coreboot_tables: Make existing alignment conventions more explicit

There seem to be some recurring vague concerns about the alignment of
coreboot table entries. While the existing implementation has been
producing tables with a well-defined alignment (4 bytes) for a long
time, the code doesn't always make it very clear. This patch adds an
explicit constant to codify that alignment, assertions to check it after
each entry, and adds explicit padding to the few entry structures that
were relying on compiler padding to return a correct sizeof() value.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: Iaeef29ef255047a855066469e03b5481812e5975
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70158
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Peter Stuge <peter@stuge.se>

1 files changed, 9 insertions, 5 deletions

diff --git a/src/lib/coreboot_table.c b/src/lib/coreboot_table.c
index 0f20735204..eaf487ff4e 100644
--- a/src/lib/coreboot_table.c
+++ b/src/lib/coreboot_table.c
@@ -76,9 +76,11 @@ struct lb_record *lb_new_record(struct lb_header *header)
 {
 	struct lb_record *rec;
 	rec = lb_last_record(header);
-	if (header->table_entries)
+	if (header->table_entries) {
+		assert(IS_ALIGNED(rec->size, LB_ENTRY_ALIGN));
 		header->table_bytes += rec->size;
-	rec = lb_last_record(header);
+		rec = lb_last_record(header);
+	}
 	header->table_entries++;
 	rec->tag = LB_TAG_UNUSED;
 	rec->size = sizeof(*rec);
@@ -301,7 +303,7 @@ static struct lb_mainboard *lb_mainboard(struct lb_header *header)
 
 	mainboard->size = ALIGN_UP(sizeof(*mainboard) +
 		strlen(mainboard_vendor) + 1 +
-		strlen(mainboard_part_number) + 1, 8);
+		strlen(mainboard_part_number) + 1, LB_ENTRY_ALIGN);
 
 	mainboard->vendor_idx = 0;
 	mainboard->part_number_idx = strlen(mainboard_vendor) + 1;
@@ -380,7 +382,7 @@ static void lb_strings(struct lb_header *header)
 		rec = (struct lb_string *)lb_new_record(header);
 		len = strlen(strings[i].string);
 		rec->tag = strings[i].tag;
-		rec->size = ALIGN_UP(sizeof(*rec) + len + 1, 8);
+		rec->size = ALIGN_UP(sizeof(*rec) + len + 1, LB_ENTRY_ALIGN);
 		memcpy(rec->string, strings[i].string, len+1);
 	}
 
@@ -422,8 +424,10 @@ static unsigned long lb_table_fini(struct lb_header *head)
 {
 	struct lb_record *rec, *first_rec;
 	rec = lb_last_record(head);
-	if (head->table_entries)
+	if (head->table_entries) {
+		assert(IS_ALIGNED(rec->size, LB_ENTRY_ALIGN));
 		head->table_bytes += rec->size;
+	}
 
 	first_rec = lb_first_record(head);
 	head->table_checksum = compute_ip_checksum(first_rec,