/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include "devnum-util.h" #include "errno-util.h" #include "fd-util.h" #include "fileio.h" #include "log.h" #include "path-util.h" #include "string-util.h" #include "time-util.h" #include "watchdog.h" static int watchdog_fd = -EBADF; static char *watchdog_device = NULL; static usec_t watchdog_timeout = 0; /* 0 → close device and USEC_INFINITY → don't change timeout */ static usec_t watchdog_pretimeout = 0; /* 0 → disable pretimeout and USEC_INFINITY → don't change pretimeout */ static usec_t watchdog_last_ping = USEC_INFINITY; static bool watchdog_supports_pretimeout = false; /* Depends on kernel state that might change at runtime */ static char *watchdog_pretimeout_governor = NULL; /* Starting from kernel version 4.5, the maximum allowable watchdog timeout is * UINT_MAX/1000U seconds (since internal calculations are done in milliseconds * using unsigned integers. However, the kernel's userspace API for the watchdog * uses signed integers for its ioctl parameters (even for timeout values and * bit flags) so this is why we must consider the maximum signed integer value * as well. */ #define WATCHDOG_TIMEOUT_MAX_SEC (CONST_MIN(UINT_MAX/1000U, (unsigned)INT_MAX)) #define WATCHDOG_GOV_NAME_MAXLEN 20 /* From the kernel watchdog driver */ static int saturated_usec_to_sec(usec_t val) { usec_t t = DIV_ROUND_UP(val, USEC_PER_SEC); return MIN(t, (usec_t) WATCHDOG_TIMEOUT_MAX_SEC); /* Saturate to watchdog max */ } static int watchdog_get_sysfs_path(const char *filename, char **ret_path) { struct stat st; if (watchdog_fd < 0) return -EBADF; if (fstat(watchdog_fd, &st)) return -errno; if (!S_ISCHR(st.st_mode)) return -EBADF; if (asprintf(ret_path, "/sys/dev/char/"DEVNUM_FORMAT_STR"/%s", DEVNUM_FORMAT_VAL(st.st_rdev), filename) < 0) return -ENOMEM; return 0; } static int watchdog_get_pretimeout_governor(char **ret_gov) { _cleanup_free_ char *sys_fn = NULL; int r; r = watchdog_get_sysfs_path("pretimeout_governor", &sys_fn); if (r < 0) return r; log_info("Watchdog: reading from %s", sys_fn); r = read_virtual_file(sys_fn, WATCHDOG_GOV_NAME_MAXLEN - 1, ret_gov, NULL); if (r < 0) return r; delete_trailing_chars(*ret_gov, WHITESPACE); return 0; } static int watchdog_set_pretimeout_governor(const char *governor) { _cleanup_free_ char *sys_fn = NULL; int r; if (isempty(governor)) return 0; /* Nothing to do */ r = watchdog_get_sysfs_path("pretimeout_governor", &sys_fn); if (r < 0) return r; log_info("Watchdog: setting pretimeout_governor to '%s' via '%s'", governor, sys_fn); r = write_string_file(sys_fn, governor, WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_VERIFY_IGNORE_NEWLINE); if (r < 0) return log_error_errno(r, "Failed to set watchdog pretimeout_governor to '%s': %m", governor); return r; } static int watchdog_set_enable(bool enable) { int flags = enable ? WDIOS_ENABLECARD : WDIOS_DISABLECARD; assert(watchdog_fd >= 0); if (ioctl(watchdog_fd, WDIOC_SETOPTIONS, &flags) < 0) { if (!enable) return log_warning_errno(errno, "Failed to disable hardware watchdog, ignoring: %m"); /* ENOTTY means the watchdog is always enabled so we're fine */ log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno, "Failed to enable hardware watchdog, ignoring: %m"); if (!ERRNO_IS_NOT_SUPPORTED(errno)) return -errno; } return 0; } static int watchdog_read_timeout(void) { int sec = 0; assert(watchdog_fd >= 0); if (ioctl(watchdog_fd, WDIOC_GETTIMEOUT, &sec) < 0) return -errno; assert(sec > 0); watchdog_timeout = sec * USEC_PER_SEC; return 0; } static int watchdog_set_timeout(void) { int sec; assert(watchdog_fd >= 0); assert(timestamp_is_set(watchdog_timeout)); sec = saturated_usec_to_sec(watchdog_timeout); if (ioctl(watchdog_fd, WDIOC_SETTIMEOUT, &sec) < 0) return -errno; assert(sec > 0); /* buggy driver ? */ watchdog_timeout = sec * USEC_PER_SEC; return 0; } static int watchdog_read_pretimeout(void) { int sec = 0; assert(watchdog_fd >= 0); if (ioctl(watchdog_fd, WDIOC_GETPRETIMEOUT, &sec) < 0) { watchdog_pretimeout = 0; return log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno, "Failed to get watchdog pretimeout value, ignoring: %m"); } watchdog_pretimeout = sec * USEC_PER_SEC; return 0; } static int watchdog_set_pretimeout(void) { int sec; assert(watchdog_fd >= 0); assert(watchdog_pretimeout != USEC_INFINITY); sec = saturated_usec_to_sec(watchdog_pretimeout); if (ioctl(watchdog_fd, WDIOC_SETPRETIMEOUT, &sec) < 0) { watchdog_pretimeout = 0; if (ERRNO_IS_NOT_SUPPORTED(errno)) { log_info("Watchdog does not support pretimeouts."); return 0; } return log_error_errno(errno, "Failed to set watchdog pretimeout to %s: %m", FORMAT_TIMESPAN(sec, USEC_PER_SEC)); } /* The set ioctl does not return the actual value set so get it now. */ (void) watchdog_read_pretimeout(); return 0; } usec_t watchdog_get_last_ping(clockid_t clock) { return map_clock_usec(watchdog_last_ping, CLOCK_BOOTTIME, clock); } static int watchdog_ping_now(void) { assert(watchdog_fd >= 0); if (ioctl(watchdog_fd, WDIOC_KEEPALIVE, 0) < 0) return log_warning_errno(errno, "Failed to ping hardware watchdog, ignoring: %m"); watchdog_last_ping = now(CLOCK_BOOTTIME); return 0; } static int watchdog_update_pretimeout(void) { _cleanup_free_ char *governor = NULL; int r, t_sec, pt_sec; if (watchdog_fd < 0) return 0; if (watchdog_timeout == USEC_INFINITY || watchdog_pretimeout == USEC_INFINITY) return 0; if (!watchdog_supports_pretimeout && watchdog_pretimeout == 0) return 0; /* Nothing to do */ /* The configuration changed, do not assume it can still work, as the module(s) * might have been unloaded. */ watchdog_supports_pretimeout = false; /* Update the pretimeout governor as well */ (void) watchdog_set_pretimeout_governor(watchdog_pretimeout_governor); r = watchdog_get_pretimeout_governor(&governor); if (r < 0) return log_warning_errno(r, "Watchdog: failed to read pretimeout governor: %m"); if (isempty(governor)) return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Watchdog: no pretimeout governor detected - is the required kernel module loaded?"); /* If we have a pretimeout governor, then pretimeout is supported. Without a governor * pretimeout does not work at all. * Note that this might require a kernel module that is not autoloaded, so we don't * cache this, but we check every time the configuration changes. */ watchdog_supports_pretimeout = true; /* Determine if the pretimeout is valid for the current watchdog timeout. */ t_sec = saturated_usec_to_sec(watchdog_timeout); pt_sec = saturated_usec_to_sec(watchdog_pretimeout); if (pt_sec >= t_sec) { r = log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Cannot set watchdog pretimeout to %is (%s watchdog timeout of %is)", pt_sec, pt_sec == t_sec ? "same as" : "longer than", t_sec); (void) watchdog_read_pretimeout(); } else r = watchdog_set_pretimeout(); if (watchdog_pretimeout == 0) log_info("Watchdog pretimeout is disabled."); else log_info("Watchdog running with a pretimeout of %s with governor '%s'.", FORMAT_TIMESPAN(watchdog_pretimeout, 0), governor); return r; } static int watchdog_update_timeout(void) { int r; usec_t previous_timeout; assert(watchdog_timeout > 0); if (watchdog_fd < 0) return 0; previous_timeout = watchdog_timeout; if (watchdog_timeout != USEC_INFINITY) { r = watchdog_set_timeout(); if (r < 0) { if (!ERRNO_IS_NOT_SUPPORTED(r)) return log_error_errno(r, "Failed to set watchdog hardware timeout to %s: %m", FORMAT_TIMESPAN(watchdog_timeout, 0)); log_info("Modifying watchdog hardware timeout is not supported, reusing the programmed timeout."); watchdog_timeout = USEC_INFINITY; } } if (watchdog_timeout == USEC_INFINITY) { r = watchdog_read_timeout(); if (r < 0) { if (!ERRNO_IS_NOT_SUPPORTED(r)) return log_error_errno(r, "Failed to query watchdog hardware timeout: %m"); log_info("Reading watchdog hardware timeout is not supported, reusing the configured timeout."); watchdog_timeout = previous_timeout; } } /* If the watchdog timeout was changed, the pretimeout could have been * changed as well by the driver or the kernel so we need to update the * pretimeout now. Or if the watchdog is being configured for the first * time, we want to configure the pretimeout before it is enabled. */ (void) watchdog_update_pretimeout(); r = watchdog_set_enable(true); if (r < 0) return r; log_info("Watchdog running with a hardware timeout of %s.", FORMAT_TIMESPAN(watchdog_timeout, 0)); return watchdog_ping_now(); } static int watchdog_open(void) { struct watchdog_info ident; char **try_order; int r; if (watchdog_fd >= 0) return 0; /* Let's prefer new-style /dev/watchdog0 (i.e. kernel 3.5+) over classic /dev/watchdog. The former * has the benefit that we can easily find the matching directory in sysfs from it, as the relevant * sysfs attributes can only be found via /sys/dev/char/: if the new-style device * major/minor is used, not the old-style. */ try_order = !watchdog_device || PATH_IN_SET(watchdog_device, "/dev/watchdog", "/dev/watchdog0") ? STRV_MAKE("/dev/watchdog0", "/dev/watchdog") : STRV_MAKE(watchdog_device); STRV_FOREACH(wd, try_order) { watchdog_fd = open(*wd, O_WRONLY|O_CLOEXEC); if (watchdog_fd >= 0) { if (free_and_strdup(&watchdog_device, *wd) < 0) { r = log_oom_debug(); goto close_and_fail; } break; } if (errno != ENOENT) return log_debug_errno(errno, "Failed to open watchdog device %s: %m", *wd); } if (watchdog_fd < 0) return log_debug_errno(SYNTHETIC_ERRNO(ENOENT), "Failed to open watchdog device %s.", watchdog_device ?: "auto"); watchdog_last_ping = USEC_INFINITY; if (ioctl(watchdog_fd, WDIOC_GETSUPPORT, &ident) < 0) log_debug_errno(errno, "Hardware watchdog %s does not support WDIOC_GETSUPPORT ioctl, ignoring: %m", watchdog_device); else log_info("Using hardware watchdog '%s', version %x, device %s", ident.identity, ident.firmware_version, watchdog_device); r = watchdog_update_timeout(); if (r < 0) goto close_and_fail; return 0; close_and_fail: watchdog_close(/* disarm= */ true); return r; } const char* watchdog_get_device(void) { return watchdog_device; } int watchdog_set_device(const char *path) { int r; r = free_and_strdup(&watchdog_device, path); if (r > 0) /* watchdog_device changed */ watchdog_close(/* disarm= */ true); return r; } int watchdog_setup(usec_t