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 #include <linux/sched/task_stack.h>
  24
  25 #include <asm/ucontext.h>
  26 #include <linux/uaccess.h>
  27 #include <asm/cacheflush.h>
  28 #include <asm/coprocessor.h>
  29 #include <asm/unistd.h>
  30
  31 #define DEBUG_SIG  0
  32
  33 extern struct task_struct *coproc_owners[];
  34
  35 struct rt_sigframe
  36 {
  37         struct siginfo info;
  38         struct ucontext uc;
  39         struct {
  40                 xtregs_opt_t opt;
  41                 xtregs_user_t user;
  42 #if XTENSA_HAVE_COPROCESSORS
  43                 xtregs_coprocessor_t cp;
  44 #endif
  45         } xtregs;
  46         unsigned char retcode[6];
  47         unsigned int window[4];
  48 };
  49
  50 /*
  51  * Flush register windows stored in pt_regs to stack.
  52  * Returns 1 for errors.
  53  */
  54
  55 int
  56 flush_window_regs_user(struct pt_regs *regs)
  57 {
  58         const unsigned long ws = regs->windowstart;
  59         const unsigned long wb = regs->windowbase;
  60         unsigned long sp = 0;
  61         unsigned long wm;
  62         int err = 1;
  63         int base;
  64
  65         /* Return if no other frames. */
  66
  67         if (regs->wmask == 1)
  68                 return 0;
  69
  70         /* Rotate windowmask and skip empty frames. */
  71
  72         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
  73         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
  74
  75         /* For call8 or call12 frames, we need the previous stack pointer. */
  76
  77         if ((regs->wmask & 2) == 0)
  78                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
  79                         goto errout;
  80
  81         /* Spill frames to stack. */
  82
  83         while (base < XCHAL_NUM_AREGS / 4) {
  84
  85                 int m = (wm >> base);
  86                 int inc = 0;
  87
  88                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
  89
  90                 if (m & 2) {                    /* call4 */
  91                         inc = 1;
  92
  93                 } else if (m & 4) {             /* call8 */
  94                         if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4),
  95                                          &regs->areg[(base + 1) * 4], 16))
  96                                 goto errout;
  97                         inc = 2;
  98
  99                 } else if (m & 8) {     /* call12 */
 100                         if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
 101                                          &regs->areg[(base + 1) * 4], 32))
 102                                 goto errout;
 103                         inc = 3;
 104                 }
 105
 106                 /* Save current frame a0..a3 under next SP */
 107
 108                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
 109                 if (copy_to_user(&SPILL_SLOT(sp, 0), &regs->areg[base * 4], 16))
 110                         goto errout;
 111
 112                 /* Get current stack pointer for next loop iteration. */
 113
 114                 sp = regs->areg[base * 4 + 1];
 115                 base += inc;
 116         }
 117
 118         regs->wmask = 1;
 119         regs->windowstart = 1 << wb;
 120
 121         return 0;
 122
 123 errout:
 124         return err;
 125 }
 126
 127 /*
 128  * Note: We don't copy double exception 'regs', we have to finish double exc.
 129  * first before we return to signal handler! This dbl.exc.handler might cause
 130  * another double exception, but I think we are fine as the situation is the
 131  * same as if we had returned to the signal handerl and got an interrupt
 132  * immediately...
 133  */
 134
 135 static int
 136 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
 137 {
 138         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 139         struct thread_info *ti = current_thread_info();
 140         int err = 0;
 141
 142 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
 143         COPY(pc);
 144         COPY(ps);
 145         COPY(lbeg);
 146         COPY(lend);
 147         COPY(lcount);
 148         COPY(sar);
 149 #undef COPY
 150
 151         err |= flush_window_regs_user(regs);
 152         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
 153         err |= __put_user(0, &sc->sc_xtregs);
 154
 155         if (err)
 156                 return err;
 157
 158 #if XTENSA_HAVE_COPROCESSORS
 159         coprocessor_flush_all(ti);
 160         coprocessor_release_all(ti);
 161         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
 162                               sizeof (frame->xtregs.cp));
 163 #endif
 164         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
 165                               sizeof (xtregs_opt_t));
 166         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
 167                               sizeof (xtregs_user_t));
 168
 169         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
 170
 171         return err;
 172 }
 173
 174 static int
 175 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
 176 {
 177         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 178         struct thread_info *ti = current_thread_info();
 179         unsigned int err = 0;
 180         unsigned long ps;
 181
 182 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
 183         COPY(pc);
 184         COPY(lbeg);
 185         COPY(lend);
 186         COPY(lcount);
 187         COPY(sar);
 188 #undef COPY
 189
 190         /* All registers were flushed to stack. Start with a prestine frame. */
 191
 192         regs->wmask = 1;
 193         regs->windowbase = 0;
 194         regs->windowstart = 1;
 195
 196         regs->syscall = -1;             /* disable syscall checks */
 197
 198         /* For PS, restore only PS.CALLINC.
 199          * Assume that all other bits are either the same as for the signal
 200          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
 201          */
 202         err |= __get_user(ps, &sc->sc_ps);
 203         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
 204
 205         /* Additional corruption checks */
 206
 207         if ((regs->lcount > 0)
 208             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
 209                 err = 1;
 210
 211         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
 212
 213         if (err)
 214                 return err;
 215
 216         /* The signal handler may have used coprocessors in which
 217          * case they are still enabled.  We disable them to force a
 218          * reloading of the original task's CP state by the lazy
 219          * context-switching mechanisms of CP exception handling.
