Archipelago » qemu

/****************************************************************************/

/*

 *  QEMU bFLT binary loader.  Based on linux/fs/binfmt_flat.c

 *

 *  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

 *  (at your option) 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, see <http://www.gnu.org/licenses/>.

 *

 *      Copyright (C) 2006 CodeSourcery.

 *        Copyright (C) 2000-2003 David McCullough <davidm@snapgear.com>

 *        Copyright (C) 2002 Greg Ungerer <gerg@snapgear.com>

 *        Copyright (C) 2002 SnapGear, by Paul Dale <pauli@snapgear.com>

 *        Copyright (C) 2000, 2001 Lineo, by David McCullough <davidm@lineo.com>

 *  based heavily on:

 *

 *  linux/fs/binfmt_aout.c:

 *      Copyright (C) 1991, 1992, 1996  Linus Torvalds

 *  linux/fs/binfmt_flat.c for 2.0 kernel

 *            Copyright (C) 1998  Kenneth Albanowski <kjahds@kjahds.com>

 *        JAN/99 -- coded full program relocation (gerg@snapgear.com)

 */

/* ??? ZFLAT and shared library support is currently disabled.  */

/****************************************************************************/

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <sys/mman.h>

#include <unistd.h>

#include "qemu.h"

#include "flat.h"

//#define DEBUG

#ifdef DEBUG

#define        DBG_FLT(...)        printf(__VA_ARGS__)

#else

#define        DBG_FLT(...)

#endif

#define flat_reloc_valid(reloc, size)             ((reloc) <= (size))

#define flat_old_ram_flag(flag)                   (flag)

#ifdef TARGET_WORDS_BIGENDIAN

#define flat_get_relocate_addr(relval)            (relval)

#else

#define flat_get_relocate_addr(relval)            bswap32(relval)

#endif

#define RELOC_FAILED 0xff00ff01                /* Relocation incorrect somewhere */

#define UNLOADED_LIB 0x7ff000ff                /* Placeholder for unused library */

struct lib_info {

    abi_ulong start_code;       /* Start of text segment */

    abi_ulong start_data;       /* Start of data segment */

    abi_ulong end_data;         /* Start of bss section */

    abi_ulong start_brk;        /* End of data segment */

    abi_ulong text_len;                /* Length of text segment */

    abi_ulong entry;                /* Start address for this module */

    abi_ulong build_date;       /* When this one was compiled */

    short loaded;                /* Has this library been loaded? */

};

#ifdef CONFIG_BINFMT_SHARED_FLAT

static int load_flat_shared_library(int id, struct lib_info *p);

#endif

struct linux_binprm;

#define ntohl(x) be32_to_cpu(x)

/****************************************************************************/

/*

 * create_flat_tables() parses the env- and arg-strings in new user

 * memory and creates the pointer tables from them, and puts their

 * addresses on the "stack", returning the new stack pointer value.

 */

/* Push a block of strings onto the guest stack.  */

static abi_ulong copy_strings(abi_ulong p, int n, char **s)

{

    int len;

    while (n-- > 0) {

        len = strlen(s[n]) + 1;

        p -= len;

        memcpy_to_target(p, s[n], len);

    }

    return p;

}

static int target_pread(int fd, abi_ulong ptr, abi_ulong len,

                        abi_ulong offset)

{

    void *buf;

    int ret;

    buf = lock_user(VERIFY_WRITE, ptr, len, 0);

    ret = pread(fd, buf, len, offset);

    unlock_user(buf, ptr, len);

    return ret;

}

/****************************************************************************/

#ifdef CONFIG_BINFMT_ZFLAT

#include <linux/zlib.h>

#define LBUFSIZE        4000

/* gzip flag byte */

#define ASCII_FLAG   0x01 /* bit 0 set: file probably ASCII text */

#define CONTINUATION 0x02 /* bit 1 set: continuation of multi-part gzip file */

#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */

#define ORIG_NAME    0x08 /* bit 3 set: original file name present */

#define COMMENT      0x10 /* bit 4 set: file comment present */

#define ENCRYPTED    0x20 /* bit 5 set: file is encrypted */

#define RESERVED     0xC0 /* bit 6,7:   reserved */

static int decompress_exec(

        struct linux_binprm *bprm,

        unsigned long offset,

        char *dst,

        long len,

        int fd)

