使用BeagleBone Black读取两个串行端口时出现分段错误错误

Question

I am getting Segmentation fault error while reading two diffentent serial communication line with using Debian GNU/Linux 7.4 on Beaglebone Black. One of them is CAN-BUS data. I am using Waveshares RS485/CAN CAPE module for this with using can-utils package. " https://github.com/linux-can/can-utils/blob/master/candump.c "

CAN log file

And the other one is UART data by a GPS module called uBlox GY-NEO6MV2 module. For the GPS I have this code which works perfectly;

    #include <stdio.h>
    #include <fcntl.h>   /* File Control Definitions           */
    #include <termios.h> /* POSIX Terminal Control Definitions */
    #include <unistd.h>  /* UNIX Standard Definitions      */ 
    #include <errno.h>   /* ERROR Number Definitions           */
    #include <string.h>  /* Array to String                   */ 

void main(void){
        int fd;/*File Descriptor*/


    /*------------------------------- Opening the Serial Port -------------------------------*/

    /* Change /dev/ttyUSB0 to the one corresponding to your system */
    while(1){
        fd = open("/dev/ttyO2",O_RDWR | O_NOCTTY);  /* ttyUSB0 is the FT232 based USB2SERIAL Converter   */
                            /* O_RDWR   - Read/Write access to serial port       */
                            /* O_NOCTTY - No terminal will control the process   */
                            /* Open in blocking mode,read will wait              */



        if(fd == -1)                        /* Error Checking */
               printf("\n  Error! in Opening ttyO2  ");
        else
               printf("\n  ttyO2 Opened Successfully ");


        /*---------- Setting the Attributes of the serial port using termios structure --------- */

        struct termios SerialPortSettings;  /* Create the structure                          */

        tcgetattr(fd, &SerialPortSettings); /* Get the current attributes of the Serial port */

        /* Setting the Baud rate */
        cfsetispeed(&SerialPortSettings,B9600); /* Set Read  Speed as 9600                       */
        cfsetospeed(&SerialPortSettings,B9600); /* Set Write Speed as 9600                       */

        /* 8N1 Mode */
        SerialPortSettings.c_cflag &= ~PARENB;   /* Disables the Parity Enable bit(PARENB),So No Parity   */
        SerialPortSettings.c_cflag &= ~CSTOPB;   /* CSTOPB = 2 Stop bits,here it is cleared so 1 Stop bit */
        SerialPortSettings.c_cflag &= ~CSIZE;    /* Clears the mask for setting the data size             */
        SerialPortSettings.c_cflag |=  CS8;      /* Set the data bits = 8                                 */

        SerialPortSettings.c_cflag &= ~CRTSCTS;       /* No Hardware flow Control                         */
        SerialPortSettings.c_cflag |= CREAD | CLOCAL; /* Enable receiver,Ignore Modem Control lines       */ 


        SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY);          /* Disable XON/XOFF flow control both i/p and o/p */
        SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);  /* Non Cannonical mode                            */

        SerialPortSettings.c_oflag &= ~OPOST;/*No Output Processing*/

        /* Setting Time outs */
        SerialPortSettings.c_cc[VMIN] = 42; /* Read at least 51 characters */
        SerialPortSettings.c_cc[VTIME] = 0; /* Wait indefinetly   */


        if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0) /* Set the attributes to the termios structure*/
            printf("\n  ERROR ! in Setting attributes");
        else
            printf("\n  BaudRate = 9600 \n  StopBits = 1 \n  Parity   = none  \n\n");

