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/freezer.h>
  23
  24 #include <asm/ucontext.h>
  25 #include <asm/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 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  33
  34 asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset);
  35
  36 extern struct task_struct *coproc_owners[];
  37
  38 struct rt_sigframe
  39 {
  40         struct siginfo info;
  41         struct ucontext uc;
  42         struct {
  43                 xtregs_opt_t opt;
  44                 xtregs_user_t user;
  45 #if XTENSA_HAVE_COPROCESSORS
  46                 xtregs_coprocessor_t cp;
  47 #endif
  48         } xtregs;
  49         unsigned char retcode[6];
  50         unsigned int window[4];
  51 };
  52
  53 /*
  54  * Flush register windows stored in pt_regs to stack.
  55  * Returns 1 for errors.
  56  */
  57
  58 int
  59 flush_window_regs_user(struct pt_regs *regs)
  60 {
  61         const unsigned long ws = regs->windowstart;
  62         const unsigned long wb = regs->windowbase;
  63         unsigned long sp = 0;
  64         unsigned long wm;
  65         int err = 1;
  66         int base;
  67
  68         /* Return if no other frames. */
  69
  70         if (regs->wmask == 1)
  71                 return 0;
  72
  73         /* Rotate windowmask and skip empty frames. */
  74
  75         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
  76         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
  77
  78         /* For call8 or call12 frames, we need the previous stack pointer. */
  79
  80         if ((regs->wmask & 2) == 0)
  81                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
  82                         goto errout;
  83
  84         /* Spill frames to stack. */
  85
  86         while (base < XCHAL_NUM_AREGS / 4) {
  87
  88                 int m = (wm >> base);
  89                 int inc = 0;
  90
  91                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
  92
  93                 if (m & 2) {                    /* call4 */
  94                         inc = 1;
  95
  96                 } else if (m & 4) {             /* call8 */
  97                         if (copy_to_user((void*)(sp - 32),
  98                                            &regs->areg[(base + 1) * 4], 16))
  99                                 goto errout;
 100                         inc = 2;
 101
 102                 } else if (m & 8) {     /* call12 */
 103                         if (copy_to_user((void*)(sp - 48),
 104                                            &regs->areg[(base + 1) * 4], 32))
 105                                 goto errout;
 106                         inc = 3;
 107                 }
 108
 109                 /* Save current frame a0..a3 under next SP */
 110
 111                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
 112                 if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
 113                         goto errout;
 114
 115                 /* Get current stack pointer for next loop iteration. */
 116
 117                 sp = regs->areg[base * 4 + 1];
 118                 base += inc;
 119         }
 120
 121         regs->wmask = 1;
 122         regs->windowstart = 1 << wb;
 123
 124         return 0;
 125
 126 errout:
 127         return err;
 128 }
 129
 130 /*
 131  * Note: We don't copy double exception 'regs', we have to finish double exc.
 132  * first before we return to signal handler! This dbl.exc.handler might cause
 133  * another double exception, but I think we are fine as the situation is the
 134  * same as if we had returned to the signal handerl and got an interrupt
 135  * immediately...
 136  */
 137
 138 static int
 139 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
 140 {
 141         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 142         struct thread_info *ti = current_thread_info();
 143         int err = 0;
 144
 145 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
 146         COPY(pc);
 147         COPY(ps);
 148         COPY(lbeg);
 149         COPY(lend);
 150         COPY(lcount);
 151         COPY(sar);
 152 #undef COPY
 153
 154         err |= flush_window_regs_user(regs);
 155         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
 156         err |= __put_user(0, &sc->sc_xtregs);
 157
 158         if (err)
 159                 return err;
 160
 161 #if XTENSA_HAVE_COPROCESSORS
 162         coprocessor_flush_all(ti);
 163         coprocessor_release_all(ti);
 164         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
 165                               sizeof (frame->xtregs.cp));
 166 #endif
 167         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
 168                               sizeof (xtregs_opt_t));
 169         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
 170                               sizeof (xtregs_user_t));
 171
 172         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
 173
 174         return err;
 175 }
 176
 177 static int
 178 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
 179 {
 180         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 181         struct thread_info *ti = current_thread_info();
 182         unsigned int err = 0;
 183         unsigned long ps;
 184
 185 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
 186         COPY(pc);
 187         COPY(lbeg);
 188         COPY(lend);
 189         COPY(lcount);
 190         COPY(sar);
 191 #undef COPY
 192
 193         /* All registers were flushed to stack. Start with a prestine frame. */
 194
 195         regs->wmask = 1;
 196         regs->windowbase = 0;
 197         regs->windowstart = 1;
 198
 199         regs->syscall = -1;             /* disable syscall checks */
 200
 201         /* For PS, restore only PS.CALLINC.