{

        unsigned char *buf;

        z_stream strm;

        loff_t fpos;

        int ret, retval;

        DBG_FLT("decompress_exec(offset=%x,buf=%x,len=%x)\n",(int)offset, (int)dst, (int)len);

        memset(&strm, 0, sizeof(strm));

        strm.workspace = kmalloc(zlib_inflate_workspacesize(), GFP_KERNEL);

        if (strm.workspace == NULL) {

                DBG_FLT("binfmt_flat: no memory for decompress workspace\n");

                return -ENOMEM;

        }

        buf = kmalloc(LBUFSIZE, GFP_KERNEL);

        if (buf == NULL) {

                DBG_FLT("binfmt_flat: no memory for read buffer\n");

                retval = -ENOMEM;

                goto out_free;

        }

        /* Read in first chunk of data and parse gzip header. */

        fpos = offset;

        ret = bprm->file->f_op->read(bprm->file, buf, LBUFSIZE, &fpos);

        strm.next_in = buf;

        strm.avail_in = ret;

        strm.total_in = 0;

        retval = -ENOEXEC;

        /* Check minimum size -- gzip header */

        if (ret < 10) {

                DBG_FLT("binfmt_flat: file too small?\n");

                goto out_free_buf;

        }

        /* Check gzip magic number */

        if ((buf[0] != 037) || ((buf[1] != 0213) && (buf[1] != 0236))) {

                DBG_FLT("binfmt_flat: unknown compression magic?\n");

                goto out_free_buf;

        }

        /* Check gzip method */

        if (buf[2] != 8) {

                DBG_FLT("binfmt_flat: unknown compression method?\n");

                goto out_free_buf;

        }

        /* Check gzip flags */

        if ((buf[3] & ENCRYPTED) || (buf[3] & CONTINUATION) ||

            (buf[3] & RESERVED)) {

                DBG_FLT("binfmt_flat: unknown flags?\n");

                goto out_free_buf;

        }

        ret = 10;

        if (buf[3] & EXTRA_FIELD) {

                ret += 2 + buf[10] + (buf[11] << 8);

                if (unlikely(LBUFSIZE == ret)) {

                        DBG_FLT("binfmt_flat: buffer overflow (EXTRA)?\n");

                        goto out_free_buf;

                }

        }

        if (buf[3] & ORIG_NAME) {

                for (; ret < LBUFSIZE && (buf[ret] != 0); ret++)

                        ;

                if (unlikely(LBUFSIZE == ret)) {

                        DBG_FLT("binfmt_flat: buffer overflow (ORIG_NAME)?\n");

                        goto out_free_buf;

                }

        }

        if (buf[3] & COMMENT) {

                for (;  ret < LBUFSIZE && (buf[ret] != 0); ret++)

                        ;

                if (unlikely(LBUFSIZE == ret)) {

                        DBG_FLT("binfmt_flat: buffer overflow (COMMENT)?\n");

                        goto out_free_buf;

                }

        }

        strm.next_in += ret;

        strm.avail_in -= ret;

        strm.next_out = dst;

        strm.avail_out = len;

        strm.total_out = 0;

        if (zlib_inflateInit2(&strm, -MAX_WBITS) != Z_OK) {

                DBG_FLT("binfmt_flat: zlib init failed?\n");

                goto out_free_buf;

        }

        while ((ret = zlib_inflate(&strm, Z_NO_FLUSH)) == Z_OK) {

                ret = bprm->file->f_op->read(bprm->file, buf, LBUFSIZE, &fpos);

                if (ret <= 0)

                        break;

                if (ret >= (unsigned long) -4096)

                        break;

                len -= ret;

                strm.next_in = buf;

                strm.avail_in = ret;

                strm.total_in = 0;

