如何写于Debian / Ubuntu系统调用 [英] How to write system calls on debian/ubuntu
问题描述
我试图写我自己的系统调用。它只是返回当前时间。我知道我应该怎么办这个概念，我也经历了几个这样的链接：
-
<一个href=\"http://www.cs.rochester.edu/users/faculty/sandhya/csc256/assignments/adding-a-system-call.html\"相对=nofollow>另一个系统调用实现的
但我仍然困惑，并没有得到预期的效果。内核没有编译和其因问题崩溃。我曾尝试它3.X.X的debian的最新的稳定版
可能有人点我到一个干净的的Hello World 样的程序来开发系统调用？
修改
要回答以下中的，这里是我的问题：
-
文件3：Linux的X.X.X /弓/ 86 /内核/ syscall_table_32.S不在我的Linux文件夹中找到。我只好即兴，因此修改了以下文件：Linux的X.X.X /弓/ 86 /系统调用/ syscall_64.tbl -
以上（1）新文件提到过的
＆LT不同的模式;数字＆GT; ＆LT; 64 / X32 /常见＆GT; ＆LT;名称＆gt; ＆LT;入口点＆GT;和我进入了'313共同 -
内核映像没有编译成功，但我不能调用该函数。它给出了一个
未定义的引用的错误当我用gcc，为什么编译它？
这仅仅是例子，如何写一个简单的内核系统调用。
考虑下面的C函数system_strcpy（），简单地复制一个字符串到另一个。）类似什么的strcpy（确实
＃包括LT＆;＆stdio.h中GT;长system_strcpy（字符* DEST，为const char * SRC）
{
INT I = 0;
而（SRC [I]！= 0）
DEST [I] = SRC [我++]; DEST [I] = 0;
返回我;
}
写作之前，获得一个内核源代码的焦油和解压它得到一个Linux X.X.X目录。
文件1：Linux的X.X.X /测试/ system_strcpy.c
在linux-XXX内，名为测试创建一个目录，并保存code作为文件 system_strcpy.c 中吧。
＃包括LT＆; Linux的/ linkage.h＆GT;
＃包括LT＆;的Linux / kernel.h＆GT;
asmlinkage长system_strcpy（字符* DEST，为const char * SRC）
{
INT I = 0;
而（SRC [I]！= 0）
DEST [I] = SRC [我++]; DEST [I] = 0;
返回我;
}
文件2：Linux的X.X.X /测试/ Makefile文件
创建您在上面创建一个的Makefile 相同试验中目录，并把此行是：
OBJ-Y：= system_strcpy.o
文件3：Linux的X.X.X /弓/ 86 /内核/ syscall_table_32.S
现在，你有你的系统调用添加到系统调用表。
追加到文件中的以下行：
。长system_strcpy
的注：对于内核3.3及更高版本的
*请参阅：Linux的3.3.xx /弓/ 86 /系统调用/ syscall_64.tbl *
，并在那里，现在下面的一系列行的末尾添加：
310 64 process_vm_readv sys_process_vm_readv
311 64 process_vm_writev sys_process_vm_writev
312 64 KCMP sys_kcmp
313 64 system_strcpy system_strcpy
对于3.3版本的格式为：数量 ABI 名称 切入点
文件4：Linux的X.X.X /弓/ 86 /有/ ASM / unistd_32.h
的注：本节是多余的3.3和更高版本的内核的
在这个文件中，所有的系统调用的名称将有一个唯一的号码相关联。最后的系统调用数对后，添加一行
的#define __NR_system_strcpy 338
（如果337是与系统中的呼叫号码对最后一个系统呼叫相关联的号码）。
然后替换 NR_syscalls 值，说明系统的总数在此情况下（加1已有数），即调用 NR_syscalls 应该已经338和新的值是339。
的#define NR_syscalls 339
文件5：Linux的X.X.X /在include / linux / syscalls.h
附加到文件中我们的函数的原型。
asmlinkage长system_strcpy（字符* DEST，字符* SRC）;
之前的文件中的 #ENDIF 行。
文件6：在Makefile文件源目录的根目录
打开的Makefile 并找到行，其中核心-Y 定义，并添加目录测试到该行的末尾。
核心-Y + =内核/ MM / FS /测试/
现在编译内核。问题：使bzImage的-j4
执行以下命令根（或root权限）安装内核：使安装
重新启动系统。
要使用最近创建的系统调用的使用：
系统调用（338，DEST，SRC）; （或系统调用（313，DEST，SRC）; 的内核3.3+），而不是常规的strcpy 库函数。
的#includeunistd.h中
＃包括SYS / syscall.h
诠释的main（）
{
字符* DEST = NULL，* SRC =你好;
DEST =（字符*）malloc的（strlen的（SRC）+1）;
系统调用（338，DEST，SRC）; //系统调用（313，DEST，SRC）;内核3.3+
的printf（％S \\ n％S \\ n，SRC，DEST）;
返回0;
}
而不是像313等号码系统调用，您也可以直接使用 __ NR_system_strcpy
这是一个普通的例子。你需要做一个小实验，看看您的特定内核版本的作品。
I am trying to write a system call of my own. It would just return the current time. I know the concept of what should I do and I did go through a couple of links like these:
But I am still confused and have not got the desired result. The kernel is not compiling and its crashing due to problems. I have tried it on debian latest stable release of 3.X.X
Could someone point me out to a clean hello world kind of program to develop system calls?
