bzimage.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_LICENCE ( GPL2_OR_LATER );

/**
 * @file
 *
 * Linux bzImage image format
 *
 */

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <realmode.h>
#include <bzimage.h>
#include <gpxe/uaccess.h>
#include <gpxe/image.h>
#include <gpxe/segment.h>
#include <gpxe/init.h>
#include <gpxe/cpio.h>
#include <gpxe/features.h>

FEATURE ( FEATURE_IMAGE, "bzImage", DHCP_EB_FEATURE_BZIMAGE, 1 );

struct image_type bzimage_image_type __image_type ( PROBE_NORMAL );

/**
 * bzImage context
 */
struct bzimage_context {
        /** Boot protocol version */
        unsigned int version;
        /** Real-mode kernel portion load segment address */
        unsigned int rm_kernel_seg;
        /** Real-mode kernel portion load address */
        userptr_t rm_kernel;
        /** Real-mode kernel portion file size */
        size_t rm_filesz;
        /** Real-mode heap top (offset from rm_kernel) */
        size_t rm_heap;
        /** Command line (offset from rm_kernel) */
        size_t rm_cmdline;
        /** Command line maximum length */
        size_t cmdline_size;
        /** Real-mode kernel portion total memory size */
        size_t rm_memsz;
        /** Non-real-mode kernel portion load address */
        userptr_t pm_kernel;
        /** Non-real-mode kernel portion file and memory size */
        size_t pm_sz;
        /** Video mode */
        unsigned int vid_mode;
        /** Memory limit */
        uint64_t mem_limit;
        /** Initrd address */
        physaddr_t ramdisk_image;
        /** Initrd size */
        physaddr_t ramdisk_size;

        /** Command line magic block */
        struct bzimage_cmdline cmdline_magic;
        /** bzImage header */
        struct bzimage_header bzhdr;
};

/**
 * Parse bzImage header
 *
 * @v image             bzImage file
 * @v bzimg             bzImage context
 * @v src               bzImage to parse
 * @ret rc              Return status code
 */
static int bzimage_parse_header ( struct image *image,
                                  struct bzimage_context *bzimg,
                                  userptr_t src ) {
        unsigned int syssize;
        int is_bzimage;

        /* Sanity check */
        if ( image->len < ( BZI_HDR_OFFSET + sizeof ( bzimg->bzhdr ) ) ) {
                DBGC ( image, "bzImage %p too short for kernel header\n",
                       image );
                return -ENOEXEC;
        }

        /* Read in header structures */
        memset ( bzimg, 0, sizeof ( *bzimg ) );
        copy_from_user ( &bzimg->cmdline_magic, src, BZI_CMDLINE_OFFSET,
                         sizeof ( bzimg->cmdline_magic ) );
        copy_from_user ( &bzimg->bzhdr, src, BZI_HDR_OFFSET,
                         sizeof ( bzimg->bzhdr ) );

        /* Calculate size of real-mode portion */
        bzimg->rm_filesz =
                ( ( bzimg->bzhdr.setup_sects ? bzimg->bzhdr.setup_sects : 4 ) + 1 ) << 9;
        if ( bzimg->rm_filesz > image->len ) {
                DBGC ( image, "bzImage %p too short for %zd byte of setup\n",
                       image, bzimg->rm_filesz );
                return -ENOEXEC;
        }
        bzimg->rm_memsz = BZI_ASSUMED_RM_SIZE;

        /* Calculate size of protected-mode portion */
        bzimg->pm_sz = ( image->len - bzimg->rm_filesz );
        syssize = ( ( bzimg->pm_sz + 15 ) / 16 );