        }

        if (ret < 0) {

                DBG_FLT("binfmt_flat: decompression failed (%d), %s\n",

                        ret, strm.msg);

                goto out_zlib;

        }

        retval = 0;

out_zlib:

        zlib_inflateEnd(&strm);

out_free_buf:

        kfree(buf);

out_free:

        kfree(strm.workspace);

out:

        return retval;

}

#endif /* CONFIG_BINFMT_ZFLAT */

/****************************************************************************/

static abi_ulong

calc_reloc(abi_ulong r, struct lib_info *p, int curid, int internalp)

{

    abi_ulong addr;

    int id;

    abi_ulong start_brk;

    abi_ulong start_data;

    abi_ulong text_len;

    abi_ulong start_code;

#ifdef CONFIG_BINFMT_SHARED_FLAT

#error needs checking

    if (r == 0)

        id = curid;        /* Relocs of 0 are always self referring */

    else {

        id = (r >> 24) & 0xff;        /* Find ID for this reloc */

        r &= 0x00ffffff;        /* Trim ID off here */

    }

    if (id >= MAX_SHARED_LIBS) {

        fprintf(stderr, "BINFMT_FLAT: reference 0x%x to shared library %d\n",

                (unsigned) r, id);

        goto failed;

    }

    if (curid != id) {

        if (internalp) {

            fprintf(stderr, "BINFMT_FLAT: reloc address 0x%x not "

                    "in same module (%d != %d)\n",

                    (unsigned) r, curid, id);

            goto failed;

        } else if ( ! p[id].loaded &&

                    load_flat_shared_library(id, p) > (unsigned long) -4096) {

            fprintf(stderr, "BINFMT_FLAT: failed to load library %d\n", id);

            goto failed;

        }

        /* Check versioning information (i.e. time stamps) */

        if (p[id].build_date && p[curid].build_date

            && p[curid].build_date < p[id].build_date) {

            fprintf(stderr, "BINFMT_FLAT: library %d is younger than %d\n",

                    id, curid);

            goto failed;

        }

    }

#else

    id = 0;

#endif

    start_brk = p[id].start_brk;

    start_data = p[id].start_data;

    start_code = p[id].start_code;

    text_len = p[id].text_len;

    if (!flat_reloc_valid(r, start_brk - start_data + text_len)) {

        fprintf(stderr, "BINFMT_FLAT: reloc outside program 0x%x "

                "(0 - 0x%x/0x%x)\n",

               (int) r,(int)(start_brk-start_code),(int)text_len);

        goto failed;

    }

    if (r < text_len)                        /* In text segment */

        addr = r + start_code;

    else                                        /* In data segment */

        addr = r - text_len + start_data;

    /* Range checked already above so doing the range tests is redundant...*/

    return(addr);

failed:

    abort();

    return RELOC_FAILED;

}

/****************************************************************************/

/* ??? This does not handle endianness correctly.  */

static void old_reloc(struct lib_info *libinfo, uint32_t rl)

{

#ifdef DEBUG

        char *segment[] = { "TEXT", "DATA", "BSS", "*UNKNOWN*" };

#endif

        uint32_t *ptr;

        uint32_t offset;

        int reloc_type;

        offset = rl & 0x3fffffff;

        reloc_type = rl >> 30;

        /* ??? How to handle this?  */

#if defined(CONFIG_COLDFIRE)

        ptr = (uint32_t *) ((unsigned long) libinfo->start_code + offset);

#else

        ptr = (uint32_t *) ((unsigned long) libinfo->start_data + offset);

#endif

#ifdef DEBUG

        fprintf(stderr, "Relocation of variable at DATASEG+%x "

                "(address %p, currently %x) into segment %s\n",

                offset, ptr, (int)*ptr, segment[reloc_type]);

#endif

        switch (reloc_type) {

        case OLD_FLAT_RELOC_TYPE_TEXT:

                *ptr += libinfo->start_code;

                break;

        case OLD_FLAT_RELOC_TYPE_DATA:

                *ptr += libinfo->start_data;

                break;

        case OLD_FLAT_RELOC_TYPE_BSS:

