Compléments

Signaux

Numéro	Nom	Description
1	SIGHUP	Instruction (HANG UP) - Fin de session
2	SIGINT	Interruption
3	SIGQUIT	Instruction (QUIT)
4	SIGILL	Instruction illégale
5	SIGTRAP	Trace trap
6	SIGABRT	(ANSI) Instruction (ABORT)
6	SIGIOT	(BSD) IOT Trap
7	SIGBUS	Bus error
8	SIGFPE	Floating-point exception - Exception arithmétique
9	SIGKILL	Instruction (KILL) - termine le processus immédiatement
10	SIGUSR1	Signal utilisateur 1
11	SIGSEGV	Violation de mémoire
12	SIGUSR2	Signal utilisateur 2
13	SIGPIPE	Broken PIPE - Erreur PIPE sans lecteur
14	SIGALRM	Alarme horloge
15	SIGTERM	Signal de terminaison
16	SIGSTKFLT	Stack Fault
17	SIGCHLD ou SIGCLD	modification du statut d’un processus fils
18	SIGCONT	Demande de reprise du processus
19	SIGSTOP	Demande de suspension imbloquable
20	SIGTSTP	Demande de suspension depuis le clavier
21	SIGTTIN	lecture terminal en arrière-plan
22	SIGTTOU	écriture terminal en arrière-plan
23	SIGURG	évènement urgent sur socket
24	SIGXCPU	temps maximum CPU écoulé
25	SIGXFSZ	taille maximale de fichier atteinte
26	SIGVTALRM	alarme horloge virtuelle
27	SIGPROF	Profiling alarm clock
28	SIGWINCH	changement de taille de fenêtre
29	SIGPOLL	(System V) occurence d’un évènement attendu
29	SIGIO	(BSD) I/O possible actuellement
30	SIGPWR	Power failure restart
31	SIGSYS	Erreur d’appel système

Daemon (sans fork)

main.c

/**
 * Copyright 2015 University of Applied Sciences Western Switzerland / Fribourg
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Project: HEIA-FR / Embedded Systems Laboratory
 *
 * Abstract: Process and daemon samples
 *
 * Purpose: This module implements a simple application to be launched from
 *          /etc/inttab.
 *          --> this application requires /opt/daemon as root directory
 *
 * Autĥor:  Daniel Gachet
 * Date:    17.11.2015
 */
#define _XOPEN_SOURCE 600
#define _DEFAULT_SOURCE

#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <syslog.h>
#include <unistd.h>

#define UNUSED(x) (void)(x)

static int signal_catched = 0;

static void catch_signal(int signal)
{
    syslog(LOG_INFO, "signal=%d catched\n", signal);
    signal_catched++;
}

int main(int argc, char* argv[])
{
    UNUSED(argc);
    UNUSED(argv);

    // daemon's steps 1 to 3 skipped

    // 4. capture all required signals
    struct sigaction act = {
        .sa_handler = catch_signal,
    };
    sigaction(SIGHUP, &act, NULL);   //  1 - hangup
    sigaction(SIGINT, &act, NULL);   //  2 - terminal interrupt
    sigaction(SIGQUIT, &act, NULL);  //  3 - terminal quit
    sigaction(SIGABRT, &act, NULL);  //  6 - abort
    sigaction(SIGTERM, &act, NULL);  // 15 - termination
    sigaction(SIGTSTP, &act, NULL);  // 19 - terminal stop signal

    // 5. update file mode creation mask
    umask(0027);

    // 6. change working directory to appropriate place
    if (chdir("/opt") == -1) {
        syslog(LOG_ERR, "ERROR while changing to working directory");
        exit(1);
    }

    // 7. close all open file descriptors
    for (int fd = sysconf(_SC_OPEN_MAX); fd >= 0; fd--) {
        close(fd);
    }

    // 8. redirect stdin, stdout and stderr to /dev/null
    if (open("/dev/null", O_RDWR) != STDIN_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stdin");
        exit(1);
    }
    if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stdout");
        exit(1);
    }
    if (dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stderr");
        exit(1);
    }

    // 9. option: open syslog for message logging
    openlog(NULL, LOG_NDELAY | LOG_PID, LOG_DAEMON);
    syslog(LOG_INFO, "Daemon has started...");

    // 10. option: get effective user and group id for appropriate's one
    struct passwd* pwd = getpwnam("daemon");
    if (pwd == 0) {
        syslog(LOG_ERR, "ERROR while reading daemon password file entry");
        exit(1);
    }

