看vmlinux的符号信息

ld的中文手册： 

 

 这里还有一本书  还不错介绍ELF。

 

用 xx-objdump 来查看 binary的信息，尤其是调试信息

 

这几天，一直在研究mips仿真器为什么不能源码级别调试汇编代码，

一直再看 vmlinux的debug symbol的相关的东西 ，特此做一些备忘录。

尤其是 一些objdump的选项。

 

又深入研究了下ELF的东西。

ELF太重要了。

 

 

以下都是 vmlinux 和 head.o为例的。

 

 

1，看起来， 每个版本的objdump的支持都不一样的。

至少输出的选项也是不一样的。

 

 

当然最有用就是：

-D : 反汇编所有的sections

-d : 反汇编executable sections

-S : 混合显示汇编代码和原始代码， 太有用了       ******

-t : 显示调试信息，尤其是可以显示出行号和文件名和路径（配合-l）

-l, --line-numbers             Include line numbers and filenames in output

下面就是endian的选择了

-EB --endian=big               Assume big endian format when disassembling

-EL --endian=little            Assume little endian format when disassembling

 

下面输出的 elf32-tradbigmips是支持的平台

 

 

[bob@localhost linux-2.6.20.9]$ /home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-objdump

-b

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-objdump: option requires an argument --

b

Usage: /home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-objdump

 Display information from object .

 At least one of the following switches must be given:

  -a, --archive-headers    Display archive header information

  -f, --file-headers       Display the contents of the overall file header

  -p, --private-headers    Display object format specific file header contents

  -h, --[section-]headers  Display the contents of the section headers

  -x, --all-headers        Display the contents of all headers

  -d, --disassemble        Display assembler contents of executable sections

  -D, --disassemble-all    Display assembler contents of all sections

  -S, --source             Intermix source code with disassembly

  -s, --full-contents      Display the full contents of all sections requested

  -g, --debugging          Display debug information in object file

  -G, --stabs              Display (in raw form) any STABS info in the file

  -t, --syms               Display the contents of the symbol table(s)

  -T, --dynamic-syms       Display the contents of the dynamic symbol table

  -r, --reloc              Display the relocation entries in the file

  -R, --dynamic-reloc      Display the dynamic relocation entries in the file

  -v, --version            Display this program's version number

  -i, --info               List object formats and architectures supported

  -H, --help               Display this information

 

 The following switches are optional:

  -b, --target=BFDNAME           Specify the target object format as BFDNAME

  -m, --architecture=MACHINE     Specify the target architecture as MACHINE

  -j, --section=NAME             Only display information for section NAME

  -M, --disassembler-options=OPT Pass text OPT on to the disassembler

  -EB --endian=big               Assume big endian format when disassembling

  -EL --endian=little            Assume little endian format when disassembling

      --file-start-context       Include context from start of file (with -S)

  -l, --line-numbers             Include line numbers and filenames in output

  -C, --demangle[=STYLE]         Decode mangled/processed symbol names

                                  The STYLE, if specified, can be `auto', 'gnu',

                                  'lucid', 'arm', 'hp', 'edg', or 'gnu-new-abi'

  -w, --wide                     Format output for more than 80 columns

  -z, --disassemble-zeroes       Do not skip blocks of zeroes when disassembling

      --start-address=ADDR       Only process data whoes address is >= ADDR

      --stop-address=ADDR        Only process data whoes address is <= ADDR

      --prefix-addresses         Print complete address alongside disassembly

      --[no-]show-raw-insn       Display hex alongside symbolic disassembly

      --adjust-vma=OFFSET        Add OFFSET to all displayed section addresses

 

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-objdump: supported targets: elf32-

tradbigmips elf32-tradlittlemips elf64-tradbigmips elf64-tradlittlemips ecoff-bigmips ecoff-

littlemips elf64-little elf64-big elf32-little elf32-big srec symbolsrec tekhex binary ihex

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-objdump: supported architectures: mips

mips:3000 mips:3900 mips:4000 mips:4010 mips:4100 mips:4111 mips:4300 mips:4400 mips:4600 mips:4650

mips:5000 mips:6000 mips:8000 mips:10000 mips:12000 mips:16 mips:mips5 mips:isa32 mips:isa64

mips:sb1

 

 

2，用法：比如

 

#mips-linux-objdump -D -l -t -x -S arch/mips/kernel/head.o

可以看到类似：

/home/work/data3/standby/dv_kernel_suspend2/linux/arch/mips/kernel/head.S:245

                li      t1, 0xFFFFFFF8              这个上面文件的245 line

  44:   3c09ffff        lui     t1,0xffff

  48:   3529fff8        ori     t1,t1,0xfff8       这两个是反汇编后的指令

 

这样我们可以很轻松的看出 li      t1, 0xFFFFFFF8 在汇编后，实际上是两条指令。

还有对应的行号和文件路径

 

其实这样，我我们就可以知道 代码实际上是如何执行的。

 

