Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf

[linux-2.6/btrfs-unstable.git] / scripts / gcc-plugins / randomize_layout_plugin.c

/*
 * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
 *                   and PaX Team <pageexec@freemail.hu>
 * Licensed under the GPL v2
 *
 * Note: the choice of the license means that the compilation process is
 *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
 *       but for the kernel it doesn't matter since it doesn't link against
 *       any of the gcc libraries
 *
 * Usage:
 * $ # for 4.5/4.6/C based 4.7
 * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 * $ # for C++ based 4.7/4.8+
 * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
 * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
 */

#include "gcc-common.h"
#include "randomize_layout_seed.h"

#if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
#error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
#endif

#define ORIG_TYPE_NAME(node) \
        (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")

#define INFORM(loc, msg, ...)   inform(loc, "randstruct: " msg, ##__VA_ARGS__)
#define MISMATCH(loc, how, ...) INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)

__visible int plugin_is_GPL_compatible;

static int performance_mode;

static struct plugin_info randomize_layout_plugin_info = {
        .version        = "201402201816vanilla",
        .help           = "disable\t\t\tdo not activate plugin\n"
                          "performance-mode\tenable cacheline-aware layout randomization\n"
};

struct whitelist_entry {
        const char *pathname;
        const char *lhs;
        const char *rhs;
};

static const struct whitelist_entry whitelist[] = {
        /* NIU overloads mapping with page struct */
        { "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
        /* unix_skb_parms via UNIXCB() buffer */
        { "net/unix/af_unix.c", "unix_skb_parms", "char" },
        /* big_key payload.data struct splashing */
        { "security/keys/big_key.c", "path", "void *" },
        /* walk struct security_hook_heads as an array of struct list_head */
        { "security/security.c", "list_head", "security_hook_heads" },
        { }
};

/* from old Linux dcache.h */
static inline unsigned long
partial_name_hash(unsigned long c, unsigned long prevhash)
{
        return (prevhash + (c << 4) + (c >> 4)) * 11;
}
static inline unsigned int
name_hash(const unsigned char *name)
{
        unsigned long hash = 0;
        unsigned int len = strlen((const char *)name);
        while (len--)
                hash = partial_name_hash(*name++, hash);
        return (unsigned int)hash;
}

static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
        tree type;

        *no_add_attrs = true;
        if (TREE_CODE(*node) == FUNCTION_DECL) {
                error("%qE attribute does not apply to functions (%qF)", name, *node);
                return NULL_TREE;
        }

        if (TREE_CODE(*node) == PARM_DECL) {
                error("%qE attribute does not apply to function parameters (%qD)", name, *node);
                return NULL_TREE;
        }

        if (TREE_CODE(*node) == VAR_DECL) {
                error("%qE attribute does not apply to variables (%qD)", name, *node);
                return NULL_TREE;
        }

        if (TYPE_P(*node)) {
                type = *node;
        } else {
                gcc_assert(TREE_CODE(*node) == TYPE_DECL);
                type = TREE_TYPE(*node);
        }

        if (TREE_CODE(type) != RECORD_TYPE) {
                error("%qE attribute used on %qT applies to struct types only", name, type);
                return NULL_TREE;
        }

        if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
                error("%qE attribute is already applied to the type %qT", name, type);
                return NULL_TREE;
        }

        *no_add_attrs = false;

        return NULL_TREE;
}

/* set on complete types that we don't need to inspect further at all */
static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
        *no_add_attrs = false;
        return NULL_TREE;
}

/*
 * set on types that we've performed a shuffle on, to prevent re-shuffling
 * this does not preclude us from inspecting its fields for potential shuffles
 */
static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
        *no_add_attrs = false;
        return NULL_TREE;
}

/*
 * 64bit variant of Bob Jenkins' public domain PRNG
 * 256 bits of internal state
 */

typedef unsigned long long u64;

typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;

