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 <sys/ucontext.h>
18 #include <sysdep/mcontext.h>
19 #include <um_malloc.h>
20
21 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
22 [SIGTRAP] = relay_signal,
23 [SIGFPE] = relay_signal,
24 [SIGILL] = relay_signal,
25 [SIGWINCH] = winch,
26 [SIGBUS] = bus_handler,
27 [SIGSEGV] = segv_handler,
28 [SIGIO] = sigio_handler,
29 [SIGALRM] = timer_handler
30 };
31
sig_handler_common(int sig,struct siginfo * si,mcontext_t * mc)32 static 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) && (sig != SIGALRM))
46 unblock_signals();
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
65 static int signals_enabled;
66 static unsigned int signals_pending;
67
sig_handler(int sig,struct siginfo * si,mcontext_t * mc)68 void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
69 {
70 int enabled;
71
72 enabled = signals_enabled;
73 if (!enabled && (sig == SIGIO)) {
74 signals_pending |= SIGIO_MASK;
75 return;
76 }
77
78 block_signals();
79
80 sig_handler_common(sig, si, mc);
81
82 set_signals(enabled);
83 }
84
timer_real_alarm_handler(mcontext_t * mc)85 static void timer_real_alarm_handler(mcontext_t *mc)
86 {
87 struct uml_pt_regs regs;
88
89 if (mc != NULL)
90 get_regs_from_mc(®s, mc);
91 timer_handler(SIGALRM, NULL, ®s);
92 }
93
timer_alarm_handler(int sig,struct siginfo * unused_si,mcontext_t * mc)94 void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
95 {
96 int enabled;
97
98 enabled = signals_enabled;
99 if (!signals_enabled) {
100 signals_pending |= SIGALRM_MASK;
101 return;
102 }
103
104 block_signals();
105
106 timer_real_alarm_handler(mc);
107 set_signals(enabled);
108 }
109
deliver_alarm(void)110 void deliver_alarm(void) {
111 timer_alarm_handler(SIGALRM, NULL, NULL);
112 }
113
timer_set_signal_handler(void)114 void timer_set_signal_handler(void)
115 {
116 set_handler(SIGALRM);
117 }
118
set_sigstack(void * sig_stack,int size)119 void set_sigstack(void *sig_stack, int size)
120 {
121 stack_t stack = {
122 .ss_flags = 0,
123 .ss_sp = sig_stack,
124 .ss_size = size - sizeof(void *)
125 };
126
127 if (sigaltstack(&stack, NULL) != 0)
128 panic("enabling signal stack failed, errno = %d\n", errno);
129 }
130
131 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
132 [SIGSEGV] = sig_handler,
133 [SIGBUS] = sig_handler,
134 [SIGILL] = sig_handler,
135 [SIGFPE] = sig_handler,
136 [SIGTRAP] = sig_handler,
137
138 [SIGIO] = sig_handler,
139 [SIGWINCH] = sig_handler,
140 [SIGALRM] = timer_alarm_handler
141 };
142
hard_handler(int sig,siginfo_t * si,void * p)143 static void hard_handler(int sig, siginfo_t *si, void *p)
144 {
145 ucontext_t *uc = p;
146 mcontext_t *mc = &uc->uc_mcontext;
147 unsigned long pending = 1UL << sig;
148
149 do {
150 int nested, bail;
151
152 /*
153 * pending comes back with one bit set for each
154 * interrupt that arrived while setting up the stack,
155 * plus a bit for this interrupt, plus the zero bit is
156 * set if this is a nested interrupt.
157 * If bail is true, then we interrupted another
158 * handler setting up the stack. In this case, we
159 * have to return, and the upper handler will deal
160 * with this interrupt.
161 */
162 bail = to_irq_stack(&pending);
163 if (bail)
164 return;
165
166 nested = pending & 1;
167 pending &= ~1;
168
169 while ((sig = ffs(pending)) != 0){
170 sig--;
171 pending &= ~(1 << sig);
172 (*handlers[sig])(sig, (struct siginfo *)si, mc);
173 }
174
175 /*
176 * Again, pending comes back with a mask of signals
177 * that arrived while tearing down the stack. If this
178 * is non-zero, we just go back, set up the stack
179 * again, and handle the new interrupts.