 

3，readelf 也可以显示 symbol信息：

 

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-readelf -s arch/mips/kernel/head.o

 

 

4， readelf -h 最有用的就是可以显示 kernel的入口点了。

 [bob@localhost linux]$ /home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-readelf -h vmlinux

ELF Header:

  Magic:   7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00

  Class:                             ELF32

  Data:                              2's complement, big endian

  Version:                           1 (current)

  OS/ABI:                            UNIX - System V

  ABI Version:                       0

  Type:                              EXEC (Executable file)

  Machine:                           MIPS R3000

  Version:                           0x1

  Entry point address:               0x8025e040

  Start of program headers:          52 (bytes into file)

  Start of section headers:          31477732 (bytes into file)

  Flags:                             0x10001001, noreorder, o32, mips2

  Size of this header:               52 (bytes)

  Size of program headers:           32 (bytes)

  Number of program headers:         3

  Size of section headers:           40 (bytes)

  Number of section headers:         31

  Section header string table index: 28

 

5，xx-ld –M  非常有用，可以到很多重要的信息

 

Xx-ld 可以跟其他的选项， man ld

Ld的中文手册： s

比如 编译kernel，最后的连接的过程：

 

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-ld -G 0 -static  -T arch/mips/ld.script arch/mips/kernel/head.o arch/mips/kernel/init_task.o init/main.o init/version.o init/do_mounts.o --start-group arch/mips/kernel/kernel.o arch/mips/mm/mm.o kernel/kernel.o mm/mm.o fs/fs.o ipc/ipc.o arch/mips/math-emu/fpu_emulator.o arch/mips/emma2_se/emma2.o  drivers/char/char.o drivers/block/block.o drivers/misc/misc.o drivers/net/net.o drivers/ide/idedriver.o drivers/pci/driver.o drivers/mtd/mtdlink.o drivers/net/wireless/wireless_net.o drivers/usb/usbdrv.o drivers/media/media.o drivers/md/mddev.o net/network.o arch/mips/lib/lib.a /home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a --end-group  -o vmlinux –M

 

你可以在后面加一个 –M 参数。

`-M'

`--print-map'

打印一个连接位图到标准输出.一个连接位图提供的关于连接的信息有如下一些:

* 目标文件和符号被映射到内存的哪些地方.

* 普通符号如何被分配空间.

* 所有被连接进来的档案文件,还有导致档案文件被包含进来的那个符号.

 

非常之详细。

 

比如：

 

.text.init     0x000000008025e000       0xb0 arch/mips/kernel/head.o

                0x000000008025e000                except_vec2_generic

                0x000000008025e038                except_vec_nmi

                0x000000008025e040                kernel_entry

                0x000000008025e028                except_vec4

                0x000000008025e030                except_vec_ejtag_debug

 .text.init     0x000000008025e0b0      0x758 init/main.o

                0x000000008025e1a4                calibrate_delay

                0x000000008025e564                start_kernel

 

 

。。。。

 

显示由谁连接来的。

LOAD arch/mips/kernel/head.o

LOAD arch/mips/kernel/init_task.o

LOAD init/main.o

LOAD init/version.o

LOAD init/do_mounts.o

START GROUP

LOAD arch/mips/kernel/kernel.o

LOAD arch/mips/mm/mm.o

LOAD kernel/kernel.o

LOAD mm/mm.o

LOAD fs/fs.o

LOAD ipc/ipc.o

LOAD arch/mips/math-emu/fpu_emulator.o

LOAD arch/mips/emma2_se/emma2.o

LOAD drivers/char/char.o

LOAD drivers/block/block.o

LOAD drivers/misc/misc.o

LOAD drivers/net/net.o

LOAD drivers/ide/idedriver.o

LOAD drivers/pci/driver.o

LOAD drivers/mtd/mtdlink.o

LOAD drivers/net/wireless/wireless_net.o

LOAD drivers/usb/usbdrv.o

LOAD drivers/media/media.o

LOAD drivers/md/mddev.o

LOAD net/network.o

LOAD arch/mips/lib/lib.a

LOAD /home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a

END GROUP

OUTPUT(vmlinux elf32-tradbigmips)

 

还可以看出 一些段上的详细内容， 不过，一些 东西，我也不知道：

。。。

.debug_line     0x0000000000000000   0x3b913a

 .debug_line    0x0000000000000000       0x93 arch/mips/kernel/head.o

 .debug_line    0x0000000000000093     0x299d arch/mips/kernel/init_task.o

 .debug_line    0x0000000000002a30     0x313e init/main.o

 .debug_line    0x0000000000005b6e       0x79 init/version.o

 .debug_line    0x0000000000005be7     0x39cd init/do_mounts.o

 .debug_line    0x00000000000095b4    0x32291 arch/mips/kernel/kernel.o

。。。

 

其他的选项：

`-s'

`--strip-all'

忽略输出文件中所有的符号信息.

