*nux编程的108种奇易做图巧计-5(rsp寄存器)


昨天在家浏览了纽约大学的一个课件，找到一个例子，很有趣，我稍微修改了一下，支持32位和64位环境：如下。
     以后该系列采用这样的模式，首篇只贴代码，续篇进行解释和分析，期间希望读者朋友能自己做实验。
     理解该代码就算对rbp，rsp寄存器以及一些调用有了直接的接触。
     里面有两个奇怪的数字17和23，这是为什么呢？续篇给予解答。
     编译方法：
     64位环境：
       g++ -g  test.cpp -o test_64    //64位代码
       g++ -g  -m32 test.cpp -o test_32        //32位代码
    32位环境：
       g++ -g  test.cpp -o test_32
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/time.h>
        
int     done = 0;
int thread1( void )
{
        printf( "Hello from thread1 
" );
        while ( !done );
        printf( "
Thread1 is quitting
" );
        exit(0);
}       
        
int thread2( void )
{       
        printf( "Hello from thread2 
" );
        while ( !done );
        printf( "
Thread2 is quitting
" );
        exit(0);
}       
int thread3( void )
{
        printf( "Hello from thread3 
" );
        while ( !done );
        printf( "
Thread3 is quitting
" );
        exit(0);
}
int thread4( void )
{
        printf( "Hello from thread4 
" );
        while ( !done );
        printf( "
Thread4 is quitting
" );
        exit(0);
}
typedef int (*THREAD)(void);
THREAD  ready[] = { thread1, thread2, thread3, thread4 }; 
const int thread_count = sizeof( ready )/sizeof( THREAD );
int     next_thread = 0;        // array-index for ready list
void upon_signal( int signum )
{
        unsigned long   *tos;   // this is used for addressing the stack-frame
        #if defined(__i386__)
        asm(" movl %%ebp, %0 " : "=m" (tos) );  // initializes frame-pointer
        tos[17] = (unsigned long)ready[ next_thread ];
        #elif defined(__x86_64__)
        asm(" mov %%rbp, %0 " : "=m" (tos) );   // initializes frame-pointer
        tos[23] = (unsigned long)ready[ next_thread ];
        #endif
        // This was useful during development -- to display the stack elements
        //for (int i = 0; i < 30; i++) printf( "before:tos[%d]=%16X 
", i, tos[i] );
        next_thread = ( 1 + next_thread ) % thread_count;  // "circular" array
        if ( signum == SIGINT ) done = 1;       // to terminate on <CONTROL>-C
}
int main( int argc, char **argv )
{
        signal( SIGINT, upon_signal );
        struct itimerval  it;
        it.it_value.tv_sec = 1;
        it.it_value.tv_usec = 0;
        it.it_interval.tv_sec = 0;
        it.it_interval.tv_usec = 200000;
        setitimer( ITIMER_REAL, &it, NULL );
        signal( SIGALRM, upon_signal );
        while ( !done );
        printf( "
Quitting
" );
}

补充：综合编程 , 其他综合 ,