source: bootcd/isolinux/syslinux-6.03/com32/lib/syslinux/load_linux.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009-2013 Intel Corporation; author: H. Peter Anvin
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * load_linux.c
 *
 * Load a Linux kernel (Image/zImage/bzImage).
 */

#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <minmax.h>
#include <errno.h>
#include <suffix_number.h>
#include <dprintf.h>

#include <syslinux/align.h>
#include <syslinux/linux.h>
#include <syslinux/bootrm.h>
#include <syslinux/movebits.h>
#include <syslinux/firmware.h>
#include <syslinux/video.h>

#define BOOT_MAGIC 0xAA55
#define LINUX_MAGIC ('H' + ('d' << 8) + ('r' << 16) + ('S' << 24))
#define OLD_CMDLINE_MAGIC 0xA33F

/* loadflags */
#define LOAD_HIGH       0x01
#define CAN_USE_HEAP    0x80

/* 
 * Find the last instance of a particular command line argument
 * (which should include the final =; do not use for boolean arguments)
 * Note: the resulting string is typically not null-terminated.
 */
static const char *find_argument(const char *cmdline, const char *argument)
{
    const char *found = NULL;
    const char *p = cmdline;
    bool was_space = true;
    size_t la = strlen(argument);

    while (*p) {
        if (isspace(*p)) {
            was_space = true;
        } else if (was_space) {
            if (!memcmp(p, argument, la))
                found = p + la;
            was_space = false;
        }
        p++;
    }

    return found;
}

/* Truncate to 32 bits, with saturate */
static inline uint32_t saturate32(unsigned long long v)
{
    return (v > 0xffffffff) ? 0xffffffff : (uint32_t) v;
}

/* Create the appropriate mappings for the initramfs */
static int map_initramfs(struct syslinux_movelist **fraglist,
                         struct syslinux_memmap **mmap,
                         struct initramfs *initramfs, addr_t addr)
{
    struct initramfs *ip;
    addr_t next_addr, len, pad;

    for (ip = initramfs->next; ip->len; ip = ip->next) {
        len = ip->len;
        next_addr = addr + len;

        /* If this isn't the last entry, extend the zero-pad region
           to enforce the alignment of the next chunk. */
        if (ip->next->len) {
            pad = -next_addr & (ip->next->align - 1);
            len += pad;
            next_addr += pad;
        }

        if (ip->data_len) {
            if (syslinux_add_movelist(fraglist, addr, (addr_t) ip->data, len))
                return -1;
        }
        if (len > ip->data_len) {
            if (syslinux_add_memmap(mmap, addr + ip->data_len,
                                    len - ip->data_len, SMT_ZERO))
                return -1;
        }
        addr = next_addr;
    }

    return 0;
}

static size_t calc_cmdline_offset(const struct syslinux_memmap *mmap,
                                  const struct linux_header *hdr,
                                  size_t cmdline_size, addr_t base,
                                  addr_t start)
{
    size_t max_offset;

    if (hdr->version >= 0x0202 && (hdr->loadflags & LOAD_HIGH))
        max_offset = 0x10000;
    else
        max_offset = 0xfff0 - cmdline_size;

    if (!syslinux_memmap_highest(mmap, SMT_FREE, &start,
                                 cmdline_size, 0xa0000, 16) ||
        !syslinux_memmap_highest(mmap, SMT_TERMINAL, &start,
                                 cmdline_size, 0xa0000, 16)) {
        

        return min(start - base, max_offset) & ~15;
    }

    dprintf("Unable to find lowmem for cmdline\n");
    return (0x9ff0 - cmdline_size) & ~15; /* Legacy value: pure hope... */
}

int bios_boot_linux(void *kernel_buf, size_t kernel_size,
                    struct initramfs *initramfs,
                    struct setup_data *setup_data,
                    char *cmdline)
{
    struct linux_header hdr, *whdr;
    size_t real_mode_size, prot_mode_size, base;
    addr_t real_mode_base, prot_mode_base, prot_mode_max;
    addr_t irf_size;
    size_t cmdline_size, cmdline_offset;
    struct setup_data *sdp;
    struct syslinux_rm_regs regs;
    struct syslinux_movelist *fraglist = NULL;
    struct syslinux_memmap *mmap = NULL;
    struct syslinux_memmap *amap = NULL;
    uint32_t memlimit = 0;
    uint16_t video_mode = 0;
    const char *arg;

    cmdline_size = strlen(cmdline) + 1;

    errno = EINVAL;
    if (kernel_size < 2 * 512) {
        dprintf("Kernel size too small\n");
        goto bail;
    }

