flatload.c

xen虚拟机源代码安装包

    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*)(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;
}