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-rw-r--r--src/vboot/vbnv_flash.c28
1 files changed, 17 insertions, 11 deletions
diff --git a/src/vboot/vbnv_flash.c b/src/vboot/vbnv_flash.c
index 81c4f087af..dd128a9235 100644
--- a/src/vboot/vbnv_flash.c
+++ b/src/vboot/vbnv_flash.c
@@ -65,6 +65,7 @@ static int init_vbnv(void)
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;
@@ -78,25 +79,30 @@ static int init_vbnv(void)
for (i = 0; i < BLOB_SIZE; i++)
empty_blob[i] = erase_value();
- offset = 0;
ctx->top_offset = region_device_sz(rdev) - BLOB_SIZE;
- /*
- * after the loop, offset is supposed to point the blob right before
- * the first empty blob, the last blob in the nvram if there is no
- * empty blob, or the base of the region if the nvram has never been
- * used.
- */
- for (i = 0; i <= ctx->top_offset; i += BLOB_SIZE) {
- if (rdev_readat(rdev, buf, i, BLOB_SIZE) < 0) {
+ /* 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))
- break;
- offset = i;
+ 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");