// SPDX-License-Identifier: GPL-2.0-only
/*
 *  LZO1X Decompressor from LZO
 *
 *  Copyright (C) 1996-2012 Markus F.X.J. Oberhumer <markus@oberhumer.com>
 *
 *  The full LZO package can be found at:
 *  http://www.oberhumer.com/opensource/lzo/
 *
 *  Changed for Linux kernel use by:
 *  Nitin Gupta <nitingupta910@gmail.com>
 *  Richard Purdie <rpurdie@openedhand.com>
 */

#ifndef STATIC
#include <linux/module.h>
#include <linux/kernel.h>
#endif
#include <linux/unaligned.h>
#include <linux/lzo.h>
#include "lzodefs.h"

#define HAVE_IP(x)      ((size_t)(ip_end - ip) >= (size_t)(x))
#define HAVE_OP(x)      ((size_t)(op_end - op) >= (size_t)(x))
#define NEED_IP(x)      if (unlikely(!HAVE_IP(x))) goto input_overrun
#define NEED_OP(x)      if (unlikely(!HAVE_OP(x))) goto output_overrun
#define TEST_LB(m_pos)  if (unlikely((m_pos) < out)) goto lookbehind_overrun

/* This MAX_255_COUNT is the maximum number of times we can add 255 to a base
 * count without overflowing an integer. The multiply will overflow when
 * multiplying 255 by more than MAXINT/255. The sum will overflow earlier
 * depending on the base count. Since the base count is taken from a u8
 * and a few bits, it is safe to assume that it will always be lower than
 * or equal to 2*255, thus we can always prevent any overflow by accepting
 * two less 255 steps. See Documentation/staging/lzo.rst for more information.
 */
#define MAX_255_COUNT      ((((size_t)~0) / 255) - 2)

int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
                          unsigned char *out, size_t *out_len)
{
        unsigned char *op;
        const unsigned char *ip;
        size_t t, next;
        size_t state = 0;
        const unsigned char *m_pos;
        const unsigned char * const ip_end = in + in_len;
        unsigned char * const op_end = out + *out_len;

        unsigned char bitstream_version;

        op = out;
        ip = in;

        if (unlikely(in_len < 3))
                goto input_overrun;

        if (likely(in_len >= 5) && likely(*ip == 17)) {
                bitstream_version = ip[1];
                ip += 2;
        } else {
                bitstream_version = 0;
        }

        if (*ip > 17) {
                t = *ip++ - 17;
                if (t < 4) {
                        next = t;
                        goto match_next;
                }
                goto copy_literal_run;
        }

        for (;;) {
                t = *ip++;
                if (t < 16) {
                        if (likely(state == 0)) {
                                if (unlikely(t == 0)) {
                                        size_t offset;
                                        const unsigned char *ip_last = ip;

                                        while (unlikely(*ip == 0)) {
                                                ip++;
                                                NEED_IP(1);
                                        }
                                        offset = ip - ip_last;
                                        if (unlikely(offset > MAX_255_COUNT))
                                                return LZO_E_ERROR;

                                        offset = (offset << 8) - offset;
                                        t += offset + 15 + *ip++;
                                }
                                t += 3;
copy_literal_run:
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
                                if (likely(HAVE_IP(t + 15) && HAVE_OP(t + 15))) {
                                        const unsigned char *ie = ip + t;
                                        unsigned char *oe = op + t;
                                        do {
                                                COPY8(op, ip);
                                                op += 8;
                                                ip += 8;
                                                COPY8(op, ip);
                                                op += 8;
                                                ip += 8;
                                        } while (ip < ie);
                                        ip = ie;
                                        op = oe;
                                } else
#endif
                                {
                                        NEED_OP(t);
                                        NEED_IP(t + 3);
                                        do {
                                                *op++ = *ip++;
                                        } while (--t > 0);
                                }
                                state = 4;
                                continue;
                        } else if (state != 4) {
                                next = t & 3;
                                m_pos = op - 1;
                                m_pos -= t >> 2;
                                m_pos -= *ip++ << 2;
                                TEST_LB(m_pos);
                                NEED_OP(2);
                                op[0] = m_pos[0];
                                op[1] = m_pos[1];
                                op += 2;
                                goto match_next;
                        } else {
                                next = t & 3;
                                m_pos = op - (1 + M2_MAX_OFFSET);
                                m_pos -= t >> 2;
                                m_pos -= *ip++ << 2;
                                t = 3;
                        }
                } else if (t >= 64) {
                        next = t & 3;
                        m_pos = op - 1;
                        m_pos -= (t >> 2) & 7;
                        m_pos -= *ip++ << 3;
                        t = (t >> 5) - 1 + (3 - 1);
                } else if (t >= 32) {
                        t = (t & 31) + (3 - 1);
                        if (unlikely(t == 2)) {
                                size_t offset;
                                const unsigned char *ip_last = ip;

