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authorRandall Spangler <rspangler@chromium.org>2016-08-26 16:01:16 -0700
committerPatrick Georgi <pgeorgi@google.com>2016-09-20 21:50:27 +0200
commitaa1d314ac2febafc5243266b420ff57b280621c5 (patch)
tree4aac4d5f9225c16385e9a5474c327db95c60b356 /src/vboot
parent57bfbb0508e81c338696539f051ce04f4ba5393d (diff)
downloadcoreboot-aa1d314ac2febafc5243266b420ff57b280621c5.tar.xz
vboot/vbnv_flash: Binary search to find last used entry
This improves the previous linear search to O(log n). No change in storage format. BUG=chromium:640656 BRANCH=none TEST=Manual (test empty) flashrom -i RW_NVRAM -e Reboot; device should boot normally. (start using records) crossystem kern_nv=0xaab0 crossystem recovery_request=1 && reboot Device should go into recovery mode with reason 1 Reboot again; it should boot normally. crossystem kern_nv (should still contain 0xaab0) Repeat steps several times with request=2, 3, etc. flashrom -i RW_NVRAM -r nvdata Modify nvdata to copy the first record across all valid records flashrom -i RW_NVRAM -w nvdata Reboot; device should boot normally. Change-Id: Ieb97563ab92bd1d18a4f6a9e1d20157efe311fb4 Signed-off-by: Martin Roth <martinroth@chromium.org> Original-Commit-Id: db9bb2d3927ad57270d7acfd42cf0652102993b1 Original-Change-Id: I1eb5fd9fa6b2ae56833f024bcd3c250147bcc7a1 Original-Signed-off-by: Randall Spangler <rspangler@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/376928 Original-Reviewed-by: Julius Werner <jwerner@chromium.org> Reviewed-on: https://review.coreboot.org/16577 Tested-by: build bot (Jenkins) Reviewed-by: Vadim Bendebury <vbendeb@chromium.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Diffstat (limited to 'src/vboot')
-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");