如何将64位进程地址空间限制为小于4G? [英] How to limit a 64-bit process address space to less than 4G?

问题描述

当我执行64位进程并查看/proc/[pid]/maps时，布局显示共享库和堆栈节位于更大的地址中；例如以下内容:

When I execute a 64-bit process and look at /proc/[pid]/maps, the layout show that the shared libraries and stack section are in a larger address; such as the following:

7ffff7ffc000-7ffff7ffd000 r--p 0001d000 08:03 16643      /lib/ld-2.11.2.so
7ffff7ffd000-7ffff7ffe000 rw-p 0001e000 08:03 16643      /lib/ld-2.11.2.so
7ffff7ffe000-7ffff7fff000 rw-p 00000000 00:00 0
7ffffffea000-7ffffffff000 rw-p 00000000 00:00 0         [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]

我可以将这些部分限制为更少的4G空间，并且它仍然必须是64位进程，而不是将其编译为32位进程吗?

Can I limit these sections to less 4G space and it must still be a 64-bit process rather than compile it into a 32-bit process?

推荐答案

prelink(8) 工具和概念遭到了广泛的憎恶(并且可能未在您的发行版中提供)，您可以使用它来将库链接成二进制文件并存储到低内存中:

While the prelink(8) tool and concept are widely detested (and probably not shipped on your distribution), you may be able to use it to link libraries into a binary into low memory:

-r --reloc-only=ADDRESS
    Instead of prelinking, just relink given shared libraries
    to the specified base address.

由于库将映射到进程的地址由ld(1)确定，因此您可以修改Makefile以调用具有不同--section-start值的ld:

Since the address that libraries will be mapped into the process is determined by ld(1), you might be able to modify your Makefile to invoke ld with different --section-start values:

--section-start SECTION=ADDRESS
                           Set address of named section
-Tbss ADDRESS               Set address of .bss section
-Tdata ADDRESS              Set address of .data section
-Ttext ADDRESS              Set address of .text section
-Ttext-segment ADDRESS      Set address of text segment

我将text和bss片段下移到较低的地址:

I moved the text and bss segments down to lower addresses:

$ gcc -Wl,-Ttext-segment=0x200000 -Wl,-Tbss=0x400000 -o broken broken.c
$ readelf -a broken
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x200450
...

如果可以使用--section-start移动可执行文件中提供的所有部分，并使用prelink(8)将库向下移动，则可以将所有代码加载到4 GB以下.

If you can move all the sections provided in the executable with --section-start and move the libraries down with prelink(8), you might be able to get all the code loaded below 4 gigabytes.

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