        /*------------------------------- Read data from serial port -----------------------------*/

        tcflush(fd, TCIFLUSH);   /* Discards old data in the rx buffer            */

        char read_buffer[42];   /* Buffer to store the data received              */
        int  bytes_read = 0;    /* Number of bytes read by the read() system call */
        int ia = 0; int a;
        int test = 0;
        char new_read[38];
        char curr_read[33];
        a = 0;
        do{
            bytes_read = read(fd,&read_buffer,42); /* Read the data                   */

            if(read_buffer[0] == '$')
                if(read_buffer[1] == 'G')
                    if(read_buffer[2] == 'P')
                        if(read_buffer[3] == 'G')
                            if(read_buffer[4] == 'G'){
                                for(ia=7;ia<bytes_read;ia++){    /*printing only the received characters*/
                                    new_read[a] = read_buffer[ia];
                                    printf("%c",read_buffer[ia]);
                                    a = a+1;
                                    test = 1;
                                }
                                strcpy(curr_read, new_read);
                                printf("\n%s \n", curr_read);
                            }
                            else
                                test = 0;
                        else
                            test = 0;
                    else
                        test = 0;
                else
                    test = 0;
            else
                test = 0;
        }while(test == 0);
        close(fd); /* Close the serial port */
    }

}

And for the CAN logging I am using the code in the link above. What I try to achive is logging two data in to same log file. I modified the code above a little to get the datas only that I need; which is timestamp and location coordinates.

GPS edited data

GPS module gives data every second so I am triyng to get one data from GPS and attach it to the next 1000 CAN data then write in to a .log file then read a new value from GPS. GPS modules communication bitrate is 9600kbps and CAN bitrate is 125000 kbps. GPS is connected to UART2 pin, CAN to UART1. When I try to combine two code into one I get the Segmentation fault error. I made a little research its UNIX error code while violeting the restiricted memory space. But these two codes works perfectly when working seperatly. This is where I got stucked. The code I tried to merge is like;

/* for hardware timestamps - since Linux 2.6.30 */
#ifndef SO_TIMESTAMPING
#define SO_TIMESTAMPING 37
#endif

/* from #include <linux/net_tstamp.h> - since Linux 2.6.30 */
#define SOF_TIMESTAMPING_SOFTWARE (1<<4)
#define SOF_TIMESTAMPING_RX_SOFTWARE (1<<3)
#define SOF_TIMESTAMPING_RAW_HARDWARE (1<<6)

#define MAXSOCK 16    /* max. number of CAN interfaces given on the cmdline */
#define MAXIFNAMES 30 /* size of receive name index to omit ioctls */
#define MAXCOL 6      /* number of different colors for colorized output */
#define ANYDEV "any"  /* name of interface to receive from any CAN interface */
#define ANL "\r\n"    /* newline in ASC mode */

#define SILENT_INI 42 /* detect user setting on commandline */
#define SILENT_OFF 0  /* no silent mode */
#define SILENT_ANI 1  /* silent mode with animation */
#define SILENT_ON  2  /* silent mode (completely silent) */

static char *cmdlinename[MAXSOCK];
static __u32 dropcnt[MAXSOCK];
static __u32 last_dropcnt[MAXSOCK];
static char devname[MAXIFNAMES][IFNAMSIZ+1];
static int  dindex[MAXIFNAMES];
static int  max_devname_len; /* to prevent frazzled device name output */ 
const int canfd_on = 1;

#define MAXANI 4
const char anichar[MAXANI] = {'|', '/', '-', '\\'};
const char extra_m_info[4][4] = {"- -", "B -", "- E", "B E"};

extern int optind, opterr, optopt;

static volatile int running = 1;

void sigterm(int signo)
{
    running = 0;
}

int idx2dindex(int ifidx, int socket) {

    int i;
    struct ifreq ifr;

    for (i=0; i < MAXIFNAMES; i++) {
        if (dindex[i] == ifidx)
            return i;
    }

