elogtool: add "clear" command

Adds "clear" command to cbfsutil/elogtool tool.
"clear" clears the RW_ELOG region by using either:
 * flashrom if no file is provided
 * or using file write if an input file is provided.

The region is filled with ELOG_TYPE_EOL. And a
ELOG_TYPE_LOG_CLEAR event is inserted.

Additionally, it does a minor cleanup to command "list", like:
 * use buffer_end()
 * add "list" to the cmds struct
 * and make elog_read() very similar to elog_write()

Usage:
$ elogtool clear

BUG=b:172210863
TEST=elogtool clear && elogtool list
     elogtool clear -f invalid.raw
     elogtool clear -f valid.raw

Change-Id: Ia28a6eb34c82103ab078a0841b022e2e5e430585
Signed-off-by: Ricardo Quesada <ricardoq@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56883
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>

util/cbfstool/elogtool.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: BSD-3-Clause */
 
 #include <getopt.h>
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -16,9 +17,24 @@
 enum elogtool_return {
 	ELOGTOOL_EXIT_SUCCESS = 0,
 	ELOGTOOL_EXIT_BAD_ARGS,
-	ELOGTOOL_EXIT_BAD_INPUT_PATH,
+	ELOGTOOL_EXIT_READ_ERROR,
+	ELOGTOOL_EXIT_WRITE_ERROR,
 	ELOGTOOL_EXIT_NOT_ENOUGH_MEMORY,
 	ELOGTOOL_EXIT_INVALID_ELOG_FORMAT,
+	ELOGTOOL_EXIT_NOT_ENOUGH_BUFFER_SPACE,
+};
+
+static int cmd_list(const struct buffer *);
+static int cmd_clear(const struct buffer *);
+
+static const struct {
+	const char *name;
+	int (*func)(const struct buffer *buf);
+	/* Whether it requires to write the buffer back */
+	bool write_back;
+} cmds[] = {
+	{"list", cmd_list, false},
+	{"clear", cmd_clear, true},
 };
 
 static struct option long_options[] = {
@@ -33,57 +49,81 @@ static void usage(char *invoked_as)
 			"USAGE:\n"
 			"\t%s COMMAND [-f <filename>]\n\n"
 			"where, COMMAND is:\n"
-			"  list = lists all the event logs in human readable format\n\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>   Input file that holds event log partition.\n"
+			"-f, --file <filename>   File that holds event log partition.\n"
-			"                        If empty it will try to read from the RW_ELOG ROM region\n"
+			"                        If empty it will try to read/write from/to\n"
+			"                        the " ELOG_RW_REGION_NAME " using flashrom.\n"
 			"-h, --help              Print this help\n",
 			invoked_as);
 }
 
-// If filename is empty, read RW_ELOG from flashrom. Otherwise read the RW_ELOG from a file.
+/*
-// Buffer must be freed by caller.
+ * If filename is empty, read RW_ELOG from flashrom.
-static int elog_read(const char *filename, struct buffer *buffer)
+ * Otherwise read the RW_ELOG from a file.
+ * It fails if the ELOG header is invalid.
+ * On success, buffer must be freed by caller.
+ */
+static int elog_read(struct buffer *buffer, const char *filename)
 {
 	if (filename == NULL) {
 		uint8_t *buf;
 		uint32_t buf_size;
 
-		if (flashrom_read(FLASHROM_PROGRAMMER_INTERNAL_AP, "RW_ELOG", &buf, &buf_size)
+		if (flashrom_read(FLASHROM_PROGRAMMER_INTERNAL_AP, ELOG_RW_REGION_NAME,
-		    != VB2_SUCCESS) {
+				  &buf, &buf_size) != VB2_SUCCESS) {
 			fprintf(stderr, "Could not read RW_ELOG region using flashrom\n");
-			return ELOGTOOL_EXIT_BAD_INPUT_PATH;
+			return ELOGTOOL_EXIT_READ_ERROR;
 		}
 		buffer_init(buffer, NULL, buf, buf_size);
-	} else {
+	} else if (buffer_from_file(buffer, filename) != 0) {
-		if (buffer_from_file(buffer, filename) != 0) {
 		fprintf(stderr, "Could not read input file: %s\n", filename);
-			return ELOGTOOL_EXIT_BAD_INPUT_PATH;
+		return ELOGTOOL_EXIT_READ_ERROR;
-		}
 	}
 
