使用gdb在Qemu上调试init [英] Debug init on Qemu using gdb

问题描述

我试图在Qemu上模拟cav octeon的mips64 linux内核。我目前在使用模式init代码时遇到了一些问题，并且想要调试init.i，我正在命令行中使用-s -S选项启动Qemu并运行gdb使用命令

ddd --debugger / OCTEON-SDK / tools / bin / mips64-octeon-linux-gnu-gdb / OCTEON-SDK / linux /kernel_2.6/linux/vmlinux

然后用命令附加gdb
$ b

target remote localhost：1234

gdb目前仅显示在内核空间中运行的指令。

我想问的是，有什么方法可以像内核空间一样，一步一步地调试usermode init和库指令？
例如，如果发布了 printf ，那么我想看看库中正在执行哪些指令以及控制是如何返回给内核的？

解决方案

我已经设法使用在是否可以使用gdb和qemu同时调试linux用户空间程序和内核空间？

您必须记住的唯一附加事项是：

• / sbin / init 只是符号链接 busybox ，因此您必须使用 / bin / busybox 作为目标文件


• main函数为 / sbin / init 实际上是 init_main ，遵循BusyBox对每个伪exe调用main的约定cutable as < exec> _main

这有点片状，但大多只是工作。

i am trying to emulate cavium octeon's mips64 linux kernel on Qemu.I am currently having some issues with use mode init code and want to debug init.i am starting the Qemu using -s -S option in the command line and running the gdb using command

ddd --debugger /OCTEON-SDK/tools/bin/mips64-octeon-linux-gnu-gdb /OCTEON-SDK/linux/kernel_2.6/linux/vmlinux

and then attaching the gdb with command

target remote localhost:1234

The gdb is currently showing only the instructions running in kernel space.

What i want to ask is there any method by which i can debug the usermode init and libraries instructions step by step as in case of kernel space? For example if printf is issued from init then i want to see that which instructions are being executed in the libraries and how the control is returned to kernel ?

解决方案

I have managed to step debug BusyBox's /sbin/init using the procedure described at: Is it possible to use gdb and qemu to debug linux user space programs and kernel space simultaneously?

The only additional things you have to keep in mind are:

• /sbin/init is just a symlink to busybox, so you must use /bin/busybox as the object file
• the "main" function for /sbin/init is actually init_main, following BusyBox' convention of calling the main for each pseudo-executable as <exec>_main

It is a bit flaky, but mostly just works.

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