        /* Check for signatures and determine version */
        if ( bzimg->bzhdr.boot_flag != BZI_BOOT_FLAG ) {
                DBGC ( image, "bzImage %p missing 55AA signature\n", image );
                return -ENOEXEC;
        }
        if ( bzimg->bzhdr.header == BZI_SIGNATURE ) {
                /* 2.00+ */
                bzimg->version = bzimg->bzhdr.version;
        } else {
                /* Pre-2.00.  Check that the syssize field is correct,
                 * as a guard against accepting arbitrary binary data,
                 * since the 55AA check is pretty lax.  Note that the
                 * syssize field is unreliable for protocols between
                 * 2.00 and 2.03 inclusive, so we should not always
                 * check this field.
                 */
                bzimg->version = 0x0100;
                if ( bzimg->bzhdr.syssize != syssize ) {
                        DBGC ( image, "bzImage %p bad syssize %x (expected "
                               "%x)\n", image, bzimg->bzhdr.syssize, syssize );
                        return -ENOEXEC;
                }
        }

        /* Determine image type */
        is_bzimage = ( ( bzimg->version >= 0x0200 ) ?
                       ( bzimg->bzhdr.loadflags & BZI_LOAD_HIGH ) : 0 );

        /* Calculate load address of real-mode portion */
        bzimg->rm_kernel_seg = ( is_bzimage ? 0x1000 : 0x9000 );
        bzimg->rm_kernel = real_to_user ( bzimg->rm_kernel_seg, 0 );

        /* Allow space for the stack and heap */
        bzimg->rm_memsz += BZI_STACK_SIZE;
        bzimg->rm_heap = bzimg->rm_memsz;

        /* Allow space for the command line */
        bzimg->rm_cmdline = bzimg->rm_memsz;
        bzimg->rm_memsz += BZI_CMDLINE_SIZE;

        /* Calculate load address of protected-mode portion */
        bzimg->pm_kernel = phys_to_user ( is_bzimage ? BZI_LOAD_HIGH_ADDR
                                        : BZI_LOAD_LOW_ADDR );

        /* Extract video mode */
        bzimg->vid_mode = bzimg->bzhdr.vid_mode;

        /* Extract memory limit */
        bzimg->mem_limit = ( ( bzimg->version >= 0x0203 ) ?
                             bzimg->bzhdr.initrd_addr_max : BZI_INITRD_MAX );

        /* Extract command line size */
        bzimg->cmdline_size = ( ( bzimg->version >= 0x0206 ) ?
                                bzimg->bzhdr.cmdline_size : BZI_CMDLINE_SIZE );

        DBGC ( image, "bzImage %p version %04x RM %#lx+%#zx PM %#lx+%#zx "
               "cmdlen %zd\n", image, bzimg->version,
               user_to_phys ( bzimg->rm_kernel, 0 ), bzimg->rm_filesz,
               user_to_phys ( bzimg->pm_kernel, 0 ), bzimg->pm_sz,
               bzimg->cmdline_size );

        return 0;
}

/**
 * Update bzImage header in loaded kernel
 *
 * @v image             bzImage file
 * @v bzimg             bzImage context
 * @v dst               bzImage to update
 */
static void bzimage_update_header ( struct image *image,
                                    struct bzimage_context *bzimg,
                                    userptr_t dst ) {

        /* Set loader type */
        if ( bzimg->version >= 0x0200 )
                bzimg->bzhdr.type_of_loader = BZI_LOADER_TYPE_GPXE;

        /* Set heap end pointer */
        if ( bzimg->version >= 0x0201 ) {
                bzimg->bzhdr.heap_end_ptr = ( bzimg->rm_heap - 0x200 );
                bzimg->bzhdr.loadflags |= BZI_CAN_USE_HEAP;
        }

        /* Set command line */
        if ( bzimg->version >= 0x0202 ) {
                bzimg->bzhdr.cmd_line_ptr = user_to_phys ( bzimg->rm_kernel,
                                                           bzimg->rm_cmdline );
        } else {
                bzimg->cmdline_magic.magic = BZI_CMDLINE_MAGIC;
                bzimg->cmdline_magic.offset = bzimg->rm_cmdline;
                bzimg->bzhdr.setup_move_size = bzimg->rm_memsz;
        }

        /* Set video mode */
        bzimg->bzhdr.vid_mode = bzimg->vid_mode;

