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Diffstat (limited to 'src/security/vboot/vbnv_flash.c')
-rw-r--r--src/security/vboot/vbnv_flash.c181
1 files changed, 181 insertions, 0 deletions
diff --git a/src/security/vboot/vbnv_flash.c b/src/security/vboot/vbnv_flash.c
new file mode 100644
index 0000000000..07569fa48d
--- /dev/null
+++ b/src/security/vboot/vbnv_flash.c
@@ -0,0 +1,181 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2014 The ChromiumOS Authors. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <arch/early_variables.h>
+#include <assert.h>
+#include <commonlib/region.h>
+#include <console/console.h>
+#include <string.h>
+#include <vb2_api.h>
+#include <vboot_nvstorage.h>
+#include <security/vboot/vboot_common.h>
+#include <security/vboot/vbnv.h>
+#include <security/vboot/vbnv_layout.h>
+
+#define BLOB_SIZE VB2_NVDATA_SIZE
+
+struct vbnv_flash_ctx {
+ /* VBNV flash is initialized */
+ int initialized;
+
+ /* Offset of the current nvdata in flash */
+ int blob_offset;
+
+ /* Offset of the topmost nvdata blob in flash */
+ int top_offset;
+
+ /* Region to store and retrieve the VBNV contents. */
+ struct region_device vbnv_dev;
+
+ /* Cache of the current nvdata */
+ uint8_t cache[BLOB_SIZE];
+};
+static struct vbnv_flash_ctx vbnv_flash CAR_GLOBAL;
+
+/*
+ * This code assumes that flash is erased to 1-bits, and write operations can
+ * only change 1-bits to 0-bits. So if the new contents only change 1-bits to
+ * 0-bits, we can reuse the current blob.
+ */
+static inline uint8_t erase_value(void)
+{
+ return 0xff;
+}
+
+static inline int can_overwrite(uint8_t current, uint8_t new)
+{
+ return (current & new) == new;
+}
+
+static int init_vbnv(void)
+{
+ struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+ struct region_device *rdev = &ctx->vbnv_dev;
+ uint8_t buf[BLOB_SIZE];
+ uint8_t empty_blob[BLOB_SIZE];
+ int used_below, empty_above;
+ int offset;
+ int i;
+
+ if (vboot_named_region_device_rw("RW_NVRAM", rdev) ||
+ region_device_sz(rdev) < BLOB_SIZE) {
+ printk(BIOS_ERR, "%s: failed to locate NVRAM\n", __func__);
+ return 1;
+ }
+
+ /* Prepare an empty blob to compare against. */
+ for (i = 0; i < BLOB_SIZE; i++)
+ empty_blob[i] = erase_value();
+
+ ctx->top_offset = region_device_sz(rdev) - BLOB_SIZE;
+
+ /* Binary search for the border between used and empty */
+ used_below = 0;
+ empty_above = region_device_sz(rdev) / BLOB_SIZE;
+
+ while (used_below + 1 < empty_above) {
+ int guess = (used_below + empty_above) / 2;
+ if (rdev_readat(rdev, buf, guess * BLOB_SIZE, BLOB_SIZE) < 0) {
+ printk(BIOS_ERR, "failed to read nvdata\n");
+ return 1;
+ }
+ if (!memcmp(buf, empty_blob, BLOB_SIZE))
+ empty_above = guess;
+ else
+ used_below = guess;
+ }
+
+ /*
+ * Offset points to the last non-empty blob. Or if all blobs are empty
+ * (nvram is totally erased), point to the first blob.
+ */
+ offset = used_below * BLOB_SIZE;
+
+ /* reread the nvdata and write it to the cache */
+ if (rdev_readat(rdev, ctx->cache, offset, BLOB_SIZE) < 0) {
+ printk(BIOS_ERR, "failed to read nvdata\n");
+ return 1;
+ }
+
+ ctx->blob_offset = offset;
+ ctx->initialized = 1;
+
+ return 0;
+}
+
+static int erase_nvram(void)
+{
+ struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+ const struct region_device *rdev = &ctx->vbnv_dev;
+
+ if (rdev_eraseat(rdev, 0, region_device_sz(rdev)) < 0) {
+ printk(BIOS_ERR, "failed to erase nvram\n");
+ return 1;
+ }
+
+ printk(BIOS_INFO, "nvram is cleared\n");
+ return 0;
+}
+
+void read_vbnv_flash(uint8_t *vbnv_copy)
+{
+ struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+
+ if (!ctx->initialized)
+ if (init_vbnv())
+ return; /* error */
+
+ memcpy(vbnv_copy, ctx->cache, BLOB_SIZE);
+}
+
+void save_vbnv_flash(const uint8_t *vbnv_copy)
+{
+ struct vbnv_flash_ctx *ctx = car_get_var_ptr(&vbnv_flash);
+ int new_offset;
+ int i;
+ const struct region_device *rdev = &ctx->vbnv_dev;
+
+ if (!ctx->initialized)
+ if (init_vbnv())
+ return; /* error */
+
+ /* Bail out if there have been no changes. */
+ if (!memcmp(vbnv_copy, ctx->cache, BLOB_SIZE))
+ return;
+
+ new_offset = ctx->blob_offset;
+
+ /* See if we can overwrite the current blob with the new one */
+ for (i = 0; i < BLOB_SIZE; i++) {
+ if (!can_overwrite(ctx->cache[i], vbnv_copy[i])) {
+ /* unable to overwrite. need to use the next blob */
+ new_offset += BLOB_SIZE;
+ if (new_offset > ctx->top_offset) {
+ if (erase_nvram())
+ return; /* error */
+ new_offset = 0;
+ }
+ break;
+ }
+ }
+
+ if (rdev_writeat(rdev, vbnv_copy, new_offset, BLOB_SIZE) == BLOB_SIZE) {
+ /* write was successful. safely move pointer forward */
+ ctx->blob_offset = new_offset;
+ memcpy(ctx->cache, vbnv_copy, BLOB_SIZE);
+ } else {
+ printk(BIOS_ERR, "failed to save nvdata\n");
+ }
+}