Loading...
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
4 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
5 * Copyright (C) 2004 PathScale, Inc
6 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
7 */
8
9#include <stdlib.h>
10#include <stdarg.h>
11#include <stdbool.h>
12#include <errno.h>
13#include <signal.h>
14#include <string.h>
15#include <strings.h>
16#include <as-layout.h>
17#include <kern_util.h>
18#include <os.h>
19#include <sysdep/mcontext.h>
20#include <um_malloc.h>
21#include <sys/ucontext.h>
22#include <timetravel.h>
23
24void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
25 [SIGTRAP] = relay_signal,
26 [SIGFPE] = relay_signal,
27 [SIGILL] = relay_signal,
28 [SIGWINCH] = winch,
29 [SIGBUS] = relay_signal,
30 [SIGSEGV] = segv_handler,
31 [SIGIO] = sigio_handler,
32};
33
34static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
35{
36 struct uml_pt_regs r;
37 int save_errno = errno;
38
39 r.is_user = 0;
40 if (sig == SIGSEGV) {
41 /* For segfaults, we want the data from the sigcontext. */
42 get_regs_from_mc(&r, mc);
43 GET_FAULTINFO_FROM_MC(r.faultinfo, mc);
44 }
45
46 /* enable signals if sig isn't IRQ signal */
47 if ((sig != SIGIO) && (sig != SIGWINCH))
48 unblock_signals_trace();
49
50 (*sig_info[sig])(sig, si, &r);
51
52 errno = save_errno;
53}
54
55/*
56 * These are the asynchronous signals. SIGPROF is excluded because we want to
57 * be able to profile all of UML, not just the non-critical sections. If
58 * profiling is not thread-safe, then that is not my problem. We can disable
59 * profiling when SMP is enabled in that case.
60 */
61#define SIGIO_BIT 0
62#define SIGIO_MASK (1 << SIGIO_BIT)
63
64#define SIGALRM_BIT 1
65#define SIGALRM_MASK (1 << SIGALRM_BIT)
66
67int signals_enabled;
68#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
69static int signals_blocked, signals_blocked_pending;
70#endif
71static unsigned int signals_pending;
72static unsigned int signals_active = 0;
73
74static void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
75{
76 int enabled = signals_enabled;
77
78#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
79 if ((signals_blocked ||
80 __atomic_load_n(&signals_blocked_pending, __ATOMIC_SEQ_CST)) &&
81 (sig == SIGIO)) {
82 /* increment so unblock will do another round */
83 __atomic_add_fetch(&signals_blocked_pending, 1,
84 __ATOMIC_SEQ_CST);
85 return;
86 }
87#endif
88
89 if (!enabled && (sig == SIGIO)) {
90 /*
91 * In TT_MODE_EXTERNAL, need to still call time-travel
92 * handlers. This will mark signals_pending by itself
93 * (only if necessary.)
94 * Note we won't get here if signals are hard-blocked
95 * (which is handled above), in that case the hard-
96 * unblock will handle things.
97 */
98 if (time_travel_mode == TT_MODE_EXTERNAL)
99 sigio_run_timetravel_handlers();
100 else
101 signals_pending |= SIGIO_MASK;
102 return;
103 }
104
105 block_signals_trace();
106
107 sig_handler_common(sig, si, mc);
108
109 um_set_signals_trace(enabled);
110}
111
112static void timer_real_alarm_handler(mcontext_t *mc)
113{
114 struct uml_pt_regs regs;
115
116 if (mc != NULL)
117 get_regs_from_mc(®s, mc);
118 else
119 memset(®s, 0, sizeof(regs));
120 timer_handler(SIGALRM, NULL, ®s);
121}
122
123static void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
124{
125 int enabled;
126
127 enabled = signals_enabled;
128 if (!signals_enabled) {
129 signals_pending |= SIGALRM_MASK;
130 return;
131 }
132
133 block_signals_trace();
134
135 signals_active |= SIGALRM_MASK;
136
137 timer_real_alarm_handler(mc);
138
139 signals_active &= ~SIGALRM_MASK;
140
141 um_set_signals_trace(enabled);
142}
143
144void deliver_alarm(void) {
145 timer_alarm_handler(SIGALRM, NULL, NULL);
146}
147
148void timer_set_signal_handler(void)
149{
150 set_handler(SIGALRM);
151}
152
153void set_sigstack(void *sig_stack, int size)
154{
155 stack_t stack = {
156 .ss_flags = 0,