#define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
static u64 ranval(ranctx *x) {
        u64 e = x->a - rot(x->b, 7);
        x->a = x->b ^ rot(x->c, 13);
        x->b = x->c + rot(x->d, 37);
        x->c = x->d + e;
        x->d = e + x->a;
        return x->d;
}

static void raninit(ranctx *x, u64 *seed) {
        int i;

        x->a = seed[0];
        x->b = seed[1];
        x->c = seed[2];
        x->d = seed[3];

        for (i=0; i < 30; ++i)
                (void)ranval(x);
}

static u64 shuffle_seed[4];

struct partition_group {
        tree tree_start;
        unsigned long start;
        unsigned long length;
};

static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
{
        unsigned long i;
        unsigned long accum_size = 0;
        unsigned long accum_length = 0;
        unsigned long group_idx = 0;

        gcc_assert(length < INT_MAX);

        memset(size_groups, 0, sizeof(struct partition_group) * length);

        for (i = 0; i < length; i++) {
                if (size_groups[group_idx].tree_start == NULL_TREE) {
                        size_groups[group_idx].tree_start = fields[i];
                        size_groups[group_idx].start = i;
                        accum_length = 0;
                        accum_size = 0;
                }
                accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
                accum_length++;
                if (accum_size >= 64) {
                        size_groups[group_idx].length = accum_length;
                        accum_length = 0;
                        group_idx++;
                }
        }

        if (size_groups[group_idx].tree_start != NULL_TREE &&
            !size_groups[group_idx].length) {
                size_groups[group_idx].length = accum_length;
                group_idx++;
        }

        *num_groups = group_idx;
}

static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
{
        unsigned long i, x;
        struct partition_group size_group[length];
        unsigned long num_groups = 0;
        unsigned long randnum;

        partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
        for (i = num_groups - 1; i > 0; i--) {
                struct partition_group tmp;
                randnum = ranval(prng_state) % (i + 1);
                tmp = size_group[i];
                size_group[i] = size_group[randnum];
                size_group[randnum] = tmp;
        }

        for (x = 0; x < num_groups; x++) {
                for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
                        tree tmp;
                        if (DECL_BIT_FIELD_TYPE(newtree[i]))
                                continue;
                        randnum = ranval(prng_state) % (i + 1);
                        // we could handle this case differently if desired
                        if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
                                continue;
                        tmp = newtree[i];
                        newtree[i] = newtree[randnum];
                        newtree[randnum] = tmp;
                }
        }
}

static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
{
        unsigned long i, randnum;

        for (i = length - 1; i > 0; i--) {
                tree tmp;
                randnum = ranval(prng_state) % (i + 1);
                tmp = newtree[i];
                newtree[i] = newtree[randnum];
                newtree[randnum] = tmp;
        }
}

/* modern in-place Fisher-Yates shuffle */
static void shuffle(const_tree type, tree *newtree, unsigned long length)
{
        unsigned long i;
        u64 seed[4];
        ranctx prng_state;
        const unsigned char *structname;

        if (length == 0)
                return;

        gcc_assert(TREE_CODE(type) == RECORD_TYPE);

        structname = ORIG_TYPE_NAME(type);

#ifdef __DEBUG_PLUGIN
        fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
#ifdef __DEBUG_VERBOSE
        debug_tree((tree)type);
#endif
#endif

        for (i = 0; i < 4; i++) {
                seed[i] = shuffle_seed[i];
                seed[i] ^= name_hash(structname);
        }

        raninit(&prng_state, (u64 *)&seed);

        if (performance_mode)
                performance_shuffle(newtree, length, &prng_state);
        else
                full_shuffle(newtree, length, &prng_state);
}

static bool is_flexible_array(const_tree field)
{
        const_tree fieldtype;
        const_tree typesize;
        const_tree elemtype;
        const_tree elemsize;

        fieldtype = TREE_TYPE(field);
        typesize = TYPE_SIZE(fieldtype);

        if (TREE_CODE(fieldtype) != ARRAY_TYPE)
                return false;

        elemtype = TREE_TYPE(fieldtype);
        elemsize = TYPE_SIZE(elemtype);

