$uname -r
2.6.18-164.el5
$stap -V
SystemTap translator/driver (version 1.5/0.137 non-git sources)
Copyright (C) 2005-2011 Red Hat, Inc. and others
This is free software; see the source for copying conditions.
enabled features: LIBRPM LIBSQLITE3 NSS BOOST_SHARED_PTR TR1_UNORDERED_MAP NLS
$sudo stap -e \'probe vfs.add_to_page_cache {print_backtrace();println("")}\'
0xffffffff8000c633 : add_to_page_cache+0x0/0xc1 [kernel]
0xffffffff800c4565 : add_to_page_cache_lru+0xe/0x22 [kernel]
0xffffffff80025a10 : find_or_create_page+0x4b/0x72 [kernel]
0xffffffff80019b72 : __getblk+0x105/0x236 [kernel]
0xffffffff8803826a
0xffff811838293600 (inexact)
...但是有时候我们并没能得到全部的符号信息， 比如# 0xffffffff8803826a 这行是谁没打印出来吧。 原因是我们的模块可能被未知的模块所调用，这些模块的符号信息没有自动加载，所以systemtap当然就不知道谁是谁了！
解决方法 man stap 文档写的很清楚:
-d MODULE
Add symbol/unwind information for the given module into the kernel object module. This may enable symbolic tracebacks from those mod-
ules/programs, even if they do not have an explicit probe placed into them.
-ldd Add symbol/unwind information for all shared libraries suspected by ldd to be necessary for user-space binaries being probe or listed
with the -d option. Caution: this can make the probe modules considerably larger.
-all-modules
Equivalent to specifying “-dkernel” and a “-d” for each kernel module that is currently loaded. Caution: this can make the probe modules
considerably larger.
$sudo stap --all-modules -e \'probe vfs.add_to_page_cache {print_backtrace();println("")}\'
0xffffffff8000c633 : add_to_page_cache+0x0/0xc1 [kernel]
0xffffffff800c4565 : add_to_page_cache_lru+0xe/0x22 [kernel]
0xffffffff80025a10 : find_or_create_page+0x4b/0x72 [kernel]
0xffffffff80019b72 : __getblk+0x105/0x236 [kernel]
0xffffffff8803826a : journal_get_descriptor_buffer+0x30/0x0 [jbd]
0xffff81183f50c000 (inexact)0xffffffff8803826a 这行我们知道是谁了把, jbd. 知道了这个模块我们就可以这样：
$sudo stap -d jbd -e \'probe vfs.add_to_page_cache {print_backtrace();println("")}\'
0xffffffff8000c633 : add_to_page_cache+0x0/0xc1 [kernel]
0xffffffff800c4565 : add_to_page_cache_lru+0xe/0x22 [kernel]
0xffffffff80025a10 : find_or_create_page+0x4b/0x72 [kernel]
0xffffffff80019b72 : __getblk+0x105/0x236 [kernel]
0xffffffff8803826a : journal_get_descriptor_buffer+0x30/0x0 [jbd]
0xffff81183f50c000 (inexact)
...二个一样的的运行效果,只是生成的模块大小不一样，我们来看下:
$sudo stap -d jbd -m demo -p4 -e \'probe vfs.add_to_page_cache {print_backtrace();println("")}\'
demo.ko
$ll demo.ko
-rw-r--r-- 1 root root 2943293 Mar 26 22:14 demo.ko
$sudo stap --all-modules -m demo -p4 -e \'probe vfs.add_to_page_cache {print_backtrace();println("")}\'
demo.ko
$ll demo.ko
-rw-r--r-- 1 root root 3890409 Mar 26 22:15 demo.ko-all-modules的生成要大不少，不过很适合我们这样的懒人！
用户空间的程序用-ldd来搞定！