source: bootcd/isolinux/syslinux-6.03/com32/mboot/map.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007-2008 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009-2010 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.
 *
 * ----------------------------------------------------------------------- */

/*
 * map.c
 *
 * Functions that deal with the memory map of various objects
 */

#include "mboot.h"

static struct syslinux_movelist *ml = NULL;
static struct syslinux_memmap *mmap = NULL, *amap = NULL;
static addr_t mboot_high_water_mark = 0x100000;

/*
 * Note: although there is no such thing in the spec, at least Xen makes
 * assumptions as to where in the memory space Grub would have loaded
 * certain things.  To support that, if "high" is set, then allocate this
 * at an address strictly above any previous allocations.
 *
 * As a precaution, this also pads the data with zero up to the next
 * alignment datum.
 */
addr_t map_data(const void *data, size_t len, size_t align, int flags)
{
    addr_t start = (flags & MAP_HIGH) ? mboot_high_water_mark : 0x2000;
    addr_t pad = (flags & MAP_NOPAD) ? 0 : -len & (align - 1);
    addr_t xlen = len + pad;

    if (syslinux_memmap_find_type(amap, SMT_FREE, &start, &xlen, align) ||
        syslinux_add_memmap(&amap, start, len + pad, SMT_ALLOC) ||
        syslinux_add_movelist(&ml, start, (addr_t) data, len) ||
        (pad && syslinux_add_memmap(&mmap, start + len, pad, SMT_ZERO))) {
        printf("Cannot map %zu bytes\n", len + pad);
        return 0;
    }

    dprintf("Mapping 0x%08x bytes (%#x pad) at 0x%08x\n", len, pad, start);

    if (start + len + pad > mboot_high_water_mark)
        mboot_high_water_mark = start + len + pad;

    return start;
}

addr_t map_string(const char *string)
{
    if (!string)
        return 0;
    else
        return map_data(string, strlen(string) + 1, 1, 0);
}

int init_map(void)
{
    /*
     * Note: mmap is the memory map (containing free and zeroed regions)
     * needed by syslinux_shuffle_boot_pm(); amap is a map where we keep
     * track ourselves which target memory ranges have already been
     * allocated.
     */
    mmap = syslinux_memory_map();
    amap = syslinux_dup_memmap(mmap);
    if (!mmap || !amap) {
        error("Failed to allocate initial memory map!\n");
        return -1;
    }

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

    return 0;
}

struct multiboot_header *map_image(void *ptr, size_t len)
{
    struct multiboot_header *mbh;
    int mbh_len;
    char *cptr = ptr;
    Elf32_Ehdr *eh = ptr;
    Elf32_Phdr *ph;
    Elf32_Shdr *sh;
    unsigned int i, mbh_offset;
    uint32_t bad_flags;

    /*
     * Search for the multiboot header...
     */
    mbh_len = 0;
    for (mbh_offset = 0; mbh_offset < MULTIBOOT_SEARCH; mbh_offset += 4) {
        mbh = (struct multiboot_header *)((char *)ptr + mbh_offset);
        if (mbh->magic != MULTIBOOT_MAGIC)
            continue;
        if (mbh->magic + mbh->flags + mbh->checksum)
            continue;
        if (mbh->flags & MULTIBOOT_VIDEO_MODE)
            mbh_len = 48;
        else if (mbh->flags & MULTIBOOT_AOUT_KLUDGE)
            mbh_len = 32;
        else
            mbh_len = 12;

        if (mbh_offset + mbh_len > len)
            mbh_len = 0;        /* Invalid... */
        else
            break;              /* Found something... */
    }

    if (mbh_len) {
        bad_flags = mbh->flags & MULTIBOOT_UNSUPPORTED;
        if (bad_flags) {
            printf("Unsupported Multiboot flags set: %#x\n", bad_flags);
            return NULL;
        }
    }

    if (len < sizeof(Elf32_Ehdr) ||
        memcmp(eh->e_ident, "\x7f" "ELF\1\1\1", 6) ||
        (eh->e_machine != EM_386 && eh->e_machine != EM_486 &&
         eh->e_machine != EM_X86_64) ||
        eh->e_version != EV_CURRENT ||
        eh->e_ehsize < sizeof(Elf32_Ehdr) || eh->e_ehsize >= len ||
        eh->e_phentsize < sizeof(Elf32_Phdr) ||
        !eh->e_phnum || eh->e_phoff + eh->e_phentsize * eh->e_phnum > len)
        eh = NULL;              /* No valid ELF header found */

