/*
 * Copyright (C) 2011 Dan Carpenter.
 *
 * 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/copyleft/gpl.txt
 */

/* Does a search for Dan Rosenberg style info leaks */

/* fixme: struct includes a struct with a hole in it */
/* function is called that clears the struct */

#include "scope.h"
#include "smatch.h"
#include "smatch_function_hashtable.h"
#include "smatch_slist.h"
#include "smatch_extra.h"

static int my_whole_id;
static int my_member_id;
static int skb_put_id;

STATE(cleared);

static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
{
        struct symbol *type;

        type = get_real_base_type(sym);
        if (!type || type->type != SYM_STRUCT)
                return;

        set_state(my_member_id, name, sym, state);
}

static void print_holey_warning(struct expression *data, const char *member)
{
        char *name;

        name = expr_to_str(data);
        if (member) {
                sm_warning("check that '%s' doesn't leak information (struct has a hole after '%s')",
                       name, member);
        } else {
                sm_warning("check that '%s' doesn't leak information (struct has holes)",
                       name);
        }
        free_string(name);
}

static int check_struct(struct expression *expr, struct symbol *type)
{
        struct symbol *tmp, *base_type;
        const char *prev = NULL;
        int align;

        if (type->ctype.alignment == 1)
                return 0;

        align = 0;
        FOR_EACH_PTR(type->symbol_list, tmp) {
                base_type = get_real_base_type(tmp);
                if (base_type && base_type->type == SYM_STRUCT) {
                        if (check_struct(expr, base_type))
                                return 1;
                }

                if (!tmp->ctype.alignment) {
                        sm_perror("cannot determine the alignment here");
                } else if (align % tmp->ctype.alignment) {
                        print_holey_warning(expr, prev);
                        return 1;
                }

                if (base_type == &bool_ctype)
                        align += 1;
                else if (type_bits(tmp) <= 0)
                        align = 0;
                else
                        align += type_bytes(tmp);

                if (tmp->ident)
                        prev = tmp->ident->name;
                else
                        prev = NULL;
        } END_FOR_EACH_PTR(tmp);

        if (align % type->ctype.alignment) {
                print_holey_warning(expr, prev);
                return 1;
        }

        return 0;
}

static int warn_on_holey_struct(struct expression *expr)
{
        struct symbol *type;
        type = get_type(expr);
        if (!type || type->type != SYM_STRUCT)
                return 0;

        return check_struct(expr, type);
}

static int has_global_scope(struct expression *expr)
{
        struct symbol *sym;

        if (expr->type != EXPR_SYMBOL)
                return FALSE;
        sym = expr->symbol;
        if (!sym)
                return FALSE;
        return toplevel(sym->scope);
}

static void match_clear(const char *fn, struct expression *expr, void *_arg_no)
{
        struct expression *ptr;
        int arg_no = PTR_INT(_arg_no);

        ptr = get_argument_from_call_expr(expr->args, arg_no);
        if (!ptr)
                return;
        ptr = strip_expr(ptr);
        if (ptr->type != EXPR_PREOP || ptr->op != '&')
                return;
        ptr = strip_expr(ptr->unop);
        set_state_expr(my_whole_id, ptr, &cleared);
}

static int was_memset(struct expression *expr)
{
        if (get_state_expr(my_whole_id, expr) == &cleared)
                return 1;
        return 0;
}

static int member_initialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
{
        char buf[256];
        struct symbol *base;

        base = get_base_type(member);
        if (!base || base->type != SYM_BASETYPE || !member->ident)
                return FALSE;

        if (pointer)
                snprintf(buf, 256, "%s->%s", name, member->ident->name);
        else
                snprintf(buf, 256, "%s.%s", name, member->ident->name);

        if (get_state(my_member_id, buf, outer))
                return TRUE;

        return FALSE;
}

static int member_uninitialized(char *name, struct symbol *outer, struct symbol *member, int pointer)
{
        char buf[256];
        struct symbol *base;
        struct sm_state *sm;

        base = get_base_type(member);
        if (!base || base->type != SYM_BASETYPE || !member->ident)
                return FALSE;

        if (pointer)
                snprintf(buf, 256, "%s->%s", name, member->ident->name);
        else
                snprintf(buf, 256, "%s.%s", name, member->ident->name);

        sm = get_sm_state(my_member_id, buf, outer);
        if (sm && !slist_has_state(sm->possible, &undefined))
                return FALSE;

        sm_warning("check that '%s' doesn't leak information", buf);
        return TRUE;
}

static int check_members_initialized(struct expression *expr)
{
        char *name;
        struct symbol *outer;
        struct symbol *sym;
        struct symbol *tmp;
        int pointer = 0;
        int printed = 0;

        sym = get_type(expr);
        if (sym && sym->type == SYM_PTR) {
                pointer = 1;
                sym = get_real_base_type(sym);
        }
        if (!sym)
                return 0;
        if (sym->type != SYM_STRUCT)
                return 0;

        name = expr_to_var_sym(expr, &outer);