157 .ss_sp = sig_stack,
158 .ss_size = size
159 };
160
161 if (sigaltstack(&stack, NULL) != 0)
162 panic("enabling signal stack failed, errno = %d\n", errno);
163}
164
165static void sigusr1_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
166{
167 uml_pm_wake();
168}
169
170void register_pm_wake_signal(void)
171{
172 set_handler(SIGUSR1);
173}
174
175static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
176 [SIGSEGV] = sig_handler,
177 [SIGBUS] = sig_handler,
178 [SIGILL] = sig_handler,
179 [SIGFPE] = sig_handler,
180 [SIGTRAP] = sig_handler,
181
182 [SIGIO] = sig_handler,
183 [SIGWINCH] = sig_handler,
184 [SIGALRM] = timer_alarm_handler,
185
186 [SIGUSR1] = sigusr1_handler,
187};
188
189static void hard_handler(int sig, siginfo_t *si, void *p)
190{
191 ucontext_t *uc = p;
192 mcontext_t *mc = &uc->uc_mcontext;
193
194 (*handlers[sig])(sig, (struct siginfo *)si, mc);
195}
196
197void set_handler(int sig)
198{
199 struct sigaction action;
200 int flags = SA_SIGINFO | SA_ONSTACK;
201 sigset_t sig_mask;
202
203 action.sa_sigaction = hard_handler;
204
205 /* block irq ones */
206 sigemptyset(&action.sa_mask);
207 sigaddset(&action.sa_mask, SIGIO);
208 sigaddset(&action.sa_mask, SIGWINCH);
209 sigaddset(&action.sa_mask, SIGALRM);
210
211 if (sig == SIGSEGV)
212 flags |= SA_NODEFER;
213
214 if (sigismember(&action.sa_mask, sig))
215 flags |= SA_RESTART; /* if it's an irq signal */
216
217 action.sa_flags = flags;
218 action.sa_restorer = NULL;
219 if (sigaction(sig, &action, NULL) < 0)
220 panic("sigaction failed - errno = %d\n", errno);
221
222 sigemptyset(&sig_mask);
223 sigaddset(&sig_mask, sig);
224 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
225 panic("sigprocmask failed - errno = %d\n", errno);
226}
227
228void send_sigio_to_self(void)
229{
230 kill(os_getpid(), SIGIO);
231}
232
233int change_sig(int signal, int on)
234{
235 sigset_t sigset;
236
237 sigemptyset(&sigset);
238 sigaddset(&sigset, signal);
239 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
240 return -errno;
241
242 return 0;
243}
244
245void block_signals(void)
246{
247 signals_enabled = 0;
248 /*
249 * This must return with signals disabled, so this barrier
250 * ensures that writes are flushed out before the return.
251 * This might matter if gcc figures out how to inline this and
252 * decides to shuffle this code into the caller.
253 */
254 barrier();
255}
256
257void unblock_signals(void)
258{
259 int save_pending;
260
261 if (signals_enabled == 1)
262 return;
263
264 signals_enabled = 1;
265#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
266 deliver_time_travel_irqs();
267#endif
268
269 /*
270 * We loop because the IRQ handler returns with interrupts off. So,
271 * interrupts may have arrived and we need to re-enable them and
272 * recheck signals_pending.
273 */
274 while (1) {
275 /*
276 * Save and reset save_pending after enabling signals. This
277 * way, signals_pending won't be changed while we're reading it.
278 *
279 * Setting signals_enabled and reading signals_pending must
280 * happen in this order, so have the barrier here.
281 */
282 barrier();
283
284 save_pending = signals_pending;
285 if (save_pending == 0)
286 return;
287
288 signals_pending = 0;
289
290 /*
291 * We have pending interrupts, so disable signals, as the
292 * handlers expect them off when they are called. They will
293 * be enabled again above. We need to trace this, as we're
294 * expected to be enabling interrupts already, but any more
295 * tracing that happens inside the handlers we call for the
296 * pending signals will mess up the tracing state.
297 */
298 signals_enabled = 0;
299 um_trace_signals_off();
300
301 /*
302 * Deal with SIGIO first because the alarm handler might
303 * schedule, leaving the pending SIGIO stranded until we come
304 * back here.
305 *
306 * SIGIO's handler doesn't use siginfo or mcontext,
307 * so they can be NULL.
