lkml.org 
[lkml]   [2014]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [tip:perf/kprobes] kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist
(2014/05/06 5:48), Tony Luck wrote:
> This patch is in linux-next ("next-20140505") and I see a
> bunch of "Failed to find blacklist" messages when booting
> on ia64:
>
> 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
>
> What do these mean?

Ah, I forgot that ia64 has function descriptor :(
That means kprobes initial code has failed to get correct
entry address of the blacklisted functions.

In include/linux/kprobes.h, I defined NOKPROBE_SYMBOL to store
the addresses of blacklisted functions as below,

#define __NOKPROBE_SYMBOL(fname) \
static unsigned long __used \
__attribute__((section("_kprobe_blacklist"))) \
_kbl_addr_##fname = (unsigned long)fname;
#define NOKPROBE_SYMBOL(fname) __NOKPROBE_SYMBOL(fname)

_kbl_addr_XX stores the address of the function, but on IA64,
it stores the address of function descriptor.

Since those addresses are only used with kallsyms to lookup
function size, I think I should use a macro to store correct
function address instead of the address of function descriptor
on ia64 (and similar arch).
But I'm not sure which macro I should use... Is there any good way
to get the address of function, instead of function descriptor?

Thank you,

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




\
 
 \ /
  Last update: 2014-05-06 11:41    [W:0.164 / U:0.860 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site