    /* create new interface index cache entry */

    /* remove index cache zombies first */
    for (i=0; i < MAXIFNAMES; i++) {
        if (dindex[i]) {
            ifr.ifr_ifindex = dindex[i];
            if (ioctl(socket, SIOCGIFNAME, &ifr) < 0)
                dindex[i] = 0;
        }
    }

    for (i=0; i < MAXIFNAMES; i++)
        if (!dindex[i]) /* free entry */
            break;

    if (i == MAXIFNAMES) {
        fprintf(stderr, "Interface index cache only supports %d interfaces.\n",
               MAXIFNAMES);
        exit(1);
    }

    dindex[i] = ifidx;

    ifr.ifr_ifindex = ifidx;
    if (ioctl(socket, SIOCGIFNAME, &ifr) < 0)
        perror("SIOCGIFNAME");

    if (max_devname_len < strlen(ifr.ifr_name))
        max_devname_len = strlen(ifr.ifr_name);

    strcpy(devname[i], ifr.ifr_name);

#ifdef DEBUG
    printf("new index %d (%s)\n", i, devname[i]);
#endif

    return i;
}

int main(int argc, char **argv)
{
    fd_set rdfs;
    int s[MAXSOCK];
    int bridge = 0;
    useconds_t bridge_delay = 0;
    unsigned char timestamp = 0;
    unsigned char hwtimestamp = 0;
    unsigned char down_causes_exit = 1;
    unsigned char dropmonitor = 0;
    unsigned char extra_msg_info = 0;
    unsigned char silent = SILENT_INI;
    unsigned char silentani = 0;
    unsigned char color = 0;
    unsigned char view = 0;
    unsigned char log = 0;
    unsigned char logfrmt = 0;
    int count = 0;
    int rcvbuf_size = 0;
    int opt, ret;
    int currmax, numfilter;
    int join_filter;
    char *ptr, *nptr;
    struct sockaddr_can addr;
    char ctrlmsg[CMSG_SPACE(sizeof(struct timeval) + 3*sizeof(struct timespec) + sizeof(__u32))];
    struct iovec iov;
    struct msghdr msg;
    struct cmsghdr *cmsg;
    struct can_filter *rfilter;
    can_err_mask_t err_mask;
    struct canfd_frame frame;
    int nbytes, i, maxdlen;
    struct ifreq ifr;
    struct timeval tv, last_tv;
    struct timeval timeout, timeout_config = { 0, 0 }, *timeout_current = NULL;
    FILE *logfile = NULL;

    int fd;/*File Descriptor*/
    struct termios SerialPortSettings;  /* Create the structure                          */


    signal(SIGTERM, sigterm);
    signal(SIGHUP, sigterm);
    signal(SIGINT, sigterm);

    last_tv.tv_sec  = 0;
    last_tv.tv_usec = 0;

    if (optind == argc) {
        print_usage(basename(argv[0]));
        exit(0);
    }

    if (logfrmt && view) {
        fprintf(stderr, "Log file format selected: Please disable ASCII/BINARY/SWAP options!\n");
        exit(0);
    }

    if (silent == SILENT_INI) {
        if (log) {
            fprintf(stderr, "Disabled standard output while logging.\n");
            silent = SILENT_ON; /* disable output on stdout */
        } else
            silent = SILENT_OFF; /* default output */
    }

    currmax = argc - optind; /* find real number of CAN devices */

    if (currmax > MAXSOCK) {
        fprintf(stderr, "More than %d CAN devices given on commandline!\n", MAXSOCK);
        return 1;
    }

    for (i=0; i < currmax; i++) {

        ptr = argv[optind+i];
        nptr = strchr(ptr, ',');

#ifdef DEBUG
        printf("open %d '%s'.\n", i, ptr);
#endif

        s[i] = socket(PF_CAN, SOCK_RAW, CAN_RAW);
        if (s[i] < 0) {
            perror("socket");
            return 1;
        }

        cmdlinename[i] = ptr; /* save pointer to cmdline name of this socket */

        if (nptr)
            nbytes = nptr - ptr;  /* interface name is up the first ',' */
        else
            nbytes = strlen(ptr); /* no ',' found => no filter definitions */

        if (nbytes >= IFNAMSIZ) {
            fprintf(stderr, "name of CAN device '%s' is too long!\n", ptr);
            return 1;
        }

        if (nbytes > max_devname_len)
            max_devname_len = nbytes; /* for nice printing */

        addr.can_family = AF_CAN;

        memset(&ifr.ifr_name, 0, sizeof(ifr.ifr_name));
        strncpy(ifr.ifr_name, ptr, nbytes);