308 */
309 if (save_pending & SIGIO_MASK)
310 sig_handler_common(SIGIO, NULL, NULL);
311
312 /* Do not reenter the handler */
313
314 if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))
315 timer_real_alarm_handler(NULL);
316
317 /* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */
318
319 if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK))
320 return;
321
322 /* Re-enable signals and trace that we're doing so. */
323 um_trace_signals_on();
324 signals_enabled = 1;
325 }
326}
327
328int um_set_signals(int enable)
329{
330 int ret;
331 if (signals_enabled == enable)
332 return enable;
333
334 ret = signals_enabled;
335 if (enable)
336 unblock_signals();
337 else block_signals();
338
339 return ret;
340}
341
342int um_set_signals_trace(int enable)
343{
344 int ret;
345 if (signals_enabled == enable)
346 return enable;
347
348 ret = signals_enabled;
349 if (enable)
350 unblock_signals_trace();
351 else
352 block_signals_trace();
353
354 return ret;
355}
356
357#if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
358void mark_sigio_pending(void)
359{
360 /*
361 * It would seem that this should be atomic so
362 * it isn't a read-modify-write with a signal
363 * that could happen in the middle, losing the
364 * value set by the signal.
365 *
366 * However, this function is only called when in
367 * time-travel=ext simulation mode, in which case
368 * the only signal ever pending is SIGIO, which
369 * is blocked while this can be called, and the
370 * timer signal (SIGALRM) cannot happen.
371 */
372 signals_pending |= SIGIO_MASK;
373}
374
375void block_signals_hard(void)
376{
377 signals_blocked++;
378 barrier();
379}
380
381void unblock_signals_hard(void)
382{
383 static bool unblocking;
384
385 if (!signals_blocked)
386 panic("unblocking signals while not blocked");
387
388 if (--signals_blocked)
389 return;
390 /*
391 * Must be set to 0 before we check pending so the
392 * SIGIO handler will run as normal unless we're still
393 * going to process signals_blocked_pending.
394 */
395 barrier();
396
397 /*
398 * Note that block_signals_hard()/unblock_signals_hard() can be called
399 * within the unblock_signals()/sigio_run_timetravel_handlers() below.
400 * This would still be prone to race conditions since it's actually a
401 * call _within_ e.g. vu_req_read_message(), where we observed this
402 * issue, which loops. Thus, if the inner call handles the recorded
403 * pending signals, we can get out of the inner call with the real
404 * signal hander no longer blocked, and still have a race. Thus don't
405 * handle unblocking in the inner call, if it happens, but only in
406 * the outermost call - 'unblocking' serves as an ownership for the
407 * signals_blocked_pending decrement.
408 */
409 if (unblocking)
410 return;
411 unblocking = true;
412
413 while (__atomic_load_n(&signals_blocked_pending, __ATOMIC_SEQ_CST)) {
414 if (signals_enabled) {
415 /* signals are enabled so we can touch this */
416 signals_pending |= SIGIO_MASK;
417 /*
418 * this is a bit inefficient, but that's
419 * not really important
420 */
421 block_signals();
422 unblock_signals();
423 } else {
424 /*
425 * we need to run time-travel handlers even
426 * if not enabled
427 */
428 sigio_run_timetravel_handlers();
429 }
430
431 /*
432 * The decrement of signals_blocked_pending must be atomic so
433 * that the signal handler will either happen before or after
434 * the decrement, not during a read-modify-write:
435 * - If it happens before, it can increment it and we'll
436 * decrement it and do another round in the loop.
437 * - If it happens after it'll see 0 for both signals_blocked
438 * and signals_blocked_pending and thus run the handler as
439 * usual (subject to signals_enabled, but that's unrelated.)
440 *
441 * Note that a call to unblock_signals_hard() within the calls
442 * to unblock_signals() or sigio_run_timetravel_handlers() above
443 * will do nothing due to the 'unblocking' state, so this cannot
444 * underflow as the only one decrementing will be the outermost
445 * one.