EDIT
To the below answer, here are my problems:
File 3: linux-x.x.x/arch/x86/kernel/syscall_table_32.Sis not found in my linux folder. I had to improvise and so modified the following file:linux-x.x.x/arch/x86/syscalls/syscall_64.tblThe above (1) new file mentioned had different pattern of
<number> <64/x32/common> <name> <entry point>and my entry was `313 commonThe kernel image did compile successfully, but I couldnt call the function. It gives an
undefined reference" errorwhen i compile it with gcc. Why?
This is just example how to write a simple kernel system call. Consider the following C function system_strcpy() that simply copies one string into another: similar to what strcpy() does.
#include<stdio.h>
long system_strcpy(char* dest, const char* src)
{
int i=0;
while(src[i]!=0)
dest[i]=src[i++];
dest[i]=0;
return i;
}
Before writing, get a kernel source tar and untar it to get a linux-x.x.x directory.
File 1: linux-x.x.x/test/system_strcpy.c
Create a directory within the linux-x.x.x, named test and save this code as file system_strcpy.c in it.
#include<linux/linkage.h>
#include<linux/kernel.h>
asmlinkage long system_strcpy(char*dest, const char* src)
{
int i=0;
while(src[i]!=0)
dest[i]=src[i++];
dest[i]=0;
return i;
}
File 2: linux-x.x.x/test/Makefile
Create a Makefile within the same test directory you created above and put this line in it:
obj-y := system_strcpy.o
File 3: linux-x.x.x/arch/x86/kernel/syscall_table_32.S Now, you have to add your system call to the system call table. Append to the file the following line:
.long system_strcpy
NOTE: For Kernel 3.3 and higher versions.
*Refer:linux-3.3.xx/arch/x86/syscalls/syscall_64.tbl*
And in there, now add at the end of the following series of lines:
310 64 process_vm_readv sys_process_vm_readv
311 64 process_vm_writev sys_process_vm_writev
312 64 kcmp sys_kcmp
313 64 system_strcpy system_strcpy
The format for the 3.3 version is in:
number abi name entry point
File 4: linux-x.x.x/arch/x86/include/asm/unistd_32.h
NOTE: This section is redundant for 3.3 and higher kernel versions
In this file, the names of all the system calls will be associated with a unique number. After the last system call-number pair, add a line
#define __NR_system_strcpy 338
(if 337 was the number associated with the last system call in the system call-number pair).
Then replace NR_syscalls value, stating total number of system calls with (the existing number incremented by 1) i.e. in this case the NR_syscalls should've been 338 and the new value is 339.
#define NR_syscalls 339
File 5: linux-x.x.x/include/linux/syscalls.h
Append to the file the prototype of our function.
asmlinkage long system_strcpy(char *dest,char *src);
just before the #endif line in the file.
File 6: Makefile at the root of source directory.
Open Makefile and find the line where core-y is defined and add the directory test to the end of that line.
core-y += kernel/ mm/ fs/ test/
Now compile the kernel. Issue:
make bzImage -j4
Install the kernel by executing the following command as root(or with root permissions):
make install
Reboot the system.
To use the recently created system call use:
syscall(338,dest,src); (or syscall(313,dest,src); for kernel 3.3+) instead of the regular strcpy library function.
#include "unistd.h"
#include "sys/syscall.h"
int main()
{
char *dest=NULL,*src="Hello";
dest=(char*)malloc(strlen(src)+1);
syscall(338,dest,src);//syscall(313,dest,src); for kernel 3.3+
printf("%s \n %s\n",src,dest);
return 0;
}
Instead of numbers like 313,etc in syscall, you can also directly use __NR_system_strcpy
This is a generic example. You will need to do a little experimentation to see what works for your specific kernel version.
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