    // 11. option: change root directory
    if (chroot(".") == -1) {
        syslog(LOG_ERR, "ERROR while changing to new root directory");
        exit(1);
    }

    // 12. option: change effective user and group id for appropriate's one
    if (setegid(pwd->pw_gid) == -1) {
        syslog(LOG_ERR, "ERROR while setting new effective group id");
        exit(1);
    }
    if (seteuid(pwd->pw_uid) == -1) {
        syslog(LOG_ERR, "ERROR while setting new effective user id");
        exit(1);
    }

    // 13. implement daemon body...
    int t = 30;
    do {
        t = sleep(t);
    } while (t > 0);

    syslog(LOG_INFO,
           "daemon stopped. Number of signals catched=%d\n",
           signal_catched);
    closelog();

    return 0;
}

Makefile

EXE=appl
SRCS=$(wildcard *.c) 

CFLAGS=-Wall -Wextra -g -c -O0 -MD -std=gnu11 

TOOLCHAIN_PATH=/buildroot/output/host/usr/bin/
TOOLCHAIN=$(TOOLCHAIN_PATH)aarch64-linux-
CFLAGS+=-mcpu=cortex-a53 -funwind-tables
##CFLAGS+=-O2 -fno-omit-frame-pointer
OBJDIR=.obj/nano
EXEC=$(EXE)

CC=$(TOOLCHAIN)gcc
LD=$(TOOLCHAIN)gcc
AR=$(TOOLCHAIN)ar
STRIP=$(TOOLCHAIN)strip

OBJDIR=.obj/$(target)
OBJS= $(addprefix $(OBJDIR)/, $(SRCS:.c=.o))

$(OBJDIR)/%o: %c
    $(CC) $(CFLAGS) $< -o $@

all: $(OBJDIR)/ $(EXEC)
    echo $(EXEC)
    echo $(SRCS)

$(EXEC): $(OBJS) $(LINKER_SCRIPT)
    $(LD) $(OBJS) $(LDFLAGS) -o $@

$(OBJDIR)/:
    mkdir -p $(OBJDIR)

clean:
    rm -Rf $(OBJDIR) $(EXEC) $(EXEC)_s *~

clean_all: clean
    rm -Rf .obj $(EXE) $(EXE)_s $(EXE)_a $(EXE)_a_s $(EXE)_h $(EXE)_h_s

-include $(OBJS:.o=.d)

.PHONY: all clean clean_all

Daemon (complet, avec fork)

daemon.c

/**
 * Copyright 2015 University of Applied Sciences Western Switzerland / Fribourg
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Project: HEIA-FR / Embedded Systems Laboratory
 *
 * Abstract: Process and daemon samples
 *
 * Purpose: This module implements a simple daemon to be launched
 *          from a /etc/init.d/S??_* script
 *          -> this application requires /opt/daemon as root directory
 *
 * Autĥor:  Daniel Gachet
 * Date:    17.11.2015
 */
#define _XOPEN_SOURCE 600
#define _DEFAULT_SOURCE

#include <fcntl.h>
#include <grp.h>
#include <pwd.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>

#define UNUSED(x) (void)(x)

static int signal_catched = 0;

static void catch_signal(int signal)
{
    syslog(LOG_INFO, "signal=%d catched\n", signal);
    signal_catched++;
}

static void fork_process()
{
    pid_t pid = fork();
    switch (pid) {
        case 0:
            break;  // child process has been created
        case -1:
            syslog(LOG_ERR, "ERROR while forking");
            exit(1);
            break;
        default:
            exit(0);  // exit parent process with success
    }
}

int main(int argc, char* argv[])
{
    UNUSED(argc);
    UNUSED(argv);

    // 1. fork off the parent process
    fork_process();

    // 2. create new session
    if (setsid() == -1) {
        syslog(LOG_ERR, "ERROR while creating new session");
        exit(1);
    }

    // 3. fork again to get rid of session leading process
    fork_process();

    // 4. capture all required signals
    struct sigaction act = {
        .sa_handler = catch_signal,
    };
    sigaction(SIGHUP, &act, NULL);   //  1 - hangup
    sigaction(SIGINT, &act, NULL);   //  2 - terminal interrupt
    sigaction(SIGQUIT, &act, NULL);  //  3 - terminal quit
    sigaction(SIGABRT, &act, NULL);  //  6 - abort
    sigaction(SIGTERM, &act, NULL);  // 15 - termination
    sigaction(SIGTSTP, &act, NULL);  // 19 - terminal stop signal

