array_index_nospec: Sanitize speculative array de-references

[linux/fpc-iii.git] / scripts / dtc / flattree.c

/*
 * (C) Copyright David Gibson <dwg@au1.ibm.com>, IBM Corporation.  2005.
 *
 *
 * 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, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *                                                                   USA
 */

#include "dtc.h"
#include "srcpos.h"

#define FTF_FULLPATH    0x1
#define FTF_VARALIGN    0x2
#define FTF_NAMEPROPS   0x4
#define FTF_BOOTCPUID   0x8
#define FTF_STRTABSIZE  0x10
#define FTF_STRUCTSIZE  0x20
#define FTF_NOPS        0x40

static struct version_info {
        int version;
        int last_comp_version;
        int hdr_size;
        int flags;
} version_table[] = {
        {1, 1, FDT_V1_SIZE,
         FTF_FULLPATH|FTF_VARALIGN|FTF_NAMEPROPS},
        {2, 1, FDT_V2_SIZE,
         FTF_FULLPATH|FTF_VARALIGN|FTF_NAMEPROPS|FTF_BOOTCPUID},
        {3, 1, FDT_V3_SIZE,
         FTF_FULLPATH|FTF_VARALIGN|FTF_NAMEPROPS|FTF_BOOTCPUID|FTF_STRTABSIZE},
        {16, 16, FDT_V3_SIZE,
         FTF_BOOTCPUID|FTF_STRTABSIZE|FTF_NOPS},
        {17, 16, FDT_V17_SIZE,
         FTF_BOOTCPUID|FTF_STRTABSIZE|FTF_STRUCTSIZE|FTF_NOPS},
};

struct emitter {
        void (*cell)(void *, cell_t);
        void (*string)(void *, char *, int);
        void (*align)(void *, int);
        void (*data)(void *, struct data);
        void (*beginnode)(void *, struct label *labels);
        void (*endnode)(void *, struct label *labels);
        void (*property)(void *, struct label *labels);
};

static void bin_emit_cell(void *e, cell_t val)
{
        struct data *dtbuf = e;

        *dtbuf = data_append_cell(*dtbuf, val);
}

static void bin_emit_string(void *e, char *str, int len)
{
        struct data *dtbuf = e;

        if (len == 0)
                len = strlen(str);

        *dtbuf = data_append_data(*dtbuf, str, len);
        *dtbuf = data_append_byte(*dtbuf, '\0');
}

static void bin_emit_align(void *e, int a)
{
        struct data *dtbuf = e;

        *dtbuf = data_append_align(*dtbuf, a);
}

static void bin_emit_data(void *e, struct data d)
{
        struct data *dtbuf = e;

        *dtbuf = data_append_data(*dtbuf, d.val, d.len);
}

static void bin_emit_beginnode(void *e, struct label *labels)
{
        bin_emit_cell(e, FDT_BEGIN_NODE);
}

static void bin_emit_endnode(void *e, struct label *labels)
{
        bin_emit_cell(e, FDT_END_NODE);
}

static void bin_emit_property(void *e, struct label *labels)
{
        bin_emit_cell(e, FDT_PROP);
}

static struct emitter bin_emitter = {
        .cell = bin_emit_cell,
        .string = bin_emit_string,
        .align = bin_emit_align,
        .data = bin_emit_data,
        .beginnode = bin_emit_beginnode,
        .endnode = bin_emit_endnode,
        .property = bin_emit_property,
};

static void emit_label(FILE *f, const char *prefix, const char *label)
{
        fprintf(f, "\t.globl\t%s_%s\n", prefix, label);
        fprintf(f, "%s_%s:\n", prefix, label);
        fprintf(f, "_%s_%s:\n", prefix, label);
}

static void emit_offset_label(FILE *f, const char *label, int offset)
{
        fprintf(f, "\t.globl\t%s\n", label);
        fprintf(f, "%s\t= . + %d\n", label, offset);
}

