c - 我在哪里可以找到 libc 目标文件中的特定函数地址？

Question

我正试图在 libc 中找到一个函数的地址。

我知道我可以在 C 中做这样的事情:

printf("%x", (int) system);

但我不知道这是否为我提供了 libc 中系统函数的基地址。我假设它从程序内部提供了某种间接指针？

我正在运行 gdb 并做了:

info files

在运行程序时，但它给了我很多片段，我不知道去哪里看，除了那些有 libc.so 的片段？

编辑:

这是我在 gdb 中得到的，我想知道在这里我能找到像“system”、“printf”、“exit”等东西。我检查了 rodata 并且能够在那里找到系统，但我不知道这是否是函数本身:

    0x08048154 - 0x08048167 is .interp
    0x08048168 - 0x08048188 is .note.ABI-tag
    0x08048188 - 0x080481ac is .note.gnu.build-id
    0x080481ac - 0x080481d0 is .gnu.hash
    0x080481d0 - 0x08048290 is .dynsym
    0x08048290 - 0x08048326 is .dynstr
    0x08048326 - 0x0804833e is .gnu.version
    0x08048340 - 0x08048380 is .gnu.version_r
    0x08048380 - 0x08048388 is .rel.dyn
    0x08048388 - 0x080483d8 is .rel.plt
    0x080483d8 - 0x080483fb is .init
    0x08048400 - 0x080484b0 is .plt
    0x080484b0 - 0x08048892 is .text
    0x08048894 - 0x080488a8 is .fini
    0x080488a8 - 0x08048994 is .rodata
    0x08048994 - 0x080489c8 is .eh_frame_hdr
    0x080489c8 - 0x08048a98 is .eh_frame
    0x08049f08 - 0x08049f0c is .init_array
    0x08049f0c - 0x08049f10 is .fini_array
    0x08049f10 - 0x08049f14 is .jcr
---Type <return> to continue, or q <return> to quit---
    0x08049f14 - 0x08049ffc is .dynamic
    0x08049ffc - 0x0804a000 is .got
    0x0804a000 - 0x0804a034 is .got.plt
    0x0804a034 - 0x0804a03c is .data
    0x0804a03c - 0x0804a054 is .bss
    0xb7fde114 - 0xb7fde138 is .note.gnu.build-id in /lib/ld-linux.so.2
    0xb7fde138 - 0xb7fde1f8 is .hash in /lib/ld-linux.so.2
    0xb7fde1f8 - 0xb7fde2dc is .gnu.hash in /lib/ld-linux.so.2
    0xb7fde2dc - 0xb7fde4ac is .dynsym in /lib/ld-linux.so.2
    0xb7fde4ac - 0xb7fde642 is .dynstr in /lib/ld-linux.so.2
    0xb7fde642 - 0xb7fde67c is .gnu.version in /lib/ld-linux.so.2
    0xb7fde67c - 0xb7fde744 is .gnu.version_d in /lib/ld-linux.so.2
    0xb7fde744 - 0xb7fde7b4 is .rel.dyn in /lib/ld-linux.so.2
    0xb7fde7b4 - 0xb7fde7e4 is .rel.plt in /lib/ld-linux.so.2
    0xb7fde7f0 - 0xb7fde860 is .plt in /lib/ld-linux.so.2
    0xb7fde860 - 0xb7ff67ac is .text in /lib/ld-linux.so.2
    0xb7ff67c0 - 0xb7ffa7a0 is .rodata in /lib/ld-linux.so.2
    0xb7ffa7a0 - 0xb7ffae24 is .eh_frame_hdr in /lib/ld-linux.so.2
    0xb7ffae24 - 0xb7ffd71c is .eh_frame in /lib/ld-linux.so.2
    0xb7ffecc0 - 0xb7ffef34 is .data.rel.ro in /lib/ld-linux.so.2
    0xb7ffef34 - 0xb7ffefec is .dynamic in /lib/ld-linux.so.2
    0xb7ffefec - 0xb7ffeff8 is .got in /lib/ld-linux.so.2
    0xb7fff000 - 0xb7fff024 is .got.plt in /lib/ld-linux.so.2
---Type <return> to continue, or q <return> to quit---
    0xb7fff040 - 0xb7fff878 is .data in /lib/ld-linux.so.2
    0xb7fff878 - 0xb7fff938 is .bss in /lib/ld-linux.so.2