    /* Look for specific command-line arguments we care about */
    if ((arg = find_argument(cmdline, "mem=")))
        memlimit = saturate32(suffix_number(arg));

    if ((arg = find_argument(cmdline, "vga="))) {
        switch (arg[0] | 0x20) {
        case 'a':               /* "ask" */
            video_mode = 0xfffd;
            break;
        case 'e':               /* "ext" */
            video_mode = 0xfffe;
            break;
        case 'n':               /* "normal" */
            video_mode = 0xffff;
            break;
        case 'c':               /* "current" */
            video_mode = 0x0f04;
            break;
        default:
            video_mode = strtoul(arg, NULL, 0);
            break;
        }
    }

    /* Copy the header into private storage */
    /* Use whdr to modify the actual kernel header */
    memcpy(&hdr, kernel_buf, sizeof hdr);
    whdr = (struct linux_header *)kernel_buf;

    if (hdr.boot_flag != BOOT_MAGIC) {
        dprintf("Invalid boot magic\n");
        goto bail;
    }

    if (hdr.header != LINUX_MAGIC) {
        hdr.version = 0x0100;   /* Very old kernel */
        hdr.loadflags = 0;
    }

    whdr->vid_mode = video_mode;

    if (!hdr.setup_sects)
        hdr.setup_sects = 4;

    if (hdr.version < 0x0203 || !hdr.initrd_addr_max)
        hdr.initrd_addr_max = 0x37ffffff;

    if (!memlimit && memlimit - 1 > hdr.initrd_addr_max)
        memlimit = hdr.initrd_addr_max + 1;     /* Zero for no limit */

    if (hdr.version < 0x0205 || !(hdr.loadflags & LOAD_HIGH))
        hdr.relocatable_kernel = 0;

    if (hdr.version < 0x0206)
        hdr.cmdline_max_len = 256;

    if (cmdline_size > hdr.cmdline_max_len) {
        cmdline_size = hdr.cmdline_max_len;
        cmdline[cmdline_size - 1] = '\0';
    }

    real_mode_size = (hdr.setup_sects + 1) << 9;
    real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
    prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
    prot_mode_max  = (hdr.loadflags & LOAD_HIGH) ? (addr_t)-1 : 0x8ffff;
    prot_mode_size = kernel_size - real_mode_size;

    /* Get the memory map */
    mmap = syslinux_memory_map();       /* Memory map for shuffle_boot */
    amap = syslinux_dup_memmap(mmap);   /* Keep track of available memory */
    if (!mmap || !amap) {
        errno = ENOMEM;
        goto bail;
    }

    cmdline_offset = calc_cmdline_offset(mmap, &hdr, cmdline_size,
                                         real_mode_base,
                                         real_mode_base + real_mode_size);
    dprintf("cmdline_offset at 0x%x\n", real_mode_base + cmdline_offset);

    if (hdr.version < 0x020a) {
        /*
         * The 3* here is a total fudge factor... it's supposed to
         * account for the fact that the kernel needs to be
         * decompressed, and then followed by the BSS and BRK regions.
         * This doesn't, however, account for the fact that the kernel
         * is decompressed into a whole other place, either.
         */
        hdr.init_size = 3 * prot_mode_size;
    }

    if (!(hdr.loadflags & LOAD_HIGH) && prot_mode_size > 512 * 1024) {
        dprintf("Kernel cannot be loaded low\n");
        goto bail;
    }