180 */
181 if (!nested)
182 pending = from_irq_stack(nested);
183 } while (pending);
184 }
185
set_handler(int sig)186 void set_handler(int sig)
187 {
188 struct sigaction action;
189 int flags = SA_SIGINFO | SA_ONSTACK;
190 sigset_t sig_mask;
191
192 action.sa_sigaction = hard_handler;
193
194 /* block irq ones */
195 sigemptyset(&action.sa_mask);
196 sigaddset(&action.sa_mask, SIGIO);
197 sigaddset(&action.sa_mask, SIGWINCH);
198 sigaddset(&action.sa_mask, SIGALRM);
199
200 if (sig == SIGSEGV)
201 flags |= SA_NODEFER;
202
203 if (sigismember(&action.sa_mask, sig))
204 flags |= SA_RESTART; /* if it's an irq signal */
205
206 action.sa_flags = flags;
207 action.sa_restorer = NULL;
208 if (sigaction(sig, &action, NULL) < 0)
209 panic("sigaction failed - errno = %d\n", errno);
210
211 sigemptyset(&sig_mask);
212 sigaddset(&sig_mask, sig);
213 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
214 panic("sigprocmask failed - errno = %d\n", errno);
215 }
216
change_sig(int signal,int on)217 int change_sig(int signal, int on)
218 {
219 sigset_t sigset;
220
221 sigemptyset(&sigset);
222 sigaddset(&sigset, signal);
223 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
224 return -errno;
225
226 return 0;
227 }
228
block_signals(void)229 void block_signals(void)
230 {
231 signals_enabled = 0;
232 /*
233 * This must return with signals disabled, so this barrier
234 * ensures that writes are flushed out before the return.
235 * This might matter if gcc figures out how to inline this and
236 * decides to shuffle this code into the caller.
237 */
238 barrier();
239 }
240
unblock_signals(void)241 void unblock_signals(void)
242 {
243 int save_pending;
244
245 if (signals_enabled == 1)
246 return;
247
248 /*
249 * We loop because the IRQ handler returns with interrupts off. So,
250 * interrupts may have arrived and we need to re-enable them and
251 * recheck signals_pending.
252 */
253 while (1) {
254 /*
255 * Save and reset save_pending after enabling signals. This
256 * way, signals_pending won't be changed while we're reading it.
257 */
258 signals_enabled = 1;
259
260 /*
261 * Setting signals_enabled and reading signals_pending must
262 * happen in this order.
263 */
264 barrier();
265
266 save_pending = signals_pending;
267 if (save_pending == 0)
268 return;
269
270 signals_pending = 0;
271
272 /*
273 * We have pending interrupts, so disable signals, as the
274 * handlers expect them off when they are called. They will
275 * be enabled again above.
276 */
277
278 signals_enabled = 0;
279
280 /*
281 * Deal with SIGIO first because the alarm handler might
282 * schedule, leaving the pending SIGIO stranded until we come
283 * back here.
284 *
285 * SIGIO's handler doesn't use siginfo or mcontext,
286 * so they can be NULL.
287 */
288 if (save_pending & SIGIO_MASK)
289 sig_handler_common(SIGIO, NULL, NULL);
290
291 if (save_pending & SIGALRM_MASK)
292 timer_real_alarm_handler(NULL);
293 }
294 }
295
get_signals(void)296 int get_signals(void)
297 {
298 return signals_enabled;
299 }
300
set_signals(int enable)301 int set_signals(int enable)
302 {
303 int ret;
304 if (signals_enabled == enable)
305 return enable;
306
307 ret = signals_enabled;
308 if (enable)
309 unblock_signals();
310 else block_signals();
311
312 return ret;
313 }
314
os_is_signal_stack(void)315 int os_is_signal_stack(void)
316 {
317 stack_t ss;
318 sigaltstack(NULL, &ss);
319
320 return ss.ss_flags & SS_ONSTACK;
321 }
322