sched/signal: Add support for disabling all signal functions

Signals in NuttX serve two primary purposes:

      1. Synchronization and wake-up:
        Signals can be used to block threads on specific signal sets and later
        wake them up by delivering the corresponding signals to those threads.

      2. Asynchronous notification:
        Signals can also be used to install callback handlers for specific signals, allowing threads to
        asynchronously invoke those handlers when the signals are delivered.

    This change introduces the ability to  disable all signal functionality to reduce footprint for NuttX.

Signed-off-by: Chengdong Wang wangchengdong@lixiang.com

fs/procfs/fs_procfsproc.c

@@ -640,10 +640,11 @@ static ssize_t proc_status(FAR struct proc_file_s *procfile,
     }
 
   /* Show the signal mask. Note: sigset_t is uint32_t on NuttX. */
-
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   linesize = procfs_snprintf(procfile->line, STATUS_LINELEN,
                              "%-12s" SIGSET_FMT "\n",
                              "SigMask:", SIGSET_ELEM(&tcb->sigprocmask));
+#endif
   copysize = procfs_memcpy(procfile->line, linesize, buffer, remaining,
                            &offset);
 

fs/vfs/Kconfig

@@ -51,6 +51,7 @@ endif # TIMER_FD
 
 config SIGNAL_FD
 	bool "SignalFD"
+	depends on !DISABLE_ALL_SIGNALS
 	default n
 	---help---
 		Create a file descriptor for accepting signals

include/nuttx/sched.h

@@ -667,9 +667,11 @@ struct tcb_s
   sq_queue_t sigpendactionq;             /* List of pending signal actions  */
   sq_queue_t sigpostedq;                 /* List of posted signals          */
 #endif /* CONFIG_ENABLE_ALL_SIGNALS*/
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   sigset_t   sigprocmask;                /* Signals that are blocked        */
   sigset_t   sigwaitmask;                /* Waiting for pending signals     */
   siginfo_t  *sigunbinfo;                /* Signal info when task unblocked */
+#endif /* !CONFIG_DISABLE_ALL_SIGNALS */
 
   /* Robust mutex support ***************************************************/
 

include/sys/syscall_lookup.h

@@ -158,11 +158,13 @@ SYSCALL_LOOKUP(tgkill,                     3)
 SYSCALL_LOOKUP(sigaction,                  3)
 SYSCALL_LOOKUP(sigpending,                 1)
 #endif
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
 SYSCALL_LOOKUP(sigprocmask,                3)
 SYSCALL_LOOKUP(sigqueue,                   3)
 SYSCALL_LOOKUP(sigsuspend,                 1)
 SYSCALL_LOOKUP(sigtimedwait,               3)
 SYSCALL_LOOKUP(sigwaitinfo,                2)
+#endif
 SYSCALL_LOOKUP(clock_nanosleep,            4)
 
 /* The following are only defined if the system clock is enabled in the

libs/libc/libc.csv

@@ -269,11 +269,11 @@
 "setlogmask","syslog.h","","int","int"
 "setpriority","sys/resource.h","","int","int","id_t","int"
 "shutdown","sys/socket.h","defined(CONFIG_NET)","int","int","int"
-"sigaddset","signal.h","","int","FAR sigset_t *","int"
-"sigdelset","signal.h","","int","FAR sigset_t *","int"
-"sigemptyset","signal.h","","int","FAR sigset_t *"
-"sigfillset","signal.h","","int","FAR sigset_t *"
-"sigismember","signal.h","","int","FAR const sigset_t *","int"
+"sigaddset","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR sigset_t *","int"
+"sigdelset","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR sigset_t *","int"
+"sigemptyset","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR sigset_t *"
+"sigfillset","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR sigset_t *"
+"sigismember","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR const sigset_t *","int"
 "signal","signal.h","defined(CONFIG_ENABLE_ALL_SIGNALS)","_sa_handler_t","int","_sa_handler_t"
 "sleep","unistd.h","","unsigned int","unsigned int"
 "snprintf","stdio.h","","int","FAR char *","size_t","FAR const IPTR char *","..."

libs/libc/signal/CMakeLists.txt

@@ -20,25 +20,27 @@
 #
 # ##############################################################################
 
