DM: add kmsg logger to sync with kernel log

kmsg logger used to output ACRN-DM log to /dev/kmsg,
it is easy to sync with kernel log.

it is better just output key info or error/failure
log to kmsg for kernel log size is limited.

Tracked-On: #3012
Signed-off-by: Minggui Cao <minggui.cao@intel.com>
Acked-by: Yin Fengwei <fengwei.yin@intel.com>

devicemodel/Makefile

@@ -156,6 +156,7 @@ SRCS += vmcfg/apl-mrb/vm1/vm1.c
 
 # log
 SRCS += log/log.c
+SRCS += log/kmsg_logger.c
 
 OBJS := $(patsubst %.c,$(DM_OBJDIR)/%.o,$(SRCS))
 

devicemodel/log/kmsg_logger.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2018 Intel Corporation. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <paths.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <fcntl.h>
+
+#include "log.h"
+
+#define KMSG_DEV_NODE "/dev/kmsg"
+#define KMSG_PREFIX  "acrn_dm: "
+
+#define KMSG_MAX_LEN    (MAX_ONE_LOG_SIZE + 64)
+#define DEFAULT_KMSG_LEVEL    LOG_NOTICE
+
+static int kmsg_fd = -1;
+
+static uint8_t kmsg_log_level = DEFAULT_KMSG_LEVEL;
+static bool kmsg_enabled = false;
+
+static bool is_kmsg_enabled(void)
+{
+	return kmsg_enabled;
+}
+
+static uint8_t get_kmsg_log_level(void)
+{
+	return kmsg_log_level;
+}
+
+static int init_kmsg_logger(bool enable, uint8_t log_level)
+{
+	kmsg_enabled = enable;
+	kmsg_log_level = log_level;
+
+	/* usually this init should be called once in DM whole life */
+	if (kmsg_fd > 0)
+		return kmsg_fd;
+
+	kmsg_fd = open(KMSG_DEV_NODE, O_RDWR | O_APPEND | O_NONBLOCK);
+	if (kmsg_fd < 0) {
+		kmsg_enabled = false;
+		perror(KMSG_PREFIX"open kmsg dev failed");
+	}
+
+	return kmsg_fd;
+}
+
+static void deinit_kmsg(void)
+{
+	if (kmsg_fd > 0) {
+		close(kmsg_fd);
+		kmsg_fd = -1;
+
+		kmsg_enabled = false;
+	}
+}
+
+static void write_to_kmsg(const char *fmt, va_list args)
+{
+	char kmsg_buf[KMSG_MAX_LEN] = KMSG_PREFIX;
+	int len1, len2;
+	int write_cnt;
+
+	if (kmsg_fd < 0)
+		return;
+
+	len1 = strlen(KMSG_PREFIX);
+	len2 = vsnprintf(kmsg_buf + len1, MAX_ONE_LOG_SIZE, fmt, args);
+
+	write_cnt = write(kmsg_fd, kmsg_buf, len1 + len2);
+	if (write_cnt < 0) {
+		perror(KMSG_PREFIX"write kmsg failed");
+		close(kmsg_fd);
+		kmsg_fd = -1;
+	}
+}
+
+struct logger_ops logger_kmsg = {
+	.name = "kmsg",
+	.is_enabled = is_kmsg_enabled,
+	.get_log_level = get_kmsg_log_level,
+	.init = init_kmsg_logger,
+	.deinit = deinit_kmsg,
+	.output = write_to_kmsg,
+};
+
+DEFINE_LOGGER_DEVICE(logger_kmsg);