    // 5. update file mode creation mask
    umask(0027);

    // 6. change working directory to appropriate place
    if (chdir("/opt") == -1) {
        syslog(LOG_ERR, "ERROR while changing to working directory");
        exit(1);
    }

    // 7. close all open file descriptors
    for (int fd = sysconf(_SC_OPEN_MAX); fd >= 0; fd--) {
        close(fd);
    }

    // 8. redirect stdin, stdout and stderr to /dev/null
    if (open("/dev/null", O_RDWR) != STDIN_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stdin");
        exit(1);
    }
    if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stdout");
        exit(1);
    }
    if (dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO) {
        syslog(LOG_ERR, "ERROR while opening '/dev/null' for stderr");
        exit(1);
    }

    // 9. option: open syslog for message logging
    openlog(NULL, LOG_NDELAY | LOG_PID, LOG_DAEMON);
    syslog(LOG_INFO, "Daemon has started...");

    // 10. option: get effective user and group id for appropriate's one
    struct passwd* pwd = getpwnam("daemon");
    if (pwd == 0) {
        syslog(LOG_ERR, "ERROR while reading daemon password file entry");
        exit(1);
    }

    // 11. option: change root directory
    if (chroot(".") == -1) {
        syslog(LOG_ERR, "ERROR while changing to new root directory");
        exit(1);
    }

    // 12. option: change effective user and group id for appropriate's one
    if (setegid(pwd->pw_gid) == -1) {
        syslog(LOG_ERR, "ERROR while setting new effective group id");
        exit(1);
    }
    if (seteuid(pwd->pw_uid) == -1) {
        syslog(LOG_ERR, "ERROR while setting new effective user id");
        exit(1);
    }

    // 13. implement daemon body...
    int t = 30;
    do {
        t = sleep(t);
    } while (t > 0);

    syslog(LOG_INFO,
           "daemon stopped. Number of signals catched=%d\n",
           signal_catched);
    closelog();

    return 0;
}

Makefile

EXE=daemon
SRCS=$(wildcard *.c) 

CFLAGS=-Wall -Wextra -g -c -O0 -MD -std=gnu11 

TOOLCHAIN_PATH=/buildroot/output/host/usr/bin/
TOOLCHAIN=$(TOOLCHAIN_PATH)aarch64-linux-
CFLAGS+=-mcpu=cortex-a53 -funwind-tables
##CFLAGS+=-O2 -fno-omit-frame-pointer
OBJDIR=.obj/nano
EXEC=$(EXE)

CC=$(TOOLCHAIN)gcc
LD=$(TOOLCHAIN)gcc
AR=$(TOOLCHAIN)ar
STRIP=$(TOOLCHAIN)strip

OBJDIR=.obj/$(target)
OBJS= $(addprefix $(OBJDIR)/, $(SRCS:.c=.o))

$(OBJDIR)/%o: %c
    $(CC) $(CFLAGS) $< -o $@

all: $(OBJDIR)/ $(EXEC)
    echo $(EXEC)
    echo $(SRCS)

$(EXEC): $(OBJS) $(LINKER_SCRIPT)
    $(LD) $(OBJS) $(LDFLAGS) -o $@

$(OBJDIR)/:
    mkdir -p $(OBJDIR)

clean:
    rm -Rf $(OBJDIR) $(EXEC) $(EXEC)_s *~

clean_all: clean
    rm -Rf .obj $(EXE) $(EXE)_s $(EXE)_a $(EXE)_a_s $(EXE)_h $(EXE)_h_s

-include $(OBJS:.o=.d)

.PHONY: all clean clean_all

Threads

main.c

/**
 * Copyright 2015 University of Applied Sciences Western Switzerland / Fribourg
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Project: HEIA-FR / Embedded Systems Laboratory
 *
 * Abstract: Multi-threading
 *
 * Purpose: This module implements a simple multi-threading demo progam
 *
 * Autĥor   Daniel Gachet / Jean-Roland Schuler
 * Date:    17.11.2015
 */

#include <pthread.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>

// ----------------------------------------------------------------------------
// Macros and constants
// ----------------------------------------------------------------------------

#define ARRAY_OF(x) (sizeof(x) / sizeof(x[0]))

// ----------------------------------------------------------------------------
// Global variables
// ----------------------------------------------------------------------------

static pthread_t thread_id[3];
static bool is_running = true;

// ----------------------------------------------------------------------------
// Local threads
// ----------------------------------------int------------------------------------

void cleaner(void* p) { printf("%s: thread end\n", (char*)p); }

// ----------------------------------------------------------------------------

void* thread_1(void* arg)
{
    pthread_cleanup_push(&cleaner, arg);