    /* Is this a Solaris kernel? */
    if (!set.solaris && eh && kernel_is_solaris(eh))
        opt.solaris = true;

    /*
     * Note: the Multiboot Specification implies that AOUT_KLUDGE should
     * have precedence over the ELF header.  However, Grub disagrees, and
     * Grub is "the reference bootloader" for the Multiboot Specification.
     * This is insane, since it makes the AOUT_KLUDGE bit functionally
     * useless, but at least Solaris apparently depends on this behavior.
     */
    if (eh && !(opt.aout && mbh_len && (mbh->flags & MULTIBOOT_AOUT_KLUDGE))) {
        regs.eip = eh->e_entry; /* Can be overridden further down... */

        ph = (Elf32_Phdr *) (cptr + eh->e_phoff);

        for (i = 0; i < eh->e_phnum; i++) {
            if (ph->p_type == PT_LOAD || ph->p_type == PT_PHDR) {
                /*
                 * This loads at p_paddr, which matches Grub.  However, if
                 * e_entry falls within the p_vaddr range of this PHDR, then
                 * adjust it to match the p_paddr range... this is how Grub
                 * behaves, so it's by definition correct (it doesn't have to
                 * make sense...)
                 */
                addr_t addr = ph->p_paddr;
                addr_t msize = ph->p_memsz;
                addr_t dsize = min(msize, ph->p_filesz);

                if (eh->e_entry >= ph->p_vaddr
                    && eh->e_entry < ph->p_vaddr + msize)
                    regs.eip = eh->e_entry + (ph->p_paddr - ph->p_vaddr);

                dprintf("Segment at 0x%08x data 0x%08x len 0x%08x\n",
                        addr, dsize, msize);

                if (syslinux_memmap_type(amap, addr, msize) != SMT_FREE) {
                    printf
                        ("Memory segment at 0x%08x (len 0x%08x) is unavailable\n",
                         addr, msize);
                    return NULL;        /* Memory region unavailable */
                }

                /* Mark this region as allocated in the available map */
                if (syslinux_add_memmap(&amap, addr, msize, SMT_ALLOC)) {
                    error("Overlapping segments found in ELF header\n");
                    return NULL;
                }

                if (ph->p_filesz) {
                    /* Data present region.  Create a move entry for it. */
                    if (syslinux_add_movelist
                        (&ml, addr, (addr_t) cptr + ph->p_offset, dsize)) {
                        error("Failed to map PHDR data\n");
                        return NULL;
                    }
                }
                if (msize > dsize) {
                    /* Zero-filled region.  Mark as a zero region in the memory map. */
                    if (syslinux_add_memmap
                        (&mmap, addr + dsize, msize - dsize, SMT_ZERO)) {
                        error("Failed to map PHDR zero region\n");
                        return NULL;
                    }
                }
                if (addr + msize > mboot_high_water_mark)
                    mboot_high_water_mark = addr + msize;
            } else {
                /* Ignore this program header */
            }

            ph = (Elf32_Phdr *) ((char *)ph + eh->e_phentsize);
        }

        /* Load the ELF symbol table */
        if (eh->e_shoff) {
            addr_t addr, len;

            sh = (Elf32_Shdr *) ((char *)eh + eh->e_shoff);

            len = eh->e_shentsize * eh->e_shnum;
            /*
             * Align this, but don't pad -- in general this means a bunch of
             * smaller sections gets packed into a single page.
             */
            addr = map_data(sh, len, 4096, MAP_HIGH | MAP_NOPAD);
            if (!addr) {
                error("Failed to map symbol table\n");
                return NULL;
            }