                *ptr += libinfo->end_data;

                break;

        default:

                fprintf(stderr, "BINFMT_FLAT: Unknown relocation type=%x\n",

                        reloc_type);

                break;

        }

        DBG_FLT("Relocation became %x\n", (int)*ptr);

}

/****************************************************************************/

static int load_flat_file(struct linux_binprm * bprm,

                struct lib_info *libinfo, int id, abi_ulong *extra_stack)

{

    struct flat_hdr * hdr;

    abi_ulong textpos = 0, datapos = 0, result;

    abi_ulong realdatastart = 0;

    abi_ulong text_len, data_len, bss_len, stack_len, flags;

    abi_ulong memp = 0; /* for finding the brk area */

    abi_ulong extra;

    abi_ulong reloc = 0, rp;

    int i, rev, relocs = 0;

    abi_ulong fpos;

    abi_ulong start_code, end_code;

    abi_ulong indx_len;

    hdr = ((struct flat_hdr *) bprm->buf);                /* exec-header */

    text_len  = ntohl(hdr->data_start);

    data_len  = ntohl(hdr->data_end) - ntohl(hdr->data_start);

    bss_len   = ntohl(hdr->bss_end) - ntohl(hdr->data_end);

    stack_len = ntohl(hdr->stack_size);

    if (extra_stack) {

        stack_len += *extra_stack;

        *extra_stack = stack_len;

    }

    relocs    = ntohl(hdr->reloc_count);

    flags     = ntohl(hdr->flags);

    rev       = ntohl(hdr->rev);

    DBG_FLT("BINFMT_FLAT: Loading file: %s\n", bprm->filename);

    if (rev != FLAT_VERSION && rev != OLD_FLAT_VERSION) {

        fprintf(stderr, "BINFMT_FLAT: bad magic/rev (0x%x, need 0x%x)\n",

                rev, (int) FLAT_VERSION);

        return -ENOEXEC;

    }

    /* Don't allow old format executables to use shared libraries */

    if (rev == OLD_FLAT_VERSION && id != 0) {

        fprintf(stderr, "BINFMT_FLAT: shared libraries are not available\n");

        return -ENOEXEC;

    }

    /*

     * fix up the flags for the older format,  there were all kinds

     * of endian hacks,  this only works for the simple cases

     */

    if (rev == OLD_FLAT_VERSION && flat_old_ram_flag(flags))

        flags = FLAT_FLAG_RAM;

#ifndef CONFIG_BINFMT_ZFLAT

    if (flags & (FLAT_FLAG_GZIP|FLAT_FLAG_GZDATA)) {

        fprintf(stderr, "Support for ZFLAT executables is not enabled\n");

        return -ENOEXEC;

    }

#endif

    /*

     * calculate the extra space we need to map in

     */

    extra = relocs * sizeof(abi_ulong);

    if (extra < bss_len + stack_len)

        extra = bss_len + stack_len;

    /* Add space for library base pointers.  Make sure this does not

       misalign the  doesn't misalign the data segment.  */

    indx_len = MAX_SHARED_LIBS * sizeof(abi_ulong);

    indx_len = (indx_len + 15) & ~(abi_ulong)15;

    /*

     * there are a couple of cases here,  the separate code/data

     * case,  and then the fully copied to RAM case which lumps

     * it all together.

     */

    if ((flags & (FLAT_FLAG_RAM|FLAT_FLAG_GZIP)) == 0) {

        /*

         * this should give us a ROM ptr,  but if it doesn't we don't

         * really care

         */

        DBG_FLT("BINFMT_FLAT: ROM mapping of file (we hope)\n");

        textpos = target_mmap(0, text_len, PROT_READ|PROT_EXEC,

                              MAP_PRIVATE, bprm->fd, 0);

        if (textpos == -1) {

            fprintf(stderr, "Unable to mmap process text\n");

            return -1;