#ifdef DEBUG
        printf("using interface name '%s'.\n", ifr.ifr_name);
#endif

        if (strcmp(ANYDEV, ifr.ifr_name)) {
            if (ioctl(s[i], SIOCGIFINDEX, &ifr) < 0) {
                perror("SIOCGIFINDEX");
                exit(1);
            }
            addr.can_ifindex = ifr.ifr_ifindex;
        } else
            addr.can_ifindex = 0; /* any can interface */

        if (nptr) {

            /* found a ',' after the interface name => check for filters */

            /* determine number of filters to alloc the filter space */
            numfilter = 0;
            ptr = nptr;
            while (ptr) {
                numfilter++;
                ptr++; /* hop behind the ',' */
                ptr = strchr(ptr, ','); /* exit condition */
            }

            rfilter = malloc(sizeof(struct can_filter) * numfilter);
            if (!rfilter) {
                fprintf(stderr, "Failed to create filter space!\n");
                return 1;
            }

            numfilter = 0;
            err_mask = 0;
            join_filter = 0;

            while (nptr) {

                ptr = nptr+1; /* hop behind the ',' */
                nptr = strchr(ptr, ','); /* update exit condition */

                if (sscanf(ptr, "%x:%x",
                       &rfilter[numfilter].can_id, 
                       &rfilter[numfilter].can_mask) == 2) {
                    rfilter[numfilter].can_mask &= ~CAN_ERR_FLAG;
                    numfilter++;
                } else if (sscanf(ptr, "%x~%x",
                          &rfilter[numfilter].can_id, 
                          &rfilter[numfilter].can_mask) == 2) {
                    rfilter[numfilter].can_id |= CAN_INV_FILTER;
                    rfilter[numfilter].can_mask &= ~CAN_ERR_FLAG;
                    numfilter++;
                } else if (*ptr == 'j' || *ptr == 'J') {
                    join_filter = 1;
                } else if (sscanf(ptr, "#%x", &err_mask) != 1) { 
                    fprintf(stderr, "Error in filter option parsing: '%s'\n", ptr);
                    return 1;
                }
            }

            if (err_mask)
                setsockopt(s[i], SOL_CAN_RAW, CAN_RAW_ERR_FILTER,
                       &err_mask, sizeof(err_mask));

            if (join_filter && setsockopt(s[i], SOL_CAN_RAW, CAN_RAW_JOIN_FILTERS,
                              &join_filter, sizeof(join_filter)) < 0) {
                perror("setsockopt CAN_RAW_JOIN_FILTERS not supported by your Linux Kernel");
                return 1;
            }

            if (numfilter)
                setsockopt(s[i], SOL_CAN_RAW, CAN_RAW_FILTER,
                       rfilter, numfilter * sizeof(struct can_filter));

            free(rfilter);

        } /* if (nptr) */

        /* try to switch the socket into CAN FD mode */
        setsockopt(s[i], SOL_CAN_RAW, CAN_RAW_FD_FRAMES, &canfd_on, sizeof(canfd_on));

        if (rcvbuf_size) {

            int curr_rcvbuf_size;
            socklen_t curr_rcvbuf_size_len = sizeof(curr_rcvbuf_size);

            /* try SO_RCVBUFFORCE first, if we run with CAP_NET_ADMIN */
            if (setsockopt(s[i], SOL_SOCKET, SO_RCVBUFFORCE,
                       &rcvbuf_size, sizeof(rcvbuf_size)) < 0) {
#ifdef DEBUG
                printf("SO_RCVBUFFORCE failed so try SO_RCVBUF ...\n");
#endif
                if (setsockopt(s[i], SOL_SOCKET, SO_RCVBUF,
                           &rcvbuf_size, sizeof(rcvbuf_size)) < 0) {
                    perror("setsockopt SO_RCVBUF");
                    return 1;
                }

                if (getsockopt(s[i], SOL_SOCKET, SO_RCVBUF,
                           &curr_rcvbuf_size, &curr_rcvbuf_size_len) < 0) {
                    perror("getsockopt SO_RCVBUF");
                    return 1;
                }

