arch/xtensa/kernel/signal.c

   1 /*
   2  * arch/xtensa/kernel/signal.c
   3  *
   4  * Default platform functions.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  *
  10  * Copyright (C) 2005, 2006 Tensilica Inc.
  11  * Copyright (C) 1991, 1992  Linus Torvalds
  12  * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
  13  *
  14  * Chris Zankel <chris@zankel.net>
  15  * Joe Taylor <joe@tensilica.com>
  16  */
  17
  18 #include <linux/signal.h>
  19 #include <linux/errno.h>
  20 #include <linux/ptrace.h>
  21 #include <linux/personality.h>
  22 #include <linux/tracehook.h>
  23
  24 #include <asm/ucontext.h>
  25 #include <linux/uaccess.h>
  26 #include <asm/cacheflush.h>
  27 #include <asm/coprocessor.h>
  28 #include <asm/unistd.h>
  29
  30 #define DEBUG_SIG  0
  31
  32 extern struct task_struct *coproc_owners[];
  33
  34 struct rt_sigframe
  35 {
  36         struct siginfo info;
  37         struct ucontext uc;
  38         struct {
  39                 xtregs_opt_t opt;
  40                 xtregs_user_t user;
  41 #if XTENSA_HAVE_COPROCESSORS
  42                 xtregs_coprocessor_t cp;
  43 #endif
  44         } xtregs;
  45         unsigned char retcode[6];
  46         unsigned int window[4];
  47 };
  48
  49 /*
  50  * Flush register windows stored in pt_regs to stack.
  51  * Returns 1 for errors.
  52  */
  53
  54 int
  55 flush_window_regs_user(struct pt_regs *regs)
  56 {
  57         const unsigned long ws = regs->windowstart;
  58         const unsigned long wb = regs->windowbase;
  59         unsigned long sp = 0;
  60         unsigned long wm;
  61         int err = 1;
  62         int base;
  63
  64         /* Return if no other frames. */
  65
  66         if (regs->wmask == 1)
  67                 return 0;
  68
  69         /* Rotate windowmask and skip empty frames. */
  70
  71         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
  72         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
  73
  74         /* For call8 or call12 frames, we need the previous stack pointer. */
  75
  76         if ((regs->wmask & 2) == 0)
  77                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
  78                         goto errout;
  79
  80         /* Spill frames to stack. */
  81
  82         while (base < XCHAL_NUM_AREGS / 4) {
  83
  84                 int m = (wm >> base);
  85                 int inc = 0;
  86
  87                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
  88
  89                 if (m & 2) {                    /* call4 */
  90                         inc = 1;
  91
  92                 } else if (m & 4) {             /* call8 */
  93                         if (copy_to_user((void*)(sp - 32),
  94                                            &regs->areg[(base + 1) * 4], 16))
  95                                 goto errout;
  96                         inc = 2;
  97
  98                 } else if (m & 8) {     /* call12 */
  99                         if (copy_to_user((void*)(sp - 48),
 100                                            &regs->areg[(base + 1) * 4], 32))
 101                                 goto errout;
 102                         inc = 3;
 103                 }
 104
 105                 /* Save current frame a0..a3 under next SP */
 106
 107                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
 108                 if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
 109                         goto errout;
 110
 111                 /* Get current stack pointer for next loop iteration. */
 112
 113                 sp = regs->areg[base * 4 + 1];
 114                 base += inc;
 115         }
 116
 117         regs->wmask = 1;
 118         regs->windowstart = 1 << wb;
 119
 120         return 0;
 121
 122 errout:
 123         return err;
 124 }
 125
 126 /*
 127  * Note: We don't copy double exception 'regs', we have to finish double exc.
 128  * first before we return to signal handler! This dbl.exc.handler might cause
 129  * another double exception, but I think we are fine as the situation is the
 130  * same as if we had returned to the signal handerl and got an interrupt
 131  * immediately...
 132  */
 133
 134 static int
 135 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
 136 {
 137         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 138         struct thread_info *ti = current_thread_info();
 139         int err = 0;
 140
 141 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
 142         COPY(pc);
 143         COPY(ps);
 144         COPY(lbeg);
 145         COPY(lend);
 146         COPY(lcount);
 147         COPY(sar);
 148 #undef COPY
 149
 150         err |= flush_window_regs_user(regs);
 151         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
 152         err |= __put_user(0, &sc->sc_xtregs);
 153
 154         if (err)
 155                 return err;
 156
 157 #if XTENSA_HAVE_COPROCESSORS
 158         coprocessor_flush_all(ti);
 159         coprocessor_release_all(ti);
 160         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
 161                               sizeof (frame->xtregs.cp));
 162 #endif
 163         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
 164                               sizeof (xtregs_opt_t));
 165         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
 166                               sizeof (xtregs_user_t));
 167
 168         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
 169
 170         return err;
 171 }
 172
 173 static int
 174 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
 175 {
 176         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 177         struct thread_info *ti = current_thread_info();
 178         unsigned int err = 0;
 179         unsigned long ps;
 180
 181 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
 182         COPY(pc);
 183         COPY(lbeg);
 184         COPY(lend);
 185         COPY(lcount);
 186         COPY(sar);
 187 #undef COPY
 188
 189         /* All registers were flushed to stack. Start with a prestine frame. */
 190
 191         regs->wmask = 1;
 192         regs->windowbase = 0;
 193         regs->windowstart = 1;
 194
 195         regs->syscall = -1;             /* disable syscall checks */
 196
 197         /* For PS, restore only PS.CALLINC.