            mbinfo.flags |= MB_INFO_ELF_SHDR;
            mbinfo.syms.e.addr = addr;
            mbinfo.syms.e.num = eh->e_shnum;
            mbinfo.syms.e.size = eh->e_shentsize;
            mbinfo.syms.e.shndx = eh->e_shstrndx;

            for (i = 0; i < eh->e_shnum; i++) {
                addr_t align;

                if (!sh[i].sh_size)
                    continue;   /* Empty section */
                if (sh[i].sh_flags & SHF_ALLOC)
                    continue;   /* SHF_ALLOC sections should have PHDRs */

                align = sh[i].sh_addralign ? sh[i].sh_addralign : 0;
                addr = map_data((char *)ptr + sh[i].sh_offset, sh[i].sh_size,
                                align, MAP_HIGH);
                if (!addr) {
                    error("Failed to map symbol section\n");
                    return NULL;
                }
                sh[i].sh_addr = addr;
            }
        }
    } else if (mbh_len && (mbh->flags & MULTIBOOT_AOUT_KLUDGE)) {
        /*
         * a.out kludge thing...
         */
        char *data_ptr;
        addr_t data_len, bss_len;
        addr_t bss_addr;

        regs.eip = mbh->entry_addr;

        data_ptr = (char *)mbh - (mbh->header_addr - mbh->load_addr);

        if (mbh->load_end_addr)
            data_len = mbh->load_end_addr - mbh->load_addr;
        else
            data_len = len - mbh_offset + (mbh->header_addr - mbh->load_addr);

        bss_addr = mbh->load_addr + data_len;

        if (mbh->bss_end_addr)
            bss_len = mbh->bss_end_addr - mbh->load_end_addr;
        else
            bss_len = 0;

        if (syslinux_memmap_type(amap, mbh->load_addr, data_len + bss_len)
            != SMT_FREE) {
            printf("Memory segment at 0x%08x (len 0x%08x) is unavailable\n",
                   mbh->load_addr, data_len + bss_len);
            return NULL;                /* Memory region unavailable */
        }
        if (syslinux_add_memmap(&amap, mbh->load_addr,
                                data_len + bss_len, SMT_ALLOC)) {
            error("Failed to claim a.out address space!\n");
            return NULL;
        }
        if (data_len)
            if (syslinux_add_movelist(&ml, mbh->load_addr, (addr_t) data_ptr,
                                      data_len)) {
                error("Failed to map a.out data\n");
                return NULL;
            }
        if (bss_len)
            if (syslinux_add_memmap
                (&mmap, bss_addr, bss_len, SMT_ZERO)) {
                error("Failed to map a.out bss\n");
                return NULL;
            }
        if (bss_addr + bss_len > mboot_high_water_mark)
            mboot_high_water_mark = bss_addr + bss_len;
    } else {
        error
            ("Invalid Multiboot image: neither ELF header nor a.out kludge found\n");
        return NULL;
    }

    return mbh;
}

/*
 * Set up a stack.  This isn't actually required by the spec, but it seems
 * like a prudent thing to do.  Also, put enough zeros at the top of the
 * stack that something that looks for an ELF invocation record will know
 * there isn't one.
 */
static void mboot_map_stack(void)
{
    addr_t start, len;

    if (syslinux_memmap_largest(amap, SMT_FREE, &start, &len) || len < 64)
        return;                 /* Not much we can do, here... */

    regs.esp = (start + len - 32) & ~15;
    dprintf("Mapping stack at 0x%08x\n", regs.esp);
    syslinux_add_memmap(&mmap, regs.esp, 32, SMT_ZERO);
}

void mboot_run(int bootflags)
{
    mboot_map_stack();

    dprintf("Running, eip = 0x%08x, ebx = 0x%08x\n", regs.eip, regs.ebx);

    regs.eax = MULTIBOOT_VALID;
    syslinux_shuffle_boot_pm(ml, mmap, bootflags, &regs);
}