[netwatch.git] / grubload / loader.c

/* loader.c
 * ELF loading subroutines
 * NetWatch multiboot loader
 *
 * Copyright (c) 2008 Jacob Potter and Joshua Wise.  All rights reserved.
 * This program is free software; you can redistribute and/or modify it under
 * the terms found in the file LICENSE in the root of this source tree. 
 *
 */

#include <elf.h>
#include <output.h>
#include <minilib.h>

static const unsigned char elf_ident[4] = { 0x7F, 'E', 'L', 'F' }; 

int load_elf (char * buf, int size) {

        Elf32_Ehdr * elf_hdr = (Elf32_Ehdr *) buf;
        Elf32_Shdr * elf_sec_hdrs = (Elf32_Shdr *) (buf + elf_hdr->e_shoff);

        /* Sanity check on ELF file */
        if (memcmp((void *)elf_hdr->e_ident, (void *)elf_ident, sizeof(elf_ident))) return -1;
        if (elf_hdr->e_type != ET_EXEC) return -1;
        if (elf_hdr->e_machine != EM_386) return -1;
        if (elf_hdr->e_version != EV_CURRENT) return -1;
        if (size < sizeof(Elf32_Ehdr)) return -1;
        if (((char *)&elf_sec_hdrs[elf_hdr->e_shnum]) > (buf + size)) return -1;

        char * string_table = buf + elf_sec_hdrs[elf_hdr->e_shstrndx].sh_offset;

        if (string_table > (buf + size)) return -1;

        int i;
        for (i = 0; i < elf_hdr->e_shnum; i++) {

                if (elf_sec_hdrs[i].sh_name == SHN_UNDEF) {
                        continue;
                }

                char * section_name = string_table + elf_sec_hdrs[i].sh_name;

                if ((elf_sec_hdrs[i].sh_type != SHT_PROGBITS) || !(elf_sec_hdrs[i].sh_flags & SHF_ALLOC)) {
                        outputf("Skipping %s", section_name);
                        continue;
                }

                outputf("Loading %s at %08x", section_name, elf_sec_hdrs[i].sh_addr);

                memcpy((void *)elf_sec_hdrs[i].sh_addr,
                       buf + elf_sec_hdrs[i].sh_offset,
                       elf_sec_hdrs[i].sh_size);
        }

        return 0;
}