-set(SRCS
-    sig_addset.c
-    sig_delset.c
-    sig_emptyset.c
-    sig_fillset.c
-    sig_nandset.c
-    sig_andset.c
-    sig_orset.c
-    sig_xorset.c
-    sig_isemptyset.c
-    sig_killpg.c
-    sig_altstack.c
-    sig_hold.c
-    sig_ismember.c
-    sig_pause.c
-    sig_psignal.c
-    sig_raise.c
-    sig_relse.c
-    sig_wait.c)
+if(NOT CONFIG_DISABLE_ALL_SIGNALS)
+  set(SRCS
+      sig_addset.c
+      sig_delset.c
+      sig_emptyset.c
+      sig_fillset.c
+      sig_nandset.c
+      sig_andset.c
+      sig_orset.c
+      sig_xorset.c
+      sig_isemptyset.c
+      sig_killpg.c
+      sig_altstack.c
+      sig_hold.c
+      sig_ismember.c
+      sig_pause.c
+      sig_psignal.c
+      sig_raise.c
+      sig_relse.c
+      sig_wait.c)
+endif()
 
 if(CONFIG_ENABLE_ALL_SIGNALS)
   list(APPEND SRCS sig_ignore.c sig_interrupt.c sig_set.c sig_signal.c)

libs/libc/signal/Make.defs

@@ -22,11 +22,13 @@
 
 # Add the signal C files to the build
 
+ifneq ($(CONFIG_DISABLE_ALL_SIGNALS),y)
 CSRCS += sig_addset.c sig_delset.c sig_emptyset.c sig_fillset.c
 CSRCS += sig_nandset.c sig_andset.c sig_orset.c sig_xorset.c
 CSRCS += sig_isemptyset.c sig_killpg.c sig_altstack.c
 CSRCS += sig_hold.c sig_ismember.c sig_pause.c sig_psignal.c
 CSRCS += sig_raise.c sig_relse.c sig_wait.c
+endif
 
 ifeq ($(CONFIG_ENABLE_ALL_SIGNALS),y)
 CSRCS += sig_ignore.c sig_interrupt.c sig_set.c sig_signal.c

libs/libc/spawn/lib_psa_init.c

@@ -87,7 +87,9 @@ int posix_spawnattr_init(posix_spawnattr_t *attr)
 
   /* Empty signal mask */
 
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   sigemptyset(&attr->sigmask);
+#endif
 
 #ifdef CONFIG_SCHED_SPORADIC
   /* Sporadic scheduling parameters */

sched/Kconfig

@@ -1578,6 +1578,21 @@ config ENABLE_PARTIAL_SIGNALS
 		  - Applications using basic signals without fork/exec
 		  - Resource-constrained real-time systems
 
+config DISABLE_ALL_SIGNALS
+	bool "Disable all signal support"
+	select DISABLE_MQUEUE_NOTIFICATION
+	---help---
+		Disable all signal-related functionality, including signal
+		handling, thread cancellation, timers, and process-related
+		notifications.
+
+		This option provides the smallest footprint and maximum
+		resource savings.
+
+		Typical use cases:
+		  - Hard real-time or safety-critical systems
+		  - Applications that do not use POSIX signals or timers
+
 endchoice
 
 config SIG_PREALLOC_ACTIONS

sched/group/CMakeLists.txt

@@ -27,8 +27,11 @@ set(SRCS
     group_setupidlefiles.c
     group_setuptaskfiles.c
     group_foreachchild.c
-    group_killchildren.c
-    group_signal.c)
+    group_killchildren.c)
+
+if(NOT CONFIG_DISABLE_ALL_SIGNALS)
+  list(APPEND SRCS group_signal.c)
+endif()
 
 if(CONFIG_SCHED_HAVE_PARENT)
   if(CONFIG_SCHED_CHILD_STATUS)

sched/group/Make.defs

@@ -22,7 +22,11 @@
 
 CSRCS += group_create.c group_join.c group_leave.c
 CSRCS += group_setupidlefiles.c group_setuptaskfiles.c
-CSRCS += group_foreachchild.c group_killchildren.c group_signal.c
+CSRCS += group_foreachchild.c group_killchildren.c
+
+ifneq ($(CONFIG_DISABLE_ALL_SIGNALS),y)
+CSRCS += group_signal.c
+endif
 
 ifeq ($(CONFIG_SCHED_HAVE_PARENT),y)
 ifeq ($(CONFIG_SCHED_CHILD_STATUS),y)