 198          * Assume that all other bits are either the same as for the signal
 199          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
 200          */
 201         err |= __get_user(ps, &sc->sc_ps);
 202         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
 203
 204         /* Additional corruption checks */
 205
 206         if ((regs->lcount > 0)
 207             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
 208                 err = 1;
 209
 210         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
 211
 212         if (err)
 213                 return err;
 214
 215         /* The signal handler may have used coprocessors in which
 216          * case they are still enabled.  We disable them to force a
 217          * reloading of the original task's CP state by the lazy
 218          * context-switching mechanisms of CP exception handling.
 219          * Also, we essentially discard any coprocessor state that the
 220          * signal handler created. */
 221
 222 #if XTENSA_HAVE_COPROCESSORS
 223         coprocessor_release_all(ti);
 224         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
 225                                 sizeof (frame->xtregs.cp));
 226 #endif
 227         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
 228                                 sizeof (xtregs_user_t));
 229         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
 230                                 sizeof (xtregs_opt_t));
 231
 232         return err;
 233 }
 234
 235
 236 /*
 237  * Do a signal return; undo the signal stack.
 238  */
 239
 240 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
 241                                     long a4, long a5, struct pt_regs *regs)
 242 {
 243         struct rt_sigframe __user *frame;
 244         sigset_t set;
 245         int ret;
 246
 247         /* Always make any pending restarted system calls return -EINTR */
 248         current->restart_block.fn = do_no_restart_syscall;
 249
 250         if (regs->depc > 64)
 251                 panic("rt_sigreturn in double exception!\n");
 252
 253         frame = (struct rt_sigframe __user *) regs->areg[1];
 254
 255         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 256                 goto badframe;
 257
 258         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 259                 goto badframe;
 260
 261         set_current_blocked(&set);
 262
 263         if (restore_sigcontext(regs, frame))
 264                 goto badframe;
 265
 266         ret = regs->areg[2];
 267
 268         if (restore_altstack(&frame->uc.uc_stack))
 269                 goto badframe;
 270
 271         return ret;
 272
 273 badframe:
 274         force_sig(SIGSEGV, current);
 275         return 0;
 276 }
 277
 278
 279
 280 /*
 281  * Set up a signal frame.
 282  */
 283
 284 static int
 285 gen_return_code(unsigned char *codemem)
 286 {
 287         int err = 0;
 288
 289         /*
 290          * The 12-bit immediate is really split up within the 24-bit MOVI
 291          * instruction.  As long as the above system call numbers fit within
 292          * 8-bits, the following code works fine. See the Xtensa ISA for
 293          * details.
 294          */
 295
 296 #if __NR_rt_sigreturn > 255
 297 # error Generating the MOVI instruction below breaks!
 298 #endif
 299
 300 #ifdef __XTENSA_EB__   /* Big Endian version */
 301         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 302         err |= __put_user(0x22, &codemem[0]);
 303         err |= __put_user(0x0a, &codemem[1]);
 304         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 305         /* Generate instruction:  SYSCALL */
 306         err |= __put_user(0x00, &codemem[3]);
 307         err |= __put_user(0x05, &codemem[4]);
 308         err |= __put_user(0x00, &codemem[5]);
 309
 310 #elif defined __XTENSA_EL__   /* Little Endian version */
 311         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 312         err |= __put_user(0x22, &codemem[0]);
 313         err |= __put_user(0xa0, &codemem[1]);
 314         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 315         /* Generate instruction:  SYSCALL */
 316         err |= __put_user(0x00, &codemem[3]);
 317         err |= __put_user(0x50, &codemem[4]);
 318         err |= __put_user(0x00, &codemem[5]);
 319 #else
 320 # error Must use compiler for Xtensa processors.