                /* Only print a warning the first time we detect the adjustment */
                /* n.b.: The wanted size is doubled in Linux in net/sore/sock.c */
                if (!i && curr_rcvbuf_size < rcvbuf_size*2)
                    fprintf(stderr, "The socket receive buffer size was "
                        "adjusted due to /proc/sys/net/core/rmem_max.\n");
            }
        }

        if (timestamp || log || logfrmt) {

            if (hwtimestamp) {
                const int timestamping_flags = (SOF_TIMESTAMPING_SOFTWARE | \
                                SOF_TIMESTAMPING_RX_SOFTWARE | \
                                SOF_TIMESTAMPING_RAW_HARDWARE);

                if (setsockopt(s[i], SOL_SOCKET, SO_TIMESTAMPING,
                        &timestamping_flags, sizeof(timestamping_flags)) < 0) {
                    perror("setsockopt SO_TIMESTAMPING is not supported by your Linux kernel");
                    return 1;
                }
            } else {
                const int timestamp_on = 1;

                if (setsockopt(s[i], SOL_SOCKET, SO_TIMESTAMP,
                           &timestamp_on, sizeof(timestamp_on)) < 0) {
                    perror("setsockopt SO_TIMESTAMP");
                    return 1;
                }
            }
        }

        if (dropmonitor) {

            const int dropmonitor_on = 1;

            if (setsockopt(s[i], SOL_SOCKET, SO_RXQ_OVFL,
                       &dropmonitor_on, sizeof(dropmonitor_on)) < 0) {
                perror("setsockopt SO_RXQ_OVFL not supported by your Linux Kernel");
                return 1;
            }
        }

        if (bind(s[i], (struct sockaddr *)&addr, sizeof(addr)) < 0) {
            perror("bind");
            return 1;
        }
    }

    if (log) {
        time_t currtime;
        struct tm now;
        char fname[sizeof("candump-2006-11-20_202026.log")+1];

        if (time(&currtime) == (time_t)-1) {
            perror("time");
            return 1;
        }

        localtime_r(&currtime, &now);

        sprintf(fname, "candump-%04d-%02d-%02d_%02d%02d%02d.log",
            now.tm_year + 1900,
            now.tm_mon + 1,
            now.tm_mday,
            now.tm_hour,
            now.tm_min,
            now.tm_sec);

        if (silent != SILENT_ON)
            printf("\nWarning: console output active while logging!");

        fprintf(stderr, "\nEnabling Logfile '%s'\n\n", fname);

        logfile = fopen(fname, "w");
        if (!logfile) {
            perror("logfile");
            return 1;
        }
    }

    /* these settings are static and can be held out of the hot path */
    iov.iov_base = &frame;
    msg.msg_name = &addr;
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;
    msg.msg_control = &ctrlmsg;

    while (running) {

        /*------------------------------- Opening the Serial Port -------------------------------*/

        /* Change /dev/ttyUSB0 to the one corresponding to your system */

        fd = open("/dev/ttyO2",O_RDWR | O_NOCTTY);  /* ttyUSB0 is the FT232 based USB2SERIAL Converter   */
                            /* O_RDWR   - Read/Write access to serial port       */
                            /* O_NOCTTY - No terminal will control the process   */
                            /* Open in blocking mode,read will wait              */


                                    /* Error Checking */
        if(fd == -1)                        
               printf("\n  Error! in Opening ttyO2  ");
        else
               printf("\n  ttyO2 Opened Successfully ");


        /*---------- Setting the Attributes of the serial port using termios structure --------- */