        /* Set initrd address */
        if ( bzimg->version >= 0x0200 ) {
                bzimg->bzhdr.ramdisk_image = bzimg->ramdisk_image;
                bzimg->bzhdr.ramdisk_size = bzimg->ramdisk_size;
        }

        /* Write out header structures */
        copy_to_user ( dst, BZI_CMDLINE_OFFSET, &bzimg->cmdline_magic,
                       sizeof ( bzimg->cmdline_magic ) );
        copy_to_user ( dst, BZI_HDR_OFFSET, &bzimg->bzhdr,
                       sizeof ( bzimg->bzhdr ) );

        DBGC ( image, "bzImage %p vidmode %d\n", image, bzimg->vid_mode );
}

/**
 * Parse kernel command line for bootloader parameters
 *
 * @v image             bzImage file
 * @v bzimg             bzImage context
 * @v cmdline           Kernel command line
 * @ret rc              Return status code
 */
static int bzimage_parse_cmdline ( struct image *image,
                                   struct bzimage_context *bzimg,
                                   const char *cmdline ) {
        char *vga;
        char *mem;

        /* Look for "vga=" */
        if ( ( vga = strstr ( cmdline, "vga=" ) ) ) {
                vga += 4;
                if ( strcmp ( vga, "normal" ) == 0 ) {
                        bzimg->vid_mode = BZI_VID_MODE_NORMAL;
                } else if ( strcmp ( vga, "ext" ) == 0 ) {
                        bzimg->vid_mode = BZI_VID_MODE_EXT;
                } else if ( strcmp ( vga, "ask" ) == 0 ) {
                        bzimg->vid_mode = BZI_VID_MODE_ASK;
                } else {
                        bzimg->vid_mode = strtoul ( vga, &vga, 0 );
                        if ( *vga && ( *vga != ' ' ) ) {
                                DBGC ( image, "bzImage %p strange \"vga=\""
                                       "terminator '%c'\n", image, *vga );
                        }
                }
        }

        /* Look for "mem=" */
        if ( ( mem = strstr ( cmdline, "mem=" ) ) ) {
                mem += 4;
                bzimg->mem_limit = strtoul ( mem, &mem, 0 );
                switch ( *mem ) {
                case 'G':
                case 'g':
                        bzimg->mem_limit <<= 10;
                case 'M':
                case 'm':
                        bzimg->mem_limit <<= 10;
                case 'K':
                case 'k':
                        bzimg->mem_limit <<= 10;
                        break;
                case '\0':
                case ' ':
                        break;
                default:
                        DBGC ( image, "bzImage %p strange \"mem=\" "
                               "terminator '%c'\n", image, *mem );
                        break;
                }
                bzimg->mem_limit -= 1;
        }

        return 0;
}

/**
 * Set command line
 *
 * @v image             bzImage image
 * @v bzimg             bzImage context
 * @v cmdline           Kernel command line
 * @ret rc              Return status code
 */
static int bzimage_set_cmdline ( struct image *image,
                                 struct bzimage_context *bzimg,
                                 const char *cmdline ) {
        size_t cmdline_len;

        /* Copy command line down to real-mode portion */
        cmdline_len = ( strlen ( cmdline ) + 1 );
        if ( cmdline_len > bzimg->cmdline_size )
                cmdline_len = bzimg->cmdline_size;
        copy_to_user ( bzimg->rm_kernel, bzimg->rm_cmdline,
                       cmdline, cmdline_len );
        DBGC ( image, "bzImage %p command line \"%s\"\n", image, cmdline );

        return 0;
}

/**
 * Load initrd
 *
 * @v image             bzImage image
 * @v initrd            initrd image
 * @v address           Address at which to load, or UNULL
 * @ret len             Length of loaded image, rounded up to 4 bytes
 */
static size_t bzimage_load_initrd ( struct image *image,
                                    struct image *initrd,
                                    userptr_t address ) {
        char *filename = initrd->cmdline;
        struct cpio_header cpio;
        size_t offset = 0;

