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