1 /*
2 * Copyright (C) 2004 PathScale, Inc
3 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4 * Licensed under the GPL
5 */
6
7 #include <stdlib.h>
8 #include <stdarg.h>
9 #include <errno.h>
10 #include <signal.h>
11 #include <strings.h>
12 #include "as-layout.h"
13 #include "kern_util.h"
14 #include "os.h"
15 #include "process.h"
16 #include "sysdep/barrier.h"
17 #include "sysdep/sigcontext.h"
18 #include "user.h"
19
20 /* Copied from linux/compiler-gcc.h since we can't include it directly */
21 #define barrier() __asm__ __volatile__("": : :"memory")
22
23 void (*sig_info[NSIG])(int, struct uml_pt_regs *) = {
24 [SIGTRAP] = relay_signal,
25 [SIGFPE] = relay_signal,
26 [SIGILL] = relay_signal,
27 [SIGWINCH] = winch,
28 [SIGBUS] = bus_handler,
29 [SIGSEGV] = segv_handler,
30 [SIGIO] = sigio_handler,
31 [SIGVTALRM] = timer_handler };
32
sig_handler_common(int sig,struct sigcontext * sc)33 static void sig_handler_common(int sig, struct sigcontext *sc)
34 {
35 struct uml_pt_regs r;
36 int save_errno = errno;
37
38 r.is_user = 0;
39 if (sig == SIGSEGV) {
40 /* For segfaults, we want the data from the sigcontext. */
41 copy_sc(&r, sc);
42 GET_FAULTINFO_FROM_SC(r.faultinfo, sc);
43 }
44
45 /* enable signals if sig isn't IRQ signal */
46 if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
47 unblock_signals();
48
49 (*sig_info[sig])(sig, &r);
50
51 errno = save_errno;
52 }
53
54 /*
55 * These are the asynchronous signals. SIGPROF is excluded because we want to
56 * be able to profile all of UML, not just the non-critical sections. If
57 * profiling is not thread-safe, then that is not my problem. We can disable
58 * profiling when SMP is enabled in that case.
59 */
60 #define SIGIO_BIT 0
61 #define SIGIO_MASK (1 << SIGIO_BIT)
62
63 #define SIGVTALRM_BIT 1
64 #define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
65
66 static int signals_enabled;
67 static unsigned int signals_pending;
68
sig_handler(int sig,struct sigcontext * sc)69 void sig_handler(int sig, struct sigcontext *sc)
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();
80
81 sig_handler_common(sig, sc);
82
83 set_signals(enabled);
84 }
85
real_alarm_handler(struct sigcontext * sc)86 static void real_alarm_handler(struct sigcontext *sc)
87 {
88 struct uml_pt_regs regs;
89
90 if (sc != NULL)
91 copy_sc(®s, sc);
92 regs.is_user = 0;
93 unblock_signals();
94 timer_handler(SIGVTALRM, ®s);
95 }
96
alarm_handler(int sig,struct sigcontext * sc)97 void alarm_handler(int sig, struct sigcontext *sc)
98 {
99 int enabled;
100
101 enabled = signals_enabled;
102 if (!signals_enabled) {
103 signals_pending |= SIGVTALRM_MASK;
104 return;
105 }
106
107 block_signals();
108
109 real_alarm_handler(sc);
110 set_signals(enabled);
111 }
112
timer_init(void)113 void timer_init(void)
114 {
115 set_handler(SIGVTALRM, (__sighandler_t) alarm_handler,
116 SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGWINCH, -1);
117 }
118
set_sigstack(void * sig_stack,int size)119 void set_sigstack(void *sig_stack, int size)
120 {
121 stack_t stack = ((stack_t) { .ss_flags = 0,
122 .ss_sp = (__ptr_t) sig_stack,
123 .ss_size = size - sizeof(void *) });
124
125 if (sigaltstack(&stack, NULL) != 0)
126 panic("enabling signal stack failed, errno = %d\n", errno);
127 }
128
129 static void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
130
handle_signal(int sig,struct sigcontext * sc)131 void handle_signal(int sig, struct sigcontext *sc)
132 {
133 unsigned long pending = 1UL << sig;
134
135 do {
136 int nested, bail;
137
138 /*
139 * pending comes back with one bit set for each
140 * interrupt that arrived while setting up the stack,
141 * plus a bit for this interrupt, plus the zero bit is
142 * set if this is a nested interrupt.