        /* size of type is represented in bits */

        if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
            TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
                return true;

        if (typesize != NULL_TREE &&
            (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
             tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
                return true;

        return false;
}

static int relayout_struct(tree type)
{
        unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
        unsigned long shuffle_length = num_fields;
        tree field;
        tree newtree[num_fields];
        unsigned long i;
        tree list;
        tree variant;
        tree main_variant;
        expanded_location xloc;
        bool has_flexarray = false;

        if (TYPE_FIELDS(type) == NULL_TREE)
                return 0;

        if (num_fields < 2)
                return 0;

        gcc_assert(TREE_CODE(type) == RECORD_TYPE);

        gcc_assert(num_fields < INT_MAX);

        if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
            lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
                return 0;

        /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
        if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
            !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
                return 0;

        /* throw out any structs in uapi */
        xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));

        if (strstr(xloc.file, "/uapi/"))
                error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));

        for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
                gcc_assert(TREE_CODE(field) == FIELD_DECL);
                newtree[i] = field;
        }

        /*
         * enforce that we don't randomize the layout of the last
         * element of a struct if it's a 0 or 1-length array
         * or a proper flexible array
         */
        if (is_flexible_array(newtree[num_fields - 1])) {
                has_flexarray = true;
                shuffle_length--;
        }

        shuffle(type, (tree *)newtree, shuffle_length);

        /*
         * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
         * as gcc provides no other way to detect such code
         */
        list = make_node(FIELD_DECL);
        TREE_CHAIN(list) = newtree[0];
        TREE_TYPE(list) = void_type_node;
        DECL_SIZE(list) = bitsize_zero_node;
        DECL_NONADDRESSABLE_P(list) = 1;
        DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
        DECL_SIZE_UNIT(list) = size_zero_node;
        DECL_FIELD_OFFSET(list) = size_zero_node;
        DECL_CONTEXT(list) = type;
        // to satisfy the constify plugin
        TREE_READONLY(list) = 1;

        for (i = 0; i < num_fields - 1; i++)
                TREE_CHAIN(newtree[i]) = newtree[i+1];
        TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;

        main_variant = TYPE_MAIN_VARIANT(type);
        for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
                TYPE_FIELDS(variant) = list;
                TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
                TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
                TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
                if (has_flexarray)
                        TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
        }

        /*
         * force a re-layout of the main variant
         * the TYPE_SIZE for all variants will be recomputed
         * by finalize_type_size()
         */
        TYPE_SIZE(main_variant) = NULL_TREE;
        layout_type(main_variant);
        gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);

        return 1;
}

/* from constify plugin */
static const_tree get_field_type(const_tree field)
{
        return strip_array_types(TREE_TYPE(field));
}

/* from constify plugin */
static bool is_fptr(const_tree fieldtype)
{
        if (TREE_CODE(fieldtype) != POINTER_TYPE)
                return false;

        return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
}

/* derived from constify plugin */
static int is_pure_ops_struct(const_tree node)
{
        const_tree field;

        gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);

        /* XXX: Do not apply randomization to all-ftpr structs yet. */
        return 0;

        for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
                const_tree fieldtype = get_field_type(field);
                enum tree_code code = TREE_CODE(fieldtype);

                if (node == fieldtype)
                        continue;

                if (!is_fptr(fieldtype))
                        return 0;

                if (code != RECORD_TYPE && code != UNION_TYPE)
                        continue;

                if (!is_pure_ops_struct(fieldtype))
                        return 0;
        }

        return 1;
}

static void randomize_type(tree type)
{
        tree variant;

        gcc_assert(TREE_CODE(type) == RECORD_TYPE);

        if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
                return;

        if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
                relayout_struct(type);

        for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
                TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
                TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
        }
#ifdef __DEBUG_PLUGIN
        fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
#ifdef __DEBUG_VERBOSE
        debug_tree(type);
#endif
#endif
}

static void update_decl_size(tree decl)
{
        tree lastval, lastidx, field, init, type, flexsize;
        unsigned HOST_WIDE_INT len;

        type = TREE_TYPE(decl);

        if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
                return;

        init = DECL_INITIAL(decl);
        if (init == NULL_TREE || init == error_mark_node)
                return;

        if (TREE_CODE(init) != CONSTRUCTOR)
                return;

        len = CONSTRUCTOR_NELTS(init);
        if (!len)
                return;

        lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
        lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;

        for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
                ;

        if (lastidx != field)
                return;

        if (TREE_CODE(lastval) != STRING_CST) {
                error("Only string constants are supported as initializers "
                      "for randomized structures with flexible arrays");
                return;
        }

        flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
                tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));

        DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);

        return;
}


static void randomize_layout_finish_decl(void *event_data, void *data)
{
        tree decl = (tree)event_data;
        tree type;

        if (decl == NULL_TREE || decl == error_mark_node)
                return;

        type = TREE_TYPE(decl);

        if (TREE_CODE(decl) != VAR_DECL)
                return;

        if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
                return;

        if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
                return;

        DECL_SIZE(decl) = 0;
        DECL_SIZE_UNIT(decl) = 0;
        SET_DECL_ALIGN(decl, 0);
        SET_DECL_MODE (decl, VOIDmode);
        SET_DECL_RTL(decl, 0);
        update_decl_size(decl);
        layout_decl(decl, 0);
}

static void finish_type(void *event_data, void *data)
{
        tree type = (tree)event_data;

        if (type == NULL_TREE || type == error_mark_node)
                return;

        if (TREE_CODE(type) != RECORD_TYPE)
                return;

        if (TYPE_FIELDS(type) == NULL_TREE)
                return;

        if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
                return;

#ifdef __DEBUG_PLUGIN
        fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
#endif
#ifdef __DEBUG_VERBOSE
        debug_tree(type);
#endif
        randomize_type(type);

        return;
}

static struct attribute_spec randomize_layout_attr = {
        .name           = "randomize_layout",
        // related to args
        .min_length     = 0,
        .max_length     = 0,
        .decl_required  = false,
        // need type declaration
        .type_required  = true,
        .function_type_required = false,
        .handler                = handle_randomize_layout_attr,
#if BUILDING_GCC_VERSION >= 4007
        .affects_type_identity  = true
#endif
};

static struct attribute_spec no_randomize_layout_attr = {
        .name           = "no_randomize_layout",
        // related to args
        .min_length     = 0,
        .max_length     = 0,
        .decl_required  = false,
        // need type declaration
        .type_required  = true,
        .function_type_required = false,
        .handler                = handle_randomize_layout_attr,
#if BUILDING_GCC_VERSION >= 4007
        .affects_type_identity  = true
#endif
};

static struct attribute_spec randomize_considered_attr = {
        .name           = "randomize_considered",
        // related to args
        .min_length     = 0,
        .max_length     = 0,
        .decl_required  = false,
        // need type declaration
        .type_required  = true,
        .function_type_required = false,
        .handler                = handle_randomize_considered_attr,
#if BUILDING_GCC_VERSION >= 4007
        .affects_type_identity  = false
#endif
};

static struct attribute_spec randomize_performed_attr = {
        .name           = "randomize_performed",
        // related to args
        .min_length     = 0,
        .max_length     = 0,
        .decl_required  = false,
        // need type declaration
        .type_required  = true,
        .function_type_required = false,
        .handler                = handle_randomize_performed_attr,
#if BUILDING_GCC_VERSION >= 4007
        .affects_type_identity  = false
#endif
};

static void register_attributes(void *event_data, void *data)
{
        register_attribute(&randomize_layout_attr);
        register_attribute(&no_randomize_layout_attr);
        register_attribute(&randomize_considered_attr);
        register_attribute(&randomize_performed_attr);
}

static void check_bad_casts_in_constructor(tree var, tree init)
{
        unsigned HOST_WIDE_INT idx;
        tree field, val;
        tree field_type, val_type;

        FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
                if (TREE_CODE(val) == CONSTRUCTOR) {
                        check_bad_casts_in_constructor(var, val);
                        continue;
                }

