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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}
1/*
2 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
3 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
4 * Copyright (C) 2004 PathScale, Inc
5 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
6 * Licensed under the GPL
7 */
8
9#include <stdlib.h>
10#include <stdarg.h>
11#include <errno.h>
12#include <signal.h>
13#include <strings.h>
14#include <as-layout.h>
15#include <kern_util.h>
16#include <os.h>
17#include <sysdep/mcontext.h>
18#include <um_malloc.h>
19
20void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
21 [SIGTRAP] = relay_signal,
22 [SIGFPE] = relay_signal,
23 [SIGILL] = relay_signal,
24 [SIGWINCH] = winch,
25 [SIGBUS] = bus_handler,
26 [SIGSEGV] = segv_handler,
27 [SIGIO] = sigio_handler,
28 [SIGALRM] = timer_handler
29};
30
31static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
32{
33 struct uml_pt_regs *r;
34 int save_errno = errno;
35
36 r = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
37 if (!r)
38 panic("out of memory");
39
40 r->is_user = 0;
41 if (sig == SIGSEGV) {
42 /* For segfaults, we want the data from the sigcontext. */
43 get_regs_from_mc(r, mc);
44 GET_FAULTINFO_FROM_MC(r->faultinfo, mc);
45 }
46
47 /* enable signals if sig isn't IRQ signal */
48 if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
49 unblock_signals();
50
51 (*sig_info[sig])(sig, si, r);
52
53 errno = save_errno;
54
55 free(r);
56}
57
58/*
59 * These are the asynchronous signals. SIGPROF is excluded because we want to
60 * be able to profile all of UML, not just the non-critical sections. If
61 * profiling is not thread-safe, then that is not my problem. We can disable
62 * profiling when SMP is enabled in that case.
63 */
64#define SIGIO_BIT 0
65#define SIGIO_MASK (1 << SIGIO_BIT)
66
67#define SIGALRM_BIT 1
68#define SIGALRM_MASK (1 << SIGALRM_BIT)
69
70static int signals_enabled;
71static unsigned int signals_pending;
72static unsigned int signals_active = 0;
73
74void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
75{
76 int enabled;
77
78 enabled = signals_enabled;
79 if (!enabled && (sig == SIGIO)) {
80 signals_pending |= SIGIO_MASK;
81 return;
82 }
83
84 block_signals();
85
86 sig_handler_common(sig, si, mc);
87
88 set_signals(enabled);
89}
90
91static void timer_real_alarm_handler(mcontext_t *mc)
92{
93 struct uml_pt_regs *regs;
94
95 regs = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
96 if (!regs)
97 panic("out of memory");
98
99 if (mc != NULL)
100 get_regs_from_mc(regs, mc);
101 timer_handler(SIGALRM, NULL, regs);
102
103 free(regs);
104}
105
106void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
107{
108 int enabled;
109
110 enabled = signals_enabled;
111 if (!signals_enabled) {
112 signals_pending |= SIGALRM_MASK;
113 return;
114 }
115
116 block_signals();
117
118 signals_active |= SIGALRM_MASK;
119
120 timer_real_alarm_handler(mc);
121
122 signals_active &= ~SIGALRM_MASK;
123
124 set_signals(enabled);
125}
126
127void deliver_alarm(void) {
128 timer_alarm_handler(SIGALRM, NULL, NULL);
129}
130
131void timer_set_signal_handler(void)
132{
133 set_handler(SIGALRM);
134}
135
136void set_sigstack(void *sig_stack, int size)
137{
138 stack_t stack = {
139 .ss_flags = 0,
140 .ss_sp = sig_stack,
141 .ss_size = size - sizeof(void *)
142 };
143
144 if (sigaltstack(&stack, NULL) != 0)
145 panic("enabling signal stack failed, errno = %d\n", errno);
146}
147
148static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
149 [SIGSEGV] = sig_handler,
150 [SIGBUS] = sig_handler,
151 [SIGILL] = sig_handler,
152 [SIGFPE] = sig_handler,
153 [SIGTRAP] = sig_handler,
154
155 [SIGIO] = sig_handler,
156 [SIGWINCH] = sig_handler,
157 [SIGALRM] = timer_alarm_handler
158};
159
160static void hard_handler(int sig, siginfo_t *si, void *p)
161{
162 struct ucontext *uc = p;
163 mcontext_t *mc = &uc->uc_mcontext;
164 unsigned long pending = 1UL << sig;
165
166 do {
167 int nested, bail;
168
169 /*
170 * pending comes back with one bit set for each
171 * interrupt that arrived while setting up the stack,
172 * plus a bit for this interrupt, plus the zero bit is
173 * set if this is a nested interrupt.