        /*
         * check that at least one member was set.  If all of them were not set
         * it's more likely a problem in the check than a problem in the kernel
         * code.
         */
        FOR_EACH_PTR(sym->symbol_list, tmp) {
                if (member_initialized(name, outer, tmp, pointer))
                        goto check;
        } END_FOR_EACH_PTR(tmp);
        goto out;

check:
        FOR_EACH_PTR(sym->symbol_list, tmp) {
                if (member_uninitialized(name, outer, tmp, pointer)) {
                        printed = 1;
                        goto out;
                }
        } END_FOR_EACH_PTR(tmp);
out:
        free_string(name);
        return printed;
}

static void check_was_initialized(struct expression *data)
{
        data = strip_expr(data);
        if (!data)
                return;
        if (data->type == EXPR_PREOP && data->op == '&')
                data = strip_expr(data->unop);
        if (data->type != EXPR_SYMBOL)
                return;

        if (has_global_scope(data))
                return;
        if (was_memset(data))
                return;
        if (warn_on_holey_struct(data))
                return;
        check_members_initialized(data);
}

static void check_skb_put(struct expression *data)
{
        data = strip_expr(data);
        if (!data)
                return;
        if (data->type == EXPR_PREOP && data->op == '&')
                data = strip_expr(data->unop);

        if (was_memset(data))
                return;
        if (warn_on_holey_struct(data))
                return;
        check_members_initialized(data);
}

static void match_copy_to_user(const char *fn, struct expression *expr, void *_arg)
{
        int arg = PTR_INT(_arg);
        struct expression *data;

        data = get_argument_from_call_expr(expr->args, arg);
        data = strip_expr(data);
        if (!data)
                return;
        if (data->type != EXPR_PREOP || data->op != '&')
                return;
        check_was_initialized(data);
}

static void db_param_cleared(struct expression *expr, int param, char *key, char *value)
{
        while (expr->type == EXPR_ASSIGNMENT)
                expr = strip_expr(expr->right);
        if (expr->type != EXPR_CALL)
                return;

        match_clear(NULL, expr, INT_PTR(param));
}

static struct smatch_state *alloc_expr_state(struct expression *expr)
{
        struct smatch_state *state;
        char *name;

        name = expr_to_str(expr);
        if (!name)
                return NULL;

        state = __alloc_smatch_state(0);
        expr = strip_expr(expr);
        state->name = alloc_sname(name);
        free_string(name);
        state->data = expr;
        return state;
}

static void match_skb_put(const char *fn, struct expression *expr, void *unused)
{
        struct symbol *type;
        struct smatch_state *state;

        type = get_type(expr->left);
        type = get_real_base_type(type);
        if (!type || type->type != SYM_STRUCT)
                return;
        state = alloc_expr_state(expr->left);
        set_state_expr(skb_put_id, expr->left, state);
}

static void match_return_skb_put(struct expression *expr)
{
        struct sm_state *sm;
        struct stree *stree;

        if (is_error_return(expr))
                return;

        stree = __get_cur_stree();

        FOR_EACH_MY_SM(skb_put_id, stree, sm) {
                check_skb_put(sm->state->data);
        } END_FOR_EACH_SM(sm);
}

static void register_clears_argument(void)
{
        struct token *token;
        const char *func;
        int arg;

        token = get_tokens_file("kernel.clears_argument");
        if (!token)
                return;
        if (token_type(token) != TOKEN_STREAMBEGIN)
                return;
        token = token->next;
        while (token_type(token) != TOKEN_STREAMEND) {
                if (token_type(token) != TOKEN_IDENT)
                        return;
                func = show_ident(token->ident);
                token = token->next;
                if (token_type(token) != TOKEN_NUMBER)
                        return;
                arg = atoi(token->number);

                add_function_hook(func, &match_clear, INT_PTR(arg));
                token = token->next;
        }
        clear_token_alloc();
}

static void register_copy_funcs_from_file(void)
{
        struct token *token;
        const char *func;
        int arg;

        token = get_tokens_file("kernel.rosenberg_funcs");
        if (!token)
                return;
        if (token_type(token) != TOKEN_STREAMBEGIN)
                return;
        token = token->next;
        while (token_type(token) != TOKEN_STREAMEND) {
                if (token_type(token) != TOKEN_IDENT)
                        return;
                func = show_ident(token->ident);
                token = token->next;
                if (token_type(token) != TOKEN_NUMBER)
                        return;
                arg = atoi(token->number);
                add_function_hook(func, &match_copy_to_user, INT_PTR(arg));
                token = token->next;
        }
        clear_token_alloc();
}

void check_rosenberg(int id)
{
        if (option_project != PROJ_KERNEL)
                return;
        my_whole_id = id;

        add_function_hook("memset", &match_clear, INT_PTR(0));
        add_function_hook("memcpy", &match_clear, INT_PTR(0));
        add_function_hook("memzero", &match_clear, INT_PTR(0));
        add_function_hook("__memset", &match_clear, INT_PTR(0));
        add_function_hook("__memcpy", &match_clear, INT_PTR(0));
        add_function_hook("__memzero", &match_clear, INT_PTR(0));
        add_function_hook("__builtin_memset", &match_clear, INT_PTR(0));
        add_function_hook("__builtin_memcpy", &match_clear, INT_PTR(0));

        register_clears_argument();
        select_return_states_hook(PARAM_CLEARED, &db_param_cleared);

        register_copy_funcs_from_file();
}

void check_rosenberg2(int id)
{
        if (option_project != PROJ_KERNEL)
                return;

        my_member_id = id;
        set_dynamic_states(my_member_id);
        add_extra_mod_hook(&extra_mod_hook);
}

void check_rosenberg3(int id)
{
        if (option_project != PROJ_KERNEL)
                return;

        skb_put_id = id;
        set_dynamic_states(skb_put_id);
        add_function_assign_hook("skb_put", &match_skb_put, NULL);
        add_hook(&match_return_skb_put, RETURN_HOOK);
}