posix: syslog: add support for syslog

This is just a simple wrapper around Zephyr's native log api.

Note: the standard LOG_ERR syslog priority does conflict with
Zephyr's LOG_ERR() macro. This will need to be worked-around on
a case-by-case basis.

Signed-off-by: Christopher Friedt <cfriedt@meta.com>

include/zephyr/posix/syslog.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef ZEPHYR_INCLUDE_POSIX_SYSLOG_H_
+#define ZEPHYR_INCLUDE_POSIX_SYSLOG_H_
+
+#include <stdarg.h>
+
+/* option */
+#define LOG_PID    1
+#define LOG_CONS   2
+#define LOG_NDELAY 4
+#define LOG_ODELAY 8
+#define LOG_NOWAIT 16
+#define LOG_PERROR 32
+
+/* facility */
+#define LOG_KERN   0
+#define LOG_USER   1
+#define LOG_MAIL   2
+#define LOG_NEWS   3
+#define LOG_UUCP   4
+#define LOG_DAEMON 5
+#define LOG_AUTH   6
+#define LOG_CRON   7
+#define LOG_LPR    8
+#define LOG_LOCAL0 9
+#define LOG_LOCAL1 10
+#define LOG_LOCAL2 11
+#define LOG_LOCAL3 12
+#define LOG_LOCAL4 13
+#define LOG_LOCAL5 14
+#define LOG_LOCAL6 15
+#define LOG_LOCAL7 16
+
+/* priority */
+#define LOG_EMERG   0
+#define LOG_ALERT   1
+#define LOG_CRIT    2
+#define LOG_ERR     3
+#define LOG_WARNING 4
+#define LOG_NOTICE  5
+#define LOG_INFO    6
+#define LOG_DEBUG   7
+
+/* generate a valid log mask */
+#define LOG_MASK(mask) ((mask) & BIT_MASK(LOG_DEBUG + 1))
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void closelog(void);
+void openlog(const char *ident, int logopt, int facility);
+int setlogmask(int maskpri);
+void syslog(int priority, const char *message, ...);
+void vsyslog(int priority, const char *format, va_list ap);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_POSIX_SYSLOG_H_ */

lib/posix/options/CMakeLists.txt

@@ -44,6 +44,7 @@ zephyr_library_sources_ifdef(CONFIG_POSIX_FS fs.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MQUEUE mqueue.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_PUTMSG stropts.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_SIGNAL signal.c ${STRSIGNAL_TABLE_H})
+zephyr_library_sources_ifdef(CONFIG_POSIX_SYSLOG syslog.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_UNAME uname.c)
 zephyr_library_sources_ifdef(CONFIG_PTHREAD_IPC _common.c)
 zephyr_library_sources_ifdef(CONFIG_PTHREAD_BARRIER barrier.c)

lib/posix/options/Kconfig

@@ -43,6 +43,7 @@ rsource "Kconfig.signal"
 rsource "Kconfig.spinlock"
 rsource "Kconfig.stropts"
 rsource "Kconfig.sysconf"
+rsource "Kconfig.syslog"
 rsource "Kconfig.timer"
 rsource "Kconfig.uname"
 

lib/posix/options/Kconfig.syslog

@@ -0,0 +1,10 @@
+# Copyright (c) 2024, Meta
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config POSIX_SYSLOG
+	bool "Support for syslog()"
+	default y if POSIX_API
+	help
+	  This option provides support for closelog(), openlog(), syslog(),
+	  setlogmask(), and vsyslog().

lib/posix/options/syslog.c

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <errno.h>
+
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#undef LOG_ERR
+#include <zephyr/posix/syslog.h>
+#include <zephyr/sys/printk.h>
+
+static struct k_spinlock syslog_lock;
+static uint8_t syslog_mask;
+
+static int syslog_priority_to_zephyr_log_level(int priority)
+{
+	switch (priority) {
+	case LOG_EMERG:
+	case LOG_ALERT:
+	case LOG_CRIT:
+	case LOG_ERR:
+		return LOG_LEVEL_ERR;
+	case LOG_WARNING:
+		return LOG_LEVEL_WRN;
+	case LOG_NOTICE:
+	case LOG_INFO:
+		return LOG_LEVEL_INF;
+	case LOG_DEBUG:
+		return LOG_LEVEL_DBG;
+	default:
+		return -EINVAL;
+	}
+}
+
+void closelog(void)
+{
+}
+
+void openlog(const char *ident, int option, int facility)
+{
+	ARG_UNUSED(ident);
+	ARG_UNUSED(option);
+	ARG_UNUSED(facility);
+}
+
+void syslog(int priority, const char *format, ...)
+{
+	va_list ap;
+
+	va_start(ap, format);
+	vsyslog(priority, format, ap);
+	va_end(ap);
+}
+
+int setlogmask(int maskpri)
+{
+	int oldpri;
+
+	K_SPINLOCK(&syslog_lock) {
+		oldpri = syslog_mask;
+		syslog_mask = maskpri;
+	}
+
+	return oldpri;
+}
+
+void vsyslog(int priority, const char *format, va_list ap)
+{
+	uint8_t mask;
+	int level = syslog_priority_to_zephyr_log_level(priority);
+
+	if (level < 0) {
+		/* invalid priority */
+		return;
+	}
+
+	K_SPINLOCK(&syslog_lock) {
+		mask = syslog_mask;
+	}
+
+	if ((BIT(level) & mask) == 0) {
+		/* masked */
+		return;
+	}
+
+#if !defined(CONFIG_LOG) || defined(CONFIG_LOG_MODE_MINIMAL)
+	vprintk(format, ap);
+#else
+	log_generic(level, format, ap);
+#endif
+}