 202          * Assume that all other bits are either the same as for the signal
 203          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
 204          */
 205         err |= __get_user(ps, &sc->sc_ps);
 206         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
 207
 208         /* Additional corruption checks */
 209
 210         if ((regs->lcount > 0)
 211             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
 212                 err = 1;
 213
 214         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
 215
 216         if (err)
 217                 return err;
 218
 219         /* The signal handler may have used coprocessors in which
 220          * case they are still enabled.  We disable them to force a
 221          * reloading of the original task's CP state by the lazy
 222          * context-switching mechanisms of CP exception handling.
 223          * Also, we essentially discard any coprocessor state that the
 224          * signal handler created. */
 225
 226 #if XTENSA_HAVE_COPROCESSORS
 227         coprocessor_release_all(ti);
 228         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
 229                                 sizeof (frame->xtregs.cp));
 230 #endif
 231         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
 232                                 sizeof (xtregs_user_t));
 233         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
 234                                 sizeof (xtregs_opt_t));
 235
 236         return err;
 237 }
 238
 239
 240 /*
 241  * Do a signal return; undo the signal stack.
 242  */
 243
 244 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
 245                                     long a4, long a5, struct pt_regs *regs)
 246 {
 247         struct rt_sigframe __user *frame;
 248         sigset_t set;
 249         int ret;
 250
 251         if (regs->depc > 64)
 252                 panic("rt_sigreturn in double exception!\n");
 253
 254         frame = (struct rt_sigframe __user *) regs->areg[1];
 255
 256         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 257                 goto badframe;
 258
 259         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 260                 goto badframe;
 261
 262         sigdelsetmask(&set, ~_BLOCKABLE);
 263         set_current_blocked(&set);
 264
 265         if (restore_sigcontext(regs, frame))
 266                 goto badframe;
 267
 268         ret = regs->areg[2];
 269
 270         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
 271                 goto badframe;
 272
 273         return ret;
 274
 275 badframe:
 276         force_sig(SIGSEGV, current);
 277         return 0;
 278 }
 279
 280
 281
 282 /*
 283  * Set up a signal frame.
 284  */
 285
 286 static int
 287 gen_return_code(unsigned char *codemem)
 288 {
 289         int err = 0;
 290
 291         /*
 292          * The 12-bit immediate is really split up within the 24-bit MOVI
 293          * instruction.  As long as the above system call numbers fit within
 294          * 8-bits, the following code works fine. See the Xtensa ISA for
 295          * details.
 296          */
 297
 298 #if __NR_rt_sigreturn > 255
 299 # error Generating the MOVI instruction below breaks!
 300 #endif
 301
 302 #ifdef __XTENSA_EB__   /* Big Endian version */
 303         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 304         err |= __put_user(0x22, &codemem[0]);
 305         err |= __put_user(0x0a, &codemem[1]);
 306         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 307         /* Generate instruction:  SYSCALL */
 308         err |= __put_user(0x00, &codemem[3]);
 309         err |= __put_user(0x05, &codemem[4]);
 310         err |= __put_user(0x00, &codemem[5]);
 311
 312 #elif defined __XTENSA_EL__   /* Little Endian version */
 313         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 314         err |= __put_user(0x22, &codemem[0]);
 315         err |= __put_user(0xa0, &codemem[1]);
 316         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 317         /* Generate instruction:  SYSCALL */
 318         err |= __put_user(0x00, &codemem[3]);
 319         err |= __put_user(0x50, &codemem[4]);
 320         err |= __put_user(0x00, &codemem[5]);
 321 #else
 322 # error Must use compiler for Xtensa processors.