446 */
447 if (__atomic_sub_fetch(&signals_blocked_pending, 1,
448 __ATOMIC_SEQ_CST) < 0)
449 panic("signals_blocked_pending underflow");
450 }
451
452 unblocking = false;
453}
454#endif
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
4 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
5 * Copyright (C) 2004 PathScale, Inc
6 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
7 */
8
9#include <stdlib.h>
10#include <stdarg.h>
11#include <errno.h>
12#include <signal.h>
13#include <string.h>
14#include <strings.h>
15#include <as-layout.h>
16#include <kern_util.h>
17#include <os.h>
18#include <sysdep/mcontext.h>
19#include <um_malloc.h>
20#include <sys/ucontext.h>
21
22void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
23 [SIGTRAP] = relay_signal,
24 [SIGFPE] = relay_signal,
25 [SIGILL] = relay_signal,
26 [SIGWINCH] = winch,
27 [SIGBUS] = bus_handler,
28 [SIGSEGV] = segv_handler,
29 [SIGIO] = sigio_handler,
30};
31
32static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
33{
34 struct uml_pt_regs r;
35 int save_errno = errno;
36
37 r.is_user = 0;
38 if (sig == SIGSEGV) {
39 /* For segfaults, we want the data from the sigcontext. */
40 get_regs_from_mc(&r, mc);
41 GET_FAULTINFO_FROM_MC(r.faultinfo, mc);
42 }
43
44 /* enable signals if sig isn't IRQ signal */
45 if ((sig != SIGIO) && (sig != SIGWINCH))
46 unblock_signals_trace();
47
48 (*sig_info[sig])(sig, si, &r);
49
50 errno = save_errno;
51}
52
53/*
54 * These are the asynchronous signals. SIGPROF is excluded because we want to
55 * be able to profile all of UML, not just the non-critical sections. If
56 * profiling is not thread-safe, then that is not my problem. We can disable
57 * profiling when SMP is enabled in that case.
58 */
59#define SIGIO_BIT 0
60#define SIGIO_MASK (1 << SIGIO_BIT)
61
62#define SIGALRM_BIT 1
63#define SIGALRM_MASK (1 << SIGALRM_BIT)
64
65static int signals_enabled;
66static unsigned int signals_pending;
67static unsigned int signals_active = 0;
68
69void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
70{
71 int enabled;
72
73 enabled = signals_enabled;
74 if (!enabled && (sig == SIGIO)) {
75 signals_pending |= SIGIO_MASK;
76 return;
77 }
78
79 block_signals_trace();
80
81 sig_handler_common(sig, si, mc);
82
83 set_signals_trace(enabled);
84}
85
86static void timer_real_alarm_handler(mcontext_t *mc)
87{
88 struct uml_pt_regs regs;
89
90 if (mc != NULL)
91 get_regs_from_mc(®s, mc);
92 else
93 memset(®s, 0, sizeof(regs));
94 timer_handler(SIGALRM, NULL, ®s);
95}
96
97void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
98{
99 int enabled;
100
101 enabled = signals_enabled;
102 if (!signals_enabled) {
103 signals_pending |= SIGALRM_MASK;
104 return;
105 }
106
107 block_signals_trace();
108
109 signals_active |= SIGALRM_MASK;
110
111 timer_real_alarm_handler(mc);
112
113 signals_active &= ~SIGALRM_MASK;
114
115 set_signals_trace(enabled);
116}
117
118void deliver_alarm(void) {
119 timer_alarm_handler(SIGALRM, NULL, NULL);
120}
121
122void timer_set_signal_handler(void)
123{
124 set_handler(SIGALRM);
125}
126
127void set_sigstack(void *sig_stack, int size)
128{
129 stack_t stack = {
130 .ss_flags = 0,
131 .ss_sp = sig_stack,
132 .ss_size = size - sizeof(void *)
133 };
134
135 if (sigaltstack(&stack, NULL) != 0)
136 panic("enabling signal stack failed, errno = %d\n", errno);
137}
138
139static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
140 [SIGSEGV] = sig_handler,
141 [SIGBUS] = sig_handler,
142 [SIGILL] = sig_handler,
143 [SIGFPE] = sig_handler,
144 [SIGTRAP] = sig_handler,
145
146 [SIGIO] = sig_handler,
147 [SIGWINCH] = sig_handler,
148 [SIGALRM] = timer_alarm_handler
149};
150
151static void hard_handler(int sig, siginfo_t *si, void *p)
152{
153 ucontext_t *uc = p;
154 mcontext_t *mc = &uc->uc_mcontext;
155 unsigned long pending = 1UL << sig;
156
157 do {
158 int nested, bail;
159
160 /*
161 * pending comes back with one bit set for each
162 * interrupt that arrived while setting up the stack,
163 * plus a bit for this interrupt, plus the zero bit is
164 * set if this is a nested interrupt.
165 * If bail is true, then we interrupted another
166 * handler setting up the stack. In this case, we
167 * have to return, and the upper handler will deal
168 * with this interrupt.
169 */
170 bail = to_irq_stack(&pending);
171 if (bail)
172 return;
173
174 nested = pending & 1;
175 pending &= ~1;
176
177 while ((sig = ffs(pending)) != 0){
178 sig--;
179 pending &= ~(1 << sig);
180 (*handlers[sig])(sig, (struct siginfo *)si, mc);
181 }
182
183 /*
184 * Again, pending comes back with a mask of signals
185 * that arrived while tearing down the stack. If this
186 * is non-zero, we just go back, set up the stack
187 * again, and handle the new interrupts.