    /* Get the size of the initramfs, if there is one */
    irf_size = initramfs_size(initramfs);

    if (irf_size && hdr.version < 0x0200) {
        dprintf("Initrd specified but not supported by kernel\n");
        goto bail;
    }

    if (hdr.version >= 0x0200) {
        whdr->type_of_loader = 0x30;    /* SYSLINUX unknown module */
        if (hdr.version >= 0x0201) {
            whdr->heap_end_ptr = cmdline_offset - 0x0200;
            whdr->loadflags |= CAN_USE_HEAP;
        }
    }

    dprintf("Initial memory map:\n");
    syslinux_dump_memmap(mmap);

    /* If the user has specified a memory limit, mark that as unavailable.
       Question: should we mark this off-limit in the mmap as well (meaning
       it's unavailable to the boot loader, which probably has already touched
       some of it), or just in the amap? */
    if (memlimit)
        if (syslinux_add_memmap(&amap, memlimit, -memlimit, SMT_RESERVED)) {
            errno = ENOMEM;
            goto bail;
        }

    /* Place the kernel in memory */

    /*
     * First, find a suitable place for the protected-mode code.  If
     * the kernel image is not relocatable, just worry if it fits (it
     * might not even be a Linux image, after all, and for !LOAD_HIGH
     * we end up decompressing into a different location anyway), but
     * if it is, make sure everything fits.
     */
    base = prot_mode_base;
    if (prot_mode_size &&
        syslinux_memmap_find(amap, &base,
                             hdr.relocatable_kernel ?
                             hdr.init_size : prot_mode_size,
                             hdr.relocatable_kernel, hdr.kernel_alignment,
                             prot_mode_base, prot_mode_max,
                             prot_mode_base, prot_mode_max)) {
        dprintf("Could not find location for protected-mode code\n");
        goto bail;
    }

    whdr->code32_start += base - prot_mode_base;

    /* Real mode code */
    if (syslinux_memmap_find(amap, &real_mode_base,
                             cmdline_offset + cmdline_size, true, 16,
                             real_mode_base, 0x90000, 0, 640*1024)) {
        dprintf("Could not find location for real-mode code\n");
        goto bail;
    }

    if (syslinux_add_movelist(&fraglist, real_mode_base, (addr_t) kernel_buf,
                              real_mode_size))
        goto bail;
    if (syslinux_add_memmap
        (&amap, real_mode_base, cmdline_offset + cmdline_size, SMT_ALLOC)) {
        errno = ENOMEM;
        goto bail;
    }

    /* Zero region between real mode code and cmdline */
    if (syslinux_add_memmap(&mmap, real_mode_base + real_mode_size,
                            cmdline_offset - real_mode_size, SMT_ZERO)) {
        errno = ENOMEM;
        goto bail;
    }

    /* Command line */
    if (syslinux_add_movelist(&fraglist, real_mode_base + cmdline_offset,
                              (addr_t) cmdline, cmdline_size)) {
        errno = ENOMEM;
        goto bail;
    }
    if (hdr.version >= 0x0202) {
        whdr->cmd_line_ptr = real_mode_base + cmdline_offset;
    } else {
        whdr->old_cmd_line_magic = OLD_CMDLINE_MAGIC;
        whdr->old_cmd_line_offset = cmdline_offset;
        if (hdr.version >= 0x0200) {
            /* Be paranoid and round up to a multiple of 16 */
            whdr->setup_move_size = (cmdline_offset + cmdline_size + 15) & ~15;
        }
    }

    /* Protected-mode code */
    if (prot_mode_size) {
        if (syslinux_add_movelist(&fraglist, prot_mode_base,
                                  (addr_t) kernel_buf + real_mode_size,
                                  prot_mode_size)) {
            errno = ENOMEM;
            goto bail;
        }
        if (syslinux_add_memmap(&amap, prot_mode_base, prot_mode_size,
                                SMT_ALLOC)) {
            errno = ENOMEM;
            goto bail;
        }
    }

