| 1 | #include "secnet.h" |
| 2 | #include <unistd.h> |
| 3 | #include <fcntl.h> |
| 4 | #include <errno.h> |
| 5 | #include <sys/wait.h> |
| 6 | #include "process.h" |
| 7 | |
| 8 | /* Advice about children from Peter: |
| 9 | Better way: before the fork, make a pipe. In the child close the |
| 10 | +reading end. Make the writing end close-on-exec. If the dup2 or exec fails, |
| 11 | +write the errno value. In the parent, close the writing end. Now you can read |
| 12 | +from it. If you get an errno value from the pipe, the process failed and you |
| 13 | +know why. If you get EOF, the exec succeeded. |
| 14 | |
| 15 | <Senji> So, close on exec only closes if exec isn't going to return then? |
| 16 | <Diziet> qu: I wouldn't bother with all that with pipes. Remember that the |
| 17 | +runtime system can still make exec fail when it's `too late'. |
| 18 | <Senji> Diz - I would rather have a coherant error message than 'child failed' |
| 19 | <Diziet> The child, if it fails to exec, should print a message to stderr |
| 20 | +(giving errno and what it was trying to execute, most likely), and exit |
| 21 | +nonzero. |
| 22 | <Diziet> It should exit calling _exit. |
| 23 | */ |
| 24 | |
| 25 | /* Process handling - subprocesses, signals, etc. */ |
| 26 | |
| 27 | static bool_t signal_handling=False; |
| 28 | static sigset_t emptyset, fullset; |
| 29 | static sigset_t registered,pending; |
| 30 | |
| 31 | struct child { |
| 32 | pid_t pid; |
| 33 | string_t desc; |
| 34 | process_callback_fn *cb; |
| 35 | void *cst; |
| 36 | bool_t finished; |
| 37 | struct child *next; |
| 38 | }; |
| 39 | |
| 40 | static struct child *children=NULL; |
| 41 | |
| 42 | struct signotify { |
| 43 | int signum; |
| 44 | signal_notify_fn *notify; |
| 45 | void *cst; |
| 46 | struct signotify *next; |
| 47 | }; |
| 48 | |
| 49 | static struct signotify *sigs=NULL; |
| 50 | |
| 51 | static int spw,spr; /* file descriptors for signal notification pipe */ |
| 52 | |
| 53 | static void set_default_signals(void); |
| 54 | |
| 55 | /* Long-lived subprocesses can only be started once we've started |
| 56 | signal processing so that we can catch SIGCHLD for them and report |
| 57 | their exit status using the callback function. We block SIGCHLD |
| 58 | until signal processing has begun. */ |
| 59 | pid_t makesubproc(process_entry_fn *entry, process_callback_fn *cb, |
| 60 | void *est, void *cst, string_t desc) |
| 61 | { |
| 62 | struct child *c; |
| 63 | pid_t p; |
| 64 | |
| 65 | c=safe_malloc(sizeof(*c),"makesubproc"); |
| 66 | c->desc=desc; |
| 67 | c->cb=cb; |
| 68 | c->cst=cst; |
| 69 | |
| 70 | if (!signal_handling) { |
| 71 | fatal("makesubproc called before signal handling started\n"); |
| 72 | } |
| 73 | p=fork(); |
| 74 | if (p==0) { |
| 75 | /* Child process */ |
| 76 | set_default_signals(); |
| 77 | sigprocmask(SIG_SETMASK,&emptyset,NULL); |
| 78 | entry(est); |
| 79 | abort(); |
| 80 | } else if (p==-1) { |
| 81 | fatal_perror("makesubproc (%s): fork",desc); |
| 82 | } |
| 83 | c->pid=p; |
| 84 | c->finished=False; |
| 85 | c->next=children; |
| 86 | children=c; |
| 87 | return p; |
| 88 | } |
| 89 | |
| 90 | static signal_notify_fn sigchld_handler; |
| 91 | static void sigchld_handler(void *st, int signum) |