        //struct termios SerialPortSettings;    /* Create the structure                          */

        tcgetattr(fd, &SerialPortSettings); /* Get the current attributes of the Serial port */

        /* Setting the Baud rate */
        cfsetispeed(&SerialPortSettings,B9600); /* Set Read  Speed as 9600                       */
        cfsetospeed(&SerialPortSettings,B9600); /* Set Write Speed as 9600                       */

        /* 8N1 Mode */
        SerialPortSettings.c_cflag &= ~PARENB;   /* Disables the Parity Enable bit(PARENB),So No Parity   */
        SerialPortSettings.c_cflag &= ~CSTOPB;   /* CSTOPB = 2 Stop bits,here it is cleared so 1 Stop bit */
        SerialPortSettings.c_cflag &= ~CSIZE;    /* Clears the mask for setting the data size             */
        SerialPortSettings.c_cflag |=  CS8;      /* Set the data bits = 8                                 */

        SerialPortSettings.c_cflag &= ~CRTSCTS;       /* No Hardware flow Control                         */
        SerialPortSettings.c_cflag |= CREAD | CLOCAL; /* Enable receiver,Ignore Modem Control lines       */ 


        SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY);          /* Disable XON/XOFF flow control both i/p and o/p */
        SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);  /* Non Cannonical mode                            */

        SerialPortSettings.c_oflag &= ~OPOST;/*No Output Processing*/

        /* Setting Time outs */
        SerialPortSettings.c_cc[VMIN] = 42; /* Read at least 42 characters */
        SerialPortSettings.c_cc[VTIME] = 0; /* Wait indefinetly   */


        if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0) /* Set the attributes to the termios structure*/
            printf("\n  ERROR ! in Setting attributes");
        else
            printf("\n  BaudRate = 9600 \n  StopBits = 1 \n  Parity   = none  \n\n");

        /*------------------------------- Read data from serial port -----------------------------*/

        tcflush(fd, TCIFLUSH);   /* Discards old data in the rx buffer */

        char read_buffer[42];   /* Buffer to store the data received              */
        int  bytes_read = 0;    /* Number of bytes read by the read() system call */
        int ia = 0; int a;
        int test = 0;
        char new_read[38];
        char curr_read[33];
        int countc = 0;
        a = 0;
        do{
            bytes_read = read(fd,&read_buffer,42); /* Read the data                   */

            if(read_buffer[0] == '$')
                if(read_buffer[1] == 'G')
                    if(read_buffer[2] == 'P')
                        if(read_buffer[3] == 'G')
                            if(read_buffer[4] == 'G'){
                                for(ia=7;ia<bytes_read;ia++){    /*printing only the received characters*/
                                    new_read[a] = read_buffer[ia];
                                    //printf("%c",read_buffer[ia]);
                                    a = a+1;
                                    test = 1;
                                }
                                strcpy(curr_read, new_read);
                                //printf("\n%s \n", curr_read);
                            }
                            else
                                test = 0;
                        else
                            test = 0;
                    else
                        test = 0;
                else
                    test = 0;
            else
                test = 0;
        }while(test == 0);

        //tcflush(fd, TCIFLUSH);   /* Discards old data in the rx buffer */

        close(fd); /* Close the serial port */

        while(countc < 1000){
            FD_ZERO(&rdfs);
            for (i=0; i<currmax; i++)
                FD_SET(s[i], &rdfs);

            if (timeout_current)
                *timeout_current = timeout_config;

            if ((ret = select(s[currmax-1]+1, &rdfs, NULL, NULL, timeout_current)) <= 0) {
                //perror("select");
                running = 0;
                continue;
            }

            for (i=0; i<currmax; i++) {  /* check all CAN RAW sockets */

                if (FD_ISSET(s[i], &rdfs)) {

                    int idx;

