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

From: "Suzuki K. Poulose" <[email-masked]>
Date: Mon, 26 May 2014 16:55:14 +0530

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 <[email-masked]>
> Reported-by: Tony Luck <[email-masked]>
> Cc: Tony Luck <[email-masked]>
> Cc: Fenghua Yu <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> Cc: Paul Mackerras <[email-masked]>
> Cc: Ananth N Mavinakayanahalli <[email-masked]>
> Cc: Kevin Hao <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> Cc: [email-masked]
> ---
>  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
Suzuki