 323 #endif
 324
 325         /* Flush generated code out of the data cache */
 326
 327         if (err == 0) {
 328                 __invalidate_icache_range((unsigned long)codemem, 6UL);
 329                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
 330         }
 331
 332         return err;
 333 }
 334
 335
 336 static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 337                        sigset_t *set, struct pt_regs *regs)
 338 {
 339         struct rt_sigframe *frame;
 340         int err = 0;
 341         int signal;
 342         unsigned long sp, ra;
 343
 344         sp = regs->areg[1];
 345
 346         if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
 347                 sp = current->sas_ss_sp + current->sas_ss_size;
 348         }
 349
 350         frame = (void *)((sp - sizeof(*frame)) & -16ul);
 351
 352         if (regs->depc > 64)
 353                 panic ("Double exception sys_sigreturn\n");
 354
 355         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
 356                 goto give_sigsegv;
 357         }
 358
 359         signal = current_thread_info()->exec_domain
 360                 && current_thread_info()->exec_domain->signal_invmap
 361                 && sig < 32
 362                 ? current_thread_info()->exec_domain->signal_invmap[sig]
 363                 : sig;
 364
 365         if (ka->sa.sa_flags & SA_SIGINFO) {
 366                 err |= copy_siginfo_to_user(&frame->info, info);
 367         }
 368
 369         /* Create the user context.  */
 370
 371         err |= __put_user(0, &frame->uc.uc_flags);
 372         err |= __put_user(0, &frame->uc.uc_link);
 373         err |= __put_user((void *)current->sas_ss_sp,
 374                           &frame->uc.uc_stack.ss_sp);
 375         err |= __put_user(sas_ss_flags(regs->areg[1]),
 376                           &frame->uc.uc_stack.ss_flags);
 377         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 378         err |= setup_sigcontext(frame, regs);
 379         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 380
 381         if (ka->sa.sa_flags & SA_RESTORER) {
 382                 ra = (unsigned long)ka->sa.sa_restorer;
 383         } else {
 384
 385                 /* Create sys_rt_sigreturn syscall in stack frame */
 386
 387                 err |= gen_return_code(frame->retcode);
 388
 389                 if (err) {
 390                         goto give_sigsegv;
 391                 }
 392                 ra = (unsigned long) frame->retcode;
 393         }
 394
 395         /*
 396          * Create signal handler execution context.
 397          * Return context not modified until this point.
 398          */
 399
 400         /* Set up registers for signal handler */
 401         start_thread(regs, (unsigned long) ka->sa.sa_handler,
 402                      (unsigned long) frame);
 403
 404         /* Set up a stack frame for a call4
 405          * Note: PS.CALLINC is set to one by start_thread
 406          */
 407         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
 408         regs->areg[6] = (unsigned long) signal;
 409         regs->areg[7] = (unsigned long) &frame->info;
 410         regs->areg[8] = (unsigned long) &frame->uc;
 411
 412         /* Set access mode to USER_DS.  Nomenclature is outdated, but
 413          * functionality is used in uaccess.h
 414          */
 415         set_fs(USER_DS);
 416
 417 #if DEBUG_SIG
 418         printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
 419                 current->comm, current->pid, signal, frame, regs->pc);
 420 #endif
 421
 422         return 0;
 423
 424 give_sigsegv:
 425         force_sigsegv(sig, current);
 426         return -EFAULT;
 427 }
 428
 429 /*
 430  * Atomically swap in the new signal mask, and wait for a signal.
