Subject: Re: [PATCH v5 2/2] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64

From: Masami Hiramatsu <[email-masked]>
Date: Tue, 08 Jul 2014 21:07:02 +0900

Ping?

This patch can be applied without 1/2, and will fix ia64/ppc64 problem.

Thank you,

(2014/07/02 16:00), 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 for kallsyms_lookup_size_offset() while initializing
> blacklist.
> 
> Changes in v5:
>  - Use arch_deref_entry_point() instead of function_entry().
> 
> Changes in v4:
>  - Add kernel_text_address() check for verifying the address.
>  - Moved on the latest linus tree.
> 
> Changes in v3:
>  - Fix a bug to get blacklist address based on function entry
>    instead of function descriptor. (Suzuki's work, Thanks!)
> 
> Changes in V2:
>  - Use function_entry() macro when lookin up symbols instead
>    of storing it.
>  - Update for the latest -next.
> 
> Signed-off-by: Masami Hiramatsu <[email-masked]>
> Reported-by: Tony Luck <[email-masked]>
> Tested-by: Tony Luck <[email-masked]>
> Cc: Michael Ellerman <[email-masked]>
> Cc: Suzuki K. Poulose <[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]
> ---
>  kernel/kprobes.c |   15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 3214289..ec370cc 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -32,6 +32,7 @@
>   *		<[email-masked]> added function-return probes.
>   */
>  #include <linux/kprobes.h>
> +#include <linux/types.h>
>  #include <linux/hash.h>
>  #include <linux/init.h>
>  #include <linux/slab.h>
> @@ -2037,19 +2038,23 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
>  {
>  	unsigned long *iter;
>  	struct kprobe_blacklist_entry *ent;
> -	unsigned long offset = 0, size = 0;
> +	unsigned long entry, offset = 0, size = 0;
>  
>  	for (iter = start; iter < end; iter++) {
> -		if (!kallsyms_lookup_size_offset(*iter, &size, &offset)) {
> -			pr_err("Failed to find blacklist %p\n", (void *)*iter);
> +		entry = arch_deref_entry_point((void *)*iter);
> +
> +		if (!kernel_text_address(entry) ||
> +		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
> +			pr_err("Failed to find blacklist at %p\n",
> +				(void *)entry);
>  			continue;
>  		}
>  
>  		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
>  		if (!ent)
>  			return -ENOMEM;
> -		ent->start_addr = *iter;
> -		ent->end_addr = *iter + size;
> +		ent->start_addr = entry;
> +		ent->end_addr = entry + size;
>  		INIT_LIST_HEAD(&ent->list);
>  		list_add_tail(&ent->list, &kprobe_blacklist);
>  	}
> 
> 
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-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email-masked]