Make elog_shrink not depend on having seperate memory/flash descriptors.

The way elog_shrink currently works is that it completely clears the data in
the flash/flash descriptor and then recreates it using the part of the log
it's going to keep as stored in the memory descriptor. That scheme depends on
there being to independent copies of the log.

This change reworks elog_shrink so that it moves the data it wants to keep
within a single descriptor and then propogates it to the other and to flash
intact. This way, when one of the descriptors goes away, all we have to do is
remove the code that would update it.

Built and booted into ChromeOS on Link. Ran mosys eventlog list. Added
2000 events to the log and ran mosys eventlog list again. Echoed a 1 into
/sys/firmware/gsmi/clear_eventlog and ran mosys eventlog list.
BRANCH=None

Change-Id: I50d77a4f00ea3c6b3e0ec8996dab1a3b31580205
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/49305
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/4240
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

1 files changed, 12 insertions, 13 deletions

diff --git a/src/drivers/elog/elog.c b/src/drivers/elog/elog.c
index fd638a5ae8..ab255d8d55 100644
--- a/src/drivers/elog/elog.c
+++ b/src/drivers/elog/elog.c
@@ -621,9 +621,11 @@ static int elog_flash_area_bootstrap(void)
 static int elog_shrink(void)
 {
 	struct elog_descriptor *mem = elog_get_mem();
+	struct elog_descriptor *flash = elog_get_flash();
 	struct event_header *event;
 	u16 discard_count = 0;
 	u16 offset = 0;
+	u16 new_size = 0;
 
 	elog_debug("elog_shrink()\n");
 
@@ -645,25 +647,22 @@ static int elog_shrink(void)
 		discard_count++;
 	}
 
-	/* Erase flash area */
-	elog_flash_erase_area();
+	new_size = mem->next_event_offset - offset;
+	memmove(&mem->data[0], &mem->data[offset], new_size);
+	memset(&mem->data[new_size], ELOG_TYPE_EOL, mem->data_size - new_size);
+	elog_reinit_descriptor(mem);
+
+	elog_flash_erase(flash->backing_store, flash->total_size);
 
 	/* Ensure the area was successfully erased */
-	if (elog_get_flash()->next_event_offset >= CONFIG_ELOG_FULL_THRESHOLD) {
+	if (mem->next_event_offset >= CONFIG_ELOG_FULL_THRESHOLD) {
 		printk(BIOS_ERR, "ELOG: Flash area was not erased!\n");
 		return -1;
 	}
 
-	/* Write new flash area */
-	elog_prepare_empty(elog_get_flash(),
-			   (u8*)elog_get_event_base(mem, offset),
-			   mem->next_event_offset - offset);
-
-	/* Update memory area from flash */
-	if (elog_sync_flash_to_mem() < 0) {
-		printk(BIOS_ERR, "Unable to update memory area from flash\n");
-		return -1;
-	}
+	elog_flash_write(flash->backing_store, mem->backing_store,
+			 mem->total_size);
+	elog_reinit_descriptor(flash);
 
 	/* Add clear event */
 	elog_add_event_word(ELOG_TYPE_LOG_CLEAR, offset);