                    /* these settings may be modified by recvmsg() */
                    iov.iov_len = sizeof(frame);
                    msg.msg_namelen = sizeof(addr);
                    msg.msg_controllen = sizeof(ctrlmsg);  
                    msg.msg_flags = 0;

                    nbytes = recvmsg(s[i], &msg, 0);
                    idx = idx2dindex(addr.can_ifindex, s[i]);

                    if (nbytes < 0) {
                        if ((errno == ENETDOWN) && !down_causes_exit) {
                            fprintf(stderr, "%s: interface down\n", devname[idx]);
                            continue;
                        }
                        perror("read");
                        return 1;
                    }

                    if ((size_t)nbytes == CAN_MTU)
                        maxdlen = CAN_MAX_DLEN;
                    else if ((size_t)nbytes == CANFD_MTU)
                        maxdlen = CANFD_MAX_DLEN;
                    else {
                        fprintf(stderr, "read: incomplete CAN frame\n");
                        return 1;
                    }

                    if (count && (--count == 0))
                        running = 0;

                    if (bridge) {
                        if (bridge_delay)
                            usleep(bridge_delay);

                        nbytes = write(bridge, &frame, nbytes);
                        if (nbytes < 0) {
                            perror("bridge write");
                            return 1;
                        } else if ((size_t)nbytes != CAN_MTU && (size_t)nbytes != CANFD_MTU) {
                            fprintf(stderr,"bridge write: incomplete CAN frame\n");
                            return 1;
                        }
                    }

                    for (cmsg = CMSG_FIRSTHDR(&msg);
                        cmsg && (cmsg->cmsg_level == SOL_SOCKET);
                        cmsg = CMSG_NXTHDR(&msg,cmsg)) {
                        if (cmsg->cmsg_type == SO_TIMESTAMP) {
                            memcpy(&tv, CMSG_DATA(cmsg), sizeof(tv));
                        } else if (cmsg->cmsg_type == SO_TIMESTAMPING) {

                            struct timespec *stamp = (struct timespec *)CMSG_DATA(cmsg);

                            /*
                            * stamp[0] is the software timestamp
                            * stamp[1] is deprecated
                            * stamp[2] is the raw hardware timestamp
                            * See chapter 2.1.2 Receive timestamps in
                            * linux/Documentation/networking/timestamping.txt
                            */
                            tv.tv_sec = stamp[2].tv_sec;
                            tv.tv_usec = stamp[2].tv_nsec/1000;
                        } else if (cmsg->cmsg_type == SO_RXQ_OVFL)
                            memcpy(&dropcnt[i], CMSG_DATA(cmsg), sizeof(__u32));
                    }

                    /* check for (unlikely) dropped frames on this specific socket */
                    if (dropcnt[i] != last_dropcnt[i]) {

                        __u32 frames = dropcnt[i] - last_dropcnt[i];

                        if (silent != SILENT_ON)
                            printf("DROPCOUNT: dropped %d CAN frame%s on '%s' socket (total drops %d)\n",
                                frames, (frames > 1)?"s":"", devname[idx], dropcnt[i]);

                        if (log)
                            fprintf(logfile, "DROPCOUNT: dropped %d CAN frame%s on '%s' socket (total drops %d)\n",
                                frames, (frames > 1)?"s":"", devname[idx], dropcnt[i]);

                        last_dropcnt[i] = dropcnt[i];
                    }

                    /* once we detected a EFF frame indent SFF frames accordingly */
                    if (frame.can_id & CAN_EFF_FLAG)
                        view |= CANLIB_VIEW_INDENT_SFF;

                    if (log) {                                                  /*   CODE GETS IN TO THIS PART  */
                        char buf[CL_CFSZ]; /* max length */                     /*   WHEN PRINTING INTO FILE    */
                                                                                /*                              */
                        /* log CAN frame with absolute timestamp & device */    /*                              */
                        sprint_canframe(buf, &frame, 0, maxdlen);               /*                              */
                        fprintf(logfile, "%s %*s %s\n",                         /*                              */
                            curr_read,                                          /*                              */
                            max_devname_len, devname[idx], buf);                /*                              */
                    }                                                           /*                              */