-	return 0;
+	if (elog_verify_header(buffer_get(buffer)) != CB_SUCCESS) {
-}
-
-static int elog_list_events(const struct buffer *buf)
-{
-	const struct event_header *event;
-	const void *data;
-	uint32_t data_len;
-	unsigned int count = 0;
-
-	data = buffer_get(buf);
-	data_len = buffer_size(buf);
-
-	if (elog_verify_header(data) != CB_SUCCESS) {
 		fprintf(stderr, "FATAL: Invalid elog header\n");
+		buffer_delete(buffer);
 		return ELOGTOOL_EXIT_INVALID_ELOG_FORMAT;
 	}
 
-	/* Point to first event */
+	return ELOGTOOL_EXIT_SUCCESS;
-	event = (const struct event_header *)(data + sizeof(struct elog_header));
+}
 
-	while ((const void *)(event) < data + data_len) {
+/*
+ * If filename is NULL, it saves the buffer using flashrom.
+ * Otherwise, it saves the buffer in the given filename.
+ */
+static int elog_write(struct buffer *buf, const char *filename)
+{
+	if (filename == NULL) {
+		if (flashrom_write(FLASHROM_PROGRAMMER_INTERNAL_AP, ELOG_RW_REGION_NAME,
+				   buffer_get(buf), buffer_size(buf)) != VB2_SUCCESS) {
+			fprintf(stderr,
+				"Failed to write to RW_ELOG region using flashrom\n");
+			return ELOGTOOL_EXIT_WRITE_ERROR;
+		}
+		return ELOGTOOL_EXIT_SUCCESS;
+	}
+
+	if (buffer_write_file(buf, filename) != 0) {
+		fprintf(stderr, "Failed to write to file %s\n", filename);
+		return ELOGTOOL_EXIT_WRITE_ERROR;
+	}
+	return ELOGTOOL_EXIT_SUCCESS;
+}
+
+static int cmd_list(const struct buffer *buf)
+{
+	const struct event_header *event;
+	unsigned int count = 0;
+
+	/* Point to the first event */
+	event = buffer_get(buf) + sizeof(struct elog_header);
+
+	while ((const void *)(event) < buffer_end(buf)) {
 		if (event->type == ELOG_TYPE_EOL || event->length == 0)
 			break;
 
@@ -95,27 +135,52 @@ static int elog_list_events(const struct buffer *buf)
 	return ELOGTOOL_EXIT_SUCCESS;
 }
 
-static int cmd_list(const char *filename)
+/*
+ * Clears the elog events from the given buffer, which is a valid RW_ELOG region.
+ * A LOG_CLEAR event is appended.
+ */
+static int cmd_clear(const struct buffer *b)
 {
-	int ret;
+	const struct event_header *event;
-
+	uint32_t used_data_size = 0;
-	// Returned buffer must be freed.
 	struct buffer buf;
-	ret = elog_read(filename, &buf);
+	void *data_offset;
-	if (ret != 0)
-		return ret;
 
-	ret = elog_list_events(&buf);
+	/* 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));
 
-	buffer_delete(&buf);
+	/*
-	return ret;
+	 * 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;
+
+		used_data_size += event->length;
+		event = elog_get_next_event(event);
 	}
 
