libc: rudimentary support for SIGALRM

This patch enables basic use cases of the POSIX 'alarm' function, which
schedules the delivery of a SIGALRM signal after a specified amount of
seconds.

Issue #5337

repos/gems/run/depot_autopilot.run

@@ -681,6 +681,7 @@ set default_test_pkgs {
 	test-libc_fifo_pipe
 	test-libc_fork
 	test-libc_getenv
+	test-libc_alarm
 	test-libc_pipe
 	test-libc_vfs
 	test-libc_vfs_audit

repos/libports/lib/mk/libc.mk

@@ -12,7 +12,7 @@ LIBS  += base vfs
 # Back end
 #
 SRC_CC = atexit.cc dummies.cc rlimit.cc sysctl.cc \
-         issetugid.cc errno.cc gai_strerror.cc time.cc \
+         issetugid.cc errno.cc gai_strerror.cc time.cc alarm.cc \
          malloc.cc progname.cc fd_alloc.cc file_operations.cc \
          plugin.cc plugin_registry.cc select.cc exit.cc environ.cc sleep.cc \
          pread_pwrite.cc readv_writev.cc poll.cc \

repos/libports/recipes/pkg/test-libc_alarm/README

@@ -0,0 +1 @@
+Libc alarm() test.

repos/libports/recipes/pkg/test-libc_alarm/archives

@@ -0,0 +1,5 @@
+_/src/init
+_/src/test-libc_alarm
+_/src/libc
+_/src/posix
+_/src/vfs

repos/libports/recipes/pkg/test-libc_alarm/hash

@@ -0,0 +1 @@
+2024-08-30 ca6e62da4a88ade9338dea365858d83409150c78

repos/libports/recipes/pkg/test-libc_alarm/runtime

@@ -0,0 +1,22 @@
+<runtime ram="3M" caps="200" binary="test-libc_alarm">
+
+	<requires> <timer/> </requires>
+
+	<fail after_seconds="13"/>
+	<succeed>triggered_alarms=3</succeed>
+
+	<content>
+		<rom label="ld.lib.so"/>
+		<rom label="test-libc_alarm"/>
+		<rom label="libc.lib.so"/>
+		<rom label="libm.lib.so"/>
+		<rom label="vfs.lib.so"/>
+		<rom label="posix.lib.so"/>
+	</content>
+
+	<config>
+		<vfs> <dir name="dev"> <log/> </dir> </vfs>
+		<libc stdout="/dev/log" stderr="/dev/log"/>
+		<arg value="test-libc_alarm"/>
+	</config>
+</runtime>

repos/libports/recipes/src/test-libc_alarm/content.mk

@@ -0,0 +1,2 @@
+SRC_DIR := src/test/libc_alarm
+include $(GENODE_DIR)/repos/base/recipes/src/content.inc

repos/libports/recipes/src/test-libc_alarm/hash

@@ -0,0 +1 @@
+2024-08-30 49e1a2b9ef6049be7c0fcee964324fbda54cbed7

repos/libports/recipes/src/test-libc_alarm/used_apis

@@ -0,0 +1,2 @@
+libc
+posix

repos/libports/src/lib/libc/alarm.cc

@@ -0,0 +1,118 @@
+/*
+ * \brief  Libc interval timer
+ * \author Norman Feske
+ * \date   2024-08-00
+ */
+
+/*
+ * Copyright (C) 2024 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+/* libc includes */
+#include <sys/time.h>
+
+/* libc-internal includes */
+#include <internal/signal.h>
+#include <internal/timer.h>
+#include <internal/init.h>
+#include <internal/errno.h>
+
+
+static Libc::Timer_accessor *_timer_accessor_ptr;
+static Libc::Signal         *_signal_ptr;
+
+void Libc::init_alarm(Timer_accessor &timer_accessor, Signal &signal)
+{
+	_timer_accessor_ptr = &timer_accessor;
+	_signal_ptr         = &signal;
+}
+
+
+namespace Libc { struct Itimer_real; }
+
+
+struct Libc::Itimer_real : Noncopyable
+{
+	struct Handler : Timeout_handler
+	{
+		Signal &_signal;
+
+		virtual void handle_timeout() override { _signal.charge(SIGALRM); }
+
+		Handler(Signal &signal) : _signal(signal) { }
+
+	} _handler;
+
+	Timer_accessor &_timer_accessor;
+
+	Constructible<Timeout> _timeout { };
+
+	void arm_or_disarm(timeval tv)
+	{
+		Libc::uint64_t const ms = tv.tv_sec*1000 + tv.tv_usec/1000;
+
+		if (ms) {
+			_timeout.construct(_timer_accessor, _handler);
+			_timeout->start(ms);
+		} else {
+			_timeout.destruct();
+		}
+	}
+
+	timeval current()
+	{
+		if (!_timeout.constructed())
+			return { };
+
+		Libc::uint64_t const ms = _timeout->duration_left();
+
+		return { .tv_sec  = long(ms/1000),
+		         .tv_usec = long((ms % 1000)*1000) };
+	}
+
+	Itimer_real(Timer_accessor &timer_accessor, Signal &signal)
+	:
+		_handler(signal), _timer_accessor(timer_accessor)
+	{ }
+};
+
+
+using namespace Libc;
+
+
+static Itimer_real &itimer_real()
+{
+	struct Missing_call_of_init_alarm : Exception { };
+	if (!_timer_accessor_ptr || !_signal_ptr)
+		throw Missing_call_of_init_alarm();
+
+	static Itimer_real itimer { *_timer_accessor_ptr, *_signal_ptr };
+	return itimer;
+}
+
+
+extern "C" int setitimer(int which, const itimerval *new_value, itimerval *old_value)
+{
+	if (which != ITIMER_REAL) {
+		warning("setitimer: timer %d unsupported");
+		return Errno(EINVAL);
+	}
+
+	if (!new_value)
+		return Errno(EFAULT);
+
+	if (new_value->it_interval.tv_sec || new_value->it_interval.tv_usec)
+		warning("setitimer: argument 'new_value->it_interval' not handled");
+
+	if (old_value) {
+		old_value->it_interval = { };
+		old_value->it_value    = itimer_real().current();
+	}
+
+	itimer_real().arm_or_disarm(new_value->it_value);
+
+	return 0;
+}