188 */
189 if (!nested)
190 pending = from_irq_stack(nested);
191 } while (pending);
192}
193
194void set_handler(int sig)
195{
196 struct sigaction action;
197 int flags = SA_SIGINFO | SA_ONSTACK;
198 sigset_t sig_mask;
199
200 action.sa_sigaction = hard_handler;
201
202 /* block irq ones */
203 sigemptyset(&action.sa_mask);
204 sigaddset(&action.sa_mask, SIGIO);
205 sigaddset(&action.sa_mask, SIGWINCH);
206 sigaddset(&action.sa_mask, SIGALRM);
207
208 if (sig == SIGSEGV)
209 flags |= SA_NODEFER;
210
211 if (sigismember(&action.sa_mask, sig))
212 flags |= SA_RESTART; /* if it's an irq signal */
213
214 action.sa_flags = flags;
215 action.sa_restorer = NULL;
216 if (sigaction(sig, &action, NULL) < 0)
217 panic("sigaction failed - errno = %d\n", errno);
218
219 sigemptyset(&sig_mask);
220 sigaddset(&sig_mask, sig);
221 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
222 panic("sigprocmask failed - errno = %d\n", errno);
223}
224
225int change_sig(int signal, int on)
226{
227 sigset_t sigset;
228
229 sigemptyset(&sigset);
230 sigaddset(&sigset, signal);
231 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
232 return -errno;
233
234 return 0;
235}
236
237void block_signals(void)
238{
239 signals_enabled = 0;
240 /*
241 * This must return with signals disabled, so this barrier
242 * ensures that writes are flushed out before the return.
243 * This might matter if gcc figures out how to inline this and
244 * decides to shuffle this code into the caller.
245 */
246 barrier();
247}
248
249void unblock_signals(void)
250{
251 int save_pending;
252
253 if (signals_enabled == 1)
254 return;
255
256 signals_enabled = 1;
257
258 /*
259 * We loop because the IRQ handler returns with interrupts off. So,
260 * interrupts may have arrived and we need to re-enable them and
261 * recheck signals_pending.
262 */
263 while (1) {
264 /*
265 * Save and reset save_pending after enabling signals. This
266 * way, signals_pending won't be changed while we're reading it.
267 *
268 * Setting signals_enabled and reading signals_pending must
269 * happen in this order, so have the barrier here.
270 */
271 barrier();
272
273 save_pending = signals_pending;
274 if (save_pending == 0)
275 return;
276
277 signals_pending = 0;
278
279 /*
280 * We have pending interrupts, so disable signals, as the
281 * handlers expect them off when they are called. They will
282 * be enabled again above. We need to trace this, as we're
283 * expected to be enabling interrupts already, but any more
284 * tracing that happens inside the handlers we call for the
285 * pending signals will mess up the tracing state.
286 */
287 signals_enabled = 0;
288 um_trace_signals_off();
289
290 /*
291 * Deal with SIGIO first because the alarm handler might
292 * schedule, leaving the pending SIGIO stranded until we come
293 * back here.
294 *
295 * SIGIO's handler doesn't use siginfo or mcontext,
296 * so they can be NULL.
297 */
298 if (save_pending & SIGIO_MASK)
299 sig_handler_common(SIGIO, NULL, NULL);
300
301 /* Do not reenter the handler */
302
303 if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))
304 timer_real_alarm_handler(NULL);
305
306 /* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */
307
308 if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK))
309 return;
310
311 /* Re-enable signals and trace that we're doing so. */
312 um_trace_signals_on();
313 signals_enabled = 1;
314 }
315}
316
317int get_signals(void)
318{
319 return signals_enabled;
320}
321
322int set_signals(int enable)
323{
324 int ret;
325 if (signals_enabled == enable)
326 return enable;
327
328 ret = signals_enabled;
329 if (enable)
330 unblock_signals();
331 else block_signals();
332
333 return ret;
334}
335
336int set_signals_trace(int enable)
337{
338 int ret;
339 if (signals_enabled == enable)
340 return enable;
341
342 ret = signals_enabled;
343 if (enable)
344 unblock_signals_trace();
345 else
346 block_signals_trace();
347
348 return ret;
349}
350
351int os_is_signal_stack(void)
352{
353 stack_t ss;
354 sigaltstack(NULL, &ss);
355
356 return ss.ss_flags & SS_ONSTACK;
357}