[Original]linux simple Beauty (ii)

Original link: Linux simple beauty (ii)

We saw in the previous chapter how to do simple things with syscall, and now we see if we can directly invoke the functions in the C standard library to do some "complex" things quickly:

1 Section . Data2FT DB"Now is %d",Ten3 4 Section . Text5 extern puts6 extern exit7 extern sleep8 extern printf9 Global MainTen  One Main: A     movEdi One - again:     -     DecEDI the     PushEDI -     Pushft -     Pagerprintf -      +     Push 1 -     PagerSleep +      A     CMPEdi0 at     jnzagain -  -     Pushmsg -     Pagerputs -      -     Push 0 in     PagerExit -      to msg: +Db"Happy xxx day!",0

The above code is simple, counting from 10 to 0, then printing one line and ending. Unlike the previous code, the function in the C standard library is called. The compilation is the same as before:

Nasm-e elf Main.asm

Let's see how to connect:

Gcc-m32-o Main MAIN.O

Good bird! It is important to note that my OS is ubuntu64, and the ASM code is 32 bits, if you start with ld-m elf_i386-lc-o main MAIN.O, you will first be prompted to find the C library, then you can enter/usr/lib, then use:

sudo ln-sv/lib/i386-linux-gun/libc.so.6 libc.so

Create a soft connect fix. But at run time prompt cannot find executable file! The file is clearly in the! Then connect with GCC, but to change the _start to main and load 32 libraries:

sudo apt-get install Ia32-libs

You will also be prompted not to find the H file, and then load the library:

sudo apt-get install G++-multilib

There are also 2 family libraries that can be loaded if necessary:

sudo apt-get install libc6:i386 libgcc1:i386 gcc-4.6-base:i386

Libstdc++5:i386 libstdc++6:i386

sudo apt-get install libc6-i386

Finally, some C code when compiling with STD=C99 will find that the hint can not get the structure size, then change to the following:

Gcc-d_gnu_source-std=c99 MAIN.C