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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

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

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

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

/**
 * 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 */
        void *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 */
        void *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 */
        void *initrd;
        /** Initrd size */
        physaddr_t initrd_size;
};

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

        /* Initialise context */
        memset ( bzimg, 0, sizeof ( *bzimg ) );

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

        /* Calculate size of real-mode portion */
        bzimg->rm_filesz = ( ( ( bzhdr->setup_sects ?
                                 bzhdr->setup_sects : 4 ) + 1 ) << 9 );
        if ( bzimg->rm_filesz > image->len ) {
                DBGC ( image, "bzImage %s too short for %zd byte of setup\n",
                       image->name, 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 ( bzhdr->boot_flag != BZI_BOOT_FLAG ) {
                DBGC ( image, "bzImage %s missing 55AA signature\n",
                       image->name );
                return -ENOEXEC;
        }
        if ( bzhdr->header == BZI_SIGNATURE ) {
                /* 2.00+ */
                bzimg->version = 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 ( bzhdr->syssize != syssize ) {
                        DBGC ( image, "bzImage %s bad syssize %x (expected "
                               "%x)\n", image->name, bzhdr->syssize,
                               syssize );
                        return -ENOEXEC;
                }
        }

        /* Determine image type */
        is_bzimage = ( ( bzimg->version >= 0x0200 ) ?
                       ( 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_virt ( 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_virt ( is_bzimage ? BZI_LOAD_HIGH_ADDR
                                        : BZI_LOAD_LOW_ADDR );

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

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

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

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

        return 0;
}

/**
 * Update bzImage header in loaded kernel
 *
 * @v image             bzImage file
 * @v bzimg             bzImage context
 */
static void bzimage_update_header ( struct image *image,
                                    struct bzimage_context *bzimg ) {
        struct bzimage_header *bzhdr = ( bzimg->rm_kernel + BZI_HDR_OFFSET );
        struct bzimage_cmdline *cmdline;

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

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

        /* Set command line */
        if ( bzimg->version >= 0x0202 ) {
                bzhdr->cmd_line_ptr = ( virt_to_phys ( bzimg->rm_kernel )
                                        + bzimg->rm_cmdline );
        } else {
                cmdline = ( bzimg->rm_kernel + BZI_CMDLINE_OFFSET );
                cmdline->magic = BZI_CMDLINE_MAGIC;
                cmdline->offset = bzimg->rm_cmdline;
                if ( bzimg->version >= 0x0200 )
                        bzhdr->setup_move_size = bzimg->rm_memsz;
        }

        /* Set video mode */
        bzhdr->vid_mode = bzimg->vid_mode;
        DBGC ( image, "bzImage %s vidmode %d\n",
               image->name, bzhdr->vid_mode );

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

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

        /* Look for "vga=" */
        if ( ( vga = image_argument ( image, "vga=" ) ) ) {
                sep = strchr ( vga, ' ' );
                if ( sep )
                        *sep = '\0';
                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, &end, 0 );
                        if ( *end ) {
                                DBGC ( image, "bzImage %s strange \"vga=\" "
                                       "terminator '%c'\n",
                                       image->name, *end );
                        }
                }
                if ( sep )
                        *sep = ' ';
        }

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

        return 0;
}

/**
 * Set command line
 *
 * @v image             bzImage image
 * @v bzimg             bzImage context
 */
static void bzimage_set_cmdline ( struct image *image,
                                  struct bzimage_context *bzimg ) {
        const char *cmdline = ( image->cmdline ? image->cmdline : "" );
        char *rm_cmdline;

        /* Copy command line down to real-mode portion */
        rm_cmdline = ( bzimg->rm_kernel + bzimg->rm_cmdline );
        snprintf ( rm_cmdline, bzimg->cmdline_size, "%s", cmdline );
        DBGC ( image, "bzImage %s command line \"%s\"\n",
               image->name, rm_cmdline );
}

