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multiboot.c
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multiboot.c
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/*
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/**
* @file
*
* Multiboot image format
*
*/
#include <errno.h>
#include <alloca.h>
#include <multiboot.h>
#include <gpxe/uaccess.h>
#include <gpxe/image.h>
#include <gpxe/segment.h>
#include <gpxe/memmap.h>
#include <gpxe/elf.h>
struct image_type multiboot_image_type __image_type;
/** Multiboot flags that we support */
#define MB_SUPPORTED_FLAGS ( MB_FLAG_PGALIGN | MB_FLAG_MEMMAP | \
MB_FLAG_VIDMODE | MB_FLAG_RAW )
/** Compulsory feature multiboot flags */
#define MB_COMPULSORY_FLAGS 0x0000ffff
/** Optional feature multiboot flags */
#define MB_OPTIONAL_FLAGS 0xffff0000
/**
* Multiboot flags that we don't support
*
* We only care about the compulsory feature flags (bits 0-15); we are
* allowed to ignore the optional feature flags.
*/
#define MB_UNSUPPORTED_FLAGS ( MB_COMPULSORY_FLAGS & ~MB_SUPPORTED_FLAGS )
/** A multiboot header descriptor */
struct multiboot_header_info {
/** The actual multiboot header */
struct multiboot_header mb;
/** Offset of header within the multiboot image */
size_t offset;
};
/**
* Build multiboot memory map
*
* @v mbinfo Multiboot information structure
* @v mbmemmap Multiboot memory map
*/
static void multiboot_build_memmap ( struct multiboot_info *mbinfo,
struct multiboot_memory_map *mbmemmap ) {
struct memory_map memmap;
unsigned int i;
/* Get memory map */
get_memmap ( &memmap );
/* Translate into multiboot format */
memset ( mbmemmap, 0, sizeof ( *mbmemmap ) );
for ( i = 0 ; i < memmap.count ; i++ ) {
mbmemmap[i].size = sizeof ( mbmemmap[i] );
mbmemmap[i].base_addr = memmap.regions[i].start;
mbmemmap[i].length = ( memmap.regions[i].end -
memmap.regions[i].start );
mbmemmap[i].type = MBMEM_RAM;
mbinfo->mmap_length += sizeof ( mbmemmap[i] );
if ( memmap.regions[i].start == 0 )
mbinfo->mem_lower = memmap.regions[i].end;
if ( memmap.regions[i].start == 0x100000 )
mbinfo->mem_upper = ( memmap.regions[i].end -
0x100000 );
}
}
/**
* Build multiboot module list
*
* @v image Multiboot image
* @v modules Module list to fill, or NULL
* @ret count Number of modules
*/
static unsigned int
multiboot_build_module_list ( struct image *image,
struct multiboot_module *modules ) {
struct image *module_image;
struct multiboot_module *module;
unsigned int count = 0;
for_each_image ( module_image ) {
/* Do not include kernel image as a module */
if ( module_image == image )
continue;
module = &modules[count++];
/* Populate module data structure, if applicable */
if ( ! modules )
continue;
module->mod_start = user_to_phys ( module_image->data, 0 );
module->mod_end = user_to_phys ( module_image->data,
module_image->len );
if ( image->cmdline )
module->string = virt_to_phys ( image->cmdline );
}
return count;
}
/**
* Execute multiboot image
*
* @v image Multiboot image
* @ret rc Return status code
*/
static int multiboot_exec ( struct image *image ) {
static const char *bootloader_name = "gPXE " VERSION;
struct multiboot_info mbinfo;
struct multiboot_memory_map mbmemmap[MAX_MEMORY_REGIONS];
struct multiboot_module *modules;
unsigned int num_modules;
/* Populate multiboot information structure */
memset ( &mbinfo, 0, sizeof ( mbinfo ) );
/* Set boot loader name */
mbinfo.boot_loader_name = virt_to_phys ( bootloader_name );
mbinfo.flags |= MBI_FLAG_LOADER;
/* Build memory map */
multiboot_build_memmap ( &mbinfo, mbmemmap );
mbinfo.mmap_addr = virt_to_phys ( &mbmemmap[0].base_addr );
mbinfo.flags |= ( MBI_FLAG_MEM | MBI_FLAG_MMAP );
/* Set command line, if present */
if ( image->cmdline ) {
mbinfo.cmdline = virt_to_phys ( image->cmdline );
mbinfo.flags |= MBI_FLAG_CMDLINE;
}
/* Construct module list */
num_modules = multiboot_build_module_list ( image, NULL );
modules = alloca ( num_modules * sizeof ( *modules ) );
multiboot_build_module_list ( image, modules );
mbinfo.mods_count = num_modules;
mbinfo.mods_addr = virt_to_phys ( modules );
mbinfo.flags |= MBI_FLAG_MODS;
/* Jump to OS with flat physical addressing */
__asm__ __volatile__ ( PHYS_CODE ( /* Preserve %ebp for alloca() */
"pushl %%ebp\n\t"
"call *%%edi\n\t"
"popl %%ebp\n\t" )
: : "a" ( MULTIBOOT_BOOTLOADER_MAGIC ),
"b" ( virt_to_phys ( &mbinfo ) ),
"D" ( image->entry )
: "ecx", "edx", "esi", "memory" );
return -ECANCELED;
}
/**
* Find multiboot header
*
* @v image Multiboot file
* @v hdr Multiboot header descriptor to fill in
* @ret rc Return status code
*/
static int multiboot_find_header ( struct image *image,
struct multiboot_header_info *hdr ) {
uint32_t buf[64];
size_t offset;
unsigned int buf_idx;
uint32_t checksum;
/* Scan through first 8kB of image file 256 bytes at a time.