#define ASM_EMIT_BELONG(f, fmt, ...) \
        { \
                fprintf((f), "\t.byte\t((" fmt ") >> 24) & 0xff\n", __VA_ARGS__); \
                fprintf((f), "\t.byte\t((" fmt ") >> 16) & 0xff\n", __VA_ARGS__); \
                fprintf((f), "\t.byte\t((" fmt ") >> 8) & 0xff\n", __VA_ARGS__); \
                fprintf((f), "\t.byte\t(" fmt ") & 0xff\n", __VA_ARGS__); \
        }

static void asm_emit_cell(void *e, cell_t val)
{
        FILE *f = e;

        fprintf(f, "\t.byte 0x%02x; .byte 0x%02x; .byte 0x%02x; .byte 0x%02x\n",
                (val >> 24) & 0xff, (val >> 16) & 0xff,
                (val >> 8) & 0xff, val & 0xff);
}

static void asm_emit_string(void *e, char *str, int len)
{
        FILE *f = e;
        char c = 0;

        if (len != 0) {
                /* XXX: ewww */
                c = str[len];
                str[len] = '\0';
        }

        fprintf(f, "\t.string\t\"%s\"\n", str);

        if (len != 0) {
                str[len] = c;
        }
}

static void asm_emit_align(void *e, int a)
{
        FILE *f = e;

        fprintf(f, "\t.balign\t%d, 0\n", a);
}

static void asm_emit_data(void *e, struct data d)
{
        FILE *f = e;
        int off = 0;
        struct marker *m = d.markers;

        for_each_marker_of_type(m, LABEL)
                emit_offset_label(f, m->ref, m->offset);

        while ((d.len - off) >= sizeof(uint32_t)) {
                asm_emit_cell(e, fdt32_to_cpu(*((uint32_t *)(d.val+off))));
                off += sizeof(uint32_t);
        }

        while ((d.len - off) >= 1) {
                fprintf(f, "\t.byte\t0x%hhx\n", d.val[off]);
                off += 1;
        }

        assert(off == d.len);
}

static void asm_emit_beginnode(void *e, struct label *labels)
{
        FILE *f = e;
        struct label *l;

        for_each_label(labels, l) {
                fprintf(f, "\t.globl\t%s\n", l->label);
                fprintf(f, "%s:\n", l->label);
        }
        fprintf(f, "\t/* FDT_BEGIN_NODE */\n");
        asm_emit_cell(e, FDT_BEGIN_NODE);
}

static void asm_emit_endnode(void *e, struct label *labels)
{
        FILE *f = e;
        struct label *l;

        fprintf(f, "\t/* FDT_END_NODE */\n");
        asm_emit_cell(e, FDT_END_NODE);
        for_each_label(labels, l) {
                fprintf(f, "\t.globl\t%s_end\n", l->label);
                fprintf(f, "%s_end:\n", l->label);
        }
}

static void asm_emit_property(void *e, struct label *labels)
{
        FILE *f = e;
        struct label *l;

        for_each_label(labels, l) {
                fprintf(f, "\t.globl\t%s\n", l->label);
                fprintf(f, "%s:\n", l->label);
        }
        fprintf(f, "\t/* FDT_PROP */\n");
        asm_emit_cell(e, FDT_PROP);
}

static struct emitter asm_emitter = {
        .cell = asm_emit_cell,
        .string = asm_emit_string,
        .align = asm_emit_align,
        .data = asm_emit_data,
        .beginnode = asm_emit_beginnode,
        .endnode = asm_emit_endnode,
        .property = asm_emit_property,
};

static int stringtable_insert(struct data *d, const char *str)
{
        int i;

        /* FIXME: do this more efficiently? */

        for (i = 0; i < d->len; i++) {
                if (streq(str, d->val + i))
                        return i;
        }

        *d = data_append_data(*d, str, strlen(str)+1);
        return i;
}

static void flatten_tree(struct node *tree, struct emitter *emit,
                         void *etarget, struct data *strbuf,
                         struct version_info *vi)
{
        struct property *prop;
        struct node *child;
        bool seen_name_prop = false;

        if (tree->deleted)
                return;

        emit->beginnode(etarget, tree->labels);

        if (vi->flags & FTF_FULLPATH)
                emit->string(etarget, tree->fullpath, 0);
        else
                emit->string(etarget, tree->name, 0);

        emit->align(etarget, sizeof(cell_t));

