System.map 注解

最新推荐文章于 2023-12-19 17:47:39 发布

Fei_Zodiac

最新推荐文章于 2023-12-19 17:47:39 发布

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分类专栏： linux 系统文章标签： centos System.map 内核

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本文解析了位于/boot目录下的System.map文件，详细介绍了该文件作为RAM内存物理地址布局的作用及其内容结构。System.map文件记录了内核版本2.6.32的线性地址类型符号，包括内核代码、数据段等关键信息。

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该文件路径为/boot/System.map

该文件为RAM内存物理地址布局，内核版本为2.6.32

system.map 格式为：线性地址类型符号

00000000 A VDSO32_PRELINK

00000000 A xen_irq_disable_direct_reloc
00000000 A xen_save_fl_direct_reloc
00000040 A VDSO32_vsyscall_eh_frame_size
000001d5 A kexec_control_code_size
000001f0 A VDSO32_NOTE_MASK
00000400 A VDSO32_sigreturn
0000040c A VDSO32_rt_sigreturn
00000414 A VDSO32_vsyscall
00000424 A VDSO32_SYSENTER_RETURN
00400000 A phys_startup_32

c0400000 T _text 内核代码第一个字节处

......

c07e9ba4 T _etext 内核代码结束位置,同时也是初始化的数据开始处

......

c0a1d688 D _edata 未初始化的数据开始处，同时也是初始化的数据结束位置

......

c099a000 D _sdata 堆栈开始开始处

......

c0a96000 D __init_end 初始化结束位置

......

类型解释：

小写字母表示局部; 大写字母表示全局(外部).
A
The symbol's value is absolute, and will not be changed by further linking.

B
The symbol is in the uninitialized data section (known as BSS).

C
The symbol is common. Common symbols are uninitialized data. When linking, multiple common symbols may appear with the same name. If the symbol is defined anywhere, the common symbols are treated as undefined references. For more details on common symbols, see the discussion of -warn-common in Linker options.

D
The symbol is in the initialized data section.

G
The symbol is in an initialized data section for small objects. Some object file formats permit more efficient access to small data objects, such as a global int variable as opposed to a large global array.

I
The symbol is an indirect reference to another symbol. This is a GNU extension to the a.out object file format which is rarely used.

N
The symbol is a debugging symbol.

R
The symbol is in a read only data section.

S
The symbol is in an uninitialized data section for small objects.

T
The symbol is in the text (code) section.

U
The symbol is undefined.

V
The symbol is a weak object. When a weak defined symbol is linked with a normal defined symbol, the normal defined symbol is used with no error. When a weak undefined symbol is linked and the symbol is not defined, the value of the weak symbol becomes zero with no error.

W
The symbol is a weak symbol that has not been specifically tagged as a weak object symbol. When a weak defined symbol is linked with a normal defined symbol, the normal defined symbol is used with no error. When a weak undefined symbol is linked and the symbol is not defined, the value of the weak symbol becomes zero with no error.