[coreboot-gerrit] Change in coreboot[master]: elogtool: add next_available_event_offset function

[Ricardo Quesada (Code Review)]

Ricardo Quesada has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/57395 )

Change subject: elogtool: add next_available_event_offset function
......................................................................

elogtool: add next_available_event_offset function

This function is "extracted" from cmd_clear().
This new function will be called from cmd_add(), and new command that
will be added in a future CL (see CL chain).

Additional minor fixes:
 - calls usage() if no valid commands are passed.
 - Slightly improves usage() output. Needed for cmd_clear()

BUG=b:172210863
TEST=elogtool clear

Change-Id: I0d8ecc893675758d7f90845282a588d367b55567
Signed-off-by: Ricardo Quesada 
---
M util/cbfstool/elogtool.c
1 file changed, 33 insertions(+), 21 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/95/57395/1

diff --git a/util/cbfstool/elogtool.c b/util/cbfstool/elogtool.c
index 4ab8494..a3cd9de 100644
--- a/util/cbfstool/elogtool.c
+++ b/util/cbfstool/elogtool.c
@@ -49,8 +49,8 @@
    		"USAGE:\n"
    		"\t%s COMMAND [-f <filename>]\n\n"
    		"where, COMMAND is:\n"
-			"  list = lists all the event logs in human readable format\n"
-			"  clear = clears all the event logs\n"
+			"  list                    lists all the event logs in human readable format\n"
+			"  clear                   clears all the event logs\n"
    		"\n"
    		"ARGS\n"
    		"-f, --file <filename>   File that holds event log partition.\n"
@@ -115,6 +115,23 @@
    return ELOGTOOL_EXIT_SUCCESS;
 }

+static int next_available_event_offset(const struct buffer *buf)
+{
+	const struct event_header *event;
+	int offset = sizeof(struct elog_header);
+
+	event = buffer_get(buf) + offset;
+	while ((const void *)(event) < buffer_end(buf)) {
+		if (event->type == ELOG_TYPE_EOL || event->length == 0)
+			break;
+
+		offset += event->length;
+		assert((size_t)offset <= buffer_size(buf) && "Out of bounds");
+		event = elog_get_next_event(event);
+	}
+	return offset;
+}
+
 static int cmd_list(const struct buffer *buf)
 {
    const struct event_header *event;
@@ -141,34 +158,27 @@
  */
 static int cmd_clear(const struct buffer *b)
 {
-	const struct event_header *event;
-	uint32_t used_data_size = 0;
+	uint32_t offset;
    struct buffer buf;
-	void *data_offset;
+	void *start;

-	/* Clone the buffer to avoid changing the offset of the original buffer */
-	buffer_clone(&buf, b);
-	/* eventlog_init_event() expects buffer to point to the event */
-	buffer_seek(&buf, sizeof(struct elog_header));
-
+	start = buffer_get(b);
    /*
     * Calculate the size of the "used" buffer, needed for ELOG_TYPE_LOG_CLEAR.
     * Then overwrite the entire buffer with ELOG_TYPE_EOL.
     * Finally insert a LOG_CLEAR event into the buffer.
     */
-	event = data_offset = buffer_get(&buf);
-	while ((const void *)(event) < buffer_end(&buf)) {
-		if (event->type == ELOG_TYPE_EOL || event->length == 0)
-			break;
+	offset = next_available_event_offset(b);
+	memset(start + sizeof(struct elog_header), ELOG_TYPE_EOL,
+	       buffer_size(b) - sizeof(struct elog_header));

-		used_data_size += event->length;
-		event = elog_get_next_event(event);
-	}
+	/* Clone the buffer to avoid changing the offset of the original buffer */
+	buffer_clone(&buf, b);
+	buffer_seek(&buf, sizeof(struct elog_header));

-	memset(data_offset, ELOG_TYPE_EOL, buffer_size(&buf));
+	offset -= sizeof(struct elog_header);

-	if (!eventlog_init_event(&buf, ELOG_TYPE_LOG_CLEAR,
-				 &used_data_size, sizeof(used_data_size)))
+	if (!eventlog_init_event(&buf, ELOG_TYPE_LOG_CLEAR, &offset, sizeof(offset)))
    	return ELOGTOOL_EXIT_NOT_ENOUGH_BUFFER_SPACE;

return ELOGTOOL_EXIT_SUCCESS;
@@ -231,8 +241,10 @@
    	}
    }

-	if (i == ARRAY_SIZE(cmds))
+	if (i == ARRAY_SIZE(cmds)) {
+		usage(argv[0]);
    	ret = ELOGTOOL_EXIT_BAD_ARGS;
+	}

if (!ret && cmds[i].write_back)
    	ret = elog_write(&buf, filename);