    /* Figure out the size of the initramfs, and where to put it.
       We should put it at the highest possible address which is
       <= hdr.initrd_addr_max, which fits the entire initramfs. */

    if (irf_size) {
        addr_t best_addr = 0;
        struct syslinux_memmap *ml;
        const addr_t align_mask = INITRAMFS_MAX_ALIGN - 1;

        if (irf_size) {
            for (ml = amap; ml->type != SMT_END; ml = ml->next) {
                addr_t adj_start = (ml->start + align_mask) & ~align_mask;
                addr_t adj_end = ml->next->start & ~align_mask;
                if (ml->type == SMT_FREE && adj_end - adj_start >= irf_size)
                    best_addr = (adj_end - irf_size) & ~align_mask;
            }

            if (!best_addr) {
                dprintf("Insufficient memory for initramfs\n");
                goto bail;
            }

            whdr->ramdisk_image = best_addr;
            whdr->ramdisk_size = irf_size;

            if (syslinux_add_memmap(&amap, best_addr, irf_size, SMT_ALLOC)) {
                errno = ENOMEM;
                goto bail;
            }

            if (map_initramfs(&fraglist, &mmap, initramfs, best_addr)) {
                errno = ENOMEM;
                goto bail;
            }
        }
    }

    if (setup_data) {
        uint64_t *prev_ptr = &whdr->setup_data;

        for (sdp = setup_data->next; sdp != setup_data; sdp = sdp->next) {
            struct syslinux_memmap *ml;
            const addr_t align_mask = 15; /* Header is 16 bytes */
            addr_t best_addr = 0;
            size_t size = sdp->hdr.len + sizeof(sdp->hdr);

            if (!sdp->data || !sdp->hdr.len)
                continue;

            if (hdr.version < 0x0209) {
                /* Setup data not supported */
                errno = ENXIO;  /* Kind of arbitrary... */
                goto bail;
            }

            for (ml = amap; ml->type != SMT_END; ml = ml->next) {
                addr_t adj_start = (ml->start + align_mask) & ~align_mask;
                addr_t adj_end = ml->next->start & ~align_mask;

                if (ml->type == SMT_FREE && adj_end - adj_start >= size)
                    best_addr = (adj_end - size) & ~align_mask;
            }

            if (!best_addr)
                goto bail;

            *prev_ptr = best_addr;
            prev_ptr = &sdp->hdr.next;

            if (syslinux_add_memmap(&amap, best_addr, size, SMT_ALLOC)) {
                errno = ENOMEM;
                goto bail;
            }
            if (syslinux_add_movelist(&fraglist, best_addr,
                                      (addr_t)&sdp->hdr, sizeof sdp->hdr)) {
                errno = ENOMEM;
                goto bail;
            }
            if (syslinux_add_movelist(&fraglist, best_addr + sizeof sdp->hdr,
                                      (addr_t)sdp->data, sdp->hdr.len)) {
                errno = ENOMEM;
                goto bail;
            }
        }
    }

    /* Set up the registers on entry */
    memset(&regs, 0, sizeof regs);
    regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
    regs.cs = (real_mode_base >> 4) + 0x20;
    /* regs.ip = 0; */
    /* Linux is OK with sp = 0 = 64K, but perhaps other things aren't... */
    regs.esp.w[0] = min(cmdline_offset, (size_t) 0xfff0);

    dprintf("Final memory map:\n");
    syslinux_dump_memmap(mmap);

    dprintf("Final available map:\n");
    syslinux_dump_memmap(amap);

    dprintf("Initial movelist:\n");
    syslinux_dump_movelist(fraglist);

    if (video_mode != 0x0f04) {
        /*
         * video_mode is not "current", so if we are in graphics mode we
         * need to revert to text mode...
         */
        dprintf("*** Calling syslinux_force_text_mode()...\n");
        syslinux_force_text_mode();
    } else {
        dprintf("*** vga=current, not calling syslinux_force_text_mode()...\n");
    }

    syslinux_shuffle_boot_rm(fraglist, mmap, 0, &regs);
    dprintf("shuffle_boot_rm failed\n");

bail:
    syslinux_free_movelist(fraglist);
    syslinux_free_memmap(mmap);
    syslinux_free_memmap(amap);
    return -1;
}

int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
                        struct initramfs *initramfs,
                        struct setup_data *setup_data,
                        char *cmdline)
{
    if (firmware->boot_linux)
        return firmware->boot_linux(kernel_buf, kernel_size, initramfs,
                                    setup_data, cmdline);

    return bios_boot_linux(kernel_buf, kernel_size, initramfs,
                           setup_data, cmdline);
}