Linux下core文件的使用方法详解
<p><span><strong>前言</strong></span></p>
<p>
有时候程序会异常退出而不带任何日志，此时就可以使用 code 文件进行分析，它会记录程序运行的内存，寄存器，堆栈指针等信息</p>
<p>
<span><strong>什么是core文件</strong></span></p>
<p>
通常在 Linux 下遇到程序异常退出或者中止，我们都会使用 core 文件进行分析，其中包含了程序运行时的内存，寄存器，堆栈指针等信息，格式为 ELF ，可以理解是程序工作当前状态转储成一个文件，通过工具分析这个文件，我们可以定位到程序异常退出或者终止时相应的堆栈调用等信息，为解决问题提供帮助。</p>
<p>
<span><strong>使用core文件调试</strong></span></p>
<p>
<strong>生成方法</strong></p>
<p>
查看当前 core 文件的状态</p>
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<code class="bash plain">$ </code><code class="bash functions">ulimit</code> <code class="bash plain">-a</code>
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<code class="bash plain">...</code>
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<code class="bash plain">-c: core </code><code class="bash functions">file</code> <code class="bash plain">size (blocks) 0 </code><code class="bash comments"># 关闭状态</code>
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<code class="bash plain">...</code>
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打开生成开关</p>
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<code class="bash functions">ulimit</code> <code class="bash plain">-c unlimited</code>
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<code class="bash functions">ulimit</code> <code class="bash plain">-a</code>
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<code class="bash plain">...</code>
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<code class="bash plain">-c: core </code><code class="bash functions">file</code> <code class="bash plain">size (blocks) unlimited</code>
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<code class="bash plain">...</code>
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对 core 文件的大小进行限制，单位为 blocks ，一般 1 block=512 bytes ，设置太小可能导致不会生成文件</p>
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<code class="bash plain">$ </code><code class="bash functions">ulimit</code> <code class="bash plain">-c 1024</code>
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<code class="bash plain">$ </code><code class="bash functions">ulimit</code> <code class="bash plain">-a</code>
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<code class="bash plain">...</code>
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<code class="bash plain">-c: core </code><code class="bash functions">file</code> <code class="bash plain">size (blocks) 1024</code>
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<code class="bash plain">...</code>
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关闭生成开关</p>
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<code class="bash functions">ulimit</code> <code class="bash plain">-c 0</code>
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<code class="bash functions">ulimit</code> <code class="bash plain">-a</code>
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<code class="bash plain">...</code>
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<code class="bash plain">-c: core </code><code class="bash functions">file</code> <code class="bash plain">size (blocks) 0</code>
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上面对 core 文件的操作仅对当前生效，若需要永久生效，则要将相应操作写入 /etc/profile</p>
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<span><strong>生成路径</strong></span></p>
<p>
core 文件默认生成在程序的工作目录，可以对生成路径进行设置，需要保证对对应目录有足够空间并具有写权限</p>
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<code class="bash functions">echo</code> <code class="bash plain">/MyCoreDumpDir/core</code><code class="bash plain">.%e.%p > </code><code class="bash plain">/proc/sys/kernel/core_pattern</code>
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<p>
其中命名使用的参数列表</p>
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<code class="bash plain">%p - insert pid into filename </code><code class="bash comments"># 添加 pid </code>
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<code class="bash plain">%u - insert current uid into filename </code><code class="bash comments"># 添加当前 uid </code>
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<code class="bash plain">%g - insert current gid into filename </code><code class="bash comments"># 添加当前 gid </code>
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<code class="bash plain">%s - insert signal that caused the coredump into the filename </code><code class="bash comments"># 添加导致产生 core 的信号 </code>
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<code class="bash plain">%t - insert UNIX </code><code class="bash functions">time</code> <code class="bash plain">that the coredump occurred into filename </code><code class="bash comments"># 添加 core 文件生成时的 unix 时间 </code>
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<code class="bash plain">%h - insert </code><code class="bash functions">hostname</code> <code class="bash plain">where the coredump happened into filename </code><code class="bash comments"># 添加主机名 </code>
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<code class="bash plain">%e - insert coredumping executable name into filename </code><code class="bash comments"># 添加命令名</code>
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<p>
/proc/sys/kernel/core_uses_pid 这个文件的值若为１，则无论时候配置 %p ,最后生成的 core 文件都会添加 pid</p>
<p>
<span><strong>调试方法</strong></span></p>
<p>
可以使用 gdb 对 core 文件进行调试，编译是需要带上 -g 选项</p>
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<code class="bash plain">$ gdb a.out</code>
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<code class="bash plain">...</code>
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<code class="bash plain">(gdb) core-</code><code class="bash functions">file</code> <code class="bash plain">core</code>
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<code class="bash plain">...</code>
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<code class="bash plain">(gdb) bt </code>
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如需要在 PC 上调试嵌入式设备产生的 core 文件，则需要选取相应平台的 gdb 工具，并在进入 gdb 后设置符号文件的位置</p>
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<code class="bash plain">$ xxx-xxx-gdb a.out</code>
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<code class="bash plain">...</code>
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<code class="bash plain">(gdb) solib-search-path xxx.so:xxx.so</code>
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<code class="bash plain">...</code>
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<code class="bash plain">(gdb) core-</code><code class="bash functions">file</code> <code class="bash plain">core</code>
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<code class="bash plain">...</code>
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<code class="bash plain">(gdb) bt</code>
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<code class="bash plain">...</code>
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<span><strong>总结</strong></span></p>
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以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。</p>
<p>
原文链接：http://answerywj.com/2018/03/07/usage-of-core-in-linux/</p>
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