diff options
| -rw-r--r-- | src/vboot/vbnv_flash.c | 28 |
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"); |