        }

        realdatastart = target_mmap(0, data_len + extra + indx_len,

                                    PROT_READ|PROT_WRITE|PROT_EXEC,

                                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

        if (realdatastart == -1) {

            fprintf(stderr, "Unable to allocate RAM for process data\n");

            return realdatastart;

        }

        datapos = realdatastart + indx_len;

        DBG_FLT("BINFMT_FLAT: Allocated data+bss+stack (%d bytes): %x\n",

                        (int)(data_len + bss_len + stack_len), (int)datapos);

        fpos = ntohl(hdr->data_start);

#ifdef CONFIG_BINFMT_ZFLAT

        if (flags & FLAT_FLAG_GZDATA) {

            result = decompress_exec(bprm, fpos, (char *) datapos,

                                     data_len + (relocs * sizeof(abi_ulong)))

        } else

#endif

        {

            result = target_pread(bprm->fd, datapos,

                                  data_len + (relocs * sizeof(abi_ulong)),

                                  fpos);

        }

        if (result < 0) {

            fprintf(stderr, "Unable to read data+bss\n");

            return result;

        }

        reloc = datapos + (ntohl(hdr->reloc_start) - text_len);

        memp = realdatastart;

    } else {

        textpos = target_mmap(0, text_len + data_len + extra + indx_len,

                              PROT_READ | PROT_EXEC | PROT_WRITE,

                              MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

        if (textpos == -1 ) {

            fprintf(stderr, "Unable to allocate RAM for process text/data\n");

            return -1;

        }

        realdatastart = textpos + ntohl(hdr->data_start);

        datapos = realdatastart + indx_len;

        reloc = (textpos + ntohl(hdr->reloc_start) + indx_len);

        memp = textpos;

#ifdef CONFIG_BINFMT_ZFLAT

#error code needs checking

        /*

         * load it all in and treat it like a RAM load from now on

         */

        if (flags & FLAT_FLAG_GZIP) {

                result = decompress_exec(bprm, sizeof (struct flat_hdr),

                                 (((char *) textpos) + sizeof (struct flat_hdr)),

                                 (text_len + data_len + (relocs * sizeof(unsigned long))

                                          - sizeof (struct flat_hdr)),

                                 0);

                memmove((void *) datapos, (void *) realdatastart,

                                data_len + (relocs * sizeof(unsigned long)));

        } else if (flags & FLAT_FLAG_GZDATA) {

                fpos = 0;

                result = bprm->file->f_op->read(bprm->file,

                                (char *) textpos, text_len, &fpos);

                if (result < (unsigned long) -4096)

                        result = decompress_exec(bprm, text_len, (char *) datapos,

                                         data_len + (relocs * sizeof(unsigned long)), 0);

        }

        else

#endif

        {

            result = target_pread(bprm->fd, textpos,

                                  text_len, 0);

            if (result >= 0) {

                result = target_pread(bprm->fd, datapos,

                    data_len + (relocs * sizeof(abi_ulong)),

                    ntohl(hdr->data_start));

            }

        }

        if (result < 0) {

            fprintf(stderr, "Unable to read code+data+bss\n");

            return result;

        }

    }

    DBG_FLT("Mapping is 0x%x, Entry point is 0x%x, data_start is 0x%x\n",

            (int)textpos, 0x00ffffff&ntohl(hdr->entry),

            ntohl(hdr->data_start));

    /* The main program needs a little extra setup in the task structure */

    start_code = textpos + sizeof (struct flat_hdr);

    end_code = textpos + text_len;

    DBG_FLT("%s %s: TEXT=%x-%x DATA=%x-%x BSS=%x-%x\n",

            id ? "Lib" : "Load", bprm->filename,

            (int) start_code, (int) end_code,

            (int) datapos,

            (int) (datapos + data_len),

            (int) (datapos + data_len),

            (int) (((datapos + data_len + bss_len) + 3) & ~3));

    text_len -= sizeof(struct flat_hdr); /* the real code len */

    /* Store the current module values into the global library structure */

    libinfo[id].start_code = start_code;

    libinfo[id].start_data = datapos;

    libinfo[id].end_data = datapos + data_len;

    libinfo[id].start_brk = datapos + data_len + bss_len;

    libinfo[id].text_len = text_len;

    libinfo[id].loaded = 1;

    libinfo[id].entry = (0x00ffffff & ntohl(hdr->entry)) + textpos;

    libinfo[id].build_date = ntohl(hdr->build_date);

    /*

     * We just load the allocations into some temporary memory to

     * help simplify all this mumbo jumbo

     *

     * We've got two different sections of relocation entries.

