跟踪对共享库的调用

Question

我正在Linux下开发一个程序。

出于调试目的，我想跟踪从我的程序到某个（最好是共享的）库的所有调用。 （我不想跟踪库内发生的调用。）

对于系统调用，有 strace。是否有任何工具可以跟踪对共享库的调用？

Answer 1

您要查找的工具名为ltrace。它允许跟踪程序对所有（或一组给定）库的任何调用。

例如，以下调用将列出对共享库加载的外部函数的任何调用：

$> ltrace ls /
__libc_start_main(0x4028c0, 2, 0x7fff1f4e72d8, 0x411e60 <unfinished ...>
strrchr("ls", '/')                               = nil
setlocale(LC_ALL, "")                            = "en_US.UTF-8"
bindtextdomain("coreutils", "/usr/share/locale") = "/usr/share/locale"
textdomain("coreutils")                          = "coreutils"
__cxa_atexit(0x40a200, 0, 0, 0x736c6974756572)   = 0
isatty(1)                                        = 0
getenv("QUOTING_STYLE")                          = nil
getenv("COLUMNS")                                = nil
ioctl(1, 21523, 0x7fff1f4e6e80)                  = -1
getenv("TABSIZE")                                = nil
getopt_long(2, 0x7fff1, "abcdfghiklmnopqrstuvw:xABCDFGHI:"..., 0x413080, -1) = -1
...
+++ exited (status 0) +++

如果您想专注于特定的库，那么您应该使用--library=pattern 选项：

-l, --library library_pattern
    Display only calls to functions implemented by libraries that match
    library_pattern. Multiple library patterns can be specified with several
    instances of this option. Syntax of library_pattern is described in 
    section FILTER EXPRESSIONS.

    Note that while this option selects calls that might be directed to the 
    selected libraries, there's no actual guarantee that the call won't be 
    directed elsewhere due to e.g. LD_PRELOAD or simply dependency ordering.
    If you want to make sure that symbols in given library are actually called,
    use -x @library_pattern instead.

因此，例如，获取对libselinux.so.1 的调用列表是这样完成的：

$ ltrace -l libselinux.so.1 ls /
ls->freecon(0, 0xffffffff, 0x7f78c4eee628, 0)                           = 0
bin dev media root sbin sys usr boot etc home lib lost+found proc run tmp
+++ exited (status 0) +++

这次运行只调用了函数freecon()。