如何在dtrace中找到参数的意思 [英] how to find arguments mean in dtrace

问题描述

代码

dtrace -n 'syscall::read:entry /execname != "dtrace"/ { @reads[execname, fds[arg0].fi_pathname] = count(); }'
   dtrace: description 'syscall::read:entry ' matched 1 probe
   ^C
   bash            /proc/1709/psinfo                                                 1
   loader          /zp/space/f2                                                      1
   nscd            /etc/user_attr                                                    1
   bash            /export/home/mauroj/.bash_history                                 2
   loader          /zp/space/f3                                                      2
   nscd            /etc/group                                                        2
   su              /etc/default/su                                                   8
   su              /devices/pseudo/sy@0:tty                                          9
   bash            /dev/pts/5                                                       66
   Xorg            /devices/pseudo/conskbd@0:kbd                                   152
   gnome-terminal  /devices/pseudo/clone@0:ptm                                     254

dtrace代码fds[arg0].fi_pathname

如何查看dtrace调用参数是什么意思，我尝试使用

how to see the dtrace call arguments what's mean,i try to use

trace -lv 'syscall:fds:read:entry' |head
   ID   PROVIDER            MODULE                          FUNCTION NAME
    1     dtrace                                                     BEGIN

    Probe Description Attributes
        Identifier Names: Stable
        Data Semantics:   Stable
        Dependency Class: Common

    Argument Attributes
        Identifier Names: Stable

但是找不到参数? 怎么看这些装饰物的意思呢? 例如fds[arg0].fi_pathname

but can't find the arguments? how see these argements mean? eg fds[arg0].fi_pathname

举另一个例子:

 dtrace -n 'io:::start { @bytes = quantize(args[0]->b_bcount); }'

如何知道args [0]-> b_count表示系统调用字节

how to known the args[0]->b_count meant syscall bytes

推荐答案

作为

As the documentation explains, for the syscall provider's entry probes, arg0, arg1 etc. are the system call's arguments themselves. For syscall::read:entry, then, looking at the read(2) man page shows

 ssize_t read(int fildes, void *buf, size_t nbyte);

，因此arg0是fildes的值.

不幸的是，fds[]似乎没有在官方文档中进行描述. fds[]与DTrace提供给将文件描述符翻译成 fileinfo_t . fileinfo_t是一种稳定的结构，可提供有关文件的有用信息，而不会向用户公开实现细节.

Unfortunately, fds[] doesn't appear to be described in the official documentation. fds[] is something, similar to a subroutine, that DTrace provides to translate a file descriptor into a fileinfo_t. The fileinfo_t is a stable structure that provides useful information about a file without exposing the implementation details to the user.

io提供程序的文档指出: ，对于io:::start，args[0]是指向struct buf的指针.这是另一个文档错误:实际上是指向struct bufinfo的指针，该指针在同一页面上进行了描述.

The documentation for the io provider states that, for io:::start, args[0] is a pointer to a struct buf. This is another documentation bug: it's actually a pointer to a struct bufinfo, which is described on the same page.

这篇关于如何在dtrace中找到参数的意思的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！