     * The first is the GOT which resides at the begining of the data segment

     * and is terminated with a -1.  This one can be relocated in place.

     * The second is the extra relocation entries tacked after the image's

     * data segment. These require a little more processing as the entry is

     * really an offset into the image which contains an offset into the

     * image.

     */

    if (flags & FLAT_FLAG_GOTPIC) {

        rp = datapos;

        while (1) {

            abi_ulong addr;

            if (get_user_ual(addr, rp))

                return -EFAULT;

            if (addr == -1)

                break;

            if (addr) {

                addr = calc_reloc(addr, libinfo, id, 0);

                if (addr == RELOC_FAILED)

                    return -ENOEXEC;

                if (put_user_ual(addr, rp))

                    return -EFAULT;

            }

            rp += sizeof(abi_ulong);

        }

    }

    /*

     * Now run through the relocation entries.

     * We've got to be careful here as C++ produces relocatable zero

     * entries in the constructor and destructor tables which are then

     * tested for being not zero (which will always occur unless we're

     * based from address zero).  This causes an endless loop as __start

     * is at zero.  The solution used is to not relocate zero addresses.

     * This has the negative side effect of not allowing a global data

     * reference to be statically initialised to _stext (I've moved

     * __start to address 4 so that is okay).

     */

    if (rev > OLD_FLAT_VERSION) {

        for (i = 0; i < relocs; i++) {

            abi_ulong addr, relval;

            /* Get the address of the pointer to be

               relocated (of course, the address has to be

               relocated first).  */

            if (get_user_ual(relval, reloc + i * sizeof(abi_ulong)))

                return -EFAULT;

            addr = flat_get_relocate_addr(relval);

            rp = calc_reloc(addr, libinfo, id, 1);

            if (rp == RELOC_FAILED)

                return -ENOEXEC;

            /* Get the pointer's value.  */

            if (get_user_ual(addr, rp))

                return -EFAULT;

            if (addr != 0) {

                /*

                 * Do the relocation.  PIC relocs in the data section are

                 * already in target order

                 */

#ifndef TARGET_WORDS_BIGENDIAN

                if ((flags & FLAT_FLAG_GOTPIC) == 0)

                    addr = bswap32(addr);

#endif

                addr = calc_reloc(addr, libinfo, id, 0);

                if (addr == RELOC_FAILED)

                    return -ENOEXEC;

                /* Write back the relocated pointer.  */

                if (put_user_ual(addr, rp))

                    return -EFAULT;

            }

        }

    } else {

        for (i = 0; i < relocs; i++) {

            abi_ulong relval;

            if (get_user_ual(relval, reloc + i * sizeof(abi_ulong)))

                return -EFAULT;

            old_reloc(&libinfo[0], relval);

        }

    }

    /* zero the BSS.  */

    memset((void *)((unsigned long)datapos + data_len), 0, bss_len);

    return 0;

}

/****************************************************************************/

#ifdef CONFIG_BINFMT_SHARED_FLAT

/*

 * Load a shared library into memory.  The library gets its own data

 * segment (including bss) but not argv/argc/environ.