    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);

    while (is_running) {
        printf(
            "%s pid=%d, tid=%ld\n", (char*)arg, getpid(), syscall(SYS_gettid));
        sleep(2);
    }

    pthread_cleanup_pop(1);
    pthread_exit((void*)1);
    return (void*)0;
}

// ----------------------------------------------------------------------------

void* thread_2(void* arg)
{
    pthread_cleanup_push(cleaner, arg);

    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);

    while (is_running) {
        printf(
            "%s pid=%d, tid=%ld\n", (char*)arg, getpid(), syscall(SYS_gettid));
        sleep(2);
    }

    pthread_cleanup_pop(0);
    pthread_exit(0);
    return (void*)2;
}

// ----------------------------------------------------------------------------

void* thread_3(void* arg)
{
    while (is_running) {
        printf(
            "%s pid=%d, tid=%ld\n", (char*)arg, getpid(), syscall(SYS_gettid));
        sleep(2);
    }
    return (void*)3;
}

// ----------------------------------------------------------------------------
// Local methods
// ----------------------------------------------------------------------------

static void catch_signal(int signal)
{
    printf("signal = %d\n", signal);
    pthread_cancel(thread_id[0]);
    is_running = 0;
}

// ----------------------------------------------------------------------------

static void install_catch_signal()
{
    struct sigaction act = {
        .sa_handler = catch_signal,
    };
    sigemptyset(&act.sa_mask);
    sigaction(SIGINT, &act, 0);
    sigaction(SIGTSTP, &act, 0);
    sigaction(SIGTERM, &act, 0);
    sigaction(SIGABRT, &act, 0);
}

// ----------------------------------------------------------------------------
// Main program
// ----------------------------------------------------------------------------

int main(void)
{
    install_catch_signal();

    printf("Create threads... (pid=%d)\n", getpid());
    pthread_create(&thread_id[0], NULL, thread_1, "thread_1");
    pthread_create(&thread_id[1], NULL, thread_2, "thread_2");
    pthread_create(&thread_id[2], NULL, thread_3, "thread_3");

    printf("Wait until threads finished...\n");
    printf("Type return to exit all threads\n");
    getchar();
    is_running = false;
    for (int i = ARRAY_OF(thread_id) - 1; i >= 0; i--) {
        void* return_msg;
        pthread_join(thread_id[i], &return_msg);
        printf("thread_%d terminated with %p\n", i + 1, return_msg);
    }

    printf("Program stops...\n");

    return 0;
}

Makefile

EXE=threads
SRCS=$(wildcard *.c) 

CFLAGS=-Wall -Wextra -g -c -O0 -MD -std=gnu11 
LDFLAGS+=-lpthread

TOOLCHAIN_PATH=~/workspace/nano/buildroot/output/host/usr/bin/
TOOLCHAIN=$(TOOLCHAIN_PATH)aarch64-linux-
CFLAGS+=-mcpu=cortex-a53 -funwind-tables
##CFLAGS+=-O2 -fno-omit-frame-pointer
OBJDIR=.obj/nano
EXEC=$(EXE)

CC=$(TOOLCHAIN)gcc
LD=$(TOOLCHAIN)gcc
AR=$(TOOLCHAIN)ar
STRIP=$(TOOLCHAIN)strip

OBJDIR=.obj/$(target)
OBJS= $(addprefix $(OBJDIR)/, $(SRCS:.c=.o))

$(OBJDIR)/%o: %c
    $(CC) $(CFLAGS) $< -o $@

all: $(OBJDIR)/ $(EXEC)

$(EXEC): $(OBJS) $(LINKER_SCRIPT)
    $(LD) $(OBJS) $(LDFLAGS) -o $@

$(OBJDIR)/:
    mkdir -p $(OBJDIR)

clean:
    rm -Rf $(OBJDIR) $(EXEC) $(EXEC)_s *~

clean_all: clean
    rm -Rf .obj $(EXE) $(EXE)_s $(EXE)_a $(EXE)_a_s $(EXE)_h $(EXE)_h_s

-include $(OBJS:.o=.d)

.PHONY: all clean clean_all

Berkeley Sockets

Protocole orienté connexion (TCP)

Appels systèmes "Socket" pour un protocole orienté connexion (TCP)

Protocole sans connexion (UDP)

Appels systèmes "Socket" pour un protocole sans connexion (UDP)