 431  */
 432
 433 asmlinkage long xtensa_rt_sigsuspend(sigset_t __user *unewset,
 434                                      size_t sigsetsize,
 435                                      long a2, long a3, long a4, long a5,
 436                                      struct pt_regs *regs)
 437 {
 438         sigset_t saveset, newset;
 439
 440         /* XXX: Don't preclude handling different sized sigset_t's.  */
 441         if (sigsetsize != sizeof(sigset_t))
 442                 return -EINVAL;
 443
 444         if (copy_from_user(&newset, unewset, sizeof(newset)))
 445                 return -EFAULT;
 446
 447         sigdelsetmask(&newset, ~_BLOCKABLE);
 448         saveset = current->blocked;
 449         set_current_blocked(&newset);
 450
 451         regs->areg[2] = -EINTR;
 452         while (1) {
 453                 current->state = TASK_INTERRUPTIBLE;
 454                 schedule();
 455                 if (do_signal(regs, &saveset))
 456                         return -EINTR;
 457         }
 458 }
 459
 460 asmlinkage long xtensa_sigaltstack(const stack_t __user *uss,
 461                                    stack_t __user *uoss,
 462                                    long a2, long a3, long a4, long a5,
 463                                    struct pt_regs *regs)
 464 {
 465         return do_sigaltstack(uss, uoss, regs->areg[1]);
 466 }
 467
 468
 469
 470 /*
 471  * Note that 'init' is a special process: it doesn't get signals it doesn't
 472  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 473  * mistake.
 474  *
 475  * Note that we go through the signals twice: once to check the signals that
 476  * the kernel can handle, and then we build all the user-level signal handling
 477  * stack-frames in one go after that.
 478  */
 479 int do_signal(struct pt_regs *regs, sigset_t *oldset)
 480 {
 481         siginfo_t info;
 482         int signr;
 483         struct k_sigaction ka;
 484
 485         if (!user_mode(regs))
 486                 return 0;
 487
 488         if (try_to_freeze())
 489                 goto no_signal;
 490
 491         if (!oldset)
 492                 oldset = &current->blocked;
 493
 494         task_pt_regs(current)->icountlevel = 0;
 495
 496         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 497
 498         if (signr > 0) {
 499                 int ret;
 500
 501                 /* Are we from a system call? */
 502
 503                 if ((signed)regs->syscall >= 0) {
 504
 505                         /* If so, check system call restarting.. */
 506
 507                         switch (regs->areg[2]) {
 508                                 case -ERESTARTNOHAND:
 509                                 case -ERESTART_RESTARTBLOCK:
 510                                         regs->areg[2] = -EINTR;
 511                                         break;
 512
 513                                 case -ERESTARTSYS:
 514                                         if (!(ka.sa.sa_flags & SA_RESTART)) {
 515                                                 regs->areg[2] = -EINTR;
 516                                                 break;
 517                                         }
 518                                         /* fallthrough */
 519                                 case -ERESTARTNOINTR:
 520                                         regs->areg[2] = regs->syscall;
 521                                         regs->pc -= 3;
 522                                         break;
 523
 524                                 default:
 525                                         /* nothing to do */
 526                                         if (regs->areg[2] != 0)
 527                                         break;
 528                         }
 529                 }
 530
 531                 /* Whee!  Actually deliver the signal.  */
 532                 /* Set up the stack frame */
 533                 ret = setup_frame(signr, &ka, &info, oldset, regs);
 534                 if (ret)
 535                         return ret;
 536
 537                 block_sigmask(&ka, signr);
 538                 if (current->ptrace & PT_SINGLESTEP)
 539                         task_pt_regs(current)->icountlevel = 1;
 540
 541                 return 1;
 542         }
 543
 544 no_signal:
 545         /* Did we come from a system call? */
 546         if ((signed) regs->syscall >= 0) {
 547                 /* Restart the system call - no handlers present */
 548                 switch (regs->areg[2]) {
 549                 case -ERESTARTNOHAND:
 550                 case -ERESTARTSYS:
 551                 case -ERESTARTNOINTR:
 552                         regs->areg[2] = regs->syscall;
 553                         regs->pc -= 3;
 554                         break;
 555                 case -ERESTART_RESTARTBLOCK:
 556                         regs->areg[2] = __NR_restart_syscall;
 557                         regs->pc -= 3;
 558                         break;
 559                 }
 560         }
 561         if (current->ptrace & PT_SINGLESTEP)
 562                 task_pt_regs(current)->icountlevel = 1;
 563         return 0;
 564 }
 565