repos/libports/src/lib/libc/dummies.cc

@@ -141,7 +141,6 @@ DUMMY(int   , -1, seteuid, (uid_t))
 DUMMY(int   , -1, setgid, (gid_t))
 DUMMY(int   , -1, setuid, (uid_t))
 DUMMY(int   , -1, setgroups, (int, const gid_t *))
-DUMMY(int   , -1, setitimer, (int, const itimerval *, itimerval *))
 DUMMY(int   , -1, setpgid, (pid_t, pid_t))
 DUMMY(int   , -1, setpriority, (int, int, int))
 DUMMY(int   , -1, setregid, (gid_t, gid_t))

repos/libports/src/lib/libc/internal/init.h

@@ -108,6 +108,7 @@ namespace Libc {
 	 */
 	void init_sleep(Monitor &);
 	void init_time(Current_time &, Current_real_time &);
+	void init_alarm(Timer_accessor &, Signal &);
 
 	/**
 	 * Socket fs

repos/libports/src/lib/libc/internal/signal.h

@@ -16,10 +16,13 @@
 
 /* Genode includes */
 #include <util/noncopyable.h>
+#include <util/reconstructible.h>
 #include <base/registry.h>
+#include <base/thread.h>
 
 /* libc includes */
 #include <signal.h>
+#include <stdlib.h>
 
 /* libc-internal includes */
 #include <internal/call_func.h>

repos/libports/src/lib/libc/kernel.cc

@@ -508,6 +508,7 @@ Libc::Kernel::Kernel(Genode::Env &env, Genode::Allocator &heap)
 	init_vfs_plugin(*this, _env.rm());
 	init_file_operations(*this, _libc_env);
 	init_time(*this, *this);
+	init_alarm(_timer_accessor, _signal);
 	init_poll(_signal, *this);
 	init_select(*this);
 	init_socket_fs(*this, *this);

repos/libports/src/test/libc_alarm/main.c

@@ -0,0 +1,52 @@
+/*
+ * \brief  Libc alarm test
+ * \author Norman Feske
+ * \date   2024-08-30
+ */
+
+/*
+ * Copyright (C) 2024 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#include <signal.h>
+#include <unistd.h>
+#include <stdio.h>
+
+static unsigned triggered_alarms;
+
+static void sigalarm_handler(int)
+{
+	triggered_alarms++;
+}
+
+int main(int, char **)
+{
+	static struct sigaction sa;
+	sa.sa_handler = sigalarm_handler;
+
+	int ret = sigaction(SIGALRM, &sa, NULL);
+	if (ret < 0) {
+		printf("sigaction unexpectedly returned %d\n", ret);
+		return 1;
+	}
+
+	signal(SIGALRM, sigalarm_handler);
+
+	unsigned observed_alarms = 0;
+
+	alarm(2);
+
+	while (observed_alarms != 3) {
+		sleep(1);
+		printf("triggered_alarms=%u\n", triggered_alarms);
+
+		if (triggered_alarms != observed_alarms) {
+			observed_alarms = triggered_alarms;
+			alarm(2);
+		}
+	}
+	return 0;
+}

repos/libports/src/test/libc_alarm/target.mk

@@ -0,0 +1,3 @@
+TARGET = test-libc_alarm
+SRC_C  = main.c
+LIBS   = posix