/*
 * Copyright (C) 2013 Oracle.
 *
 * 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"
#include "smatch_extra.h"
#include "smatch_slist.h"

static int my_id;

static int is_comparison_call(struct expression *expr)
{
        expr = expr_get_parent_expr(expr);
        if (!expr || expr->type != EXPR_COMPARE)
                return 0;
        if (expr->op != SPECIAL_EQUAL && expr->op != SPECIAL_NOTEQUAL)
                return 0;
        return 1;
}

static int next_line_is_if(struct expression *expr)
{
        struct expression *next;

        if (!__next_stmt || __next_stmt->type != STMT_IF)
                return 0;

        next = strip_expr(__next_stmt->if_conditional);
        while (next->type == EXPR_PREOP && next->op == '!')
                next = strip_expr(next->unop);
        if (expr_equiv(expr, next))
                return 1;
        return 0;
}

static int next_line_checks_IS_ERR(struct expression *call, struct expression *arg)
{
        struct expression *next;
        struct expression *tmp;

        tmp = expr_get_parent_expr(call);
        if (tmp && tmp->type == EXPR_ASSIGNMENT) {
                if (next_line_checks_IS_ERR(NULL, tmp->left))
                        return 1;
        }

        if (!__next_stmt || __next_stmt->type != STMT_IF)
                return 0;

        next = strip_expr(__next_stmt->if_conditional);
        while (next->type == EXPR_PREOP && next->op == '!')
                next = strip_expr(next->unop);
        if (!next || next->type != EXPR_CALL)
                return 0;
        if (next->fn->type != EXPR_SYMBOL || !next->fn->symbol ||
            !next->fn->symbol->ident ||
            (strcmp(next->fn->symbol->ident->name, "IS_ERR") != 0 &&
             strcmp(next->fn->symbol->ident->name, "IS_ERR_OR_NULL") != 0))
                return 0;
        next = get_argument_from_call_expr(next->args, 0);
        return expr_equiv(next, arg);
}

static int is_non_zero_int(struct range_list *rl)
{
        struct data_range *tmp;
        int cnt = -1;

        FOR_EACH_PTR(rl, tmp) {
                cnt++;

                if (cnt == 0) {
                        if (tmp->min.value == INT_MIN &&
                            tmp->max.value == -1)
                                continue;
                } else if (cnt == 1) {
                        if (tmp->min.value == 1 &&
                            tmp->max.value == INT_MAX)
                                return 1;
                }
                return 0;
        } END_FOR_EACH_PTR(tmp);
        return 0;
}

static int is_valid_ptr(sval_t sval)
{
        if (sval.value == INT_MIN || sval.value == INT_MAX)
                return 0;

        if (sval_cmp(valid_ptr_min_sval, sval) <= 0 &&
            sval_cmp(valid_ptr_max_sval, sval) >= 0) {
                return 1;
        }
        return 0;
}

static int has_distinct_zero(struct range_list *rl)
{
        struct data_range *tmp;

        FOR_EACH_PTR(rl, tmp) {
                if (tmp->min.value == 0 || tmp->max.value == 0)
                        return 1;
        } END_FOR_EACH_PTR(tmp);
        return 0;
}

static void match_err_ptr(const char *fn, struct expression *expr, void *data)
{
        struct expression *arg_expr;
        struct sm_state *sm, *tmp;

        if (is_impossible_path())
                return;

        arg_expr = get_argument_from_call_expr(expr->args, 0);
        sm = get_sm_state_expr(SMATCH_EXTRA, arg_expr);
        if (!sm)
                return;

        if (is_comparison_call(expr))
                return;

        if (next_line_checks_IS_ERR(expr, arg_expr))
                return;
        if (strcmp(fn, "ERR_PTR") == 0 &&
            next_line_is_if(arg_expr))
                return;

        FOR_EACH_PTR(sm->possible, tmp) {
                if (!estate_rl(tmp->state))
                        continue;
                if (is_non_zero_int(estate_rl(tmp->state)))
                        continue;
                if (has_distinct_zero(estate_rl(tmp->state))) {
                        sm_warning("passing zero to '%s'", fn);
                        return;
                }
                if (strcmp(fn, "PTR_ERR") != 0)
                        continue;
                if (is_valid_ptr(estate_min(tmp->state)) &&
                    is_valid_ptr(estate_max(tmp->state))) {
                        sm_warning("passing a valid pointer to '%s'", fn);
                        return;
                }
        } END_FOR_EACH_PTR(tmp);
}

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

        my_id = id;
        add_function_hook("ERR_PTR", &match_err_ptr, NULL);
        add_function_hook("ERR_CAST", &match_err_ptr, NULL);
        add_function_hook("PTR_ERR", &match_err_ptr, NULL);
}