`-S'

`--strip-debug'

忽略输出文件中所有的调试符号信息(但不是所有符号).

`-t'

`--trace'

打印'ld'处理的所有输入文件的名字.

 

命令例子1：-y function_name  :可以显示哪些.o 调用这个function

#mips-linux/bin/mips-linux-ld -G 0 -static  -T arch/mips/ld.script arch/mips/kernel/head.o arch/mips/kernel/init_task.o init/main.o init/version.o init/do_mounts.o --start-group arch/mips/kernel/kernel.o arch/mips/mm/mm.o kernel/kernel.o mm/mm.o fs/fs.o ipc/ipc.o arch/mips/math-emu/fpu_emulator.o arch/mips/emma2_se/emma2.o  drivers/char/char.o drivers/block/block.o drivers/misc/misc.o drivers/net/net.o drivers/ide/idedriver.o drivers/pci/driver.o drivers/mtd/mtdlink.o drivers/net/wireless/wireless_net.o drivers/usb/usbdrv.o drivers/media/media.o drivers/md/mddev.o net/network.o arch/mips/lib/lib.a /home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a --end-group  -o vmlinux  -y printk

===输出=== 可以看出 都有那些文件调用了printk ，不过好像不全

init/main.o: reference to printk

init/do_mounts.o: reference to printk

arch/mips/kernel/kernel.o: reference to printk

arch/mips/mm/mm.o: reference to printk

kernel/kernel.o: definition of printk

mm/mm.o: reference to printk

fs/fs.o: reference to printk

ipc/ipc.o: reference to printk

arch/mips/math-emu/fpu_emulator.o: reference to printk

arch/mips/emma2_se/emma2.o: reference to printk

drivers/char/char.o: reference to printk

drivers/block/block.o: reference to printk

drivers/net/net.o: reference to printk

drivers/ide/idedriver.o: reference to printk

drivers/pci/driver.o: reference to printk

drivers/mtd/mtdlink.o: reference to printk

drivers/usb/usbdrv.o: reference to printk

drivers/media/media.o: reference to printk

net/network.o: reference to printk

arch/mips/lib/lib.a(rtc-no.o): reference to printk

arch/mips/lib/lib.a(dump_tlb.o): reference to printk

/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a(dump_stack.o): reference to printk

 

 

命令例子2：你可以加 –t选项，知道哪些文件构成了vmlinux.

 

[bob@localhost linux]$ /home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-ld -G 0 -static  -T arch/mips/ld.script arch/mips/kernel/head.o arch/mips/kernel/init_task.o init/main.o init/version.o init/do_mounts.o --start-group arch/mips/kernel/kernel.o arch/mips/mm/mm.o kernel/kernel.o mm/mm.o fs/fs.o ipc/ipc.o arch/mips/math-emu/fpu_emulator.o arch/mips/emma2_se/emma2.o  drivers/char/char.o drivers/block/block.o drivers/misc/misc.o drivers/net/net.o drivers/ide/idedriver.o drivers/pci/driver.o drivers/mtd/mtdlink.o drivers/net/wireless/wireless_net.o drivers/usb/usbdrv.o drivers/media/media.o drivers/md/mddev.o net/network.o arch/mips/lib/lib.a /home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a --end-group  -o vmlinux  -t

 

======命令输出=========

/home/bob/gcc-3.2.2-uClibc-0.9.19/mips-linux/bin/mips-linux-ld: mode elf32btsmip

arch/mips/kernel/head.o

arch/mips/kernel/init_task.o

init/main.o

init/version.o

init/do_mounts.o

arch/mips/kernel/kernel.o

arch/mips/mm/mm.o

kernel/kernel.o

mm/mm.o

fs/fs.o

ipc/ipc.o

arch/mips/math-emu/fpu_emulator.o

arch/mips/emma2_se/emma2.o

drivers/char/char.o

drivers/block/block.o

drivers/net/net.o

drivers/ide/idedriver.o

drivers/pci/driver.o

drivers/mtd/mtdlink.o

drivers/usb/usbdrv.o

drivers/media/media.o

net/network.o

(arch/mips/lib/lib.a)csum_partial.o

(arch/mips/lib/lib.a)csum_partial_copy.o

(arch/mips/lib/lib.a)rtc-no.o

(arch/mips/lib/lib.a)memcpy.o

(arch/mips/lib/lib.a)memset.o

(arch/mips/lib/lib.a)strlen_user.o

(arch/mips/lib/lib.a)strncpy_user.o

(arch/mips/lib/lib.a)strnlen_user.o

(arch/mips/lib/lib.a)dump_tlb.o

(arch/mips/lib/lib.a)ide-no.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)errno.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)ctype.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)string.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)vsprintf.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)cmdline.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)rbtree.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)dump_stack.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)rwsem-spinlock.o

(/home/work/data3/standby/dv_kernel_suspend2/linux/lib/lib.a)zlib_inflate.o

 

 

 

 

 ELF的加载过程：