 321 #endif
 322
 323         /* Flush generated code out of the data cache */
 324
 325         if (err == 0) {
 326                 __invalidate_icache_range((unsigned long)codemem, 6UL);
 327                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
 328         }
 329
 330         return err;
 331 }
 332
 333
 334 static int setup_frame(struct ksignal *ksig, sigset_t *set,
 335                        struct pt_regs *regs)
 336 {
 337         struct rt_sigframe *frame;
 338         int err = 0, sig = ksig->sig;
 339         unsigned long sp, ra, tp;
 340
 341         sp = regs->areg[1];
 342
 343         if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
 344                 sp = current->sas_ss_sp + current->sas_ss_size;
 345         }
 346
 347         frame = (void *)((sp - sizeof(*frame)) & -16ul);
 348
 349         if (regs->depc > 64)
 350                 panic ("Double exception sys_sigreturn\n");
 351
 352         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
 353                 return -EFAULT;
 354         }
 355
 356         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 357                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 358         }
 359
 360         /* Create the user context.  */
 361
 362         err |= __put_user(0, &frame->uc.uc_flags);
 363         err |= __put_user(0, &frame->uc.uc_link);
 364         err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
 365         err |= setup_sigcontext(frame, regs);
 366         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 367
 368         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 369                 ra = (unsigned long)ksig->ka.sa.sa_restorer;
 370         } else {
 371
 372                 /* Create sys_rt_sigreturn syscall in stack frame */
 373
 374                 err |= gen_return_code(frame->retcode);
 375
 376                 if (err) {
 377                         return -EFAULT;
 378                 }
 379                 ra = (unsigned long) frame->retcode;
 380         }
 381
 382         /*
 383          * Create signal handler execution context.
 384          * Return context not modified until this point.
 385          */
 386
 387         /* Set up registers for signal handler; preserve the threadptr */
 388         tp = regs->threadptr;
 389         start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
 390                      (unsigned long) frame);
 391
 392         /* Set up a stack frame for a call4
 393          * Note: PS.CALLINC is set to one by start_thread
 394          */
 395         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
 396         regs->areg[6] = (unsigned long) sig;
 397         regs->areg[7] = (unsigned long) &frame->info;
 398         regs->areg[8] = (unsigned long) &frame->uc;
 399         regs->threadptr = tp;
 400
 401 #if DEBUG_SIG
 402         printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
 403                 current->comm, current->pid, sig, frame, regs->pc);
 404 #endif
 405
 406         return 0;
 407 }
 408
 409 /*
 410  * Note that 'init' is a special process: it doesn't get signals it doesn't
 411  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 412  * mistake.
 413  *
 414  * Note that we go through the signals twice: once to check the signals that
 415  * the kernel can handle, and then we build all the user-level signal handling
 416  * stack-frames in one go after that.
 417  */
 418 static void do_signal(struct pt_regs *regs)
 419 {
 420         struct ksignal ksig;
 421
 422         task_pt_regs(current)->icountlevel = 0;
 423
 424         if (get_signal(&ksig)) {
 425                 int ret;
 426
 427                 /* Are we from a system call? */
 428
 429                 if ((signed)regs->syscall >= 0) {
 430
 431                         /* If so, check system call restarting.. */
 432
 433                         switch (regs->areg[2]) {
 434                                 case -ERESTARTNOHAND:
 435                                 case -ERESTART_RESTARTBLOCK:
 436                                         regs->areg[2] = -EINTR;
 437                                         break;
 438
 439                                 case -ERESTARTSYS:
 440                                         if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
 441                                                 regs->areg[2] = -EINTR;
 442                                                 break;
 443                                         }
 444                                         /* fallthrough */
 445                                 case -ERESTARTNOINTR:
 446                                         regs->areg[2] = regs->syscall;
 447                                         regs->pc -= 3;
 448                                         break;
 449
 450                                 default:
 451                                         /* nothing to do */
 452                                         if (regs->areg[2] != 0)
 453                                         break;
 454                         }
 455                 }
 456
 457                 /* Whee!  Actually deliver the signal.  */
 458                 /* Set up the stack frame */
 459                 ret = setup_frame(&ksig, sigmask_to_save(), regs);
 460                 signal_setup_done(ret, &ksig, 0);
 461                 if (current->ptrace & PT_SINGLESTEP)
 462                         task_pt_regs(current)->icountlevel = 1;
 463
 464                 return;
 465         }
 466
 467         /* Did we come from a system call? */
 468         if ((signed) regs->syscall >= 0) {
 469                 /* Restart the system call - no handlers present */
 470                 switch (regs->areg[2]) {
 471                 case -ERESTARTNOHAND:
 472                 case -ERESTARTSYS:
 473                 case -ERESTARTNOINTR:
 474                         regs->areg[2] = regs->syscall;
 475                         regs->pc -= 3;
 476                         break;
 477                 case -ERESTART_RESTARTBLOCK:
 478                         regs->areg[2] = __NR_restart_syscall;
 479                         regs->pc -= 3;
 480                         break;
 481                 }
 482         }
 483
 484         /* If there's no signal to deliver, we just restore the saved mask.  */
 485         restore_saved_sigmask();
 486
 487         if (current->ptrace & PT_SINGLESTEP)
 488                 task_pt_regs(current)->icountlevel = 1;
 489         return;
 490 }
 491
 492 void do_notify_resume(struct pt_regs *regs)
 493 {
 494         if (test_thread_flag(TIF_SIGPENDING))
 495                 do_signal(regs);
 496
 497         if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
 498                 tracehook_notify_resume(regs);
 499 }