src/virtualization/bin/vmm/device/virtio_magma_generic.h.gen.py

#!/usr/bin/env python2.7
# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import sys

def usage():
  print 'Usage:'
  print '  virtio_magma_generic.h.gen.py INPUT OUTPUT'
  print '    INPUT    json file containing the magma interface definition'
  print '    OUTPUT   destination path for the header file to generate'
  print '  Example: virtio_magma_generic.h.gen.py magma.json virtio_magma_generic.h'
  print '  Generates a generic "glue" class that directly translates between'
  print '  virtmagma structs and magma commands, that may be overridden.'

# License string for the top of the file.
def license():
  ret = ''
  ret += '// Copyright 2019 The Fuchsia Authors. All rights reserved.\n'
  ret += '// Use of this source code is governed by a BSD-style license that can be\n'
  ret += '// found in the LICENSE file.\n'
  return ret

# Warning string about auto-generation
def warning():
  ret = ''
  ret += '// NOTE: DO NOT EDIT THIS FILE! It is generated automatically by:\n'
  ret += '//   //src/virtualization/bin/vmm/device/virtio_magma_generic.h.gen.py\n'
  return ret

# Guard macro that goes at the beginning/end of the header (after license).
def guards(begin):
  macro = 'SRC_VIRTUALIZATION_BIN_VMM_DEVICE_VIRTIO_MAGMA_GENERIC_H_'
  if begin:
    return '#ifndef ' + macro + '\n#define ' + macro + '\n'
  return '#endif // ' + macro

# Includes lists.
def includes():
  ret = ''
  ret += '#include <fbl/unique_fd.h>\n'
  ret += '#include <src/lib/fxl/macros.h>\n'
  ret += '#include <trace/event.h>\n'
  ret += '#include <zircon/status.h>\n'
  ret += '#include "src/virtualization/bin/vmm/device/virtio_queue.h"\n'
  return ret

# Extract the non-"magma_" portion of the name of an export
def get_name(export):
  return export['name'][len('magma_'):]

# Generate a method that does simple validation of a virtio command struct,
# passes it on to magma, and populates the corresponding response struct.
def generate_generic_method(export):
  name = get_name(export)
  ret = ''
  ret += '  virtual zx_status_t Handle_' + name + '(\n'
  ret += '    const virtio_magma_' + name + '_ctrl_t* request,\n'
  ret += '    virtio_magma_' + name + '_resp_t* response) {\n'
  ret += '    TRACE_DURATION("machina", "VirtioMagmaGeneric::Handle_' + name + '");\n'
  ret += '    FXL_DCHECK(request->hdr.type == VIRTIO_MAGMA_CMD_' + name.upper() + ');\n'
  invocation_args = ''
  copy_temporaries = ''
  for argument in export['arguments']:
    invocation_args += '      '
    if argument['name'].find('_out') != -1:
      assert(argument['type'][-1] == '*'), 'output argument not a pointer'
      # Create locals for output parameters. This is necessary due to struct packing.
      temp_name = 'temp_' + argument['name']
      ret += '    ' + argument['type'][:-1] + ' ' + temp_name + '{};\n'
      invocation_args += '&' + temp_name + ',\n'
      copy_temporaries += '    response->' + argument['name'] + ' = (__typeof(response->' + argument['name'] + '))' + temp_name + ';\n'
    else:
      invocation_args += '(' + argument['type'] + ')request->' + argument['name'] + ',\n'

  ret += '    '
  if export['type'] != 'void':
    ret += 'response->result_return = '
  ret += export['name'] + '(\n'
  ret += invocation_args[:-2] + ');\n'
  ret += copy_temporaries
  ret += '    response->hdr.type = VIRTIO_MAGMA_RESP_' + name.upper() + ';\n'
  ret += '    return ZX_OK;\n'
  ret += '  }\n'
  return ret