        for_each_property(tree, prop) {
                int nameoff;

                if (streq(prop->name, "name"))
                        seen_name_prop = true;

                nameoff = stringtable_insert(strbuf, prop->name);

                emit->property(etarget, prop->labels);
                emit->cell(etarget, prop->val.len);
                emit->cell(etarget, nameoff);

                if ((vi->flags & FTF_VARALIGN) && (prop->val.len >= 8))
                        emit->align(etarget, 8);

                emit->data(etarget, prop->val);
                emit->align(etarget, sizeof(cell_t));
        }

        if ((vi->flags & FTF_NAMEPROPS) && !seen_name_prop) {
                emit->property(etarget, NULL);
                emit->cell(etarget, tree->basenamelen+1);
                emit->cell(etarget, stringtable_insert(strbuf, "name"));

                if ((vi->flags & FTF_VARALIGN) && ((tree->basenamelen+1) >= 8))
                        emit->align(etarget, 8);

                emit->string(etarget, tree->name, tree->basenamelen);
                emit->align(etarget, sizeof(cell_t));
        }

        for_each_child(tree, child) {
                flatten_tree(child, emit, etarget, strbuf, vi);
        }

        emit->endnode(etarget, tree->labels);
}

static struct data flatten_reserve_list(struct reserve_info *reservelist,
                                 struct version_info *vi)
{
        struct reserve_info *re;
        struct data d = empty_data;
        static struct fdt_reserve_entry null_re = {0,0};
        int    j;

        for (re = reservelist; re; re = re->next) {
                d = data_append_re(d, &re->re);
        }
        /*
         * Add additional reserved slots if the user asked for them.
         */
        for (j = 0; j < reservenum; j++) {
                d = data_append_re(d, &null_re);
        }

        return d;
}

static void make_fdt_header(struct fdt_header *fdt,
                            struct version_info *vi,
                            int reservesize, int dtsize, int strsize,
                            int boot_cpuid_phys)
{
        int reserve_off;

        reservesize += sizeof(struct fdt_reserve_entry);

        memset(fdt, 0xff, sizeof(*fdt));

        fdt->magic = cpu_to_fdt32(FDT_MAGIC);
        fdt->version = cpu_to_fdt32(vi->version);
        fdt->last_comp_version = cpu_to_fdt32(vi->last_comp_version);

        /* Reserve map should be doubleword aligned */
        reserve_off = ALIGN(vi->hdr_size, 8);

        fdt->off_mem_rsvmap = cpu_to_fdt32(reserve_off);
        fdt->off_dt_struct = cpu_to_fdt32(reserve_off + reservesize);
        fdt->off_dt_strings = cpu_to_fdt32(reserve_off + reservesize
                                          + dtsize);
        fdt->totalsize = cpu_to_fdt32(reserve_off + reservesize + dtsize + strsize);

        if (vi->flags & FTF_BOOTCPUID)
                fdt->boot_cpuid_phys = cpu_to_fdt32(boot_cpuid_phys);
        if (vi->flags & FTF_STRTABSIZE)
                fdt->size_dt_strings = cpu_to_fdt32(strsize);
        if (vi->flags & FTF_STRUCTSIZE)
                fdt->size_dt_struct = cpu_to_fdt32(dtsize);
}

void dt_to_blob(FILE *f, struct boot_info *bi, int version)
{
        struct version_info *vi = NULL;
        int i;
        struct data blob       = empty_data;
        struct data reservebuf = empty_data;
        struct data dtbuf      = empty_data;
        struct data strbuf     = empty_data;
        struct fdt_header fdt;
        int padlen = 0;

        for (i = 0; i < ARRAY_SIZE(version_table); i++) {
                if (version_table[i].version == version)
                        vi = &version_table[i];
        }
        if (!vi)
                die("Unknown device tree blob version %d\n", version);

        flatten_tree(bi->dt, &bin_emitter, &dtbuf, &strbuf, vi);
        bin_emit_cell(&dtbuf, FDT_END);

        reservebuf = flatten_reserve_list(bi->reservelist, vi);

        /* Make header */
        make_fdt_header(&fdt, vi, reservebuf.len, dtbuf.len, strbuf.len,
                        bi->boot_cpuid_phys);