    0xb7e16174 - 0xb7e16198 is .note.gnu.build-id in /lib/i386-linux-gnu/libc.so.6
    0xb7e16198 - 0xb7e161b8 is .note.ABI-tag in /lib/i386-linux-gnu/libc.so.6
    0xb7e161b8 - 0xb7e19ec8 is .gnu.hash in /lib/i386-linux-gnu/libc.so.6
    0xb7e19ec8 - 0xb7e23438 is .dynsym in /lib/i386-linux-gnu/libc.so.6
    0xb7e23438 - 0xb7e2915e is .dynstr in /lib/i386-linux-gnu/libc.so.6
    0xb7e2915e - 0xb7e2a40c is .gnu.version in /lib/i386-linux-gnu/libc.so.6
    0xb7e2a40c - 0xb7e2a898 is .gnu.version_d in /lib/i386-linux-gnu/libc.so.6
    0xb7e2a898 - 0xb7e2a8d8 is .gnu.version_r in /lib/i386-linux-gnu/libc.so.6
    0xb7e2a8d8 - 0xb7e2d2e8 is .rel.dyn in /lib/i386-linux-gnu/libc.so.6
    0xb7e2d2e8 - 0xb7e2d348 is .rel.plt in /lib/i386-linux-gnu/libc.so.6
    0xb7e2d350 - 0xb7e2d420 is .plt in /lib/i386-linux-gnu/libc.so.6
    0xb7e2d420 - 0xb7f5eb6e is .text in /lib/i386-linux-gnu/libc.so.6
    0xb7f5eb70 - 0xb7f5fafb is __libc_freeres_fn in /lib/i386-linux-gnu/libc.so.6
    0xb7f5fb00 - 0xb7f5fcfe is __libc_thread_freeres_fn in /lib/i386-linux-gnu/libc.so.6
---Type <return> to continue, or q <return> to quit---
    0xb7f5fd00 - 0xb7f81754 is .rodata in /lib/i386-linux-gnu/libc.so.6
    0xb7f81754 - 0xb7f81767 is .interp in /lib/i386-linux-gnu/libc.so.6
    0xb7f81768 - 0xb7f88c0c is .eh_frame_hdr in /lib/i386-linux-gnu/libc.so.6
    0xb7f88c0c - 0xb7fb9f68 is .eh_frame in /lib/i386-linux-gnu/libc.so.6
    0xb7fb9f68 - 0xb7fba3c6 is .gcc_except_table in /lib/i386-linux-gnu/libc.so.6
    0xb7fba3c8 - 0xb7fbd928 is .hash in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe1d4 - 0xb7fbe1dc is .tdata in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe1dc - 0xb7fbe220 is .tbss in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe1dc - 0xb7fbe1e8 is .init_array in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe1e8 - 0xb7fbe260 is __libc_subfreeres in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe260 - 0xb7fbe264 is __libc_atexit in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe264 - 0xb7fbe274 is __libc_thread_subfreeres in /lib/i386-linux-gnu/libc.so.6
    0xb7fbe280 - 0xb7fbfda8 is .data.rel.ro in /lib/i386-linux-gnu/libc.so.6
    0xb7fbfda8 - 0xb7fbfe98 is .dynamic in /lib/i386-linux-gnu/libc.so.6
    0xb7fbfe98 - 0xb7fbfff4 is .got in /lib/i386-linux-gnu/libc.so.6
    0xb7fc0000 - 0xb7fc003c is .got.plt in /lib/i386-linux-gnu/libc.so.6
    0xb7fc0040 - 0xb7fc0ebc is .data in /lib/i386-linux-gnu/libc.so.6

Answer 1

这是找到映射到可执行文件中的函数地址的方法。

$ gdb program 
Reading symbols from ...done.
(gdb) print main
$1 = {int (int, char **)} 0x400d61 <main>
(gdb) print exit
$2 = {<text variable, no debug info>} 0x400910 <exit@plt>