 */

static int load_flat_shared_library(int id, struct lib_info *libs)

{

        struct linux_binprm bprm;

        int res;

        char buf[16];

        /* Create the file name */

        sprintf(buf, "/lib/lib%d.so", id);

        /* Open the file up */

        bprm.filename = buf;

        bprm.file = open_exec(bprm.filename);

        res = PTR_ERR(bprm.file);

        if (IS_ERR(bprm.file))

                return res;

        res = prepare_binprm(&bprm);

        if (res <= (unsigned long)-4096)

                res = load_flat_file(&bprm, libs, id, NULL);

        if (bprm.file) {

                allow_write_access(bprm.file);

                fput(bprm.file);

                bprm.file = NULL;

        }

        return(res);

}

#endif /* CONFIG_BINFMT_SHARED_FLAT */

int load_flt_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,

                    struct image_info * info)

{

    struct lib_info libinfo[MAX_SHARED_LIBS];

    abi_ulong p = bprm->p;

    abi_ulong stack_len;

    abi_ulong start_addr;

    abi_ulong sp;

    int res;

    int i, j;

    memset(libinfo, 0, sizeof(libinfo));

    /*

     * We have to add the size of our arguments to our stack size

     * otherwise it's too easy for users to create stack overflows

     * by passing in a huge argument list.  And yes,  we have to be

     * pedantic and include space for the argv/envp array as it may have

     * a lot of entries.

     */

#define TOP_OF_ARGS (TARGET_PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *))

    stack_len = TOP_OF_ARGS - bprm->p;             /* the strings */

    stack_len += (bprm->argc + 1) * 4; /* the argv array */

    stack_len += (bprm->envc + 1) * 4; /* the envp array */

    res = load_flat_file(bprm, libinfo, 0, &stack_len);

    if (res > (unsigned long)-4096)

            return res;

    /* Update data segment pointers for all libraries */

    for (i=0; i<MAX_SHARED_LIBS; i++) {

        if (libinfo[i].loaded) {

            abi_ulong p;

            p = libinfo[i].start_data;

            for (j=0; j<MAX_SHARED_LIBS; j++) {

                p -= 4;

                /* FIXME - handle put_user() failures */

                if (put_user_ual(libinfo[j].loaded

                                 ? libinfo[j].start_data

                                 : UNLOADED_LIB,

                                 p))

                    return -EFAULT;

            }

        }

    }

    p = ((libinfo[0].start_brk + stack_len + 3) & ~3) - 4;

    DBG_FLT("p=%x\n", (int)p);

    /* Copy argv/envp.  */

    p = copy_strings(p, bprm->envc, bprm->envp);

    p = copy_strings(p, bprm->argc, bprm->argv);

    /* Align stack.  */

    sp = p & ~(abi_ulong)(sizeof(abi_ulong) - 1);

    /* Enforce final stack alignment of 16 bytes.  This is sufficient

       for all current targets, and excess alignment is harmless.  */

    stack_len = bprm->envc + bprm->argc + 2;

    stack_len += 3;        /* argc, arvg, argp */

    stack_len *= sizeof(abi_ulong);

    if ((sp + stack_len) & 15)

        sp -= 16 - ((sp + stack_len) & 15);

    sp = loader_build_argptr(bprm->envc, bprm->argc, sp, p, 1);

    /* Fake some return addresses to ensure the call chain will

     * initialise library in order for us.  We are required to call

     * lib 1 first, then 2, ... and finally the main program (id 0).

     */

    start_addr = libinfo[0].entry;

#ifdef CONFIG_BINFMT_SHARED_FLAT

#error here

    for (i = MAX_SHARED_LIBS-1; i>0; i--) {

            if (libinfo[i].loaded) {

                    /* Push previos first to call address */

                    --sp;

                    if (put_user_ual(start_addr, sp))

                        return -EFAULT;

                    start_addr = libinfo[i].entry;

            }

    }

#endif

    /* Stash our initial stack pointer into the mm structure */

    info->start_code = libinfo[0].start_code;

    info->end_code = libinfo[0].start_code = libinfo[0].text_len;

    info->start_data = libinfo[0].start_data;

    info->end_data = libinfo[0].end_data;

    info->start_brk = libinfo[0].start_brk;

    info->start_stack = sp;

    info->entry = start_addr;

    info->code_offset = info->start_code;

    info->data_offset = info->start_data - libinfo[0].text_len;

    DBG_FLT("start_thread(entry=0x%x, start_stack=0x%x)\n",

            (int)info->entry, (int)info->start_stack);

    return 0;

}