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Capable of loading a multiboot image into memory
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Michael Brown
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Jan 11, 2007
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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. | ||
| */ | ||
|
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||
| /** | ||
| * @file | ||
| * | ||
| * Multiboot image format | ||
| * | ||
| */ | ||
|
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| #include <errno.h> | ||
| #include <multiboot.h> | ||
| #include <gpxe/uaccess.h> | ||
| #include <gpxe/image.h> | ||
| #include <gpxe/segment.h> | ||
| #include <gpxe/elf.h> | ||
|
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| /** Boot modules must be page aligned */ | ||
| #define MB_FLAG_PGALIGN 0x00000001 | ||
|
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| /** Memory map must be provided */ | ||
| #define MB_FLAG_MEMMAP 0x00000002 | ||
|
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| /** Video mode information must be provided */ | ||
| #define MB_FLAG_VIDMODE 0x00000004 | ||
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| /** Image is a raw multiboot image (not ELF) */ | ||
| #define MB_FLAG_RAW 0x00010000 | ||
|
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| /** Multiboot flags that we support */ | ||
| #define MB_SUPPORTED_FLAGS ( MB_FLAG_PGALIGN | MB_FLAG_MEMMAP | \ | ||
| MB_FLAG_VIDMODE | MB_FLAG_RAW ) | ||
|
|
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| /** Compulsory feature multiboot flags */ | ||
| #define MB_COMPULSORY_FLAGS 0x0000ffff | ||
|
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| /** Optional feature multiboot flags */ | ||
| #define MB_OPTIONAL_FLAGS 0xffff0000 | ||
|
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||
| /** | ||
| * 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 ) | ||
|
|
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| /** 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; | ||
| }; | ||
|
|
||
| /** | ||
| * Execute multiboot image | ||
| * | ||
| * @v image ELF file | ||
| * @ret rc Return status code | ||
| */ | ||
| static int multiboot_execute ( struct image *image __unused ) { | ||
| return -ENOTSUP; | ||
| } | ||
|
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||
| /** | ||
| * 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; | ||
|
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||
| /* 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; | ||
| } | ||
|
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||
| /* No multiboot header found */ | ||
| return -ENOEXEC; | ||
| } | ||
|
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| /** | ||
| * 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; | ||
|
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| /* 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; | ||
| } | ||
|
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| /* Copy image to segment */ | ||
| copy_user ( buffer, 0, image->data, offset, filesz ); | ||
|
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| /* Record execution entry point */ | ||
| image->entry = hdr->mb.entry_addr; | ||
| image->execute = multiboot_execute; | ||
|
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| return 0; | ||
| } | ||
|
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| /** | ||
| * 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; | ||
|
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| /* Load ELF image*/ | ||
| if ( ( rc = elf_load ( image ) ) != 0 ) { | ||
| DBG ( "Multiboot ELF image failed to load: %s\n", | ||
| strerror ( rc ) ); | ||
| /* We must translate "not an ELF image" (i.e. ENOEXEC) | ||
| * into "invalid multiboot image", to avoid screwing | ||
| * up the image probing logic. | ||
| */ | ||
| if ( rc == -ENOEXEC ) { | ||
| return -ENOTSUP; | ||
| } else { | ||
| return rc; | ||
| } | ||
| } | ||
|
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| /* Capture execution method */ | ||
| if ( image->execute ) | ||
| image->execute = multiboot_execute; | ||
|
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| return 0; | ||
| } | ||
|
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| /** | ||
| * 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; | ||
|
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| /* 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 ); | ||
|
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| /* 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; | ||
| } | ||
|
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| /* 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; | ||
| } | ||
|
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| return 0; | ||
| } | ||
|
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| /** Multiboot image type */ | ||
| struct image_type multiboot_image_type __image_type = { | ||
| .name = "Multiboot", | ||
| .load = multiboot_load, | ||
| }; |