为什么在使用gdb和/ proc / kcore时，我的vmlinux中没有调试符号？ [英] Why are there no debug symbols in my vmlinux when using gdb with /proc/kcore?

问题描述

我将所有 CONFIG_DEBUG _ 相关选项配置为 y ，但是当我尝试调试内核时，它发现没有调试符号：

I've configure all CONFIG_DEBUG_ related options to y,but when I try to debug the kernel,it says no debug symbols found:

gdb /usr/src/linux-2.6.32.9/vmlinux /proc/kcore

Reading symbols from /usr/src/linux-2.6.32.9/vmlinux...(no debugging symbols found)...done.

为什么？

推荐答案

这是我迄今为止最好的猜测：我不知道，也没关系。

Here is my best guess so far: I don't know, and it doesn't matter.

我不知道为什么GDB是打印消息（找不到调试符号）。我在构建自己的内核时实际上已经看到了这一点。我将内核配置为使用调试符号，但GDB在查看内核映像时仍会打印此消息。我从不费心去研究它，因为我的图像仍然可以很好地调试。尽管有消息，GDB仍然可以反汇编功能，添加断点，查找符号和单步执行功能。我从来没有注意到缺少调试功能。我猜你同样的事情发生在你身上。

I don't know why GDB is printing the message "(no debugging symbols found)". I've actually seen this when building my own kernels. I configure a kernel to use debug symbols, but GDB still prints this message when it looks at the kernel image. I never bothered to look into it, because my image can still be debugged fine. Despite the message, GDB can still disassemble functions, add breakpoints, look up symbols, and single-step through functions. I never noticed a lack of debugging functionality. I'm guessing that the same thing is happening to you.

编辑：根据你对这个问题的评论，它看起来像你正在用您的调试器搜索错误的符号。系统调用处理程序以 sys _ 的前缀开头，但您无法通过查看代码来判断。宏 SYSCALL_DEFINE4（ptrace，...）最后声明函数为 asmlinkage long sys_ptrace（...），尽管它有一些其他的疯狂的东西，如果你有 ftrace 启用。

Based on the your comments to the question, it looks like you were searching for the wrong symbol with your debugger. System call handlers start with a prefix of sys_, but you can't tell from looking at the code. The macro SYSCALL_DEFINE4(ptrace, ...) just ends up declaring the function as asmlinkage long sys_ptrace(...), although it does some other crazy stuff if you have ftrace enabled.

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