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 #include <sys/ucontext.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 = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
38 if (!r)
39 panic("out of memory");
40
41 r->is_user = 0;
42 if (sig == SIGSEGV) {
43 /* For segfaults, we want the data from the sigcontext. */
44 get_regs_from_mc(r, mc);
45 GET_FAULTINFO_FROM_MC(r->faultinfo, mc);
46 }
47
48 /* enable signals if sig isn't IRQ signal */
49 if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
50 unblock_signals();
51
52 (*sig_info[sig])(sig, si, r);
53
54 errno = save_errno;
55
56 free(r);
57 }
58
59 /*
60 * These are the asynchronous signals. SIGPROF is excluded because we want to
61 * be able to profile all of UML, not just the non-critical sections. If
62 * profiling is not thread-safe, then that is not my problem. We can disable
63 * profiling when SMP is enabled in that case.
64 */
65 #define SIGIO_BIT 0
66 #define SIGIO_MASK (1 << SIGIO_BIT)
67
68 #define SIGALRM_BIT 1
69 #define SIGALRM_MASK (1 << SIGALRM_BIT)
70
71 static int signals_enabled;
72 static unsigned int signals_pending;
73 static unsigned int signals_active = 0;
74
sig_handler(int sig,struct siginfo * si,mcontext_t * mc)75 void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
76 {
77 int enabled;
78
79 enabled = signals_enabled;
80 if (!enabled && (sig == SIGIO)) {
81 signals_pending |= SIGIO_MASK;
82 return;
83 }
84
85 block_signals();
86
87 sig_handler_common(sig, si, mc);
88
89 set_signals(enabled);
90 }
91
timer_real_alarm_handler(mcontext_t * mc)92 static void timer_real_alarm_handler(mcontext_t *mc)
93 {
94 struct uml_pt_regs *regs;
95
96 regs = uml_kmalloc(sizeof(struct uml_pt_regs), UM_GFP_ATOMIC);
97 if (!regs)
98 panic("out of memory");
99
100 if (mc != NULL)
101 get_regs_from_mc(regs, mc);
102 timer_handler(SIGALRM, NULL, regs);
103
104 free(regs);
105 }
106
timer_alarm_handler(int sig,struct siginfo * unused_si,mcontext_t * mc)107 void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
108 {
109 int enabled;
110
111 enabled = signals_enabled;
112 if (!signals_enabled) {
113 signals_pending |= SIGALRM_MASK;
114 return;
115 }
116
117 block_signals();
118
119 signals_active |= SIGALRM_MASK;
120
121 timer_real_alarm_handler(mc);
122
123 signals_active &= ~SIGALRM_MASK;
124
125 set_signals(enabled);
126 }
127
deliver_alarm(void)128 void deliver_alarm(void) {
129 timer_alarm_handler(SIGALRM, NULL, NULL);
130 }
131
timer_set_signal_handler(void)132 void timer_set_signal_handler(void)
133 {
134 set_handler(SIGALRM);
135 }
136
set_sigstack(void * sig_stack,int size)137 void set_sigstack(void *sig_stack, int size)
138 {
139 stack_t stack = {
140 .ss_flags = 0,
141 .ss_sp = sig_stack,
142 .ss_size = size - sizeof(void *)
143 };
144
145 if (sigaltstack(&stack, NULL) != 0)
146 panic("enabling signal stack failed, errno = %d\n", errno);
147 }
148
149 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
150 [SIGSEGV] = sig_handler,
151 [SIGBUS] = sig_handler,
152 [SIGILL] = sig_handler,
153 [SIGFPE] = sig_handler,
154 [SIGTRAP] = sig_handler,
155
156 [SIGIO] = sig_handler,
157 [SIGWINCH] = sig_handler,
158 [SIGALRM] = timer_alarm_handler
159 };
160
hard_handler(int sig,siginfo_t * si,void * p)161 static void hard_handler(int sig, siginfo_t *si, void *p)
162 {
163 ucontext_t *uc = p;
164 mcontext_t *mc = &uc->uc_mcontext;
165 unsigned long pending = 1UL << sig;
166
167 do {
168 int nested, bail;
169
170 /*
171 * pending comes back with one bit set for each
172 * interrupt that arrived while setting up the stack,
173 * plus a bit for this interrupt, plus the zero bit is
174 * set if this is a nested interrupt.
175 * If bail is true, then we interrupted another
176 * handler setting up the stack. In this case, we
177 * have to return, and the upper handler will deal
178 * with this interrupt.
