Add NV storage API to vboot reference

firmware/lib/vboot_nvstorage.c

+/* 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.
+ */
+
+/* Non-volatile storage routines.
+ */
+
+#include "utility.h"
+#include "vboot_common.h"
+#include "vboot_nvstorage.h"
+
+/* Constants for NV storage.  We use this rather than structs and
+ * bitfields so the data format is consistent across platforms and
+ * compilers. */
+#define HEADER_OFFSET                0
+#define HEADER_MASK                    0xC0
+#define HEADER_SIGNATURE               0x40
+#define HEADER_FIRMWARE_SETTINGS_RESET 0x20
+#define HEADER_KERNEL_SETTINGS_RESET   0x10
+
+#define BOOT_OFFSET                  1
+#define BOOT_DEBUG_RESET_MODE          0x80
+#define BOOT_TRY_B_COUNT               0x0F
+
+#define RECOVERY_OFFSET              2
+#define LOCALIZATION_OFFSET          3
+#define KERNEL_FIELD_OFFSET         11
+#define CRC_OFFSET                  15
+
+
+/* Return CRC-8 of the data, using x^8 + x^2 + x + 1 polynomial.  A
+ * table-based algorithm would be faster, but for only 15 bytes isn't
+ * worth the code size. */
+static uint8_t Crc8(const uint8_t* data, int len) {
+  unsigned crc = 0;
+  int i, j;
+
+  for (j = len; j; j--, data++) {
+    crc ^= (*data << 8);
+    for(i = 8; i; i--) {
+      if (crc & 0x8000)
+        crc ^= (0x1070 << 3);
+      crc <<= 1;
+    }
+  }
+
+  return (uint8_t)(crc >> 8);
+}
+
+
+int VbNvOpen(VbNvContext* context) {
+  uint8_t* raw = context->raw;
+
+  /* TODO: implement locking when called from OS */
+
+  /* Nothing has changed yet. */
+  context->raw_changed = 0;
+  context->regenerate_crc = 0;
+
+  /* Check data for consistency */
+  if ((HEADER_SIGNATURE != (raw[HEADER_OFFSET] & HEADER_MASK))
+      || (Crc8(raw, CRC_OFFSET) != raw[CRC_OFFSET])) {
+
+    /* Data is inconsistent (bad CRC or header), so reset defaults */
+    Memset(raw, 0, NV_BLOCK_SIZE);
+    raw[HEADER_OFFSET] = (HEADER_SIGNATURE | HEADER_FIRMWARE_SETTINGS_RESET |
+                          HEADER_KERNEL_SETTINGS_RESET);
+
+    /* Regenerate CRC on exit */
+    context->regenerate_crc = 1;
+  }
+
+  return 0;
+}
+
+
+int VbNvClose(VbNvContext* context) {
+
+  if (context->regenerate_crc) {
+    context->raw[CRC_OFFSET] = Crc8(context->raw, CRC_OFFSET);
+    context->regenerate_crc = 0;
+    context->raw_changed = 1;
+  }
+
+  /* TODO: implement locking when called from OS */
+  return 0;
+}
+
+
+int VbNvGet(VbNvContext* context, VbNvParam param, uint32_t* dest) {
+  const uint8_t* raw = context->raw;
+
+  switch (param) {
+    case VBNV_FIRMWARE_SETTINGS_RESET:
+      *dest = (raw[HEADER_OFFSET] & HEADER_FIRMWARE_SETTINGS_RESET ? 1 : 0);
+      return 0;
+
+    case VBNV_KERNEL_SETTINGS_RESET:
+      *dest = (raw[HEADER_OFFSET] & HEADER_KERNEL_SETTINGS_RESET ? 1 : 0);
+      return 0;
+
+    case VBNV_DEBUG_RESET_MODE:
+      *dest = (raw[BOOT_OFFSET] & BOOT_DEBUG_RESET_MODE ? 1 : 0);
+      return 0;
+
+    case VBNV_TRY_B_COUNT:
+      *dest = raw[BOOT_OFFSET] & BOOT_TRY_B_COUNT;
+      return 0;
+
+    case VBNV_RECOVERY_REQUEST:
+      *dest = raw[RECOVERY_OFFSET];
+      return 0;
+
+    case VBNV_LOCALIZATION_INDEX:
+      *dest = raw[LOCALIZATION_OFFSET];
+      return 0;
+
+    case VBNV_KERNEL_FIELD:
+      *dest = (raw[KERNEL_FIELD_OFFSET]
+               | (raw[KERNEL_FIELD_OFFSET + 1] << 8)
+               | (raw[KERNEL_FIELD_OFFSET + 2] << 16)
+               | (raw[KERNEL_FIELD_OFFSET + 3] << 24));
+      return 0;
+
+    default:
+      return 1;
+  }
+}
+
+
+int VbNvSet(VbNvContext* context, VbNvParam param, uint32_t value) {
+  uint8_t* raw = context->raw;
+  uint32_t current;
+
+  /* If we're not changing the value, we don't need to regenerate the CRC. */
+  if (0 == VbNvGet(context, param, &current) && current == value)
+    return 0;
+
+  switch (param) {
+    case VBNV_FIRMWARE_SETTINGS_RESET:
+      if (value)
+        raw[HEADER_OFFSET] |= HEADER_FIRMWARE_SETTINGS_RESET;
+      else
+        raw[HEADER_OFFSET] &= ~HEADER_FIRMWARE_SETTINGS_RESET;
+      break;
+
+    case VBNV_KERNEL_SETTINGS_RESET:
+      if (value)
+        raw[HEADER_OFFSET] |= HEADER_KERNEL_SETTINGS_RESET;
+      else
+        raw[HEADER_OFFSET] &= ~HEADER_KERNEL_SETTINGS_RESET;
+      break;
+
+    case VBNV_DEBUG_RESET_MODE:
+      if (value)
+        raw[BOOT_OFFSET] |= BOOT_DEBUG_RESET_MODE;
+      else
+        raw[BOOT_OFFSET] &= BOOT_DEBUG_RESET_MODE;
+      break;
+
+    case VBNV_TRY_B_COUNT:
+      raw[BOOT_OFFSET] &= ~BOOT_TRY_B_COUNT;
+      raw[BOOT_OFFSET] |= (uint8_t)(value & BOOT_TRY_B_COUNT);
+      break;
+
+    case VBNV_RECOVERY_REQUEST:
+      raw[RECOVERY_OFFSET] = (uint8_t)value;
+      break;
+
+    case VBNV_LOCALIZATION_INDEX:
+      raw[LOCALIZATION_OFFSET] = (uint8_t)value;
+      break;
+
+    case VBNV_KERNEL_FIELD:
+      raw[KERNEL_FIELD_OFFSET] = (uint8_t)(value);
+      raw[KERNEL_FIELD_OFFSET + 1] = (uint8_t)(value >> 8);
+      raw[KERNEL_FIELD_OFFSET + 2] = (uint8_t)(value >> 16);
+      raw[KERNEL_FIELD_OFFSET + 3] = (uint8_t)(value >> 24);
+      break;
+
+    default:
+      return 1;
+  }
+
+  /* Need to regenerate CRC, since the value changed. */
+  context->regenerate_crc = 1;
+  return 0;
+}