        /*
         * If the user asked for more space than is used, adjust the totalsize.
         */
        if (minsize > 0) {
                padlen = minsize - fdt32_to_cpu(fdt.totalsize);
                if ((padlen < 0) && (quiet < 1))
                        fprintf(stderr,
                                "Warning: blob size %d >= minimum size %d\n",
                                fdt32_to_cpu(fdt.totalsize), minsize);
        }

        if (padsize > 0)
                padlen = padsize;

        if (padlen > 0) {
                int tsize = fdt32_to_cpu(fdt.totalsize);
                tsize += padlen;
                fdt.totalsize = cpu_to_fdt32(tsize);
        }

        /*
         * Assemble the blob: start with the header, add with alignment
         * the reserve buffer, add the reserve map terminating zeroes,
         * the device tree itself, and finally the strings.
         */
        blob = data_append_data(blob, &fdt, vi->hdr_size);
        blob = data_append_align(blob, 8);
        blob = data_merge(blob, reservebuf);
        blob = data_append_zeroes(blob, sizeof(struct fdt_reserve_entry));
        blob = data_merge(blob, dtbuf);
        blob = data_merge(blob, strbuf);

        /*
         * If the user asked for more space than is used, pad out the blob.
         */
        if (padlen > 0)
                blob = data_append_zeroes(blob, padlen);

        if (fwrite(blob.val, blob.len, 1, f) != 1) {
                if (ferror(f))
                        die("Error writing device tree blob: %s\n",
                            strerror(errno));
                else
                        die("Short write on device tree blob\n");
        }

        /*
         * data_merge() frees the right-hand element so only the blob
         * remains to be freed.
         */
        data_free(blob);
}

static void dump_stringtable_asm(FILE *f, struct data strbuf)
{
        const char *p;
        int len;

        p = strbuf.val;

        while (p < (strbuf.val + strbuf.len)) {
                len = strlen(p);
                fprintf(f, "\t.string \"%s\"\n", p);
                p += len+1;
        }
}

void dt_to_asm(FILE *f, struct boot_info *bi, int version)
{
        struct version_info *vi = NULL;
        int i;
        struct data strbuf = empty_data;
        struct reserve_info *re;
        const char *symprefix = "dt";

        for (i = 0; i < ARRAY_SIZE(version_table); i++) {
                if (version_table[i].version == version)
                        vi = &version_table[i];
        }
        if (!vi)
                die("Unknown device tree blob version %d\n", version);

        fprintf(f, "/* autogenerated by dtc, do not edit */\n\n");

        emit_label(f, symprefix, "blob_start");
        emit_label(f, symprefix, "header");
        fprintf(f, "\t/* magic */\n");
        asm_emit_cell(f, FDT_MAGIC);
        fprintf(f, "\t/* totalsize */\n");
        ASM_EMIT_BELONG(f, "_%s_blob_abs_end - _%s_blob_start",
                        symprefix, symprefix);
        fprintf(f, "\t/* off_dt_struct */\n");
        ASM_EMIT_BELONG(f, "_%s_struct_start - _%s_blob_start",
                symprefix, symprefix);
        fprintf(f, "\t/* off_dt_strings */\n");
        ASM_EMIT_BELONG(f, "_%s_strings_start - _%s_blob_start",
                symprefix, symprefix);
        fprintf(f, "\t/* off_mem_rsvmap */\n");
        ASM_EMIT_BELONG(f, "_%s_reserve_map - _%s_blob_start",
                symprefix, symprefix);
        fprintf(f, "\t/* version */\n");
        asm_emit_cell(f, vi->version);
        fprintf(f, "\t/* last_comp_version */\n");
        asm_emit_cell(f, vi->last_comp_version);

        if (vi->flags & FTF_BOOTCPUID) {
                fprintf(f, "\t/* boot_cpuid_phys */\n");
                asm_emit_cell(f, bi->boot_cpuid_phys);
        }

        if (vi->flags & FTF_STRTABSIZE) {
                fprintf(f, "\t/* size_dt_strings */\n");
                ASM_EMIT_BELONG(f, "_%s_strings_end - _%s_strings_start",
                                symprefix, symprefix);
        }

        if (vi->flags & FTF_STRUCTSIZE) {
                fprintf(f, "\t/* size_dt_struct */\n");
                ASM_EMIT_BELONG(f, "_%s_struct_end - _%s_struct_start",
                        symprefix, symprefix);
        }

