apps/init/exe_elf.c

   1 /*
   2     meinOS - A unix-like x86 microkernel operating system
   3     Copyright (C) 2008  Janosch Gräf <janosch.graef@gmx.net>
   4
   5     This program is free software: you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation, either version 3 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 #include <sys/types.h>
  20 #include <stdlib.h>
  21 #include <fcntl.h>
  22 #include <unistd.h>
  23 #include <misc.h>
  24 #include <proc.h>
  25 #include <limits.h>
  26
  27 #include "exe_elf.h"
  28
  29 /**
  30  * Validates ELF header
  31  *  @param header Pointer to ELF header
  32  *  @return Whether header is valid
  33  */
  34 static int elf_validate(elf_header_t *header) {
  35   if (header->ident[EI_MAG0]!=ELFMAG0 || header->ident[EI_MAG1]!=ELFMAG1 || header->ident[EI_MAG2]!=ELFMAG2 || header->ident[EI_MAG3]!=ELFMAG3) return 0;
  36   if (header->machine!=EM_386) return 0;
  37   if (header->ident[EI_CLASS]!=ELFCLASS32) return 0;
  38   if (header->ident[EI_DATA]!=ELFDATA2LSB) return 0;
  39   if (header->ident[EI_VERSION]!=header->version) return 0;
  40   return 1;
  41 }
  42 #include <stdio.h>
  43 static int elf_loadseg(pid_t pid,int fh,void *mem_addr,size_t mem_size,size_t file_addr,size_t file_size,int writable) {
  44   if (mem_addr<(void*)USERSPACE_ADDRESS) return -1;
  45   size_t i;
  46   int ret = 0;
  47   pid_t own_pid = getpid();
  48
  49   lseek(fh,file_addr,SEEK_SET);
  50
  51   for (i=0;i<mem_size;i+=PAGE_SIZE) {
  52     void *buf = mem_alloc(PAGE_SIZE);
  53     size_t cur_count = i>file_size?0:(i+PAGE_SIZE>file_size?file_size%PAGE_SIZE:PAGE_SIZE);
  54     if (cur_count>0) read(fh,buf,cur_count);
  55     else memset(buf,0,PAGE_SIZE);
  56     if (proc_memmap(pid,mem_addr+i,mem_getphysaddr(buf),writable,1,0)==0) proc_memunmap(own_pid,buf);
  57     else {
  58       proc_memfree(own_pid,buf);
  59       ret = -1;
  60       break;
  61     }
  62   }
  63   return ret;
  64 }
  65
  66 void *elf_load(pid_t pid,const char *file) {
  67   int fh = open(file,O_RDONLY);
  68   if (fh!=-1) {
  69     size_t i;
  70     void *entrypoint;
  71     elf_header_t header;
  72     elf_progheader_t *progheader;
  73
  74     // Header
  75     read(fh,&header,sizeof(header));
  76     if (!elf_validate(&header)) return NULL;
  77     entrypoint = (void*)(header.entry);
  78
  79     // Program Headers
  80     progheader = malloc(sizeof(elf_progheader_t)*header.phnum);
  81     lseek(fh,header.phoff,SEEK_SET);
  82     read(fh,progheader,sizeof(elf_progheader_t)*header.phnum);
  83     for (i=0;i<header.phnum;i++) {
  84       if (progheader[i].type==PT_LOAD) {
  85         if (elf_loadseg(pid,fh,(void*)(progheader[i].vaddr),progheader[i].memsz,progheader[i].offset,progheader[i].filesz,(progheader[i].flags&PF_W)==PF_W)==-1) {
  86           entrypoint = NULL;
  87           break;
  88         }
  89       }
  90     }
  91
  92     free(progheader);
  93     close(fh);
  94     return entrypoint;
  95   }
  96   else return NULL;
  97 }