timeout) { usec_t previous_timeout; int r; /* timeout=0 closes the device whereas passing timeout=USEC_INFINITY opens it (if needed) * without configuring any particular timeout and thus reuses the programmed value (therefore * it's a nop if the device is already opened). */ if (timeout == 0) { watchdog_close(true); return 0; } /* Let's shortcut duplicated requests */ if (watchdog_fd >= 0 && (timeout == watchdog_timeout || timeout == USEC_INFINITY)) return 0; /* Initialize the watchdog timeout with the caller value. This value is going to be updated by * update_timeout() with the closest value supported by the driver */ previous_timeout = watchdog_timeout; watchdog_timeout = timeout; if (watchdog_fd < 0) return watchdog_open(); r = watchdog_update_timeout(); if (r < 0) watchdog_timeout = previous_timeout; return r; } int watchdog_setup_pretimeout(usec_t timeout) { /* timeout=0 disables the pretimeout whereas timeout=USEC_INFINITY is a nop. */ if ((watchdog_fd >= 0 && timeout == watchdog_pretimeout) || timeout == USEC_INFINITY) return 0; /* Initialize the watchdog timeout with the caller value. This value is * going to be updated by update_pretimeout() with the running value, * even if it fails to update the timeout. */ watchdog_pretimeout = timeout; return watchdog_update_pretimeout(); } int watchdog_setup_pretimeout_governor(const char *governor) { if (free_and_strdup(&watchdog_pretimeout_governor, governor) < 0) return -ENOMEM; return watchdog_set_pretimeout_governor(watchdog_pretimeout_governor); } static usec_t watchdog_calc_timeout(void) { /* Calculate the effective timeout which accounts for the watchdog * pretimeout if configured and supported. */ if (watchdog_supports_pretimeout && timestamp_is_set(watchdog_pretimeout) && watchdog_timeout >= watchdog_pretimeout) return watchdog_timeout - watchdog_pretimeout; else return watchdog_timeout; } usec_t watchdog_runtime_wait(void) { usec_t timeout = watchdog_calc_timeout(); if (!timestamp_is_set(timeout)) return USEC_INFINITY; /* Sleep half the watchdog timeout since the last successful ping at most */ if (timestamp_is_set(watchdog_last_ping)) { usec_t ntime = now(CLOCK_BOOTTIME); assert(ntime >= watchdog_last_ping); return usec_sub_unsigned(watchdog_last_ping + (timeout / 2), ntime); } return timeout / 2; } int watchdog_ping(void) { usec_t ntime, timeout; if (watchdog_timeout == 0) return 0; if (watchdog_fd < 0) /* open_watchdog() will automatically ping the device for us if necessary */ return watchdog_open(); ntime = now(CLOCK_BOOTTIME); timeout = watchdog_calc_timeout(); /* Never ping earlier than watchdog_timeout/4 and try to ping * by watchdog_timeout/2 plus scheduling latencies at the latest */ if (timestamp_is_set(watchdog_last_ping)) { assert(ntime >= watchdog_last_ping); if ((ntime - watchdog_last_ping) < (timeout / 4)) return 0; } return watchdog_ping_now(); } void watchdog_close(bool disarm) { /* Once closed, pinging the device becomes a NOP and we request a new * call to watchdog_setup() to open the device again. */ watchdog_timeout = 0; if (watchdog_fd < 0) return; if (disarm) { (void) watchdog_set_enable(false); /* To be sure, use magic close logic, too */ for (;;) { static const char v = 'V'; if (write(watchdog_fd, &v, 1) > 0) break; if (errno != EINTR) { log_warning_errno(errno, "Failed to disarm watchdog timer, ignoring: %m"); break; } } } watchdog_fd = safe_close(watchdog_fd); }