        /*
         * Reserve map entries.
         * Align the reserve map to a doubleword boundary.
         * Each entry is an (address, size) pair of u64 values.
         * Always supply a zero-sized temination entry.
         */
        asm_emit_align(f, 8);
        emit_label(f, symprefix, "reserve_map");

        fprintf(f, "/* Memory reserve map from source file */\n");

        /*
         * Use .long on high and low halfs of u64s to avoid .quad
         * as it appears .quad isn't available in some assemblers.
         */
        for (re = bi->reservelist; re; re = re->next) {
                struct label *l;

                for_each_label(re->labels, l) {
                        fprintf(f, "\t.globl\t%s\n", l->label);
                        fprintf(f, "%s:\n", l->label);
                }
                ASM_EMIT_BELONG(f, "0x%08x", (unsigned int)(re->re.address >> 32));
                ASM_EMIT_BELONG(f, "0x%08x",
                                (unsigned int)(re->re.address & 0xffffffff));
                ASM_EMIT_BELONG(f, "0x%08x", (unsigned int)(re->re.size >> 32));
                ASM_EMIT_BELONG(f, "0x%08x", (unsigned int)(re->re.size & 0xffffffff));
        }
        for (i = 0; i < reservenum; i++) {
                fprintf(f, "\t.long\t0, 0\n\t.long\t0, 0\n");
        }

        fprintf(f, "\t.long\t0, 0\n\t.long\t0, 0\n");

        emit_label(f, symprefix, "struct_start");
        flatten_tree(bi->dt, &asm_emitter, f, &strbuf, vi);

        fprintf(f, "\t/* FDT_END */\n");
        asm_emit_cell(f, FDT_END);
        emit_label(f, symprefix, "struct_end");

        emit_label(f, symprefix, "strings_start");
        dump_stringtable_asm(f, strbuf);
        emit_label(f, symprefix, "strings_end");

        emit_label(f, symprefix, "blob_end");

        /*
         * If the user asked for more space than is used, pad it out.
         */
        if (minsize > 0) {
                fprintf(f, "\t.space\t%d - (_%s_blob_end - _%s_blob_start), 0\n",
                        minsize, symprefix, symprefix);
        }
        if (padsize > 0) {
                fprintf(f, "\t.space\t%d, 0\n", padsize);
        }
        emit_label(f, symprefix, "blob_abs_end");

        data_free(strbuf);
}

struct inbuf {
        char *base, *limit, *ptr;
};

static void inbuf_init(struct inbuf *inb, void *base, void *limit)
{
        inb->base = base;
        inb->limit = limit;
        inb->ptr = inb->base;
}

static void flat_read_chunk(struct inbuf *inb, void *p, int len)
{
        if ((inb->ptr + len) > inb->limit)
                die("Premature end of data parsing flat device tree\n");

        memcpy(p, inb->ptr, len);

        inb->ptr += len;
}

static uint32_t flat_read_word(struct inbuf *inb)
{
        uint32_t val;

        assert(((inb->ptr - inb->base) % sizeof(val)) == 0);

        flat_read_chunk(inb, &val, sizeof(val));

        return fdt32_to_cpu(val);
}

static void flat_realign(struct inbuf *inb, int align)
{
        int off = inb->ptr - inb->base;

        inb->ptr = inb->base + ALIGN(off, align);
        if (inb->ptr > inb->limit)
                die("Premature end of data parsing flat device tree\n");
}

static char *flat_read_string(struct inbuf *inb)
{
        int len = 0;
        const char *p = inb->ptr;
        char *str;

        do {
                if (p >= inb->limit)
                        die("Premature end of data parsing flat device tree\n");
                len++;
        } while ((*p++) != '\0');

        str = xstrdup(inb->ptr);

        inb->ptr += len;

        flat_realign(inb, sizeof(uint32_t));