+	memset(data_offset, ELOG_TYPE_EOL, buffer_size(&buf));
+
+	if (!eventlog_init_event(&buf, ELOG_TYPE_LOG_CLEAR,
+				 &used_data_size, sizeof(used_data_size)))
+		return ELOGTOOL_EXIT_NOT_ENOUGH_BUFFER_SPACE;
+
+	return ELOGTOOL_EXIT_SUCCESS;
+}
 
 int main(int argc, char **argv)
 {
+	char *filename = NULL;
+	struct buffer buf;
+	unsigned int i;
 	int argflag;
-	char *input_file = NULL;
+	int ret;
 
 	if (argc < 2) {
 		usage(argv[0]);
@@ -140,7 +205,7 @@ int main(int argc, char **argv)
 				return ELOGTOOL_EXIT_BAD_ARGS;
 			}
 
-			input_file = optarg;
+			filename = optarg;
 			break;
 
 		default:
@@ -154,8 +219,25 @@ int main(int argc, char **argv)
 		return ELOGTOOL_EXIT_BAD_ARGS;
 	}
 
-	if (!strcmp(argv[optind], "list"))
+	/* Returned buffer must be freed. */
-		return cmd_list(input_file);
+	ret = elog_read(&buf, filename);
+	if (ret)
+		return ret;
 
-	return ELOGTOOL_EXIT_SUCCESS;
+	for (i = 0; i < ARRAY_SIZE(cmds); i++) {
+		if (!strcmp(cmds[i].name, argv[optind])) {
+			ret = cmds[i].func(&buf);
+			break;
+		}
+	}
+
+	if (i == ARRAY_SIZE(cmds))
+		ret = ELOGTOOL_EXIT_BAD_ARGS;
+
+	if (!ret && cmds[i].write_back)
+		ret = elog_write(&buf, filename);
+
+	buffer_delete(&buf);
+
+	return ret;
 }

util/cbfstool/eventlog.c

@@ -11,6 +11,7 @@
 #include <commonlib/bsd/elog.h>
 #include <vb2_api.h>
 
+#include "common.h"
 #include "valstr.h"
 
 #define PATH_PCI_BUS_SHIFT		8
@@ -634,3 +635,42 @@ void eventlog_print_event(const struct event_header *event, int count)
 	eventlog_printf_ignore_separator_once = 1;
 	eventlog_printf("\n");
 }
+
+/*
+ * Initializes the eventlog header with the given type and data,
+ * and calculates the checksum.
+ * buffer_get() points to the event to be initialized.
+ * On success it returns 1, otherwise 0.
+ */
+int eventlog_init_event(const struct buffer *buf, uint8_t type,
+			const void *data, int data_size)
+{
+	struct event_header *event;
+	time_t secs = time(NULL);
+	struct tm tm;
+
+	/* Must have at least size for data + checksum byte */
+	if (buffer_size(buf) < (size_t)data_size + 1)
+		return 0;
+
+	event = buffer_get(buf);
+
+	event->type = type;
+	gmtime_r(&secs, &tm);
+	elog_fill_timestamp(event, tm.tm_sec, tm.tm_min, tm.tm_hour,
+			    tm.tm_mday, tm.tm_mon, tm.tm_year);
+
+	if (data && data_size) {
+		uint32_t *ptr = (uint32_t *)&event[1];
+		memcpy(ptr, data, data_size);
+	}
+
+	/* Header + data + checksum */
+	event->length = sizeof(*event) + data_size + 1;
+
+	/* Zero the checksum byte and then compute checksum */
+	elog_update_checksum(event, 0);
+	elog_update_checksum(event, -(elog_checksum_event(event)));
+
+	return 1;
+}

util/cbfstool/eventlog.h

@@ -3,8 +3,13 @@
 #ifndef EVENTLOG_H_
 #define EVENTLOG_H_
 
+#include <stdint.h>
+
 struct event_header;
+struct buffer;
 
 void eventlog_print_event(const struct event_header *event, int count);
+int eventlog_init_event(const struct buffer *buf, uint8_t type,
+			const void *data, int data_size);
 
 #endif // EVENTLOG_H_