174 * If bail is true, then we interrupted another
175 * handler setting up the stack. In this case, we
176 * have to return, and the upper handler will deal
177 * with this interrupt.
178 */
179 bail = to_irq_stack(&pending);
180 if (bail)
181 return;
182
183 nested = pending & 1;
184 pending &= ~1;
185
186 while ((sig = ffs(pending)) != 0){
187 sig--;
188 pending &= ~(1 << sig);
189 (*handlers[sig])(sig, (struct siginfo *)si, mc);
190 }
191
192 /*
193 * Again, pending comes back with a mask of signals
194 * that arrived while tearing down the stack. If this
195 * is non-zero, we just go back, set up the stack
196 * again, and handle the new interrupts.
197 */
198 if (!nested)
199 pending = from_irq_stack(nested);
200 } while (pending);
201}
202
203void set_handler(int sig)
204{
205 struct sigaction action;
206 int flags = SA_SIGINFO | SA_ONSTACK;
207 sigset_t sig_mask;
208
209 action.sa_sigaction = hard_handler;
210
211 /* block irq ones */
212 sigemptyset(&action.sa_mask);
213 sigaddset(&action.sa_mask, SIGIO);
214 sigaddset(&action.sa_mask, SIGWINCH);
215 sigaddset(&action.sa_mask, SIGALRM);
216
217 if (sig == SIGSEGV)
218 flags |= SA_NODEFER;
219
220 if (sigismember(&action.sa_mask, sig))
221 flags |= SA_RESTART; /* if it's an irq signal */
222
223 action.sa_flags = flags;
224 action.sa_restorer = NULL;
225 if (sigaction(sig, &action, NULL) < 0)
226 panic("sigaction failed - errno = %d\n", errno);
227
228 sigemptyset(&sig_mask);
229 sigaddset(&sig_mask, sig);
230 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
231 panic("sigprocmask failed - errno = %d\n", errno);
232}
233
234int change_sig(int signal, int on)
235{
236 sigset_t sigset;
237
238 sigemptyset(&sigset);
239 sigaddset(&sigset, signal);
240 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
241 return -errno;
242
243 return 0;
244}
245
246void block_signals(void)
247{
248 signals_enabled = 0;
249 /*
250 * This must return with signals disabled, so this barrier
251 * ensures that writes are flushed out before the return.
252 * This might matter if gcc figures out how to inline this and
253 * decides to shuffle this code into the caller.
254 */
255 barrier();
256}
257
258void unblock_signals(void)
259{
260 int save_pending;
261
262 if (signals_enabled == 1)
263 return;
264
265 /*
266 * We loop because the IRQ handler returns with interrupts off. So,
267 * interrupts may have arrived and we need to re-enable them and
268 * recheck signals_pending.
269 */
270 while (1) {
271 /*
272 * Save and reset save_pending after enabling signals. This
273 * way, signals_pending won't be changed while we're reading it.
274 */
275 signals_enabled = 1;
276
277 /*
278 * Setting signals_enabled and reading signals_pending must
279 * happen in this order.
280 */
281 barrier();
282
283 save_pending = signals_pending;
284 if (save_pending == 0)
285 return;
286
287 signals_pending = 0;
288
289 /*
290 * We have pending interrupts, so disable signals, as the
291 * handlers expect them off when they are called. They will
292 * be enabled again above.
293 */
294
295 signals_enabled = 0;
296
297 /*
298 * Deal with SIGIO first because the alarm handler might
299 * schedule, leaving the pending SIGIO stranded until we come
300 * back here.
301 *
302 * SIGIO's handler doesn't use siginfo or mcontext,
303 * so they can be NULL.
304 */
305 if (save_pending & SIGIO_MASK)
306 sig_handler_common(SIGIO, NULL, NULL);
307
308 /* Do not reenter the handler */
309
310 if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))
311 timer_real_alarm_handler(NULL);
312
313 /* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */
314
315 if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK))
316 return;
317
318 }
319}
320
321int get_signals(void)
322{
323 return signals_enabled;
324}
325
326int set_signals(int enable)
327{
328 int ret;
329 if (signals_enabled == enable)
330 return enable;
331
332 ret = signals_enabled;
333 if (enable)
334 unblock_signals();
335 else block_signals();
336
337 return ret;
338}
339
340int os_is_signal_stack(void)
341{
342 stack_t ss;
343 sigaltstack(NULL, &ss);
344
345 return ss.ss_flags & SS_ONSTACK;
346}