        /* Do not include kernel image itself as an initrd */
        if ( initrd == image )
                return 0;

        /* Create cpio header before non-prebuilt images */
        if ( filename && filename[0] ) {
                size_t name_len = ( strlen ( filename ) + 1 );

                DBGC ( image, "bzImage %p inserting initrd %p as %s\n",
                       image, initrd, filename );
                memset ( &cpio, '0', sizeof ( cpio ) );
                memcpy ( cpio.c_magic, CPIO_MAGIC, sizeof ( cpio.c_magic ) );
                cpio_set_field ( cpio.c_mode, 0100644 );
                cpio_set_field ( cpio.c_nlink, 1 );
                cpio_set_field ( cpio.c_filesize, initrd->len );
                cpio_set_field ( cpio.c_namesize, name_len );
                if ( address ) {
                        copy_to_user ( address, offset, &cpio,
                                       sizeof ( cpio ) );
                }
                offset += sizeof ( cpio );
                if ( address ) {
                        copy_to_user ( address, offset, filename,
                                       name_len );
                }
                offset += name_len;
                offset = ( ( offset + 0x03 ) & ~0x03 );
        }

        /* Copy in initrd image body */
        if ( address )
                memcpy_user ( address, offset, initrd->data, 0, initrd->len );
        offset += initrd->len;
        if ( address ) {
                DBGC ( image, "bzImage %p has initrd %p at [%lx,%lx)\n",
                       image, initrd, user_to_phys ( address, 0 ),
                       user_to_phys ( address, offset ) );
        }

        /* Round up to 4-byte boundary */
        offset = ( ( offset + 0x03 ) & ~0x03 );
        return offset;
}

/**
 * Load initrds, if any
 *
 * @v image             bzImage image
 * @v bzimg             bzImage context
 * @ret rc              Return status code
 */
static int bzimage_load_initrds ( struct image *image,
                                  struct bzimage_context *bzimg ) {
        struct image *initrd;
        size_t total_len = 0;
        physaddr_t address;
        int rc;

        /* Add up length of all initrd images */
        for_each_image ( initrd )
                total_len += bzimage_load_initrd ( image, initrd, UNULL );

        /* Give up if no initrd images found */
        if ( ! total_len )
                return 0;

        /* Find a suitable start address.  Try 1MB boundaries,
         * starting from the downloaded kernel image itself and
         * working downwards until we hit an available region.
         */
        for ( address = ( user_to_phys ( image->data, 0 ) & ~0xfffff ) ; ;
              address -= 0x100000 ) {
                /* Check that we're not going to overwrite the
                 * kernel itself.  This check isn't totally
                 * accurate, but errs on the side of caution.
                 */
                if ( address <= ( BZI_LOAD_HIGH_ADDR + image->len ) ) {
                        DBGC ( image, "bzImage %p could not find a location "
                               "for initrd\n", image );
                        return -ENOBUFS;
                }
                /* Check that we are within the kernel's range */
                if ( ( address + total_len - 1 ) > bzimg->mem_limit )
                        continue;
                /* Prepare and verify segment */
                if ( ( rc = prep_segment ( phys_to_user ( address ), 0,
                                           total_len ) ) != 0 )
                        continue;
                /* Use this address */
                break;
        }

        /* Record initrd location */
        bzimg->ramdisk_image = address;
        bzimg->ramdisk_size = total_len;

        /* Construct initrd */
        DBGC ( image, "bzImage %p constructing initrd at [%lx,%lx)\n",
               image, address, ( address + total_len ) );
        for_each_image ( initrd ) {
                address += bzimage_load_initrd ( image, initrd,
                                                 phys_to_user ( address ) );
        }

        return 0;
}

/**
 * Execute bzImage image
 *
 * @v image             bzImage image
 * @ret rc              Return status code
 */
static int bzimage_exec ( struct image *image ) {
        struct bzimage_context bzimg;
        const char *cmdline = ( image->cmdline ? image->cmdline : "" );
        int rc;

