loader.c

一个mips虚拟机非常好代码,使用C++来编写的,希望大家多学学,

//#include "stdarg.h"
#include "elf.h"
#include "stdlib.h"

/*

	panic(str, ...)
	--------------------------------------------------------------

	Print a message and abort.

*/

void panic(
    const char* message)
{
    puts("Loader panic:");
    puts(message);
    putchar('\n');
    abort();
}

/*

 	load_image()
	--------------------------------------------------------------

*/

extern int _etext; /* label at the end of the text segment */

char *ld_start = "loader starting\n";

int load_image(void)
{
    const char* image = (void*)(((long)&_etext + 3) & -8);
    Elf32_Ehdr* ehdr;
    Elf32_Phdr* phdr;
    int i;

    puts (ld_start);
    ehdr = (Elf32_Ehdr*)image;

    /* Verify the magic. */
    if (bcmp(ehdr->e_ident, ELFMAG, 4) != 0) {
	//panic(">>>%#s<<<", ehdr->e_ident);
	panic("No ELF header found in the boot image");
    }

    /* Go through the program headers, loading each one. */
    phdr = (Elf32_Phdr*)(image + ehdr->e_phoff);
 
    if (phdr == 0 || ehdr->e_phnum == 0)
	panic("No program headers found in the boot image");

    if (ehdr->e_phentsize != sizeof(Elf32_Phdr))
	panic("Bad program header size");

    for (i = 0; i < ehdr->e_phnum; ++i) {
    	puts ("Loader: Relocating section sized ");
        put_hex (phdr[i].p_filesz, 8, 1, 1, 'A');
        puts (" from ");
        put_hex (image + phdr[i].p_offset, 8, 1, 1, 'A');
        puts (" to ");
        put_hex (phdr[i].p_paddr, 8, 1, 1, 'A');
        puts (".\n");
	/*printf("Loader: relocating 0x%05x bytes from %p to %p\n",
	       (long)(phdr[i].p_filesz),
	       (long)(image + phdr[i].p_offset),
	       (long)(int)(phdr[i].p_paddr));*/
//	if (phdr[i].p_vaddr != phdr[i].p_paddr)
//	    panic("Paddr and vaddr differ");// in section %d", i);
	bcopy(image + phdr[i].p_offset,
	      (void*)(long)(int)(phdr[i].p_paddr), phdr[i].p_filesz);
    }

    puts ("Loader: jumping to entry pt ");
    put_hex (ehdr->e_entry, 8, 1, 1, 'A');
 //   printf("Loader: jumping to %p\n", (long)(int)(ehdr->e_entry));
    return ehdr->e_entry;
}