| 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 "os.h" |
| 13 | #include "sysdep/barrier.h" |
| 14 | #include "sysdep/sigcontext.h" |
| 15 | #include "user.h" |
| 16 | |
| 17 | /* |
| 18 | * These are the asynchronous signals. SIGPROF is excluded because we want to |
| 19 | * be able to profile all of UML, not just the non-critical sections. If |
| 20 | * profiling is not thread-safe, then that is not my problem. We can disable |
| 21 | * profiling when SMP is enabled in that case. |
| 22 | */ |
| 23 | #define SIGIO_BIT 0 |
| 24 | #define SIGIO_MASK (1 << SIGIO_BIT) |
| 25 | |
| 26 | #define SIGVTALRM_BIT 1 |
| 27 | #define SIGVTALRM_MASK (1 << SIGVTALRM_BIT) |
| 28 | |
| 29 | /* |
| 30 | * These are used by both the signal handlers and |
| 31 | * block/unblock_signals. I don't want modifications cached in a |
| 32 | * register - they must go straight to memory. |
| 33 | */ |
| 34 | static volatile int signals_enabled = 1; |
| 35 | static volatile int pending = 0; |
| 36 | |
| 37 | void sig_handler(int sig, struct sigcontext *sc) |
| 38 | { |
| 39 | int enabled; |
| 40 | |
| 41 | enabled = signals_enabled; |
| 42 | if (!enabled && (sig == SIGIO)) { |
| 43 | pending |= SIGIO_MASK; |
| 44 | return; |
| 45 | } |
| 46 | |
| 47 | block_signals(); |
| 48 | |
| 49 | sig_handler_common_skas(sig, sc); |
| 50 | |
| 51 | set_signals(enabled); |
| 52 | } |
| 53 | |
| 54 | static void real_alarm_handler(struct sigcontext *sc) |
| 55 | { |
| 56 | struct uml_pt_regs regs; |
| 57 | |
| 58 | if (sc != NULL) |
| 59 | copy_sc(®s, sc); |
| 60 | regs.is_user = 0; |
| 61 | unblock_signals(); |
| 62 | timer_handler(SIGVTALRM, ®s); |
| 63 | } |
| 64 | |
| 65 | void alarm_handler(int sig, struct sigcontext *sc) |
| 66 | { |
| 67 | int enabled; |
| 68 | |
| 69 | enabled = signals_enabled; |
| 70 | if (!signals_enabled) { |
| 71 | pending |= SIGVTALRM_MASK; |
| 72 | return; |
| 73 | } |
| 74 | |
| 75 | block_signals(); |
| 76 | |
| 77 | real_alarm_handler(sc); |
| 78 | set_signals(enabled); |
| 79 | } |
| 80 | |
| 81 | void timer_init(void) |
| 82 | { |
| 83 | set_handler(SIGVTALRM, (__sighandler_t) alarm_handler, |
| 84 | SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGWINCH, -1); |
| 85 | } |
| 86 | |
| 87 | void set_sigstack(void *sig_stack, int size) |
| 88 | { |
| 89 | stack_t stack = ((stack_t) { .ss_flags = 0, |
| 90 | .ss_sp = (__ptr_t) sig_stack, |
| 91 | .ss_size = size - sizeof(void *) }); |
| 92 | |
| 93 | if (sigaltstack(&stack, NULL) != 0) |
| 94 | panic("enabling signal stack failed, errno = %d\n", errno); |
| 95 | } |
| 96 | |
| 97 | void remove_sigstack(void) |
| 98 | { |
| 99 | stack_t stack = ((stack_t) { .ss_flags = SS_DISABLE, |
| 100 | .ss_sp = NULL, |
| 101 | .ss_size = 0 }); |
| 102 | |
| 103 | if (sigaltstack(&stack, NULL) != 0) |
| 104 | panic("disabling signal stack failed, errno = %d\n", errno); |
| 105 | } |
| 106 | |
| 107 | void (*handlers[_NSIG])(int sig, struct sigcontext *sc); |
| 108 | |
| 109 | void handle_signal(int sig, struct sigcontext *sc) |
| 110 | { |
| 111 | unsigned long pending = 1UL << sig; |
| 112 | |
| 113 | do { |
| 114 | int nested, bail; |
| 115 | |
| 116 | /* |
| 117 | * pending comes back with one bit set for each |
| 118 | * interrupt that arrived while setting up the stack, |
| 119 | * plus a bit for this interrupt, plus the zero bit is |
| 120 | * set if this is a nested interrupt. |
| 121 | * If bail is true, then we interrupted another |
| 122 | * handler setting up the stack. In this case, we |
| 123 | * have to return, and the upper handler will deal |
| 124 | * with this interrupt. |
| 125 | */ |
| 126 | bail = to_irq_stack(&pending); |
| 127 | if (bail) |
| 128 | return; |
| 129 | |
| 130 | nested = pending & 1; |
| 131 | pending &= ~1; |
| 132 | |
| 133 | while ((sig = ffs(pending)) != 0){ |
| 134 | sig--; |
| 135 | pending &= ~(1 << sig); |
| 136 | (*handlers[sig])(sig, sc); |
| 137 | } |
| 138 | |
| 139 | /* |
| 140 | * Again, pending comes back with a mask of signals |
| 141 | * that arrived while tearing down the stack. If this |
| 142 | * is non-zero, we just go back, set up the stack |
| 143 | * again, and handle the new interrupts. |