                                while (unlikely(*ip == 0)) {
                                        ip++;
                                        NEED_IP(1);
                                }
                                offset = ip - ip_last;
                                if (unlikely(offset > MAX_255_COUNT))
                                        return LZO_E_ERROR;

                                offset = (offset << 8) - offset;
                                t += offset + 31 + *ip++;
                                NEED_IP(2);
                        }
                        m_pos = op - 1;
                        next = get_unaligned_le16(ip);
                        ip += 2;
                        m_pos -= next >> 2;
                        next &= 3;
                } else {
                        NEED_IP(2);
                        next = get_unaligned_le16(ip);
                        if (((next & 0xfffc) == 0xfffc) &&
                            ((t & 0xf8) == 0x18) &&
                            likely(bitstream_version)) {
                                NEED_IP(3);
                                t &= 7;
                                t |= ip[2] << 3;
                                t += MIN_ZERO_RUN_LENGTH;
                                NEED_OP(t);
                                memset(op, 0, t);
                                op += t;
                                next &= 3;
                                ip += 3;
                                goto match_next;
                        } else {
                                m_pos = op;
                                m_pos -= (t & 8) << 11;
                                t = (t & 7) + (3 - 1);
                                if (unlikely(t == 2)) {
                                        size_t offset;
                                        const unsigned char *ip_last = ip;

                                        while (unlikely(*ip == 0)) {
                                                ip++;
                                                NEED_IP(1);
                                        }
                                        offset = ip - ip_last;
                                        if (unlikely(offset > MAX_255_COUNT))
                                                return LZO_E_ERROR;

                                        offset = (offset << 8) - offset;
                                        t += offset + 7 + *ip++;
                                        NEED_IP(2);
                                        next = get_unaligned_le16(ip);
                                }
                                ip += 2;
                                m_pos -= next >> 2;
                                next &= 3;
                                if (m_pos == op)
                                        goto eof_found;
                                m_pos -= 0x4000;
                        }
                }
                TEST_LB(m_pos);
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
                if (op - m_pos >= 8) {
                        unsigned char *oe = op + t;
                        if (likely(HAVE_OP(t + 15))) {
                                do {
                                        COPY8(op, m_pos);
                                        op += 8;
                                        m_pos += 8;
                                        COPY8(op, m_pos);
                                        op += 8;
                                        m_pos += 8;
                                } while (op < oe);
                                op = oe;
                                if (HAVE_IP(6)) {
                                        state = next;
                                        COPY4(op, ip);
                                        op += next;
                                        ip += next;
                                        continue;
                                }
                        } else {
                                NEED_OP(t);
                                do {
                                        *op++ = *m_pos++;
                                } while (op < oe);
                        }
                } else
#endif
                {
                        unsigned char *oe = op + t;
                        NEED_OP(t);
                        op[0] = m_pos[0];
                        op[1] = m_pos[1];
                        op += 2;
                        m_pos += 2;
                        do {
                                *op++ = *m_pos++;
                        } while (op < oe);
                }
match_next:
                state = next;
                t = next;
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
                if (likely(HAVE_IP(6) && HAVE_OP(4))) {
                        COPY4(op, ip);
                        op += t;
                        ip += t;
                } else
#endif
                {
                        NEED_IP(t + 3);
                        NEED_OP(t);
                        while (t > 0) {
                                *op++ = *ip++;
                                t--;
                        }
                }
        }

eof_found:
        *out_len = op - out;
        return (t != 3       ? LZO_E_ERROR :
                ip == ip_end ? LZO_E_OK :
                ip <  ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN);

input_overrun:
        *out_len = op - out;
        return LZO_E_INPUT_OVERRUN;

output_overrun:
        *out_len = op - out;
        return LZO_E_OUTPUT_OVERRUN;

lookbehind_overrun:
        *out_len = op - out;
        return LZO_E_LOOKBEHIND_OVERRUN;
}
#ifndef STATIC
EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LZO1X Decompressor");

#endif