                /* pipacs' plugin creates franken-arrays that differ from those produced by
                   normal code which all have valid 'field' trees. work around this */
                if (field == NULL_TREE)
                        continue;
                field_type = TREE_TYPE(field);
                val_type = TREE_TYPE(val);

                if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
                        continue;

                if (field_type == val_type)
                        continue;

                field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
                val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));

                if (field_type == void_type_node)
                        continue;
                if (field_type == val_type)
                        continue;
                if (TREE_CODE(val_type) != RECORD_TYPE)
                        continue;

                if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
                        continue;
                MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
        }
}

/* derived from the constify plugin */
static void check_global_variables(void *event_data, void *data)
{
        struct varpool_node *node;
        tree init;

        FOR_EACH_VARIABLE(node) {
                tree var = NODE_DECL(node);
                init = DECL_INITIAL(var);
                if (init == NULL_TREE)
                        continue;

                if (TREE_CODE(init) != CONSTRUCTOR)
                        continue;

                check_bad_casts_in_constructor(var, init);
        }
}

static bool dominated_by_is_err(const_tree rhs, basic_block bb)
{
        basic_block dom;
        gimple dom_stmt;
        gimple call_stmt;
        const_tree dom_lhs;
        const_tree poss_is_err_cond;
        const_tree poss_is_err_func;
        const_tree is_err_arg;

        dom = get_immediate_dominator(CDI_DOMINATORS, bb);
        if (!dom)
                return false;

        dom_stmt = last_stmt(dom);
        if (!dom_stmt)
                return false;

        if (gimple_code(dom_stmt) != GIMPLE_COND)
                return false;

        if (gimple_cond_code(dom_stmt) != NE_EXPR)
                return false;

        if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
                return false;

        poss_is_err_cond = gimple_cond_lhs(dom_stmt);

        if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
                return false;

        call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);

        if (gimple_code(call_stmt) != GIMPLE_CALL)
                return false;

        dom_lhs = gimple_get_lhs(call_stmt);
        poss_is_err_func = gimple_call_fndecl(call_stmt);
        if (!poss_is_err_func)
                return false;
        if (dom_lhs != poss_is_err_cond)
                return false;
        if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
                return false;

        is_err_arg = gimple_call_arg(call_stmt, 0);
        if (!is_err_arg)
                return false;

        if (is_err_arg != rhs)
                return false;

        return true;
}

static void handle_local_var_initializers(void)
{
        tree var;
        unsigned int i;

        FOR_EACH_LOCAL_DECL(cfun, i, var) {
                tree init = DECL_INITIAL(var);
                if (!init)
                        continue;
                if (TREE_CODE(init) != CONSTRUCTOR)
                        continue;
                check_bad_casts_in_constructor(var, init);
        }
}

static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
{
        const char *type_name;

        if (type_tree == NULL_TREE)
                return false;

        switch (TREE_CODE(type_tree)) {
        case RECORD_TYPE:
                type_name = TYPE_NAME_POINTER(type_tree);
                break;
        case INTEGER_TYPE:
                if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
                        type_name = "char";
                else {
                        INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
                        debug_tree(type_tree);
                        return false;
                }
                break;
        case POINTER_TYPE:
                if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
                        type_name = "void *";
                        break;
                } else {
                        INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
                        debug_tree(type_tree);
                        return false;
                }
        default:
                INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
                debug_tree(type_tree);
                return false;
        }

        return strcmp(type_name, wanted_name) == 0;
}

static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
{
        const struct whitelist_entry *entry;
        expanded_location xloc = expand_location(gimple_location(stmt));

        for (entry = whitelist; entry->pathname; entry++) {
                if (!strstr(xloc.file, entry->pathname))
                        continue;

                if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
                        return true;
        }

        return false;
}

/*
 * iterate over all statements to find "bad" casts:
 * those where the address of the start of a structure is cast
 * to a pointer of a structure of a different type, or a
 * structure pointer type is cast to a different structure pointer type
 */
static unsigned int find_bad_casts_execute(void)
{
        basic_block bb;

        handle_local_var_initializers();