                    if (logfrmt) {
                        char buf[CL_CFSZ]; /* max length */

                        /* print CAN frame in log file style to stdout */
                        sprint_canframe(buf, &frame, 0, maxdlen);
                        printf("(%010ld.%06ld) %*s %s\n",
                            tv.tv_sec, tv.tv_usec,
                            max_devname_len, devname[idx], buf);
                        goto out_fflush; /* no other output to stdout */
                    }

                    if (silent != SILENT_OFF){
                        if (silent == SILENT_ANI) {
                            printf("%c\b", anichar[silentani%=MAXANI]);
                            silentani++;
                        }
                        goto out_fflush; /* no other output to stdout */
                    }

                    printf(" %s", (color>2)?col_on[idx%MAXCOL]:"");

                    switch (timestamp) {

                    case 'a': /* absolute with timestamp */
                        printf("(%010ld.%06ld) ", tv.tv_sec, tv.tv_usec);
                        break;

                    case 'A': /* absolute with date */
                    {
                        struct tm tm;
                        char timestring[25];

                        tm = *localtime(&tv.tv_sec);
                        strftime(timestring, 24, "%Y-%m-%d %H:%M:%S", &tm);
                        printf("(%s.%06ld) ", timestring, tv.tv_usec);
                    }
                    break;

                    case 'd': /* delta */
                    case 'z': /* starting with zero */
                    {
                        struct timeval diff;

                        if (last_tv.tv_sec == 0)   /* first init */
                            last_tv = tv;
                        diff.tv_sec  = tv.tv_sec  - last_tv.tv_sec;
                        diff.tv_usec = tv.tv_usec - last_tv.tv_usec;
                        if (diff.tv_usec < 0)
                            diff.tv_sec--, diff.tv_usec += 1000000;
                        if (diff.tv_sec < 0)
                            diff.tv_sec = diff.tv_usec = 0;
                        printf("(%03ld.%06ld) ", diff.tv_sec, diff.tv_usec);

                        if (timestamp == 'd')
                            last_tv = tv; /* update for delta calculation */
                    }
                    break;

                    default: /* no timestamp output */
                        break;
                    }

                    printf(" %s", (color && (color<3))?col_on[idx%MAXCOL]:"");
                    printf("%*s", max_devname_len, devname[idx]);

                    if (extra_msg_info) {

                        if (msg.msg_flags & MSG_DONTROUTE)
                            printf ("  TX %s", extra_m_info[frame.flags & 3]);
                        else
                            printf ("  RX %s", extra_m_info[frame.flags & 3]);
                    }

                    printf("%s  ", (color==1)?col_off:"");

                    fprint_long_canframe(stdout, &frame, NULL, view, maxdlen);

                    printf("%s", (color>1)?col_off:"");
                    printf("\n");
                }

            out_fflush:
                fflush(stdout);
            }
            countc = countc +1;
        }   
    }


    for (i=0; i<currmax; i++)
        close(s[i]);

    if (bridge)
        close(bridge);

    if (log)
        fclose(logfile);

    return 0;
}

Actually everything matters works in while(running) block. Inside this block when I make the bytes_read = read(fd,&read_buffer,42); as comment, it didn't write anything but also doesn't give the Segmentation fault error. Same also happens when I connect the GPS' TX pin in to BBB. So the problem starts to occur when the data is coming from the GPS and read by the BBB.

Segmentation Fault Err

What should I do about it?

Thanks.

Answer 1

Your GPS reading code

char new_read[38];
char curr_read[33];

strcpy(curr_read, new_read);

is copying a 38 char buffer into a 33 char buffer, which can result in bad things.

Strcpy will copy the contents of the source buffer into the destination buffer until it reads NULL from the source buffer. If the NULL char is at the 36th position in new_read, strcpy will be writing in random memory which can cause the segmentation fault.

I am guessing that when you run your GPS reading code as stand-alone, the writing into random memory goes un-noticed, but when you combine it with the CAN bus reading, it writes into allocated space and the error happens.