# Generate the main command switch method
def generate_handle_command(magma):
  ret = '''  zx_status_t HandleCommand(VirtioChain chain) {
    TRACE_DURATION("machina", "VirtioMagma::HandleCommand");
    VirtioDescriptor request_desc{};
    if (!chain.NextDescriptor(&request_desc)) {
      FXL_LOG(ERROR) << "Failed to read request descriptor";
      return ZX_ERR_INTERNAL;
    }
    const auto request_header = reinterpret_cast<virtio_magma_ctrl_hdr_t*>(request_desc.addr);
    const uint32_t command_type = request_header->type;
    if (!chain.HasDescriptor()) {
      FXL_LOG(ERROR) << "MAGMA command (" << command_type << ") missing response descriptor";
      return ZX_ERR_INVALID_ARGS;
    }
    VirtioDescriptor response_desc{};
    if (!chain.NextDescriptor(&response_desc)) {
      FXL_LOG(ERROR) << "Failed to read response descriptor";
      return ZX_ERR_INTERNAL;
    }
    if (!response_desc.writable) {
      FXL_LOG(ERROR) << "MAGMA command (" << command_type << ") response descriptor not writable";
      return ZX_ERR_INVALID_ARGS;
    }
    if (!device_fd_.is_valid()) {
      auto response_header = reinterpret_cast<virtio_magma_ctrl_hdr_t*>(response_desc.addr);
      response_header->type = VIRTIO_MAGMA_RESP_ERR_HOST_DISCONNECTED;
      chain.Return();
      return ZX_OK;
    }
    switch (command_type) {
'''
  for export in magma['exports']:
    name = get_name(export)
    ret += '      case VIRTIO_MAGMA_CMD_' + name.upper() + ': {\n'
    ret += '        auto request = reinterpret_cast<const virtio_magma_' + name + '_ctrl_t*>(request_desc.addr);\n'
    ret += '        auto response = reinterpret_cast<virtio_magma_' + name + '_resp_t*>(response_desc.addr);\n'
    ret += '#ifdef VIRTMAGMA_DEBUG\n'
    ret += '        FXL_LOG(INFO) << "Received MAGMA command (" << command_type << "):\\n"\\\n'
    ret += '          "  hdr = { " << virtio_magma_ctrl_type_string((virtio_magma_ctrl_type)request->hdr.type) << ", " << request->hdr.flags << " }"\\\n'
    for argument in export['arguments']:
      if argument['name'].find('_out') == -1:
        ret += '          "\\n  ' + argument['name'] + ' = " << static_cast<uint64_t>(request->' + argument['name'] + ') << ""\\\n'
    ret += '          "";\n'
    ret += '#endif // VIRTMAGMA_DEBUG\n'
    ret += '        if (response_desc.len < sizeof(*response)) {\n'
    ret += '          FXL_LOG(ERROR) << "MAGMA command (" << command_type << ") response descriptor too small";\n'
    ret += '          chain.Return();\n'
    ret += '          return ZX_ERR_INVALID_ARGS;\n'
    ret += '        }\n'
    ret += '        zx_status_t status = Handle_' + name + '(request, response);\n'
    ret += '        if (status != ZX_OK) {\n'
    ret += '          FXL_LOG(ERROR) << "Handle_' + name + ' failed (" << zx_status_get_string(status) << ")";\n'
    ret += '          chain.Return();\n'
    ret += '          return status;\n'
    ret += '        }\n'
    ret += '#ifdef VIRTMAGMA_DEBUG\n'
    ret += '        FXL_LOG(INFO) << "Sending MAGMA response:\\n"\\\n'
    ret += '          "  hdr = { " << virtio_magma_ctrl_type_string((virtio_magma_ctrl_type)response->hdr.type) << ", " << response->hdr.flags << " }"\\\n'
    for argument in export['arguments']:
      if argument['name'].find('_out') != -1:
        ret += '          "\\n  ' + argument['name'] + ' = " << static_cast<uint64_t>(response->' + argument['name'] + ') << ""\\\n'
    if export['type'] != 'void':
      ret += '          "\\n  result_return = " << static_cast<uint64_t>(response->result_return) << ""\\\n'
    ret += '          "";\n'
    ret += '#endif // VIRTMAGMA_DEBUG\n'
    ret += '        *chain.Used() = sizeof(*response);\n'
    ret += '      } break;\n'
  ret += '''      default: {
        FXL_LOG(ERROR) << "Unsupported MAGMA command (" << command_type << ")";
        auto response = reinterpret_cast<virtio_magma_ctrl_hdr_t*>(response_desc.addr);
        response->type = VIRTIO_MAGMA_RESP_ERR_INVALID_COMMAND;
        *chain.Used() = sizeof(*response);
      } break;
    }
    chain.Return();
    return ZX_OK;
  }'''
  return ret

def main():
  if (len(sys.argv) != 3):
    usage()
    exit(-1)
  with open(sys.argv[1], 'r') as file:
    with open(sys.argv[2], 'w') as dest:
      magma = json.load(file)['magma-interface']
      header = license() + '\n'
      header += warning() + '\n'
      header += guards(True) + '\n'
      header += includes() + '\n'
      header += 'class VirtioMagmaGeneric {\n'
      header += ' public:\n'
      for export in magma['exports']:
        header += generate_generic_method(export) + '\n'
      header += generate_handle_command(magma) + '\n'
      header += ' protected:\n'
      header += '  fbl::unique_fd device_fd_;\n'
      header += '};\n'
      header += guards(False) + '\n'
      dest.write(header)

if __name__ == '__main__':
  sys.exit(main())