如何在gdb中使用逻辑地址？ [英] How to use a logical address in gdb?

问题描述

gdb提供读取或写入特定线性地址的功能，例如：

  （gdb）x / 1wx 0x080483e4 
 0x80483e4< main> ;: 0x83e58955 
（gdb）
  

但你如何指定一个逻辑地址？我来到以下指令：

  0x0804841a< + 6>：mov％gs：0x14，％eax 
  

如何在gdb的％gs：0x14处读取内存，或将此逻辑地址转换为线性地址我可以在 x 命令中使用吗？

注意：我知道我可以在此指令后简单读取％eax ，但这不是我关心的问题。 gdb中的0x14

您不能：GDB无法知道％gs 指已设置。

或将此逻辑地址转换为线性地址，即i可以在x命令中使用

同样，你不能一般这样做。但是，您似乎在32位x86 Linux上，并且可以 ％gs 设置为指向线程描述符通过 set_thread_area 系统调用。

您可以执行 catch syscall set_thread_area 在GDB中，并检查参数（每个线程将有一个这样的调用）。实际执行的代码是这里。一旦你知道如何设置％gs ，只需将0x14加入 base_addr 中即可。 / p>


gdb provides functionality to read or write to a specific linear address, for example:

(gdb) x/1wx 0x080483e4
0x80483e4 <main>:       0x83e58955
(gdb) 

but how do you specify a logical address ? I came accross the following instruction:

   0x0804841a <+6>:     mov    %gs:0x14,%eax

how can i read the memory at "%gs:0x14" in gdb, or translate this logical address to a linear address that i could use in x command ?

note: i know that i could simply read %eax after this instruction, but that is not my concern

解决方案

how can i read the memory at "%gs:0x14" in gdb

You can't: there is no way for GDB to know how the segment to which %gs refers to has been set up.

or translate this logical address to a linear address that i could use in x command

Again, you can't do this in general. However, you appear to be on 32-bit x86 Linux, and there you can do that -- the %gs is set up to point to the thread descriptor via set_thread_area system call.

You can do catch syscall set_thread_area in GDB, and examine the parameters (each thread will have one such call). The code to actually do that is here. Once you know how %gs has been set up, just add 0x14 to the base_addr, and you are done.

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