179 */
180 bail = to_irq_stack(&pending);
181 if (bail)
182 return;
183
184 nested = pending & 1;
185 pending &= ~1;
186
187 while ((sig = ffs(pending)) != 0){
188 sig--;
189 pending &= ~(1 << sig);
190 (*handlers[sig])(sig, (struct siginfo *)si, mc);
191 }
192
193 /*
194 * Again, pending comes back with a mask of signals
195 * that arrived while tearing down the stack. If this
196 * is non-zero, we just go back, set up the stack
197 * again, and handle the new interrupts.
198 */
199 if (!nested)
200 pending = from_irq_stack(nested);
201 } while (pending);
202 }
203
set_handler(int sig)204 void set_handler(int sig)
205 {
206 struct sigaction action;
207 int flags = SA_SIGINFO | SA_ONSTACK;
208 sigset_t sig_mask;
209
210 action.sa_sigaction = hard_handler;
211
212 /* block irq ones */
213 sigemptyset(&action.sa_mask);
214 sigaddset(&action.sa_mask, SIGIO);
215 sigaddset(&action.sa_mask, SIGWINCH);
216 sigaddset(&action.sa_mask, SIGALRM);
217
218 if (sig == SIGSEGV)
219 flags |= SA_NODEFER;
220
221 if (sigismember(&action.sa_mask, sig))
222 flags |= SA_RESTART; /* if it's an irq signal */
223
224 action.sa_flags = flags;
225 action.sa_restorer = NULL;
226 if (sigaction(sig, &action, NULL) < 0)
227 panic("sigaction failed - errno = %d\n", errno);
228
229 sigemptyset(&sig_mask);
230 sigaddset(&sig_mask, sig);
231 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
232 panic("sigprocmask failed - errno = %d\n", errno);
233 }
234
change_sig(int signal,int on)235 int change_sig(int signal, int on)
236 {
237 sigset_t sigset;
238
239 sigemptyset(&sigset);
240 sigaddset(&sigset, signal);
241 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
242 return -errno;
243
244 return 0;
245 }
246
block_signals(void)247 void block_signals(void)
248 {
249 signals_enabled = 0;
250 /*
251 * This must return with signals disabled, so this barrier
252 * ensures that writes are flushed out before the return.
253 * This might matter if gcc figures out how to inline this and
254 * decides to shuffle this code into the caller.
255 */
256 barrier();
257 }
258
unblock_signals(void)259 void unblock_signals(void)
260 {
261 int save_pending;
262
263 if (signals_enabled == 1)
264 return;
265
266 /*
267 * We loop because the IRQ handler returns with interrupts off. So,
268 * interrupts may have arrived and we need to re-enable them and
269 * recheck signals_pending.
270 */
271 while (1) {
272 /*
273 * Save and reset save_pending after enabling signals. This
274 * way, signals_pending won't be changed while we're reading it.
275 */
276 signals_enabled = 1;
277
278 /*
279 * Setting signals_enabled and reading signals_pending must
280 * happen in this order.
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.
294 */
295
296 signals_enabled = 0;
297
298 /*
299 * Deal with SIGIO first because the alarm handler might
300 * schedule, leaving the pending SIGIO stranded until we come
301 * back here.
302 *
303 * SIGIO's handler doesn't use siginfo or mcontext,
304 * so they can be NULL.
305 */
306 if (save_pending & SIGIO_MASK)
307 sig_handler_common(SIGIO, NULL, NULL);
308
309 /* Do not reenter the handler */
310
311 if ((save_pending & SIGALRM_MASK) && (!(signals_active & SIGALRM_MASK)))
312 timer_real_alarm_handler(NULL);
313
314 /* Rerun the loop only if there is still pending SIGIO and not in TIMER handler */
315
316 if (!(signals_pending & SIGIO_MASK) && (signals_active & SIGALRM_MASK))
317 return;
318
319 }
320 }
321
get_signals(void)322 int get_signals(void)
323 {
324 return signals_enabled;
325 }
326
set_signals(int enable)327 int set_signals(int enable)
328 {
329 int ret;
330 if (signals_enabled == enable)
331 return enable;
332
333 ret = signals_enabled;
334 if (enable)
335 unblock_signals();
336 else block_signals();
337
338 return ret;
339 }
340
os_is_signal_stack(void)341 int os_is_signal_stack(void)
342 {
343 stack_t ss;
344 sigaltstack(NULL, &ss);
345
346 return ss.ss_flags & SS_ONSTACK;
347 }
348
