1
熟悉Linux环境编程的童鞋,对gcc一定不是很陌生,它可以高效地将C/C++代码编译成可执行文件。在嵌入式开发领域,gcc更是无比的强大,采用不同编译平台的gcc编译器,对应地就可以生成该平台的bin文件。由于gcc功能强大,在编译Linux内核时,gcc会是编译器的首选。
熟悉编译原理的童鞋对map文件一定很熟悉,但若是平时对底层编译不是很清晰,或者主要开发工作集中在应用层的童鞋,可能对其了解就神乎其微了。这个时候,你就需要好好阅读本文,了解下map文件了。本文要给大家分享生成map文件的方法,后续笔者会再写相关的文章介绍map文件的具体内容。
假设我们有以下的测试源码,功能很简单:
#include
static int test_function(int arg)
{
printf("This is a function called: %s\n", __func__);
return arg;
}
int main(int argc, const char **argv)
{
test_function(0);
return 0;
}
通常我们要得到可执行文件,我们会输入编译命令:
gcc -o gcc_create_map_file gcc_create_map_file.c
得到输出结果,测试如下:
运行结果完全符合我们的期望,编译命令完成后,在当前目录下,生成了gcc_create_map_file这个可执行文件。
但是,如果我们要编译输出可执行文件的同时,也得到可执行文件对应的map文件呢?我们可以这样输入编译命令:
gcc -o gcc_create_map_file gcc_create_map_file.c -Wl,-Map=gcc.map
测试输出,完全没有问题:
编辑
我们对比2个编译命令可以发现,其实就是在原编译命令的后面加上了 "-Wl,-Map=gcc.map";其中-Wl,是告诉gcc编译器,这个是ld的选项参数;而-Map=xxx.map就是指定map文件输出的文件名称,这个名称xxx可以随意定义,map文件的路径可以是相对路径,也可以是绝对路径。以下就是map文件的详细内容,后续会有文章对它进行详细分析,现在大家先有个感官认识。
Archive member included to satisfy reference by file (symbol)
/usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o (__libc_csu_init)
Discarded input sections
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
.note.GNU-stack
0x0000000000000000 0x0 /tmp/cc6AliJG.o
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/crtend.o
.note.GNU-stack
0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crtn.o
Memory Configuration
Name Origin Length Attributes
*default* 0x0000000000000000 0xffffffffffffffff
Linker script and memory map
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
LOAD /tmp/cc6AliJG.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/libgcc.a
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/libgcc_s.so
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libc.so
START GROUP
LOAD /lib/x86_64-linux-gnu/libc.so.6
LOAD /usr/lib/x86_64-linux-gnu/libc_nonshared.a
LOAD /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
END GROUP
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/libgcc.a
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/libgcc_s.so
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/crtend.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crtn.o
[!provide] PROVIDE (__executable_start, 0x400000)
0x0000000000400238 . = (0x400000 + SIZEOF_HEADERS)
.interp 0x0000000000400238 0x1c
*(.interp)
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.note.gnu.build-id
0x0000000000400274 0x24
*(.note.gnu.build-id)
.note.gnu.build-id
0x0000000000400274 0x24 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
.hash
*(.hash)
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*(.gnu.hash)
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.dynsym 0x00000000004002b8 0x60
*(.dynsym)
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.dynstr 0x0000000000400318 0x3f
*(.dynstr)
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.gnu.version 0x0000000000400358 0x8
*(.gnu.version)
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.gnu.version_d 0x0000000000400360 0x0
*(.gnu.version_d)
.gnu.version_d
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.gnu.version_r 0x0000000000400360 0x20
*(.gnu.version_r)
.gnu.version_r
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[!provide] PROVIDE (__rela_iplt_end, .)
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.plt.got 0x0000000000400420 0x8
*(.plt.got)
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.text.unlikely
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*(.text.exit .text.exit.*)
*(.text.startup .text.startup.*)
*(.text.hot .text.hot.*)
*(.text .stub .text.* .gnu.linkonce.t.*)
.text 0x0000000000400430 0x2a /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
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.text 0x000000000040045a 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o
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*(.gnu.warning)
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*(SORT(.fini))
.fini 0x00000000004005e4 0x4 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o
0x00000000004005e4 _fini
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[!provide] PROVIDE (__etext, .)
[!provide] PROVIDE (_etext, .)
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.rodata 0x00000000004005f0 0x36
*(.rodata .rodata.* .gnu.linkonce.r.*)
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.rodata1
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0x58 (size before relaxing)
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0x78 (size before relaxing)
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*(.eh_frame.*)
.gcc_except_table
*(.gcc_except_table .gcc_except_table.*)
.gnu_extab
*(.gnu_extab*)
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*(.eh_frame)
*(.eh_frame.*)
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*(.exception_ranges .exception_ranges*)
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*(.tdata .tdata.* .gnu.linkonce.td.*)
.tbss
*(.tbss .tbss.* .gnu.linkonce.tb.*)
*(.tcommon)
.preinit_array 0x0000000000600e10 0x0
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*(.preinit_array)
[!provide] PROVIDE (__preinit_array_end, .)
.init_array 0x0000000000600e10 0x8
0x0000000000600e10 PROVIDE (__init_array_start, .)
*(SORT(.init_array.*) SORT(.ctors.*))
*(.init_array EXCLUDE_FILE(*crtend?.o *crtend.o *crtbegin?.o *crtbegin.o) .ctors)
.init_array 0x0000000000600e10 0x8 /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
0x0000000000600e18 PROVIDE (__init_array_end, .)
.fini_array 0x0000000000600e18 0x8
[!provide] PROVIDE (__fini_array_start, .)
*(SORT(.fini_array.*) SORT(.dtors.*))
*(.fini_array EXCLUDE_FILE(*crtend?.o *crtend.o *crtbegin?.o *crtbegin.o) .dtors)
.fini_array 0x0000000000600e18 0x8 /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
[!provide] PROVIDE (__fini_array_end, .)
.ctors
*crtbegin.o(.ctors)
*crtbegin?.o(.ctors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
*(SORT(.ctors.*))
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.dtors
*crtbegin.o(.dtors)
*crtbegin?.o(.dtors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
*(SORT(.dtors.*))
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.jcr 0x0000000000600e20 0x8
*(.jcr)
.jcr 0x0000000000600e20 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
.jcr 0x0000000000600e20 0x8 /usr/lib/gcc/x86_64-linux-gnu/5/crtend.o
.data.rel.ro
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*(.data.rel.ro .data.rel.ro.* .gnu.linkonce.d.rel.ro.*)
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0x0000000000600e28 _DYNAMIC
.got 0x0000000000600ff8 0x8
*(.got)
.got 0x0000000000600ff8 0x8 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
*(.igot)
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*(.got.plt)
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*(.igot.plt)
.igot.plt 0x0000000000601028 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
.data 0x0000000000601028 0x10
*(.data .data.* .gnu.linkonce.d.*)
.data 0x0000000000601028 0x4 /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o
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0x0000000000601028 __data_start
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0x0000000000601030 __dso_handle
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.tm_clone_table
0x0000000000601038 0x0
.tm_clone_table
0x0000000000601038 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o
.tm_clone_table
0x0000000000601038 0x0 /usr/lib/gcc/x86_64-linux-gnu/5/crtend.o
.data1
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0x36 (size before relaxing)
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/DISCARD/
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*(.gnu.lto_*)
OUTPUT(gcc_create_map_file elf64-x86-64)
好了,本文对使用gcc生成map文件的方法就介绍到这里了,如有疑问的话,可以与博主联系哦。
审核编辑:汤梓红
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