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 18 void (*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 28 static 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 61 static int signals_enabled; 62 static unsigned int signals_pending; 63 64 void 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 81 static 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 92 void 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 } 107 108 void timer_init(void) 109 { 110 set_handler(SIGVTALRM); 111 } 112 113 void set_sigstack(void *sig_stack, int size) 114 { 115 stack_t stack = { 116 .ss_flags = 0, 117 .ss_sp = sig_stack, 118 .ss_size = size - sizeof(void *) 119 }; 120 121 if (sigaltstack(&stack, NULL) != 0) 122 panic("enabling signal stack failed, errno = %d\n", errno); 123 } 124 125 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = { 126 [SIGSEGV] = sig_handler, 127 [SIGBUS] = sig_handler, 128 [SIGILL] = sig_handler, 129 [SIGFPE] = sig_handler, 130 [SIGTRAP] = sig_handler, 131 132 [SIGIO] = sig_handler, 133 [SIGWINCH] = sig_handler, 134 [SIGVTALRM] = alarm_handler 135 }; 136 137 138 static void hard_handler(int sig, siginfo_t *si, void *p) 139 { 140 struct ucontext *uc = p; 141 mcontext_t *mc = &uc->uc_mcontext; 142 unsigned long pending = 1UL << sig; 143 144 do { 145 int nested, bail; 146 147 /* 148 * pending comes back with one bit set for each 149 * interrupt that arrived while setting up the stack, 150 * plus a bit for this interrupt, plus the zero bit is 151 * set if this is a nested interrupt. 152 * If bail is true, then we interrupted another 153 * handler setting up the stack. In this case, we 154 * have to return, and the upper handler will deal 155 * with this interrupt. 156 */ 157 bail = to_irq_stack(&pending); 158 if (bail) 159 return; 160 161 nested = pending & 1; 162 pending &= ~1; 163 164 while ((sig = ffs(pending)) != 0){ 165 sig--; 166 pending &= ~(1 << sig); 167 (*handlers[sig])(sig, (struct siginfo *)si, mc); 168 } 169 170 /* 171 * Again, pending comes back with a mask of signals 172 * that arrived while tearing down the stack. If this 173 * is non-zero, we just go back, set up the stack 174 * again, and handle the new interrupts. 175 */ 176 if (!nested) 177 pending = from_irq_stack(nested); 178 } while (pending); 179 } 180 181 void set_handler(int sig) 182 { 183 struct sigaction action; 184 int flags = SA_SIGINFO | SA_ONSTACK; 185 sigset_t sig_mask; 186 187 action.sa_sigaction = hard_handler; 188 189 /* block irq ones */ 190 sigemptyset(&action.sa_mask); 191 sigaddset(&action.sa_mask, SIGVTALRM); 192 sigaddset(&action.sa_mask, SIGIO); 193 sigaddset(&action.sa_mask, SIGWINCH); 194 195 if (sig == SIGSEGV) 196 flags |= SA_NODEFER; 197 198 if (sigismember(&action.sa_mask, sig)) 199 flags |= SA_RESTART; /* if it's an irq signal */ 200 201 action.sa_flags = flags; 202 action.sa_restorer = NULL; 203 if (sigaction(sig, &action, NULL) < 0) 204 panic("sigaction failed - errno = %d\n", errno); 205 206 sigemptyset(&sig_mask); 207 sigaddset(&sig_mask, sig); 208 if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0) 209 panic("sigprocmask failed - errno = %d\n", errno); 210 } 211 212 int change_sig(int signal, int on) 213 { 214 sigset_t sigset; 215 216 sigemptyset(&sigset); 217 sigaddset(&sigset, signal); 218 if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, NULL) < 0) 219 return -errno; 220 221 return 0; 222 } 223 224 void block_signals(void) 225 { 226 signals_enabled = 0; 227 /* 228 * This must return with signals disabled, so this barrier 229 * ensures that writes are flushed out before the return. 230 * This might matter if gcc figures out how to inline this and 231 * decides to shuffle this code into the caller. 232 */ 233 barrier(); 234 } 235 236 void unblock_signals(void) 237 { 238 int save_pending; 239 240 if (signals_enabled == 1) 241 return; 242 243 /* 244 * We loop because the IRQ handler returns with interrupts off. So, 245 * interrupts may have arrived and we need to re-enable them and 246 * recheck signals_pending. 247 */ 248 while (1) { 249 /* 250 * Save and reset save_pending after enabling signals. This 251 * way, signals_pending won't be changed while we're reading it. 252 */ 253 signals_enabled = 1; 254 255 /* 256 * Setting signals_enabled and reading signals_pending must 257 * happen in this order. 258 */ 259 barrier(); 260 261 save_pending = signals_pending; 262 if (save_pending == 0) 263 return; 264 265 signals_pending = 0; 266 267 /* 268 * We have pending interrupts, so disable signals, as the 269 * handlers expect them off when they are called. They will 270 * be enabled again above. 271 */ 272 273 signals_enabled = 0; 274 275 /* 276 * Deal with SIGIO first because the alarm handler might 277 * schedule, leaving the pending SIGIO stranded until we come 278 * back here. 279 * 280 * SIGIO's handler doesn't use siginfo or mcontext, 281 * so they can be NULL. 282 */ 283 if (save_pending & SIGIO_MASK) 284 sig_handler_common(SIGIO, NULL, NULL); 285 286 if (save_pending & SIGVTALRM_MASK) 287 real_alarm_handler(NULL); 288 } 289 } 290 291 int get_signals(void) 292 { 293 return signals_enabled; 294 } 295 296 int set_signals(int enable) 297 { 298 int ret; 299 if (signals_enabled == enable) 300 return enable; 301 302 ret = signals_enabled; 303 if (enable) 304 unblock_signals(); 305 else block_signals(); 306 307 return ret; 308 } 309 310 int os_is_signal_stack(void) 311 { 312 stack_t ss; 313 sigaltstack(NULL, &ss); 314 315 return ss.ss_flags & SS_ONSTACK; 316 } 317