        return str;
}

static struct data flat_read_data(struct inbuf *inb, int len)
{
        struct data d = empty_data;

        if (len == 0)
                return empty_data;

        d = data_grow_for(d, len);
        d.len = len;

        flat_read_chunk(inb, d.val, len);

        flat_realign(inb, sizeof(uint32_t));

        return d;
}

static char *flat_read_stringtable(struct inbuf *inb, int offset)
{
        const char *p;

        p = inb->base + offset;
        while (1) {
                if (p >= inb->limit || p < inb->base)
                        die("String offset %d overruns string table\n",
                            offset);

                if (*p == '\0')
                        break;

                p++;
        }

        return xstrdup(inb->base + offset);
}

static struct property *flat_read_property(struct inbuf *dtbuf,
                                           struct inbuf *strbuf, int flags)
{
        uint32_t proplen, stroff;
        char *name;
        struct data val;

        proplen = flat_read_word(dtbuf);
        stroff = flat_read_word(dtbuf);

        name = flat_read_stringtable(strbuf, stroff);

        if ((flags & FTF_VARALIGN) && (proplen >= 8))
                flat_realign(dtbuf, 8);

        val = flat_read_data(dtbuf, proplen);

        return build_property(name, val);
}


static struct reserve_info *flat_read_mem_reserve(struct inbuf *inb)
{
        struct reserve_info *reservelist = NULL;
        struct reserve_info *new;
        struct fdt_reserve_entry re;

        /*
         * Each entry is a pair of u64 (addr, size) values for 4 cell_t's.
         * List terminates at an entry with size equal to zero.
         *
         * First pass, count entries.
         */
        while (1) {
                flat_read_chunk(inb, &re, sizeof(re));
                re.address  = fdt64_to_cpu(re.address);
                re.size = fdt64_to_cpu(re.size);
                if (re.size == 0)
                        break;

                new = build_reserve_entry(re.address, re.size);
                reservelist = add_reserve_entry(reservelist, new);
        }

        return reservelist;
}


static char *nodename_from_path(const char *ppath, const char *cpath)
{
        int plen;

        plen = strlen(ppath);

        if (!strneq(ppath, cpath, plen))
                die("Path \"%s\" is not valid as a child of \"%s\"\n",
                    cpath, ppath);

        /* root node is a special case */
        if (!streq(ppath, "/"))
                plen++;

        return xstrdup(cpath + plen);
}

static struct node *unflatten_tree(struct inbuf *dtbuf,
                                   struct inbuf *strbuf,
                                   const char *parent_flatname, int flags)
{
        struct node *node;
        char *flatname;
        uint32_t val;

        node = build_node(NULL, NULL);

        flatname = flat_read_string(dtbuf);

        if (flags & FTF_FULLPATH)
                node->name = nodename_from_path(parent_flatname, flatname);
        else
                node->name = flatname;

        do {
                struct property *prop;
                struct node *child;

                val = flat_read_word(dtbuf);
                switch (val) {
                case FDT_PROP:
                        if (node->children)
                                fprintf(stderr, "Warning: Flat tree input has "
                                        "subnodes preceding a property.\n");
                        prop = flat_read_property(dtbuf, strbuf, flags);
                        add_property(node, prop);
                        break;

                case FDT_BEGIN_NODE:
                        child = unflatten_tree(dtbuf,strbuf, flatname, flags);
                        add_child(node, child);
                        break;

                case FDT_END_NODE:
                        break;

                case FDT_END:
                        die("Premature FDT_END in device tree blob\n");
                        break;

                case FDT_NOP:
                        if (!(flags & FTF_NOPS))
                                fprintf(stderr, "Warning: NOP tag found in flat tree"
                                        " version <16\n");

