gpu/command_buffer/service/cmd_parser.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file contains the implementation of the command parser.
   6
   7 #include "gpu/command_buffer/service/cmd_parser.h"
   8
   9 #include "base/logging.h"
  10 #include "base/debug/trace_event.h"
  11
  12 namespace gpu {
  13
  14 CommandParser::CommandParser(AsyncAPIInterface* handler)
  15     : get_(0),
  16       put_(0),
  17       buffer_(NULL),
  18       entry_count_(0),
  19       handler_(handler) {
  20 }
  21
  22 void CommandParser::SetBuffer(
  23     void* shm_address,
  24     size_t shm_size,
  25     ptrdiff_t offset,
  26     size_t size) {
  27   // check proper alignments.
  28   DCHECK_EQ(0, (reinterpret_cast<intptr_t>(shm_address)) % 4);
  29   DCHECK_EQ(0, offset % 4);
  30   DCHECK_EQ(0u, size % 4);
  31   // check that the command buffer fits into the memory buffer.
  32   DCHECK_GE(shm_size, offset + size);
  33   get_ = 0;
  34   put_ = 0;
  35   char* buffer_begin = static_cast<char*>(shm_address) + offset;
  36   buffer_ = reinterpret_cast<CommandBufferEntry*>(buffer_begin);
  37   entry_count_ = size / 4;
  38 }
  39
  40 // Process one command, reading the header from the command buffer, and
  41 // forwarding the command index and the arguments to the handler.
  42 // Note that:
  43 // - validation needs to happen on a copy of the data (to avoid race
  44 // conditions). This function only validates the header, leaving the arguments
  45 // validation to the handler, so it can pass a reference to them.
  46 // - get_ is modified *after* the command has been executed.
  47 error::Error CommandParser::ProcessCommands(int num_commands) {
  48   int num_entries = put_ < get_ ? entry_count_ - get_ : put_ - get_;
  49   int entries_processed = 0;
  50
  51   error::Error result = handler_->DoCommands(
  52       num_commands, buffer_ + get_, num_entries, &entries_processed);
  53
  54   get_ += entries_processed;
  55   if (get_ == entry_count_)
  56     get_ = 0;
  57
  58   return result;
  59 }
  60
  61 // Processes all the commands, while the buffer is not empty. Stop if an error
  62 // is encountered.
  63 error::Error CommandParser::ProcessAllCommands() {
  64   while (!IsEmpty()) {
  65     error::Error error = ProcessCommands(kParseCommandsSlice);
  66     if (error)
  67       return error;
  68   }
  69   return error::kNoError;
  70 }
  71
  72 // Decode multiple commands, and call the corresponding GL functions.
  73 // NOTE: buffer is a pointer to the command buffer. As such, it could be
  74 // changed by a (malicious) client at any time, so if validation has to happen,
  75 // it should operate on a copy of them.
  76 error::Error AsyncAPIInterface::DoCommands(unsigned int num_commands,
  77                                            const void* buffer,
  78                                            int num_entries,
  79                                            int* entries_processed) {
  80   int commands_to_process = num_commands;
  81   error::Error result = error::kNoError;
  82   const CommandBufferEntry* cmd_data =
  83       static_cast<const CommandBufferEntry*>(buffer);
  84   int process_pos = 0;
  85
  86   while (process_pos < num_entries && result == error::kNoError &&
  87          commands_to_process--) {
  88     CommandHeader header = cmd_data->value_header;
  89     if (header.size == 0) {
  90       DVLOG(1) << "Error: zero sized command in command buffer";
  91       return error::kInvalidSize;
  92     }
  93
  94     if (static_cast<int>(header.size) + process_pos > num_entries) {
  95       DVLOG(1) << "Error: get offset out of bounds";
  96       return error::kOutOfBounds;
  97     }
  98
  99     const unsigned int command = header.command;
 100     const unsigned int arg_count = header.size - 1;
 101
 102     result = DoCommand(command, arg_count, cmd_data);
 103
 104     if (result != error::kDeferCommandUntilLater) {
 105       process_pos += header.size;
 106       cmd_data += header.size;
 107     }
 108   }
 109
 110   if (entries_processed)
 111     *entries_processed = process_pos;
 112
 113   return result;
 114 }
 115
 116 }  // namespace gpu