/**
 * Check that initrds can be loaded
 *
 * @v image             bzImage image
 * @v bzimg             bzImage context
 * @ret rc              Return status code
 */
static int bzimage_check_initrds ( struct image *image,
                                   struct bzimage_context *bzimg ) {
        struct memmap_region region;
        physaddr_t min;
        physaddr_t max;
        physaddr_t dest;
        int rc;

        /* Calculate total loaded length of initrds */
        bzimg->initrd_size = initrd_len();

        /* Succeed if there are no initrds */
        if ( ! bzimg->initrd_size )
                return 0;

        /* Calculate available load region after reshuffling */
        if ( ( rc = initrd_region ( bzimg->initrd_size, &region ) ) != 0 ) {
                DBGC ( image, "bzImage %s no region for initrds: %s\n",
                       image->name, strerror ( rc ) );
                return rc;
        }

        /* Limit region to avoiding kernel itself */
        min = virt_to_phys ( bzimg->pm_kernel + bzimg->pm_sz );
        if ( min < region.min )
                min = region.min;

        /* Limit region to kernel's memory limit */
        max = region.max;
        if ( max > bzimg->mem_limit )
                max = bzimg->mem_limit;

        /* Calculate installation address */
        if ( max < ( bzimg->initrd_size - 1 ) ) {
                DBGC ( image, "bzImage %s not enough space for initrds\n",
                       image->name );
                return -ENOBUFS;
        }
        dest = ( ( max + 1 - bzimg->initrd_size ) & ~( INITRD_ALIGN - 1 ) );
        if ( dest < min ) {
                DBGC ( image, "bzImage %s not enough space for initrds\n",
                       image->name );
                return -ENOBUFS;
        }
        bzimg->initrd = phys_to_virt ( dest );

        DBGC ( image, "bzImage %s loading initrds from %#08lx downwards\n",
               image->name, max );
        return 0;
}

/**
 * Load initrds, if any
 *
 * @v image             bzImage image
 * @v bzimg             bzImage context
 */
static void bzimage_load_initrds ( struct image *image,
                                   struct bzimage_context *bzimg ) {
        size_t len;

        /* Do nothing if there are no initrds */
        if ( ! bzimg->initrd )
                return;

        /* Reshuffle initrds into desired order */
        initrd_reshuffle();

        /* Load initrds */
        DBGC ( image, "bzImage %s initrds at [%#08lx,%#08lx)\n",
               image->name, virt_to_phys ( bzimg->initrd ),
               ( virt_to_phys ( bzimg->initrd ) + bzimg->initrd_size ) );
        len = initrd_load_all ( bzimg->initrd );
        assert ( len == bzimg->initrd_size );
}

/**
 * Execute bzImage image
 *
 * @v image             bzImage image
 * @ret rc              Return status code
 */
static int bzimage_exec ( struct image *image ) {
        struct bzimage_context bzimg;
        int rc;

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

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

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

        /* Check that initrds can be loaded */
        if ( ( rc = bzimage_check_initrds ( image, &bzimg ) ) != 0 )
                return rc;

        /* Remove kernel from image list (without invalidating image pointer) */
        unregister_image ( image_get ( image ) );

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

        /* Store command line */
        bzimage_set_cmdline ( image, &bzimg );

        /* Prepare for exiting.  Must do this before loading initrds,
         * since loading the initrds will corrupt the external heap.
         */
        shutdown_boot();

        /* Load any initrds */
        bzimage_load_initrds ( image, &bzimg );

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

        DBGC ( image, "bzImage %s jumping to RM kernel at %04x:0000 (stack "
               "%04x:%04zx)\n", image->name, ( 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 */
}

/**
 * Probe bzImage image
 *
 * @v image             bzImage file
 * @ret rc              Return status code
 */
int bzimage_probe ( struct image *image ) {
        struct bzimage_context bzimg;
        int rc;

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

        return 0;
}

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