143 * If bail is true, then we interrupted another
144 * handler setting up the stack. In this case, we
145 * have to return, and the upper handler will deal
146 * with this interrupt.
147 */
148 bail = to_irq_stack(&pending);
149 if (bail)
150 return;
151
152 nested = pending & 1;
153 pending &= ~1;
154
155 while ((sig = ffs(pending)) != 0){
156 sig--;
157 pending &= ~(1 << sig);
158 (*handlers[sig])(sig, sc);
159 }
160
161 /*
162 * Again, pending comes back with a mask of signals
163 * that arrived while tearing down the stack. If this
164 * is non-zero, we just go back, set up the stack
165 * again, and handle the new interrupts.
166 */
167 if (!nested)
168 pending = from_irq_stack(nested);
169 } while (pending);
170 }
171
172 extern void hard_handler(int sig);
173
set_handler(int sig,void (* handler)(int),int flags,...)174 void set_handler(int sig, void (*handler)(int), int flags, ...)
175 {
176 struct sigaction action;
177 va_list ap;
178 sigset_t sig_mask;
179 int mask;
180
181 handlers[sig] = (void (*)(int, struct sigcontext *)) handler;
182 action.sa_handler = hard_handler;
183
184 sigemptyset(&action.sa_mask);
185
186 va_start(ap, flags);
187 while ((mask = va_arg(ap, int)) != -1)
188 sigaddset(&action.sa_mask, mask);
189 va_end(ap);
190
191 if (sig == SIGSEGV)
192 flags |= SA_NODEFER;
193
194 action.sa_flags = flags;
195 action.sa_restorer = NULL;
196 if (sigaction(sig, &action, NULL) < 0)
197 panic("sigaction failed - errno = %d\n", errno);
198
199 sigemptyset(&sig_mask);
200 sigaddset(&sig_mask, sig);
201 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0)
202 panic("sigprocmask failed - errno = %d\n", errno);
203 }
204
change_sig(int signal,int on)205 int change_sig(int signal, int on)
206 {
207 sigset_t sigset;
208
209 sigemptyset(&sigset);
210 sigaddset(&sigset, signal);
211 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0)
212 return -errno;
213
214 return 0;
215 }
216
block_signals(void)217 void block_signals(void)
218 {
219 signals_enabled = 0;
220 /*
221 * This must return with signals disabled, so this barrier
222 * ensures that writes are flushed out before the return.
223 * This might matter if gcc figures out how to inline this and
224 * decides to shuffle this code into the caller.
225 */
226 barrier();
227 }
228
unblock_signals(void)229 void unblock_signals(void)
230 {
231 int save_pending;
232
233 if (signals_enabled == 1)
234 return;
235
236 /*
237 * We loop because the IRQ handler returns with interrupts off. So,
238 * interrupts may have arrived and we need to re-enable them and
239 * recheck signals_pending.
240 */
241 while (1) {
242 /*
243 * Save and reset save_pending after enabling signals. This
244 * way, signals_pending won't be changed while we're reading it.
245 */
246 signals_enabled = 1;
247
248 /*
249 * Setting signals_enabled and reading signals_pending must
250 * happen in this order.
251 */
252 barrier();
253
254 save_pending = signals_pending;
255 if (save_pending == 0)
256 return;
257
258 signals_pending = 0;
259
260 /*
261 * We have pending interrupts, so disable signals, as the
262 * handlers expect them off when they are called. They will
263 * be enabled again above.
264 */
265
266 signals_enabled = 0;
267
268 /*
269 * Deal with SIGIO first because the alarm handler might
270 * schedule, leaving the pending SIGIO stranded until we come
271 * back here.
272 */
273 if (save_pending & SIGIO_MASK)
274 sig_handler_common(SIGIO, NULL);
275
276 if (save_pending & SIGVTALRM_MASK)
277 real_alarm_handler(NULL);
278 }
279 }
280
get_signals(void)281 int get_signals(void)
282 {
283 return signals_enabled;
284 }
285
set_signals(int enable)286 int set_signals(int enable)
287 {
288 int ret;
289 if (signals_enabled == enable)
290 return enable;
291
292 ret = signals_enabled;
293 if (enable)
294 unblock_signals();
295 else block_signals();
296
297 return ret;
298 }
299