load.c

一款类linux的操作系统源码

/* 
 *  Roadrunner/pk
 *    Copyright (C) 1989-2001  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <errno.h>
#include <fcntl.h>
#include <fs.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys.h>
#include <sys/ioctl.h>
#include <sys/load.h>

static int
start_sym_search(sections_t s, char *start_sym, char **start)
{
    int i;

    for (i = 1; i < s->symtabentries; i++)
	if (strcmp(s->strtab + s->symtab[i].st_name, start_sym) == 0) {
	    *start = (char *) (s->textoff + s->symtab[i].st_value - s->shdrtab[s->textndx].sh_addr);
#if _DEBUG
	    kprintf("%s %08x\n",
		    start_sym, (u_int) * start);
#endif
	    return 1;
	}
#if _DEBUG
    kprintf("start_sym_search: %s not found\n", start_sym);
#endif
    return 0;
}

int
load(char *path, char **prog, u_long * size, char **start)
{
    file_t file;
    u_long filesize;
    char *filebuf;
    struct sections s;
    int i, result, undefcnt;
	u_long *PICPID_DELTA;
	
    if (path == NULL || prog == NULL || size == NULL || start == NULL)
	return EINVAL;

    result = file_open(path, O_RDONLY, &file);
    if (result < 0) {
#if _DEBUG
	kprintf("load: could not open %s (%s)\n", path, strerror(result));
#endif
	return result;
    }

    result = file_ioctl(file, GET_FILE_SIZE, &filesize);
    if (result < 0) {
#if _DEBUG
	kprintf("load: could not get file size (%s)\n", strerror(result));
#endif
	file_close(file);
	return result;
    }

    filebuf = (char *) malloc(filesize);
    if (filebuf == NULL) {
#if _DEBUG
	kprintf("load: could not allocate file buffer\n");
#endif
	file_close(file);
	return ENOMEM;
    }

    /* XXX Read program file into memory in its entirety */
    result = file_read(file, filebuf, (int *) &filesize);
    if (result < 0) {
#if _DEBUG
	kprintf("load: could not read program file (%s)\n", strerror(result));
#endif
	free(filebuf);
	file_close(file);
	return result;
    }
    file_close(file);

    /* Determine program section information */
    result = init_sections(filebuf, &s);

    /* Search for undefined symbols */
    for (undefcnt = 0, i = 1; i < s.symtabentries; i++)
	if (s.symtab[i].st_shndx == SHN_UNDEF) {
	    if (undefcnt++ == 0)
		kprintf("load: undefined symbols:");
	    kprintf(" %s", s.strtab + s.symtab[i].st_name);
	}
    if (undefcnt > 0) {
	kprintf("\n");
	return ENOEXEC;
    }

    /* Determine amount of memory needed to load the program */
    *size = s.shdrtab[s.textndx].sh_size;
    
    if (s.datandx1 >= 0)
	*size += s.shdrtab[s.datandx1].sh_size;

    if (s.datandx2 >= 0)
	*size += s.shdrtab[s.datandx2].sh_size;
	
    if (s.datandx3 >= 0)
	*size += s.shdrtab[s.datandx3].sh_size;

    if (s.datandx4 >= 0)
	*size += s.shdrtab[s.datandx4].sh_size;

    /* Allocate and zero program memory */
    *prog = malloc(*size);
    if (*prog == NULL) {
#if _DEBUG
	kprintf("load: could not allocate program memory\n");
#endif
	free(filebuf);
	return ENOMEM;
    }
    bzero(*prog, *size);

    /* Load program sections into their executable locations */
    load_sections(&s, filebuf, *prog);

    /* Find start symbol */
    if (!start_sym_search(&s, STARTUP, start)) {
#if _DEBUG
	kprintf("load: no start symbol\n");
#endif
	free(filebuf);
	return ENOEXEC;
    }
    
    // PICPID_DELTA 程序LOAD的偏移值
    PICPID_DELTA = (u_long *)(*start + 2);
	*PICPID_DELTA = (u_long)*prog - s.shdrtab[s.textndx].sh_addr;
	
    free(filebuf);
    return 0;
}