sched/misc/assert.c

@@ -405,7 +405,9 @@ static void dump_task(FAR struct tcb_s *tcb, FAR void *arg)
 #endif
          " %3d %-8s %-7s %-3c"
          " %-18s"
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
          " " SIGSET_FMT
+#endif
          " %p"
          "   %7zu"
 #ifdef CONFIG_STACK_COLORATION
@@ -427,7 +429,9 @@ static void dump_task(FAR struct tcb_s *tcb, FAR void *arg)
                         >> TCB_FLAG_TTYPE_SHIFT]
          , tcb->flags & TCB_FLAG_EXIT_PROCESSING ? 'P' : '-'
          , state
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
          , SIGSET_ELEM(&tcb->sigprocmask)
+#endif
          , tcb->stack_base_ptr
          , tcb->adj_stack_size
 #ifdef CONFIG_STACK_COLORATION

sched/pthread/pthread_exit.c

@@ -65,7 +65,9 @@
 void nx_pthread_exit(FAR void *exit_value)
 {
   FAR struct tcb_s *tcb = this_task();
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   sigset_t set;
+#endif
   int status;
 
   sinfo("exit_value=%p\n", exit_value);
@@ -76,8 +78,10 @@ void nx_pthread_exit(FAR void *exit_value)
    * are performing the JOIN handshake.
    */
 
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   sigfillset(&set);
   nxsig_procmask(SIG_SETMASK, &set, NULL);
+#endif
 
   /* Complete pending join operations */
 

sched/signal/CMakeLists.txt

@@ -20,23 +20,25 @@
 #
 # ##############################################################################
 
-set(SRCS
-    sig_procmask.c
-    sig_suspend.c
-    sig_kill.c
-    sig_tgkill.c
-    sig_queue.c
-    sig_waitinfo.c
-    sig_timedwait.c
-    sig_lowest.c
-    sig_notification.c
-    sig_dispatch.c
-    sig_pause.c
-    sig_nanosleep.c
-    sig_usleep.c
-    sig_sleep.c
-    sig_ppoll.c
-    sig_pselect.c)
+if(NOT CONFIG_DISABLE_ALL_SIGNALS)
+  set(SRCS
+      sig_procmask.c
+      sig_suspend.c
+      sig_kill.c
+      sig_tgkill.c
+      sig_queue.c
+      sig_waitinfo.c
+      sig_timedwait.c
+      sig_lowest.c
+      sig_notification.c
+      sig_dispatch.c
+      sig_pause.c
+      sig_nanosleep.c
+      sig_usleep.c
+      sig_sleep.c
+      sig_ppoll.c
+      sig_pselect.c)
+endif()
 
 if(CONFIG_ENABLE_ALL_SIGNALS)
   list(

sched/signal/Make.defs

@@ -19,11 +19,12 @@
 # under the License.
 #
 ############################################################################
-
+ifneq ($(CONFIG_DISABLE_ALL_SIGNALS),y)
 CSRCS += sig_dispatch.c sig_kill.c sig_lowest.c sig_nanosleep.c
 CSRCS += sig_notification.c sig_pause.c sig_ppoll.c sig_procmask.c
 CSRCS += sig_pselect.c sig_queue.c sig_sleep.c sig_suspend.c sig_tgkill.c
 CSRCS += sig_timedwait.c sig_usleep.c sig_waitinfo.c
+endif
 
 ifeq ($(CONFIG_ENABLE_ALL_SIGNALS),y)
 CSRCS += sig_action.c sig_allocpendingsigaction.c sig_cleanup.c sig_deliver.c

sched/task/task_restart.c

@@ -122,7 +122,9 @@ static void nxtask_reset_task(FAR struct tcb_s *tcb, bool remove)
 #ifdef CONFIG_ENABLE_ALL_SIGNALS
   nxsig_cleanup(tcb);             /* Deallocate Signal lists */
 #endif
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   sigemptyset(&tcb->sigprocmask); /* Reset sigprocmask */
+#endif
 
   /* Reset the current task priority  */
 

sched/task/task_setup.c

@@ -461,7 +461,9 @@ static int nxthread_setup_scheduler(FAR struct tcb_s *tcb, int priority,
        * inherit the signal mask of the parent thread.
        */
 
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
       tcb->sigprocmask = rtcb->sigprocmask;
+#endif
 