                        /* Ignore */
                        break;

                default:
                        die("Invalid opcode word %08x in device tree blob\n",
                            val);
                }
        } while (val != FDT_END_NODE);

        return node;
}


struct boot_info *dt_from_blob(const char *fname)
{
        FILE *f;
        uint32_t magic, totalsize, version, size_dt, boot_cpuid_phys;
        uint32_t off_dt, off_str, off_mem_rsvmap;
        int rc;
        char *blob;
        struct fdt_header *fdt;
        char *p;
        struct inbuf dtbuf, strbuf;
        struct inbuf memresvbuf;
        int sizeleft;
        struct reserve_info *reservelist;
        struct node *tree;
        uint32_t val;
        int flags = 0;

        f = srcfile_relative_open(fname, NULL);

        rc = fread(&magic, sizeof(magic), 1, f);
        if (ferror(f))
                die("Error reading DT blob magic number: %s\n",
                    strerror(errno));
        if (rc < 1) {
                if (feof(f))
                        die("EOF reading DT blob magic number\n");
                else
                        die("Mysterious short read reading magic number\n");
        }

        magic = fdt32_to_cpu(magic);
        if (magic != FDT_MAGIC)
                die("Blob has incorrect magic number\n");

        rc = fread(&totalsize, sizeof(totalsize), 1, f);
        if (ferror(f))
                die("Error reading DT blob size: %s\n", strerror(errno));
        if (rc < 1) {
                if (feof(f))
                        die("EOF reading DT blob size\n");
                else
                        die("Mysterious short read reading blob size\n");
        }

        totalsize = fdt32_to_cpu(totalsize);
        if (totalsize < FDT_V1_SIZE)
                die("DT blob size (%d) is too small\n", totalsize);

        blob = xmalloc(totalsize);

        fdt = (struct fdt_header *)blob;
        fdt->magic = cpu_to_fdt32(magic);
        fdt->totalsize = cpu_to_fdt32(totalsize);

        sizeleft = totalsize - sizeof(magic) - sizeof(totalsize);
        p = blob + sizeof(magic)  + sizeof(totalsize);

        while (sizeleft) {
                if (feof(f))
                        die("EOF before reading %d bytes of DT blob\n",
                            totalsize);

                rc = fread(p, 1, sizeleft, f);
                if (ferror(f))
                        die("Error reading DT blob: %s\n",
                            strerror(errno));

                sizeleft -= rc;
                p += rc;
        }

        off_dt = fdt32_to_cpu(fdt->off_dt_struct);
        off_str = fdt32_to_cpu(fdt->off_dt_strings);
        off_mem_rsvmap = fdt32_to_cpu(fdt->off_mem_rsvmap);
        version = fdt32_to_cpu(fdt->version);
        boot_cpuid_phys = fdt32_to_cpu(fdt->boot_cpuid_phys);

        if (off_mem_rsvmap >= totalsize)
                die("Mem Reserve structure offset exceeds total size\n");

        if (off_dt >= totalsize)
                die("DT structure offset exceeds total size\n");

        if (off_str > totalsize)
                die("String table offset exceeds total size\n");

        if (version >= 3) {
                uint32_t size_str = fdt32_to_cpu(fdt->size_dt_strings);
                if (off_str+size_str > totalsize)
                        die("String table extends past total size\n");
                inbuf_init(&strbuf, blob + off_str, blob + off_str + size_str);
        } else {
                inbuf_init(&strbuf, blob + off_str, blob + totalsize);
        }

        if (version >= 17) {
                size_dt = fdt32_to_cpu(fdt->size_dt_struct);
                if (off_dt+size_dt > totalsize)
                        die("Structure block extends past total size\n");
        }

        if (version < 16) {
                flags |= FTF_FULLPATH | FTF_NAMEPROPS | FTF_VARALIGN;
        } else {
                flags |= FTF_NOPS;
        }

        inbuf_init(&memresvbuf,
                   blob + off_mem_rsvmap, blob + totalsize);
        inbuf_init(&dtbuf, blob + off_dt, blob + totalsize);

        reservelist = flat_read_mem_reserve(&memresvbuf);

        val = flat_read_word(&dtbuf);

        if (val != FDT_BEGIN_NODE)
                die("Device tree blob doesn't begin with FDT_BEGIN_NODE (begins with 0x%08x)\n", val);

        tree = unflatten_tree(&dtbuf, &strbuf, "", flags);

        val = flat_read_word(&dtbuf);
        if (val != FDT_END)
                die("Device tree blob doesn't end with FDT_END\n");

        free(blob);

        fclose(f);

        return build_boot_info(reservelist, tree, boot_cpuid_phys);
}