| 144 | */ |
| 145 | if (!nested) |
| 146 | pending = from_irq_stack(nested); |
| 147 | } while (pending); |
| 148 | } |
| 149 | |
| 150 | extern void hard_handler(int sig); |
| 151 | |
| 152 | void set_handler(int sig, void (*handler)(int), int flags, ...) |
| 153 | { |
| 154 | struct sigaction action; |
| 155 | va_list ap; |
| 156 | sigset_t sig_mask; |
| 157 | int mask; |
| 158 | |
| 159 | handlers[sig] = (void (*)(int, struct sigcontext *)) handler; |
| 160 | action.sa_handler = hard_handler; |
| 161 | |
| 162 | sigemptyset(&action.sa_mask); |
| 163 | |
| 164 | va_start(ap, flags); |
| 165 | while ((mask = va_arg(ap, int)) != -1) |
| 166 | sigaddset(&action.sa_mask, mask); |
| 167 | va_end(ap); |
| 168 | |
| 169 | action.sa_flags = flags; |
| 170 | action.sa_restorer = NULL; |
| 171 | if (sigaction(sig, &action, NULL) < 0) |
| 172 | panic("sigaction failed - errno = %d\n", errno); |
| 173 | |
| 174 | sigemptyset(&sig_mask); |
| 175 | sigaddset(&sig_mask, sig); |
| 176 | if (sigprocmask(SIG_UNBLOCK, &sig_mask, NULL) < 0) |
| 177 | panic("sigprocmask failed - errno = %d\n", errno); |
| 178 | } |
| 179 | |
| 180 | int change_sig(int signal, int on) |
| 181 | { |
| 182 | sigset_t sigset, old; |
| 183 | |
| 184 | sigemptyset(&sigset); |
| 185 | sigaddset(&sigset, signal); |
| 186 | if (sigprocmask(on ? SIG_UNBLOCK : SIG_BLOCK, &sigset, &old) < 0) |
| 187 | return -errno; |
| 188 | return !sigismember(&old, signal); |
| 189 | } |
| 190 | |
| 191 | void block_signals(void) |
| 192 | { |
| 193 | signals_enabled = 0; |
| 194 | /* |
| 195 | * This must return with signals disabled, so this barrier |
| 196 | * ensures that writes are flushed out before the return. |
| 197 | * This might matter if gcc figures out how to inline this and |
| 198 | * decides to shuffle this code into the caller. |
| 199 | */ |
| 200 | mb(); |
| 201 | } |
| 202 | |
| 203 | void unblock_signals(void) |
| 204 | { |
| 205 | int save_pending; |
| 206 | |
| 207 | if (signals_enabled == 1) |
| 208 | return; |
| 209 | |
| 210 | /* |
| 211 | * We loop because the IRQ handler returns with interrupts off. So, |
| 212 | * interrupts may have arrived and we need to re-enable them and |
| 213 | * recheck pending. |
| 214 | */ |
| 215 | while(1) { |
| 216 | /* |
| 217 | * Save and reset save_pending after enabling signals. This |
| 218 | * way, pending won't be changed while we're reading it. |
| 219 | */ |
| 220 | signals_enabled = 1; |
| 221 | |
| 222 | /* |
| 223 | * Setting signals_enabled and reading pending must |
| 224 | * happen in this order. |
| 225 | */ |
| 226 | mb(); |
| 227 | |
| 228 | save_pending = pending; |
| 229 | if (save_pending == 0) { |
| 230 | /* |
| 231 | * This must return with signals enabled, so |
| 232 | * this barrier ensures that writes are |
| 233 | * flushed out before the return. This might |
| 234 | * matter if gcc figures out how to inline |
| 235 | * this (unlikely, given its size) and decides |
| 236 | * to shuffle this code into the caller. |
| 237 | */ |
| 238 | mb(); |
| 239 | return; |
| 240 | } |
| 241 | |
| 242 | pending = 0; |
| 243 | |
| 244 | /* |
| 245 | * We have pending interrupts, so disable signals, as the |
| 246 | * handlers expect them off when they are called. They will |
| 247 | * be enabled again above. |
| 248 | */ |
| 249 | |
| 250 | signals_enabled = 0; |
| 251 | |
| 252 | /* |
| 253 | * Deal with SIGIO first because the alarm handler might |
| 254 | * schedule, leaving the pending SIGIO stranded until we come |
| 255 | * back here. |
| 256 | */ |
| 257 | if (save_pending & SIGIO_MASK) |
| 258 | sig_handler_common_skas(SIGIO, NULL); |
| 259 | |
| 260 | if (save_pending & SIGVTALRM_MASK) |
| 261 | real_alarm_handler(NULL); |
| 262 | } |
| 263 | } |
| 264 | |
| 265 | int get_signals(void) |
| 266 | { |
| 267 | return signals_enabled; |
| 268 | } |
| 269 | |
| 270 | int set_signals(int enable) |
| 271 | { |
| 272 | int ret; |
| 273 | if (signals_enabled == enable) |
| 274 | return enable; |
| 275 | |
| 276 | ret = signals_enabled; |
| 277 | if (enable) |
| 278 | unblock_signals(); |
| 279 | else block_signals(); |
| 280 | |
| 281 | return ret; |
| 282 | } |