       /* Initialize the task state.  It does not get a valid state
        * until it is activated.

sched/task/task_spawnparms.c

@@ -157,6 +157,7 @@ int spawn_execattrs(pid_t pid, FAR const posix_spawnattr_t *attr)
 
   /* Firstly, set the signal mask if requested to do so */
 
+#ifndef CONFIG_DISABLE_ALL_SIGNALS
   if ((attr->flags & POSIX_SPAWN_SETSIGMASK) != 0)
     {
       FAR struct tcb_s *tcb = nxsched_get_tcb(pid);
@@ -165,6 +166,7 @@ int spawn_execattrs(pid_t pid, FAR const posix_spawnattr_t *attr)
           tcb->sigprocmask = attr->sigmask;
         }
     }
+#endif
 
   /* If we are only setting the priority, then call sched_setparm()
    * to set the priority of the of the new task.

syscall/syscall.csv

@@ -105,10 +105,10 @@
 "pipe2","unistd.h","defined(CONFIG_PIPES) && CONFIG_DEV_PIPE_SIZE > 0","int","int [2]|FAR int *","int"
 "poll","poll.h","","int","FAR struct pollfd *","nfds_t","int"
 "posix_spawn","spawn.h","!defined(CONFIG_BINFMT_DISABLE) && defined(CONFIG_LIBC_EXECFUNCS)","int","FAR pid_t *","FAR const char *","FAR const posix_spawn_file_actions_t *","FAR const posix_spawnattr_t *","FAR char * const []|FAR char * const *","FAR char * const []|FAR char * const *"
-"ppoll","poll.h","","int","FAR struct pollfd *","nfds_t","FAR const struct timespec *","FAR const sigset_t *"
+"ppoll","poll.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR struct pollfd *","nfds_t","FAR const struct timespec *","FAR const sigset_t *"
 "prctl","sys/prctl.h","","int","int","...","uintptr_t","uintptr_t"
 "pread","unistd.h","","ssize_t","int","FAR void *","size_t","off_t"
-"pselect","sys/select.h","","int","int","FAR fd_set *","FAR fd_set *","FAR fd_set *","FAR const struct timespec *","FAR const sigset_t *"
+"pselect","sys/select.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","int","FAR fd_set *","FAR fd_set *","FAR fd_set *","FAR const struct timespec *","FAR const sigset_t *"
 "pthread_cancel","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","pthread_t"
 "pthread_cond_broadcast","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","FAR pthread_cond_t *"
 "pthread_cond_clockwait","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","FAR pthread_cond_t *","FAR pthread_mutex_t *","clockid_t","FAR const struct timespec *"
@@ -177,11 +177,11 @@
 "signal","signal.h","defined(CONFIG_ENABLE_ALL_SIGNALS)","_sa_handler_t","int","_sa_handler_t"
 "signalfd","sys/signalfd.h","defined(CONFIG_SIGNAL_FD)","int","int","FAR const sigset_t *","int"
 "sigpending","signal.h","defined(CONFIG_ENABLE_ALL_SIGNALS)","int","FAR sigset_t *"
-"sigprocmask","signal.h","","int","int","FAR const sigset_t *","FAR sigset_t *"
-"sigqueue","signal.h","","int","int","int","union sigval|FAR void *|sival_ptr"
-"sigsuspend","signal.h","","int","FAR const sigset_t *"
-"sigtimedwait","signal.h","","int","FAR const sigset_t *","FAR struct siginfo *","FAR const struct timespec *"
-"sigwaitinfo","signal.h","","int","FAR const sigset_t *","FAR struct siginfo *"
+"sigprocmask","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","int","FAR const sigset_t *","FAR sigset_t *"
+"sigqueue","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","int","int","union sigval|FAR void *|sival_ptr"
+"sigsuspend","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR const sigset_t *"
+"sigtimedwait","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR const sigset_t *","FAR struct siginfo *","FAR const struct timespec *"
+"sigwaitinfo","signal.h","!defined(CONFIG_DISABLE_ALL_SIGNALS)","int","FAR const sigset_t *","FAR struct siginfo *"
 "socket","sys/socket.h","defined(CONFIG_NET)","int","int","int","int"
 "socketpair","sys/socket.h","defined(CONFIG_NET)","int","int","int","int","int [2]|FAR int *"
 "stat","sys/stat.h","","int","FAR const char *","FAR struct stat *"