* (Use the buffering to avoid the overhead of a
* copy_from_user() for every dword.)
*/
for ( offset = 0 ; offset < 8192 ; offset += sizeof ( buf[0] ) ) {
/* Check for end of image */
if ( offset > image->len )
break;
/* Refill buffer if applicable */
buf_idx = ( ( offset % sizeof ( buf ) ) / sizeof ( buf[0] ) );
if ( buf_idx == 0 ) {
copy_from_user ( buf, image->data, offset,
sizeof ( buf ) );
}
/* Check signature */
if ( buf[buf_idx] != MULTIBOOT_HEADER_MAGIC )
continue;
/* Copy header and verify checksum */
copy_from_user ( &hdr->mb, image->data, offset,
sizeof ( hdr->mb ) );
checksum = ( hdr->mb.magic + hdr->mb.flags +
hdr->mb.checksum );
if ( checksum != 0 )
continue;
/* Record offset of multiboot header and return */
hdr->offset = offset;
return 0;
}
/* No multiboot header found */
return -ENOEXEC;
}
/**
* Load raw multiboot image into memory
*
* @v image Multiboot file
* @v hdr Multiboot header descriptor
* @ret rc Return status code
*/
static int multiboot_load_raw ( struct image *image,
struct multiboot_header_info *hdr ) {
size_t offset;
size_t filesz;
size_t memsz;
userptr_t buffer;
int rc;
/* Verify and prepare segment */
offset = ( hdr->offset - hdr->mb.header_addr + hdr->mb.load_addr );
filesz = ( hdr->mb.load_end_addr - hdr->mb.load_addr );
memsz = ( hdr->mb.bss_end_addr - hdr->mb.load_addr );
buffer = phys_to_user ( hdr->mb.load_addr );
if ( ( rc = prep_segment ( buffer, filesz, memsz ) ) != 0 ) {
DBG ( "Multiboot could not prepare segment: %s\n",
strerror ( rc ) );
return rc;
}
/* Copy image to segment */
copy_user ( buffer, 0, image->data, offset, filesz );
/* Record execution entry point */
image->entry = hdr->mb.entry_addr;
return 0;
}
/**
* Load ELF multiboot image into memory
*
* @v image Multiboot file
* @ret rc Return status code
*/
static int multiboot_load_elf ( struct image *image ) {
int rc;
/* Load ELF image*/
if ( ( rc = elf_load ( image ) ) != 0 ) {
DBG ( "Multiboot ELF image failed to load: %s\n",
strerror ( rc ) );
return rc;
}
return 0;
}
/**
* Load multiboot image into memory
*
* @v image Multiboot file
* @ret rc Return status code
*/
int multiboot_load ( struct image *image ) {
struct multiboot_header_info hdr;
int rc;
/* Locate multiboot header, if present */
if ( ( rc = multiboot_find_header ( image, &hdr ) ) != 0 ) {
DBG ( "No multiboot header\n" );
return rc;
}
DBG ( "Found multiboot header with flags %08lx\n", hdr.mb.flags );
/* This is a multiboot image, valid or otherwise */
if ( ! image->type )
image->type = &multiboot_image_type;
/* Abort if we detect flags that we cannot support */
if ( hdr.mb.flags & MB_UNSUPPORTED_FLAGS ) {
DBG ( "Multiboot flags %08lx not supported\n",
( hdr.mb.flags & MB_UNSUPPORTED_FLAGS ) );
return -ENOTSUP;
}
/* Load the actual image */
if ( hdr.mb.flags & MB_FLAG_RAW ) {
if ( ( rc = multiboot_load_raw ( image, &hdr ) ) != 0 )
return rc;
} else {
if ( ( rc = multiboot_load_elf ( image ) ) != 0 )
return rc;
}
return 0;
}
/** Multiboot image type */
struct image_type multiboot_image_type __image_type = {
.name = "Multiboot",
.load = multiboot_load,
.exec = multiboot_exec,
};