如何设置最早的可能断点 [英] How to set earliest possible breakpoint

问题描述

我试图在模块加载到gdb之后立即停止。让我们假设二进制文件完全从所有符号信息中除去，所以没有main。

I'm trying to stop right after the module is loaded in gdb. Let's assume that the binary is completely stripped out of all symbol informations, so there's no main.

理想情况下，我会在入口点设置断点，但是这个想法会中断由于重定位：

Ideally I'd set the breakpoint on the entry point, but that idea breaks down due to relocations:

(gdb) info target
Symbols from "./application".
Local exec file:
    `./application', file type elf64-x86-64.
    Entry point: 0xc154
...
(gdb) break *0xc154
Breakpoint 1 at 0xc154
(gdb) r
Starting program: ./application 
Warning:
Cannot insert breakpoint 1.
Error accessing memory address 0xc154: Input/output error.

(gdb) info target
Symbols from "./application".
Unix child process:
    Using the running image of child process 22835.
    While running this, GDB does not access memory from...
Local exec file:
    `./application', file type elf64-x86-64.
    Entry point: 0x555555560154

即使那种作品（我可以设置一个新的新地址上的断点并禁用原始地址），它不能通过gdb脚本/批处理模式轻松执行，因为它在中间有一个失败的指令。

Even though that kind-of works (I could set a new breakpoint on the new address and disable the original), it cannot be easily executed via gdb script / batch mode, because it has a failing instruction in the middle.

一个方法来做到这一点？理想情况下，像运行单一指令，而不是运行将是有用的。

Is there a way to do that? Ideally something like "run single instruction", rather than "run" would be useful.

推荐答案

入口点：0xc154

Entry point: 0xc154

这是一个动态链接的，与位置无关的（PIE）二进制文件。

This is a dynamically-linked, position-independent (PIE) binary.

您希望在二进制文件被加载并重新定位之后，但在它执行任何操作之前，停止在动态链接器中。

You want to stop in the dynamic linker after that binary is loaded and relocated, but before it executed anything.

(gdb) set stop-on-solib-events 1
(gdb) run
Starting program: /tmp/a.out 
Stopped due to shared library event (no libraries added or removed)
(gdb) info target
Symbols from "/tmp/a.out".
Unix child process:
        Using the running image of child process 13746.
        While running this, GDB does not access memory from...
Local exec file:
        `/tmp/a.out', file type elf64-x86-64.
        Entry point: 0x5555555545f0
        ...

(gdb) bt
#0  __GI__dl_debug_state () at dl-debug.c:77
#1  0x00007ffff7ddd488 in dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=0x7ffff7ffe870) at rtld.c:1678
#2  0x00007ffff7defb24 in _dl_sysdep_start (start_argptr=<optimized out>, dl_main=0x7ffff7ddc6e0 <dl_main>) at ../elf/dl-sysdep.c:244
#3  0x00007ffff7ddf365 in _dl_start_final (arg=0x7fffffffe440) at rtld.c:338
#4  _dl_start (arg=0x7fffffffe440) at rtld.c:564
#5  0x00007ffff7ddb6b8 in _start () from /lib64/ld-linux-x86-64.so.2

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