4 ++++
>>  4 files changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/ia64/include/asm/types.h b/arch/ia64/include/asm/types.h
>> index 4c351b1..6ab7b6c 100644
>> --- a/arch/ia64/include/asm/types.h
>> +++ b/arch/ia64/include/asm/types.h
>> @@ -27,5 +27,7 @@ struct fnptr {
>>  	unsigned long gp;
>>  };
>>  
>> +#define constant_function_entry(fn) (((struct fnptr *)(fn))->ip)
>> +
>>  #endif /* !__ASSEMBLY__ */
>>  #endif /* _ASM_IA64_TYPES_H */
>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>> index bfb6ded..fd297b8 100644
>> --- a/arch/powerpc/include/asm/types.h
>> +++ b/arch/powerpc/include/asm/types.h
>> @@ -25,6 +25,17 @@ typedef struct {
>>  	unsigned long env;
>>  } func_descr_t;
>>  
>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF = 1)
>> +/*
>> + * On PPC64 ABIv1 the function pointer actually points to the
>> + * function's descriptor. The first entry in the descriptor is the
>> + * address of the function text.
>> + */
>> +#define constant_function_entry(fn)	(((func_descr_t *)(fn))->entry)
>> +#else
>> +#define constant_function_entry(fn)	((unsigned long)(fn))
>> +#endif
>> +
>>  #endif /* __ASSEMBLY__ */
>>  
>>  #endif /* _ASM_POWERPC_TYPES_H */
>> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
>> index e059507..637eafe 100644
>> --- a/include/linux/kprobes.h
>> +++ b/include/linux/kprobes.h
>> @@ -40,6 +40,7 @@
>>  #include <linux/rcupdate.h>
>>  #include <linux/mutex.h>
>>  #include <linux/ftrace.h>
>> +#include <linux/types.h>
>>  
>>  #ifdef CONFIG_KPROBES
>>  #include <asm/kprobes.h>
>> @@ -485,7 +486,7 @@ static inline int enable_jprobe(struct jprobe *jp)
>>  #define __NOKPROBE_SYMBOL(fname)			\
>>  static unsigned long __used				\
>>  	__attribute__((section("_kprobe_blacklist")))	\
>> -	_kbl_addr_##fname = (unsigned long)fname;
>> +	_kbl_addr_##fname = constant_function_entry(fname);
>>  #define NOKPROBE_SYMBOL(fname)	__NOKPROBE_SYMBOL(fname)
> 
> 
> Throws up build errors for me :
> 
>   CC      kernel/notifier.o
> kernel/notifier.c:105:1: error: initializer element is not constant
>  NOKPROBE_SYMBOL(notifier_call_chain);
>  ^
> kernel/notifier.c:188:1: error: initializer element is not constant
>  NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
>  ^
> kernel/notifier.c:196:1: error: initializer element is not constant
>  NOKPROBE_SYMBOL(atomic_notifier_call_chain);
>  ^
> kernel/notifier.c:546:1: error: initializer element is not constant
>  NOKPROBE_SYMBOL(notify_die);
>  ^
> make[1]: *** [kernel/notifier.o] Error 1
> make: *** [kernel] Error 2

Thanks for the test!

>> +#define constant_function_entry(fn)	(((func_descr_t *)(fn))->entry)

Ah! right, This is not allowed for initialization...
I'll update it to deref pointer when it is used.

Thank you again!


> 
> Thanks
> Suzuki
> 
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com