Pass VbSharedData between LoadFirmware() and LoadKernel()

firmware/include/vboot_struct.h

-/* Copyright (c) 2010-2011 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Data structure definitions for verified boot, for on-disk / in-eeprom
  * data.
  */
 
 #ifndef VBOOT_REFERENCE_VBOOT_STRUCT_H_
 #define VBOOT_REFERENCE_VBOOT_STRUCT_H_
 
@@ skipping 112 matching lines @@
   VbSignature body_signature;        /* Signature for the kernel body */
 } __attribute__((packed)) VbKernelPreambleHeader;
 /* This should be followed by:
  *   2) The signature data for the kernel body, pointed to by
  *      body_signature.sig_offset.
  *   3) The signature data for (VBFirmwarePreambleHeader + body signature
  *      data), pointed to by preamble_signature.sig_offset. */
 
 #define EXPECTED_VBKERNELPREAMBLEHEADER_SIZE 96
 
+/* Data shared between LoadFirmware() and LoadKernel() */
+typedef struct VbSharedDataHeader {
+  /* Fields present in version 1 */
+  uint32_t struct_version;            /* Version of this structure */
+  uint64_t struct_size;               /* Size of this structure in bytes */
+  uint64_t data_size;                 /* Size of shared data buffer in bytes */

[Bill Richardson, 2011/03/09 20:52:20]

So the idea is that a single big blob of memory is passed around, and this
header is always going to sit at the beginning of it? Please add some
explanatory comments.

[Randall Spangler, 2011/03/09 21:11:35]

Done.

+  uint64_t data_used;                 /* Amount of shared data used */
+
+  VbPublicKey kernel_subkey;          /* Kernel subkey, from firmware */
+  uint64_t kernel_subkey_data_offset; /* Offset of kernel subkey data from
+                                       * start of this struct */
+  uint64_t kernel_subkey_data_size;   /* Offset of kernel subkey data */
+
+  uint64_t flags;                     /* Flags */
+
+  /* After read-only firmware which uses version 1 is released, any additional
+   * fields must be added below, and the struct version must be increased.
+   * Before reading/writing those fields, make sure that the struct being
+   * accessed is at least version 2.
+   *
+   * It's always ok for an older firmware to access a newer struct, since all
+   * the fields it knows about are present.  Newer firmware needs to use
+   * reasonable defaults when accessing older structs. */
+
+} __attribute__((packed)) VbSharedDataHeader;
+
+#define VB_SHARED_DATA_VERSION 1      /* Version for struct_version */
+
 __pragma(pack(pop)) /* Support packing for MSVC. */
 
 #endif  /* VBOOT_REFERENCE_VBOOT_STRUCT_H_ */