0x08048000 之前的内存用于 32 位机器是什么? [英] What's the memory before 0x08048000 used for in 32 bit machine?

问题描述

在 Linux 中，我了解到每个进程在 32 位机器中存储从 0x08048000 开始的数据(在 64 位机器中存储从 0x00400000 开始的数据.

In Linux, I learned that every process stores data starting at 0x08048000 in 32 bit machine (and 0x00400000 in 64 bit machine).

但我不知道从那里开始的原因.0x08048000之前之前的内存是干什么用的?

But I don't know the reason why starting from there. What's the memory before 0x08048000 used for?

更新:有些人认为它是为内核映射的.不过据我所知，Linux内核使用的是用户栈之后的高端内存.

Update: Some people think it's mapped for the kernel. However as far as I know, Linux kernel uses the high-end memory starting after the user stack.

推荐答案

答案真的是:一堆东西.可执行文件的加载地址没有神奇的意义，几乎任何东西都可以映射到较低的地址.常见的例子包括:C 库(如 C 库)、动态加载器 ld.so 和内核 VDSO(内核映射的动态代码库，它为 x86 Linux 中的内核提供一些接口).但是你可以使用 mmap() 系统调用来映射任何你想要的东西.

The answer is really: a bunch of things. There is no magical meaning to the load address of the executable and pretty much anything can be mapped to the lower addresses. Common examples including: C library (such as the C library), the dynamic loader ld.so and the kernel VDSO (kernel mapped dynamic code library that provides some of the interface to the kernel in x86 Linux). But you can pretty much map anything you desire there, using the mmap() system call.

例如在我的特定机器上，地图如下(获得但cat/proc/self/maps"):

For example on my specific machine the map is as follows (acquired but "cat /proc/self/maps"):

gby@watson:~$ cat /proc/self/maps 
001c0000-00317000 r-xp 00000000 08:01 245836     /lib/libc-2.12.1.so
00317000-00318000 ---p 00157000 08:01 245836     /lib/libc-2.12.1.so
00318000-0031a000 r--p 00157000 08:01 245836     /lib/libc-2.12.1.so
0031a000-0031b000 rw-p 00159000 08:01 245836     /lib/libc-2.12.1.so
0031b000-0031e000 rw-p 00000000 00:00 0 
00376000-00377000 r-xp 00000000 00:00 0          [vdso]
00852000-0086e000 r-xp 00000000 08:01 245783     /lib/ld-2.12.1.so
0086e000-0086f000 r--p 0001b000 08:01 245783     /lib/ld-2.12.1.so
0086f000-00870000 rw-p 0001c000 08:01 245783     /lib/ld-2.12.1.so
08048000-08051000 r-xp 00000000 08:01 2244617    /bin/cat
08051000-08052000 r--p 00008000 08:01 2244617    /bin/cat
08052000-08053000 rw-p 00009000 08:01 2244617    /bin/cat
09ab5000-09ad6000 rw-p 00000000 00:00 0          [heap]
b7502000-b7702000 r--p 00000000 08:01 4456455    /usr/lib/locale/locale-archive
b7702000-b7703000 rw-p 00000000 00:00 0 
b771b000-b771c000 r--p 002a1000 08:01 4456455    /usr/lib/locale/locale-archive
b771c000-b771e000 rw-p 00000000 00:00 0 
bfbd9000-bfbfa000 rw-p 00000000 00:00 0          [stack]

这篇关于0x08048000 之前的内存用于 32 位机器是什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！