| 92 | { |
| 93 | struct child *i,*n,**p; |
| 94 | struct work { |
| 95 | pid_t pid; |
| 96 | process_callback_fn *cb; |
| 97 | void *cst; |
| 98 | int status; |
| 99 | struct work *next; |
| 100 | }; |
| 101 | struct work *w=NULL, *nw; |
| 102 | pid_t rv; |
| 103 | int status; |
| 104 | |
| 105 | for (i=children; i; i=i->next) { |
| 106 | rv=waitpid(i->pid,&status,WNOHANG); |
| 107 | if (rv==-1) { |
| 108 | fatal_perror("sigchld_handler: waitpid"); |
| 109 | } |
| 110 | if (rv==i->pid) { |
| 111 | i->finished=True; |
| 112 | |
| 113 | nw=safe_malloc(sizeof(*nw),"sigchld_handler"); |
| 114 | nw->pid=i->pid; |
| 115 | nw->cb=i->cb; |
| 116 | nw->cst=i->cst; |
| 117 | nw->status=status; |
| 118 | nw->next=w; |
| 119 | w=nw; |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | /* Remove all the finished tasks from the list of children */ |
| 124 | for (i=children, p=&children; i; i=n) { |
| 125 | n=i->next; |
| 126 | if (i->finished) { |
| 127 | free(i); |
| 128 | *p=n; |
| 129 | } else { |
| 130 | p=&i->next; |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | /* Notify as appropriate, then free the list */ |
| 135 | while (w) { |
| 136 | w->cb(w->cst,w->pid,w->status); |
| 137 | nw=w; |
| 138 | w=w->next; |
| 139 | free(nw); |
| 140 | } |
| 141 | } |
| 142 | |
| 143 | int sys_cmd(const char *path, char *arg, ...) |
| 144 | { |
| 145 | va_list ap; |
| 146 | int rv; |
| 147 | pid_t c; |
| 148 | |
| 149 | va_start(ap,arg); |
| 150 | c=fork(); |
| 151 | if (c) { |
| 152 | /* Parent -> wait for child */ |
| 153 | waitpid(c,&rv,0); |
| 154 | } else if (c==0) { |
| 155 | char *args[100]; |
| 156 | int i; |
| 157 | /* Child -> exec command */ |
| 158 | args[0]=arg; |
| 159 | i=1; |
| 160 | while ((args[i++]=va_arg(ap,char *))); |
| 161 | execvp(path,args); |
| 162 | exit(1); |
| 163 | } else { |
| 164 | /* Error */ |
| 165 | fatal_perror("sys_cmd(%s,%s,...)"); |
| 166 | } |
| 167 | |
| 168 | va_end(ap); |
| 169 | return rv; |
| 170 | } |
| 171 | |
| 172 | static beforepoll_fn signal_beforepoll; |
| 173 | static int signal_beforepoll(void *st, struct pollfd *fds, int *nfds_io, |
| 174 | int *timeout_io, const struct timeval *tv_now, |
| 175 | uint64_t *now) |
| 176 | { |
| 177 | if (*nfds_io<1) { |
| 178 | *nfds_io=1; |
| 179 | return ERANGE; |
| 180 | } |
| 181 | *nfds_io=1; |
| 182 | fds[0].fd=spr; |
| 183 | fds[0].events=POLLIN; |
| 184 | return 0; |
| 185 | } |
| 186 | |
| 187 | static afterpoll_fn signal_afterpoll; |
| 188 | static void signal_afterpoll(void *st, struct pollfd *fds, int nfds, |
| 189 | const struct timeval *tv, uint64_t *now) |
| 190 | { |
| 191 | uint8_t buf[16]; |
| 192 | struct signotify *n; |
| 193 | sigset_t todo,old; |
| 194 | |
| 195 | if (nfds && (fds->revents & POLLIN)) { |
| 196 | read(spr,buf,16); /* We don't actually care what we read; as |
| 197 | long as there was at least one byte |
| 198 | (which there was) we'll pick up the |
| 199 | signals in the pending set */ |
| 200 | |
| 201 | /* We reset 'pending' before processing any of the signals |
| 202 | that were pending so that we don't miss any signals that |
| 203 | are delivered partway-through processing (all we assume |
| 204 | about signal notification routines is that they handle all |
