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flashrom: only perform WP unlock for write/erase operations

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Don't unlock using WP for read/verify operations because WP will only
disable write locks. Most chips don't have read locks anyway, but some
do, so we still call the chip's unlock function for read/verify
operations.

Unconditionally unlocking using WP slows down flashrom significantly
with some programmers, particularly linux_mtd due to inefficiency in the
current kernel MTD interface.

BUG=b:283779258
BRANCH=none
TEST=`ninja test`
TEST=`flashrom -{r,w,E,v}` on strongbad
TEST=`flashrom --wp-enable; flashrom -{w,E}` on strongbad

Change-Id: I5dc66474a0b7969b51b86ac9f5daa2c95ae968f1
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/75991
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
This commit is contained in:
Nikolai Artemiev
2023-06-21 10:27:04 +10:00
parent 910ef0cad6
commit d59287d982
1 changed files with 41 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
flashrom.c
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@ -2052,24 +2052,49 @@ static int save_initial_flash_wp(struct flashctx *const flash)
return 0;
}
static int unlock_flash_wp(struct flashctx *const flash)
static int unlock_flash_wp(struct flashctx *const flash,
const bool write_it, const bool erase_it)
{
/* Save original WP state to be restored later */
if (save_initial_flash_wp(flash))
int ret = 0;
/* WP only disables write protection, so only use WP to unlock
* for write/erase operations.
*
* For read/verify operations, we still call the chip's unlock
* function, which may disable read locks if the chip has them.
*/
if (!write_it && !erase_it) {
msg_cdbg("Skipping writeprotect-based unlocking for read/verify operations.\n");
return -1;
}
/* Save original WP state to be restored later */
if (save_initial_flash_wp(flash)) {
ret = -1;
goto warn_out;
}
/* Disable WP */
struct flashrom_wp_cfg *unlocked_wp_cfg;
if (flashrom_wp_cfg_new(&unlocked_wp_cfg) != FLASHROM_WP_OK)
return -1;
if (flashrom_wp_cfg_new(&unlocked_wp_cfg) != FLASHROM_WP_OK) {
ret = -1;
goto warn_out;
}
flashrom_wp_set_range(unlocked_wp_cfg, 0, 0);
flashrom_wp_set_mode(unlocked_wp_cfg, FLASHROM_WP_MODE_DISABLED);
enum flashrom_wp_result ret = flashrom_wp_write_cfg(flash, unlocked_wp_cfg);
if (flashrom_wp_write_cfg(flash, unlocked_wp_cfg) != FLASHROM_WP_OK) {
ret = -1;
}
flashrom_wp_cfg_release(unlocked_wp_cfg);
return (ret == FLASHROM_WP_OK) ? 0 : -1;
warn_out:
if (ret)
msg_cerr("Failed to unlock flash status reg with wp support.\n");
return ret;
}
int prepare_flash_access(struct flashctx *const flash,
@ -2092,14 +2117,19 @@ int prepare_flash_access(struct flashctx *const flash,
/* Initialize chip_restore_fn_count before chip unlock calls. */
flash->chip_restore_fn_count = 0;
/* Given the existence of read locks, we want to unlock for read, erase and write. */
int ret = 1;
if (flash->chip->decode_range != NO_DECODE_RANGE_FUNC ||
(flash->mst->buses_supported & BUS_PROG && flash->mst->opaque.wp_write_cfg)) {
ret = unlock_flash_wp(flash);
if (ret)
msg_cerr("Failed to unlock flash status reg with wp support.\n");
ret = unlock_flash_wp(flash, write_it, erase_it);
}
/*
* Fall back to chip unlock function if we haven't already successfully
* unlocked using WP (e.g. WP unlocking failed, chip had no WP support,
* WP was skipped for read/verify ops).
*
* Given the existence of read locks, we want to unlock for read,
* erase, write, and verify.
*/
blockprotect_func_t *bp_func = lookup_blockprotect_func_ptr(flash->chip);
if (ret && bp_func)
bp_func(flash);