        /* Read and parse header from loaded kernel */
        if ( ( rc = bzimage_parse_header ( image, &bzimg,
                                           image->priv.user ) ) != 0 )
                return rc;
        assert ( bzimg.rm_kernel == image->priv.user );

        /* Parse command line for bootloader parameters */
        if ( ( rc = bzimage_parse_cmdline ( image, &bzimg, cmdline ) ) != 0)
                return rc;

        /* Store command line */
        if ( ( rc = bzimage_set_cmdline ( image, &bzimg, cmdline ) ) != 0 )
                return rc;

        /* Load any initrds */
        if ( ( rc = bzimage_load_initrds ( image, &bzimg ) ) != 0 )
                return rc;

        /* Update kernel header */
        bzimage_update_header ( image, &bzimg, bzimg.rm_kernel );

        /* Prepare for exiting */
        shutdown ( SHUTDOWN_BOOT );

        DBGC ( image, "bzImage %p jumping to RM kernel at %04x:0000 "
               "(stack %04x:%04zx)\n", image, ( bzimg.rm_kernel_seg + 0x20 ),
               bzimg.rm_kernel_seg, bzimg.rm_heap );

        /* Jump to the kernel */
        __asm__ __volatile__ ( REAL_CODE ( "movw %w0, %%ds\n\t"
                                           "movw %w0, %%es\n\t"
                                           "movw %w0, %%fs\n\t"
                                           "movw %w0, %%gs\n\t"
                                           "movw %w0, %%ss\n\t"
                                           "movw %w1, %%sp\n\t"
                                           "pushw %w2\n\t"
                                           "pushw $0\n\t"
                                           "lret\n\t" )
                               : : "r" ( bzimg.rm_kernel_seg ),
                                   "r" ( bzimg.rm_heap ),
                                   "r" ( bzimg.rm_kernel_seg + 0x20 ) );

        /* There is no way for the image to return, since we provide
         * no return address.
         */
        assert ( 0 );

        return -ECANCELED; /* -EIMPOSSIBLE */
}

/**
 * Load bzImage image into memory
 *
 * @v image             bzImage file
 * @ret rc              Return status code
 */
int bzimage_load ( struct image *image ) {
        struct bzimage_context bzimg;
        int rc;

        /* Read and parse header from image */
        if ( ( rc = bzimage_parse_header ( image, &bzimg,
                                           image->data ) ) != 0 )
                return rc;

        /* This is a bzImage image, valid or otherwise */
        if ( ! image->type )
                image->type = &bzimage_image_type;

        /* Prepare segments */
        if ( ( rc = prep_segment ( bzimg.rm_kernel, bzimg.rm_filesz,
                                   bzimg.rm_memsz ) ) != 0 ) {
                DBGC ( image, "bzImage %p could not prepare RM segment: %s\n",
                       image, strerror ( rc ) );
                return rc;
        }
        if ( ( rc = prep_segment ( bzimg.pm_kernel, bzimg.pm_sz,
                                   bzimg.pm_sz ) ) != 0 ) {
                DBGC ( image, "bzImage %p could not prepare PM segment: %s\n",
                       image, strerror ( rc ) );
                return rc;
        }

        /* Load segments */
        memcpy_user ( bzimg.rm_kernel, 0, image->data,
                      0, bzimg.rm_filesz );
        memcpy_user ( bzimg.pm_kernel, 0, image->data,
                      bzimg.rm_filesz, bzimg.pm_sz );

        /* Update and write out header */
        bzimage_update_header ( image, &bzimg, bzimg.rm_kernel );

        /* Record real-mode segment in image private data field */
        image->priv.user = bzimg.rm_kernel;

        return 0;
}

/** Linux bzImage image type */
struct image_type bzimage_image_type __image_type ( PROBE_NORMAL ) = {
        .name = "bzImage",
        .load = bzimage_load,
        .exec = bzimage_exec,
};