/*
 * Copyright (C) 2010 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
 */

#include "smatch.h"

static int my_id;

static int can_overflow(struct expression *expr)
{
        sval_t max;
        int uncapped = 0;

        expr = strip_expr(expr);

        if (expr->type == EXPR_BINOP) {
                uncapped += can_overflow(expr->left);
                uncapped += can_overflow(expr->right);

                if (uncapped &&
                        (expr->op == '+' || expr->op == '*' || expr->op == SPECIAL_LEFTSHIFT))
                        return 1;

                return 0;
        }

        if (get_implied_max(expr, &max))
                return 0;
        if (get_absolute_max(expr, &max) && sval_cmp_val(max, 4096) <= 0)
                return 0;
        return 1;
}

static void match_size(struct expression *size_expr)
{
        char *name;

        size_expr = strip_expr(size_expr);
        if (!size_expr)
                return;
        if (size_expr->type != EXPR_BINOP) {
                size_expr = get_assigned_expr(size_expr);
                if (!size_expr || size_expr->type != EXPR_BINOP)
                        return;
        }
        if (!can_overflow(size_expr))
                return;

        name = expr_to_str(size_expr);
        sm_warning("math in access_ok() is dangerous '%s'", name);

        free_string(name);
}

static void match_access_ok(const char *fn, struct expression *expr, void *data)
{
        struct expression *size_expr;

        size_expr = get_argument_from_call_expr(expr->args, 1);
        match_size(size_expr);
}

static void split_asm_constraints(struct expression_list *expr_list)
{
        struct expression *expr;
        int i;

        i = 0;
        FOR_EACH_PTR(expr_list, expr) {
                i++;
                if (expr->type != EXPR_ASM_OPERAND)
                        continue;
                if (i == 1)
                        match_size(expr->expr);
        } END_FOR_EACH_PTR(expr);
}

static void match_asm_stmt(struct statement *stmt)
{
        char *name;

        name = get_macro_name(stmt->pos);
        if (!name || strcmp(name, "access_ok") != 0)
                return;
        split_asm_constraints(stmt->asm_inputs);
}

void check_access_ok_math(int id)
{
        my_id = id;
        if (option_project != PROJ_KERNEL)
                return;
        if (!option_spammy)
                return;
        add_function_hook("__access_ok", &match_access_ok, NULL);
        add_hook(&match_asm_stmt, ASM_HOOK);
}