        FOR_EACH_BB_FN(bb, cfun) {
                gimple_stmt_iterator gsi;

                for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
                        gimple stmt;
                        const_tree lhs;
                        const_tree lhs_type;
                        const_tree rhs1;
                        const_tree rhs_type;
                        const_tree ptr_lhs_type;
                        const_tree ptr_rhs_type;
                        const_tree op0;
                        const_tree op0_type;
                        enum tree_code rhs_code;

                        stmt = gsi_stmt(gsi);

#ifdef __DEBUG_PLUGIN
#ifdef __DEBUG_VERBOSE
                        debug_gimple_stmt(stmt);
                        debug_tree(gimple_get_lhs(stmt));
#endif
#endif

                        if (gimple_code(stmt) != GIMPLE_ASSIGN)
                                continue;

#ifdef __DEBUG_PLUGIN
#ifdef __DEBUG_VERBOSE
                        debug_tree(gimple_assign_rhs1(stmt));
#endif
#endif


                        rhs_code = gimple_assign_rhs_code(stmt);

                        if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
                                continue;

                        lhs = gimple_get_lhs(stmt);
                        lhs_type = TREE_TYPE(lhs);
                        rhs1 = gimple_assign_rhs1(stmt);
                        rhs_type = TREE_TYPE(rhs1);

                        if (TREE_CODE(rhs_type) != POINTER_TYPE ||
                            TREE_CODE(lhs_type) != POINTER_TYPE)
                                continue;

                        ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
                        ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));

                        if (ptr_rhs_type == void_type_node)
                                continue;

                        if (ptr_lhs_type == void_type_node)
                                continue;

                        if (dominated_by_is_err(rhs1, bb))
                                continue;

                        if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
#ifndef __DEBUG_PLUGIN
                                if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
#endif
                                {
                                        if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
                                                MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
                                }
                                continue;
                        }

                        if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
                                continue;

                        if (rhs_code == ADDR_EXPR) {
                                op0 = TREE_OPERAND(rhs1, 0);

                                if (op0 == NULL_TREE)
                                        continue;

                                if (TREE_CODE(op0) != VAR_DECL)
                                        continue;

                                op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
                                if (op0_type == ptr_lhs_type)
                                        continue;

#ifndef __DEBUG_PLUGIN
                                if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
#endif
                                {
                                        if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
                                                MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
                                }
                        } else {
                                const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
                                /* skip bogus type casts introduced by container_of */
                                if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 
                                    !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
                                        continue;
#ifndef __DEBUG_PLUGIN
                                if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
#endif
                                {
                                        if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
                                                MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
                                }
                        }

                }
        }
        return 0;
}

#define PASS_NAME find_bad_casts
#define NO_GATE
#define TODO_FLAGS_FINISH TODO_dump_func
#include "gcc-generate-gimple-pass.h"

__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
{
        int i;
        const char * const plugin_name = plugin_info->base_name;
        const int argc = plugin_info->argc;
        const struct plugin_argument * const argv = plugin_info->argv;
        bool enable = true;
        int obtained_seed = 0;
        struct register_pass_info find_bad_casts_pass_info;

        find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
        find_bad_casts_pass_info.reference_pass_name    = "ssa";
        find_bad_casts_pass_info.ref_pass_instance_number       = 1;
        find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;

        if (!plugin_default_version_check(version, &gcc_version)) {
                error(G_("incompatible gcc/plugin versions"));
                return 1;
        }

        if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
                inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
                enable = false;
        }

        for (i = 0; i < argc; ++i) {
                if (!strcmp(argv[i].key, "disable")) {
                        enable = false;
                        continue;
                }
                if (!strcmp(argv[i].key, "performance-mode")) {
                        performance_mode = 1;
                        continue;
                }
                error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
        }

        if (strlen(randstruct_seed) != 64) {
                error(G_("invalid seed value supplied for %s plugin"), plugin_name);
                return 1;
        }
        obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
                &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
        if (obtained_seed != 4) {
                error(G_("Invalid seed supplied for %s plugin"), plugin_name);
                return 1;
        }

        register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
        if (enable) {
                register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
                register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
                register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
                register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
        }
        register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);

        return 0;
}