OpenHarmony喂狗源码解读之Linux内核原生喂狗配置 原创

春节不停更，此文正在参加「星光计划-春节更帖活动」https://harmonyos.51cto.com/posts/9923

@[toc](OpenHarmony3.1Beta喂狗Linux原生喂狗配置解读

一、内核编译选项

CONFIG_WATCHDOG=y
CONFIG_WATCHDOG_CORE=y
CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED=y
CONFIG_WATCHDOG_OPEN_TIMEOUT=0
CONFIG_ARM_SP805_WATCHDOG=y

二、内核DTS配置

watchdog: watchdog@12051000 {
	 compatible = "arm,sp805-wdt", "arm,primecell";
	 arm,primecell-periphid = <0x00141805>;
	 reg = <0x12051000 0x1000>;
	 clocks = <&clk_3m>,<&clk_apb>;
	 clock-names = "wdog_clk", "apb_pclk";
	 status = "okay";
};

三、用户态喂狗代码

代码为busyBox的示例代码

#include "libbb.h"
#include <linux/types.h> /* for __u32 */
#include <linux/watchdog.h>

#ifndef WDIOC_SETOPTIONS
# define WDIOC_SETOPTIONS 0x5704
#endif
#ifndef WDIOC_SETTIMEOUT
# define WDIOC_SETTIMEOUT 0x5706
#endif
#ifndef WDIOC_GETTIMEOUT
# define WDIOC_GETTIMEOUT 0x5707
#endif
#ifndef WDIOS_ENABLECARD
# define WDIOS_ENABLECARD 2
#endif

#define OPT_FOREGROUND  (1 << 0)
#define OPT_STIMER      (1 << 1)
#define OPT_HTIMER      (1 << 2)

static void shutdown_watchdog(void)
{
	static const char V = 'V';
	write(3, &V, 1);  /* Magic, see watchdog-api.txt in kernel */
	close(3);
}

static void shutdown_on_signal(int sig UNUSED_PARAM)
{
	remove_pidfile_std_path_and_ext("watchdog");
	shutdown_watchdog();
	_exit(EXIT_SUCCESS);
}

static void watchdog_open(const char* device)
{
	/* Use known fd # - avoid needing global 'int fd' */
	xmove_fd(xopen(device, O_WRONLY), 3);

	/* If the watchdog driver can do something other than cause a reboot
	 * on a timeout, then it's possible this program may be starting from
	 * a state when the watchdog hadn't been previously stopped with
	 * the magic write followed by a close.  In this case the driver may
	 * not start properly, so always do the proper stop first just in case.
	 */
	shutdown_watchdog();

	xmove_fd(xopen(device, O_WRONLY), 3);
}

int watchdog_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int watchdog_main(int argc UNUSED_PARAM, char **argv)
{
	static const int enable = WDIOS_ENABLECARD;
	static const struct suffix_mult suffixes[] = {
		{ "ms", 1 },
		{ "", 1000 },
		{ "", 0 }
	};

	unsigned opts;
	unsigned stimer_duration; /* how often to restart */
	unsigned htimer_duration = 60000; /* reboots after N ms if not restarted */
	char *st_arg;
	char *ht_arg;

	opts = getopt32(argv, "^" "Ft:T:" "\0" "=1"/*must have exactly 1 arg*/,
				&st_arg, &ht_arg
	);

	/* We need to daemonize *before* opening the watchdog as many drivers
	 * will only allow one process at a time to do so.  Since daemonizing
	 * is not perfect (child may run before parent finishes exiting), we
	 * can't rely on parent exiting before us (let alone *cleanly* releasing
	 * the watchdog fd -- something else that may not even be allowed).
	 */
	if (!(opts & OPT_FOREGROUND))
		bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);

	/* maybe bb_logenv_override(); here for LOGGING=syslog to work? */

	if (opts & OPT_HTIMER)
		htimer_duration = xatou_sfx(ht_arg, suffixes);
	stimer_duration = htimer_duration / 2;
	if (opts & OPT_STIMER)
		stimer_duration = xatou_sfx(st_arg, suffixes);

	bb_signals(BB_FATAL_SIGS, shutdown_on_signal);

	watchdog_open(argv[optind]);

	/* WDIOC_SETTIMEOUT takes seconds, not milliseconds */
	htimer_duration = htimer_duration / 1000;
	ioctl_or_warn(3, WDIOC_SETOPTIONS, (void*) &enable);
	ioctl_or_warn(3, WDIOC_SETTIMEOUT, &htimer_duration);
#if 0
	ioctl_or_warn(3, WDIOC_GETTIMEOUT, &htimer_duration);
	printf("watchdog: SW timer is %dms, HW timer is %ds\n",
		stimer_duration, htimer_duration * 1000);
#endif

	write_pidfile_std_path_and_ext("watchdog");

	while (1) {
		/*
		 * Make sure we clear the counter before sleeping,
		 * as the counter value is undefined at this point -- PFM
		 */
		write(3, "", 1); /* write zero byte */
		usleep(stimer_duration * 1000L);
	}
	return EXIT_SUCCESS; /* - not reached, but gcc 4.2.1 is too dumb! */
}