Commit | Line | Data |
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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; | |
fe5e9cc4 | 33 | cstring_t desc; |
7138d0c5 SE |
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 | 59 | pid_t makesubproc(process_entry_fn *entry, process_callback_fn *cb, |
fe5e9cc4 | 60 | void *est, void *cst, cstring_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) { | |
4f5e39ec | 71 | fatal("makesubproc called before signal handling started"); |
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 | ||
fe5e9cc4 | 143 | int sys_cmd(const char *path, const char *arg, ...) |
7138d0c5 SE |
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 */ | |
fe5e9cc4 SE |
158 | /* Really we ought to strcpy() the arguments into the args array, |
159 | since the arguments are const char *. Since we'll exit anyway | |
160 | if the execvp() fails this seems somewhat pointless, and | |
161 | increases the chance of the child process failing before it | |
162 | gets to exec(). */ | |
163 | args[0]=(char *)arg; | |
7138d0c5 SE |
164 | i=1; |
165 | while ((args[i++]=va_arg(ap,char *))); | |
166 | execvp(path,args); | |
167 | exit(1); | |
168 | } else { | |
169 | /* Error */ | |
170 | fatal_perror("sys_cmd(%s,%s,...)"); | |
171 | } | |
172 | ||
173 | va_end(ap); | |
174 | return rv; | |
175 | } | |
176 | ||
177 | static beforepoll_fn signal_beforepoll; | |
178 | static int signal_beforepoll(void *st, struct pollfd *fds, int *nfds_io, | |
90a39563 | 179 | int *timeout_io) |
7138d0c5 SE |
180 | { |
181 | if (*nfds_io<1) { | |
182 | *nfds_io=1; | |
183 | return ERANGE; | |
184 | } | |
185 | *nfds_io=1; | |
186 | fds[0].fd=spr; | |
187 | fds[0].events=POLLIN; | |
188 | return 0; | |
189 | } | |
190 | ||
191 | static afterpoll_fn signal_afterpoll; | |
90a39563 | 192 | static void signal_afterpoll(void *st, struct pollfd *fds, int nfds) |
7138d0c5 SE |
193 | { |
194 | uint8_t buf[16]; | |
195 | struct signotify *n; | |
196 | sigset_t todo,old; | |
197 | ||
198 | if (nfds && (fds->revents & POLLIN)) { | |
199 | read(spr,buf,16); /* We don't actually care what we read; as | |
200 | long as there was at least one byte | |
201 | (which there was) we'll pick up the | |
202 | signals in the pending set */ | |
203 | ||
204 | /* We reset 'pending' before processing any of the signals | |
205 | that were pending so that we don't miss any signals that | |
206 | are delivered partway-through processing (all we assume | |
207 | about signal notification routines is that they handle all | |
208 | the work available at their _start_ and only optionally any | |
209 | work that arrives part-way through their execution). */ | |
210 | sigprocmask(SIG_SETMASK,&fullset,&old); | |
211 | todo=pending; | |
212 | sigemptyset(&pending); | |
213 | sigprocmask(SIG_SETMASK,&old,NULL); | |
214 | ||
215 | for (n=sigs; n; n=n->next) | |
216 | if (sigismember(&todo,n->signum)) | |
217 | n->notify(n->cst,n->signum); | |
218 | } | |
219 | } | |
220 | ||
221 | static void set_default_signals(void) | |
222 | { | |
223 | struct signotify *n; | |
224 | sigset_t done; | |
225 | struct sigaction sa; | |
226 | ||
227 | sigemptyset(&done); | |
228 | for (n=sigs; n; n=n->next) | |
229 | if (!sigismember(&done,n->signum)) { | |
230 | sigaddset(&done,n->signum); | |
231 | sa.sa_handler=SIG_DFL; | |
232 | sa.sa_mask=emptyset; | |
233 | sa.sa_flags=0; | |
234 | sigaction(n->signum,&sa,NULL); | |
235 | } | |
236 | } | |
237 | ||
238 | static void signal_handler(int signum) | |
239 | { | |
ff05a229 | 240 | int saved_errno; |
7138d0c5 SE |
241 | uint8_t thing=0; |
242 | sigaddset(&pending,signum); | |
ff05a229 SE |
243 | /* XXX the write() may set errno, which can make the main program fail. |
244 | However, signal handlers aren't allowed to modify anything which | |
245 | is not of type sig_atomic_t. The world is broken. */ | |
246 | /* I have decided to save and restore errno anyway; on most | |
247 | architectures on which secnet can run modifications to errno | |
248 | will be atomic, and it seems to be the lesser of the two | |
249 | evils. */ | |
250 | saved_errno=errno; | |
7138d0c5 SE |
251 | write(spw,&thing,1); /* We don't care if this fails (i.e. the pipe |
252 | is full) because the service routine will | |
253 | spot the pending signal anyway */ | |
ff05a229 | 254 | errno=saved_errno; |
7138d0c5 SE |
255 | } |
256 | ||
257 | static void register_signal_handler(struct signotify *s) | |
258 | { | |
259 | struct sigaction sa; | |
260 | int rv; | |
261 | ||
262 | if (!signal_handling) return; | |
263 | ||
264 | if (sigismember(®istered,s->signum)) return; | |
265 | sigaddset(®istered,s->signum); | |
266 | ||
267 | sa.sa_handler=signal_handler; | |
268 | sa.sa_mask=fullset; | |
269 | sa.sa_flags=0; | |
270 | rv=sigaction(s->signum,&sa,NULL); | |
271 | if (rv!=0) { | |
272 | fatal_perror("register_signal_handler: sigaction(%d)",s->signum); | |
273 | } | |
274 | } | |
275 | ||
276 | void request_signal_notification(int signum, signal_notify_fn *notify, | |
277 | void *cst) | |
278 | { | |
279 | struct signotify *s; | |
280 | sigset_t old; | |
281 | ||
282 | s=safe_malloc(sizeof(*s),"request_signal_notification"); | |
283 | s->signum=signum; | |
284 | s->notify=notify; | |
285 | s->cst=cst; | |
286 | s->next=sigs; | |
287 | sigprocmask(SIG_SETMASK,&fullset,&old); | |
288 | sigs=s; | |
289 | register_signal_handler(s); | |
290 | sigprocmask(SIG_SETMASK,&old,NULL); | |
291 | } | |
292 | ||
293 | void start_signal_handling(void) | |
294 | { | |
295 | int p[2]; | |
296 | struct signotify *i; | |
297 | ||
298 | sigemptyset(&emptyset); | |
299 | sigfillset(&fullset); | |
300 | sigemptyset(®istered); | |
301 | sigemptyset(&pending); | |
302 | ||
303 | if (pipe(p)!=0) { | |
304 | fatal_perror("start_signal_handling: pipe"); | |
305 | } | |
306 | spw=p[1]; | |
307 | spr=p[0]; | |
308 | if (fcntl(spw, F_SETFL, fcntl(spw, F_GETFL)|O_NONBLOCK)==-1) { | |
309 | fatal_perror("start_signal_handling: fcntl(O_NONBLOCK)"); | |
310 | } | |
311 | ||
312 | register_for_poll(NULL,signal_beforepoll,signal_afterpoll,1,"signal"); | |
313 | signal_handling=True; | |
314 | ||
315 | /* Register signal handlers for all the signals we're interested in */ | |
316 | for (i=sigs; i; i=i->next) { | |
317 | register_signal_handler(i); | |
318 | } | |
319 | ||
320 | request_signal_notification(SIGCHLD,sigchld_handler,NULL); | |
321 | } |