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7138d0c5 SE |
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 | ||
794f2398 SE |
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 | ||
7138d0c5 SE |
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. */ | |
042a8da9 SE |
59 | pid_t makesubproc(process_entry_fn *entry, process_callback_fn *cb, |
60 | void *est, void *cst, string_t desc) | |
7138d0c5 SE |
61 | { |
62 | struct child *c; | |
7138d0c5 SE |
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) { | |
042a8da9 | 71 | fatal("makesubproc called before signal handling started\n"); |
7138d0c5 SE |
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; | |
042a8da9 | 87 | return p; |
7138d0c5 SE |
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 | { | |
ff05a229 | 237 | int saved_errno; |
7138d0c5 SE |
238 | uint8_t thing=0; |
239 | sigaddset(&pending,signum); | |
ff05a229 SE |
240 | /* XXX the write() may set errno, which can make the main program fail. |
241 | However, signal handlers aren't allowed to modify anything which | |
242 | is not of type sig_atomic_t. The world is broken. */ | |
243 | /* I have decided to save and restore errno anyway; on most | |
244 | architectures on which secnet can run modifications to errno | |
245 | will be atomic, and it seems to be the lesser of the two | |
246 | evils. */ | |
247 | saved_errno=errno; | |
7138d0c5 SE |
248 | write(spw,&thing,1); /* We don't care if this fails (i.e. the pipe |
249 | is full) because the service routine will | |
250 | spot the pending signal anyway */ | |
ff05a229 | 251 | errno=saved_errno; |
7138d0c5 SE |
252 | } |
253 | ||
254 | static void register_signal_handler(struct signotify *s) | |
255 | { | |
256 | struct sigaction sa; | |
257 | int rv; | |
258 | ||
259 | if (!signal_handling) return; | |
260 | ||
261 | if (sigismember(®istered,s->signum)) return; | |
262 | sigaddset(®istered,s->signum); | |
263 | ||
264 | sa.sa_handler=signal_handler; | |
265 | sa.sa_mask=fullset; | |
266 | sa.sa_flags=0; | |
267 | rv=sigaction(s->signum,&sa,NULL); | |
268 | if (rv!=0) { | |
269 | fatal_perror("register_signal_handler: sigaction(%d)",s->signum); | |
270 | } | |
271 | } | |
272 | ||
273 | void request_signal_notification(int signum, signal_notify_fn *notify, | |
274 | void *cst) | |
275 | { | |
276 | struct signotify *s; | |
277 | sigset_t old; | |
278 | ||
279 | s=safe_malloc(sizeof(*s),"request_signal_notification"); | |
280 | s->signum=signum; | |
281 | s->notify=notify; | |
282 | s->cst=cst; | |
283 | s->next=sigs; | |
284 | sigprocmask(SIG_SETMASK,&fullset,&old); | |
285 | sigs=s; | |
286 | register_signal_handler(s); | |
287 | sigprocmask(SIG_SETMASK,&old,NULL); | |
288 | } | |
289 | ||
290 | void start_signal_handling(void) | |
291 | { | |
292 | int p[2]; | |
293 | struct signotify *i; | |
294 | ||
295 | sigemptyset(&emptyset); | |
296 | sigfillset(&fullset); | |
297 | sigemptyset(®istered); | |
298 | sigemptyset(&pending); | |
299 | ||
300 | if (pipe(p)!=0) { | |
301 | fatal_perror("start_signal_handling: pipe"); | |
302 | } | |
303 | spw=p[1]; | |
304 | spr=p[0]; | |
305 | if (fcntl(spw, F_SETFL, fcntl(spw, F_GETFL)|O_NONBLOCK)==-1) { | |
306 | fatal_perror("start_signal_handling: fcntl(O_NONBLOCK)"); | |
307 | } | |
308 | ||
309 | register_for_poll(NULL,signal_beforepoll,signal_afterpoll,1,"signal"); | |
310 | signal_handling=True; | |
311 | ||
312 | /* Register signal handlers for all the signals we're interested in */ | |
313 | for (i=sigs; i; i=i->next) { | |
314 | register_signal_handler(i); | |
315 | } | |
316 | ||
317 | request_signal_notification(SIGCHLD,sigchld_handler,NULL); | |
318 | } |