osfmk/kdp/kdp_serial.c

   1 /*
   2  * Copyright (c) 2008 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include "kdp_serial.h"
  29 #include <libkern/zlib.h>
  30 #include <stdint.h>
  31 #include <stdbool.h>
  32
  33 #define SKDP_START_CHAR 0xFA
  34 #define SKDP_END_CHAR 0xFB
  35 #define SKDP_ESC_CHAR 0xFE
  36
  37 static enum {DS_WAITSTART, DS_READING, DS_ESCAPED} dsState;
  38 static unsigned char dsBuffer[1518];
  39 static int dsPos;
  40 static uint32_t dsCRC;
  41 static bool dsHaveCRC;
  42
  43
  44 static void kdp_serial_out(unsigned char byte, void (*outFunc)(char))
  45 {
  46         //need to escape '\n' because the kernel serial output turns it into a cr/lf
  47         if(byte == SKDP_START_CHAR || byte == SKDP_END_CHAR || byte == SKDP_ESC_CHAR || byte == '\n')
  48         {
  49                 outFunc(SKDP_ESC_CHAR);
  50                 byte = ~byte;
  51         }
  52         outFunc(byte);
  53 }
  54
  55 void kdp_serialize_packet(unsigned char *packet, unsigned int len, void (*outFunc)(char))
  56 {
  57         unsigned int  index;
  58         unsigned char byte;
  59         uint32_t      crc;
  60
  61         // insert the CRC between back to back STARTs which is compatible with old clients
  62         crc = (uint32_t) z_crc32(0, packet, len);
  63         outFunc(SKDP_START_CHAR);
  64         kdp_serial_out((crc >> 0),  outFunc);
  65         kdp_serial_out((crc >> 8),  outFunc);
  66         kdp_serial_out((crc >> 16), outFunc);
  67         kdp_serial_out((crc >> 24), outFunc);
  68
  69         outFunc(SKDP_START_CHAR);
  70         for (index = 0; index < len; index++) {
  71                 byte = *packet++;
  72                 kdp_serial_out(byte, outFunc);
  73         }
  74         outFunc(SKDP_END_CHAR);
  75 }
  76
  77 unsigned char *kdp_unserialize_packet(unsigned char byte, unsigned int *len)
  78 {
  79         uint32_t crc;
  80
  81         switch(dsState)
  82         {
  83                 case DS_WAITSTART:
  84                         if(byte == SKDP_START_CHAR)
  85                         {
  86 //                              printf("got start char\n");
  87                                 dsState = DS_READING;
  88                                 dsPos = 0;
  89                                 *len = SERIALIZE_READING;
  90                                 dsHaveCRC = false;
  91                                 return 0;
  92                         }
  93                         *len = SERIALIZE_WAIT_START;
  94                         break;
  95                 case DS_READING:
  96                         if(byte == SKDP_ESC_CHAR)
  97                         {
  98                                 dsState = DS_ESCAPED;
  99                                 *len = SERIALIZE_READING;
 100                                 return 0;
 101                         }
 102                         if(byte == SKDP_START_CHAR)
 103                         {
 104                                 if (dsPos >= 4)
 105                                 {
 106                                         dsHaveCRC = true;
 107                                         dsCRC = dsBuffer[0] | (dsBuffer[1] << 8) | (dsBuffer[2] << 16) | (dsBuffer[3] << 24);
 108                                 }
 109                                 //else                          printf("unexpected start char, resetting\n");
 110                                 dsPos = 0;
 111                                 *len = SERIALIZE_READING;
 112                                 return 0;
 113                         }
 114                         if(byte == SKDP_END_CHAR)
 115                         {
 116                                 dsState = DS_WAITSTART;
 117                                 if (dsHaveCRC)
 118                                 {
 119                                         crc = (uint32_t) z_crc32(0, &dsBuffer[0], dsPos);
 120                                         if (crc != dsCRC)
 121                                         {
 122 //                                              printf("bad packet crc 0x%x != 0x%x\n", crc, dsCRC);
 123                                                 dsPos = 0;
 124                                                 *len = SERIALIZE_WAIT_START;
 125                                                 return 0;
 126                                         }
 127                                 }
 128                                 *len = dsPos;
 129                                 dsPos = 0;
 130                                 return dsBuffer;
 131                         }
 132                         dsBuffer[dsPos++] = byte;
 133                         break;
 134                 case DS_ESCAPED:
 135 //                      printf("unescaping %02x to %02x\n", byte, ~byte);
 136                         dsBuffer[dsPos++] = ~byte;
 137                         dsState = DS_READING;
 138                         *len = SERIALIZE_READING;
 139                         break;
 140         }
 141         if(dsPos == sizeof(dsBuffer)) //too much data...forget this packet
 142         {
 143                 dsState = DS_WAITSTART;
 144                 dsPos = 0;
 145                 *len = SERIALIZE_WAIT_START;
 146         }
 147
 148         return 0;
 149 }