/* OpenIDA - Outil d'analyse de fichiers binaires
 * specins.c - gestion des instructions spéciales de la VM Dalvik
 *
 * Copyright (C) 2011 Cyrille Bagard
 *
 *  This file is part of OpenIDA.
 *
 *  OpenIDA 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  OpenIDA 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 Foobar.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "specins.h"


#include "../../common/endianness.h"



/******************************************************************************
*                                                                             *
*  Paramètres  : ctx  = contexte lié à l'exécution du processeur.             *
*                data = flux de données à analyser.                           *
*                pos  = position courante dans ce flux.                       *
*                len  = taille totale des données à analyser.                 *
*                addr = adresse virtuelle de l'instruction.                   *
*                                                                             *
*  Description : Détermine si du code doit être écarté du traitement.         *
*                                                                             *
*  Retour      : true si une nouvelle zone de données est à écarter.          *
*                                                                             *
*  Remarques   : -                                                            *
*                                                                             *
******************************************************************************/

bool g_dalvik_guess_special_instruction(GDalvikContext *ctx, const bin_t *data, off_t pos, off_t len, vmpa_t addr)
{
    bool result;                            /* Bilan à retourner           */
    uint16_t ident;                         /* Valeur lue dans le code     */
    vmpa_t start;                           /* Début d'une zone de données */
    vmpa_t end;                             /* Fin d'une zone de données   */
    uint16_t switch_size;                   /* Taille du switch considéré  */
    uint16_t array_width;                   /* Taille des éléments         */
    uint32_t array_size;                    /* Taille du tableau           */

    /* Vérification astucieuse et rapide...*/
    if (data[pos] != 0x00 /* DOP_NOP */) return false; 

    if (!read_u16(&ident, data, &pos, len, SRE_LITTLE))
        return false;

    start = addr + sizeof(ident);
    end = start;

    switch (ident)
    {
        case DID_PACKED_SWITCH:

            if (!read_u16(&switch_size, data, &pos, len, SRE_LITTLE))
                return false;

            end += sizeof(switch_size) + (1 + switch_size) * sizeof(uint32_t);

            g_dalvik_context_skip_new_area(ctx, start, end);
            result = true;

            break;

        case DID_SPARSE_SWITCH:

            if (!read_u16(&switch_size, data, &pos, len, SRE_LITTLE))
                return false;

            end += sizeof(switch_size) + (2 * switch_size) * sizeof(uint32_t);

            g_dalvik_context_skip_new_area(ctx, start, end);
            result = true;

            break;

        case DID_FILL_ARRAY_DATA:

            if (!read_u16(&array_width, data, &pos, len, SRE_LITTLE))
                return false;
            if (!read_u32(&array_size, data, &pos, len, SRE_LITTLE))
                return false;

            end += sizeof(array_width) + sizeof(array_size)
                + array_width * array_size;

            g_dalvik_context_skip_new_area(ctx, start, end);
            result = true;

            break;

        default:
            result = false;
            break;

    }

    return result;

}