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
  45 kdp_serial_out(unsigned char byte, void (*outFunc)(char))
  46 {
  47         //need to escape '\n' because the kernel serial output turns it into a cr/lf
  48         if (byte == SKDP_START_CHAR || byte == SKDP_END_CHAR || byte == SKDP_ESC_CHAR || byte == '\n') {
  49                 outFunc(SKDP_ESC_CHAR);
  50                 byte = ~byte;
  51         }
  52         outFunc((char)byte);
  53 }
  54
  55 void
  56 kdp_serialize_packet(unsigned char *packet, unsigned int len, void (*outFunc)(char))
  57 {
  58         unsigned int  index;
  59         unsigned char byte;
  60         uint32_t      crc;
  61
  62         // insert the CRC between back to back STARTs which is compatible with old clients
  63         crc = (uint32_t) z_crc32(0, packet, len);
  64         outFunc(SKDP_START_CHAR);
  65         kdp_serial_out((unsigned char)(crc >> 0), outFunc);
  66         kdp_serial_out((unsigned char)(crc >> 8), outFunc);
  67         kdp_serial_out((unsigned char)(crc >> 16), outFunc);
  68         kdp_serial_out((unsigned char)(crc >> 24), outFunc);
  69
  70         outFunc(SKDP_START_CHAR);
  71         for (index = 0; index < len; index++) {
  72                 byte = *packet++;
  73                 kdp_serial_out(byte, outFunc);
  74         }
  75         outFunc(SKDP_END_CHAR);
  76 }
  77
  78 unsigned char *
  79 kdp_unserialize_packet(unsigned char byte, unsigned int *len)
  80 {
  81         uint32_t crc;
  82
  83         switch (dsState) {
  84         case DS_WAITSTART:
  85                 if (byte == SKDP_START_CHAR) {
  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                         dsState = DS_ESCAPED;
  98                         *len = SERIALIZE_READING;
  99                         return 0;
 100                 }
 101                 if (byte == SKDP_START_CHAR) {
 102                         if (dsPos >= 4) {
 103                                 dsHaveCRC = true;
 104                                 dsCRC = dsBuffer[0] | (dsBuffer[1] << 8) | (dsBuffer[2] << 16) | (dsBuffer[3] << 24);
 105                         }
 106                         //else                          printf("unexpected start char, resetting\n");
 107                         dsPos = 0;
 108                         *len = SERIALIZE_READING;
 109                         return 0;
 110                 }
 111                 if (byte == SKDP_END_CHAR) {
 112                         dsState = DS_WAITSTART;
 113                         if (dsHaveCRC) {
 114                                 crc = (uint32_t) z_crc32(0, &dsBuffer[0], dsPos);
 115                                 if (crc != dsCRC) {
 116 //                                              printf("bad packet crc 0x%x != 0x%x\n", crc, dsCRC);
 117                                         dsPos = 0;
 118                                         *len = SERIALIZE_WAIT_START;
 119                                         return 0;
 120                                 }
 121                         }
 122                         *len = dsPos;
 123                         dsPos = 0;
 124                         return dsBuffer;
 125                 }
 126                 dsBuffer[dsPos++] = byte;
 127                 break;
 128         case DS_ESCAPED:
 129 //                      printf("unescaping %02x to %02x\n", byte, ~byte);
 130                 dsBuffer[dsPos++] = ~byte;
 131                 dsState = DS_READING;
 132                 *len = SERIALIZE_READING;
 133                 break;
 134         }
 135         if (dsPos == sizeof(dsBuffer)) { //too much data...forget this packet
 136                 dsState = DS_WAITSTART;
 137                 dsPos = 0;
 138                 *len = SERIALIZE_WAIT_START;
 139         }
 140
 141         return 0;
 142 }