| 205 | the work available at their _start_ and only optionally any |
| 206 | work that arrives part-way through their execution). */ |
| 207 | sigprocmask(SIG_SETMASK,&fullset,&old); |
| 208 | todo=pending; |
| 209 | sigemptyset(&pending); |
| 210 | sigprocmask(SIG_SETMASK,&old,NULL); |
| 211 | |
| 212 | for (n=sigs; n; n=n->next) |
| 213 | if (sigismember(&todo,n->signum)) |
| 214 | n->notify(n->cst,n->signum); |
| 215 | } |
| 216 | } |
| 217 | |
| 218 | static void set_default_signals(void) |
| 219 | { |
| 220 | struct signotify *n; |
| 221 | sigset_t done; |
| 222 | struct sigaction sa; |
| 223 | |
| 224 | sigemptyset(&done); |
| 225 | for (n=sigs; n; n=n->next) |
| 226 | if (!sigismember(&done,n->signum)) { |
| 227 | sigaddset(&done,n->signum); |
| 228 | sa.sa_handler=SIG_DFL; |
| 229 | sa.sa_mask=emptyset; |
| 230 | sa.sa_flags=0; |
| 231 | sigaction(n->signum,&sa,NULL); |
| 232 | } |
| 233 | } |
| 234 | |
| 235 | static void signal_handler(int signum) |
| 236 | { |
| 237 | uint8_t thing=0; |
| 238 | sigaddset(&pending,signum); |
| 239 | write(spw,&thing,1); /* We don't care if this fails (i.e. the pipe |
| 240 | is full) because the service routine will |
| 241 | spot the pending signal anyway */ |
| 242 | } |
| 243 | |
| 244 | static void register_signal_handler(struct signotify *s) |
| 245 | { |
| 246 | struct sigaction sa; |
| 247 | int rv; |
| 248 | |
| 249 | if (!signal_handling) return; |
| 250 | |
| 251 | if (sigismember(®istered,s->signum)) return; |
| 252 | sigaddset(®istered,s->signum); |
| 253 | |
| 254 | sa.sa_handler=signal_handler; |
| 255 | sa.sa_mask=fullset; |
| 256 | sa.sa_flags=0; |
| 257 | rv=sigaction(s->signum,&sa,NULL); |
| 258 | if (rv!=0) { |
| 259 | fatal_perror("register_signal_handler: sigaction(%d)",s->signum); |
| 260 | } |
| 261 | } |
| 262 | |
| 263 | void request_signal_notification(int signum, signal_notify_fn *notify, |
| 264 | void *cst) |
| 265 | { |
| 266 | struct signotify *s; |
| 267 | sigset_t old; |
| 268 | |
| 269 | s=safe_malloc(sizeof(*s),"request_signal_notification"); |
| 270 | s->signum=signum; |
| 271 | s->notify=notify; |
| 272 | s->cst=cst; |
| 273 | s->next=sigs; |
| 274 | sigprocmask(SIG_SETMASK,&fullset,&old); |
| 275 | sigs=s; |
| 276 | register_signal_handler(s); |
| 277 | sigprocmask(SIG_SETMASK,&old,NULL); |
| 278 | } |
| 279 | |
| 280 | void start_signal_handling(void) |
| 281 | { |
| 282 | int p[2]; |
| 283 | struct signotify *i; |
| 284 | |
| 285 | sigemptyset(&emptyset); |
| 286 | sigfillset(&fullset); |
| 287 | sigemptyset(®istered); |
| 288 | sigemptyset(&pending); |
| 289 | |
| 290 | if (pipe(p)!=0) { |
| 291 | fatal_perror("start_signal_handling: pipe"); |
| 292 | } |
| 293 | spw=p[1]; |
| 294 | spr=p[0]; |
| 295 | if (fcntl(spw, F_SETFL, fcntl(spw, F_GETFL)|O_NONBLOCK)==-1) { |
| 296 | fatal_perror("start_signal_handling: fcntl(O_NONBLOCK)"); |
| 297 | } |
| 298 | |
| 299 | register_for_poll(NULL,signal_beforepoll,signal_afterpoll,1,"signal"); |
| 300 | signal_handling=True; |
| 301 | |
| 302 | /* Register signal handlers for all the signals we're interested in */ |
| 303 | for (i=sigs; i; i=i->next) { |
| 304 | register_signal_handler(i); |
| 305 | } |
| 306 | |
| 307 | request_signal_notification(SIGCHLD,sigchld_handler,NULL); |
| 308 | } |