Linux Modify Virtual Memory

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

/**
 * main - uses strdup to create a new string, loops forever-ever
 *
 * Return: EXIT_FAILURE if malloc failed. Other never returns
 */
int main(void)
{
     char *s;
     unsigned long int i;

     s = strdup("Hello virtual memory");
     if (s == NULL)
     {
          fprintf(stderr, "Can't allocate mem with malloc\n");
          return (EXIT_FAILURE);
     }
     i = 0;
     while (s)
     {
          printf("[%lu] %s (%p)\n", i, s, (void *)s);
          sleep(2);
          i++;
     }
     return (EXIT_SUCCESS);
}

./loop 
[0] Hello virtual memory (0x5cdeb6ed72a0)
[1] Hello virtual memory (0x5cdeb6ed72a0)

# 更改 1 个字节的数据
echo -ne "\x42" | sudo dd of=/proc/$(pidof loop)/mem bs=1 count=1 seek=$((0x5cdeb6ed72a0)) conv=notrunc

# 更改 4 个字节的数据
echo -ne "\x41\x42\x43\x44" | sudo dd of=/proc/$(pidof loop)/mem bs=1 count=4 seek=$((0x5cdeb6ed72a0)) conv=notrunc

# 更改 5 个字节的数据
echo -ne "\x41\x42\x43\x44\x00" | sudo dd of=/proc/$(pidof loop)/mem bs=1 count=5 seek=$((0x5cdeb6ed72a0)) conv=notrunc


echo -ne "\x41\x42\x43\x44\x44" | sudo dd of=/proc/$(pidof loop)/mem bs=1 count=5 seek=$((0x5cdeb6ed72a0)) conv=notrunc

sudo gdb -p $(pidof loop) -batch -ex "set {int}0x6515df2922a0 = 0x41424344" -ex "detach" -ex "quit"

sudo gdb -p $(pidof loop) -batch -ex "set {char}0x6515df2922a0 = 0x41" -ex "detach" -ex "quit"