 220          * Also, we essentially discard any coprocessor state that the
 221          * signal handler created. */
 222
 223 #if XTENSA_HAVE_COPROCESSORS
 224         coprocessor_release_all(ti);
 225         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
 226                                 sizeof (frame->xtregs.cp));
 227 #endif
 228         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
 229                                 sizeof (xtregs_user_t));
 230         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
 231                                 sizeof (xtregs_opt_t));
 232
 233         return err;
 234 }
 235
 236
 237 /*
 238  * Do a signal return; undo the signal stack.
 239  */
 240
 241 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
 242                                     long a4, long a5, struct pt_regs *regs)
 243 {
 244         struct rt_sigframe __user *frame;
 245         sigset_t set;
 246         int ret;
 247
 248         /* Always make any pending restarted system calls return -EINTR */
 249         current->restart_block.fn = do_no_restart_syscall;
 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         set_current_blocked(&set);
 263
 264         if (restore_sigcontext(regs, frame))
 265                 goto badframe;
 266
 267         ret = regs->areg[2];
 268
 269         if (restore_altstack(&frame->uc.uc_stack))
 270                 goto badframe;
 271
 272         return ret;
 273
 274 badframe:
 275         force_sig(SIGSEGV, current);
 276         return 0;
 277 }
 278
 279
 280
 281 /*
 282  * Set up a signal frame.
 283  */
 284
 285 static int
 286 gen_return_code(unsigned char *codemem)
 287 {
 288         int err = 0;
 289
 290         /*
 291          * The 12-bit immediate is really split up within the 24-bit MOVI
 292          * instruction.  As long as the above system call numbers fit within
 293          * 8-bits, the following code works fine. See the Xtensa ISA for
 294          * details.
 295          */
 296
 297 #if __NR_rt_sigreturn > 255
 298 # error Generating the MOVI instruction below breaks!
 299 #endif
 300
 301 #ifdef __XTENSA_EB__   /* Big Endian version */
 302         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 303         err |= __put_user(0x22, &codemem[0]);
 304         err |= __put_user(0x0a, &codemem[1]);
 305         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 306         /* Generate instruction:  SYSCALL */
 307         err |= __put_user(0x00, &codemem[3]);
 308         err |= __put_user(0x05, &codemem[4]);
 309         err |= __put_user(0x00, &codemem[5]);
 310
 311 #elif defined __XTENSA_EL__   /* Little Endian version */
 312         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 313         err |= __put_user(0x22, &codemem[0]);
 314         err |= __put_user(0xa0, &codemem[1]);
 315         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 316         /* Generate instruction:  SYSCALL */
 317         err |= __put_user(0x00, &codemem[3]);
 318         err |= __put_user(0x50, &codemem[4]);
 319         err |= __put_user(0x00, &codemem[5]);
 320 #else
 321 # error Must use compiler for Xtensa processors.
 322 #endif
 323
 324         /* Flush generated code out of the data cache */
 325
 326         if (err == 0) {
 327                 __invalidate_icache_range((unsigned long)codemem, 6UL);
 328                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
 329         }
 330
 331         return err;
 332 }
 333
 334
 335 static int setup_frame(struct ksignal *ksig, sigset_t *set,
 336                        struct pt_regs *regs)
 337 {
 338         struct rt_sigframe *frame;
 339         int err = 0, sig = ksig->sig;
 340         unsigned long sp, ra, tp;
 341
 342         sp = regs->areg[1];
 343
 344         if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
 345                 sp = current->sas_ss_sp + current->sas_ss_size;
 346         }
 347
 348         frame = (void *)((sp - sizeof(*frame)) & -16ul);
 349
 350         if (regs->depc > 64)
 351                 panic ("Double exception sys_sigreturn\n");
 352
 353         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
 354                 return -EFAULT;
 355         }
 356
 357         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 358                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 359         }
 360
 361         /* Create the user context.  */
 362
 363         err |= __put_user(0, &frame->uc.uc_flags);
 364         err |= __put_user(0, &frame->uc.uc_link);
 365         err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
 366         err |= setup_sigcontext(frame, regs);
 367         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 368
 369         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 370                 ra = (unsigned long)ksig->ka.sa.sa_restorer;
 371         } else {
 372
 373                 /* Create sys_rt_sigreturn syscall in stack frame */
 374
 375                 err |= gen_return_code(frame->retcode);
 376
 377                 if (err) {
 378                         return -EFAULT;
 379                 }
 380                 ra = (unsigned long) frame->retcode;
 381         }
 382
 383         /*
 384          * Create signal handler execution context.
 385          * Return context not modified until this point.
 386          */
 387
 388         /* Set up registers for signal handler; preserve the threadptr */
 389         tp = regs->threadptr;
 390         start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
 391                      (unsigned long) frame);
 392
 393         /* Set up a stack frame for a call4
 394          * Note: PS.CALLINC is set to one by start_thread
 395          */
 396         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
 397         regs->areg[6] = (unsigned long) sig;
 398         regs->areg[7] = (unsigned long) &frame->info;
 399         regs->areg[8] = (unsigned long) &frame->uc;
 400         regs->threadptr = tp;
 401
 402 #if DEBUG_SIG
 403         printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
 404                 current->comm, current->pid, sig, frame, regs->pc);
 405 #endif
 406
 407         return 0;
 408 }
 409
 410 /*
 411  * Note that 'init' is a special process: it doesn't get signals it doesn't
 412  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 413  * mistake.
 414  *
 415  * Note that we go through the signals twice: once to check the signals that
 416  * the kernel can handle, and then we build all the user-level signal handling
 417  * stack-frames in one go after that.
 418  */
 419 static void do_signal(struct pt_regs *regs)
 420 {
 421         struct ksignal ksig;
 422
 423         task_pt_regs(current)->icountlevel = 0;
 424
 425         if (get_signal(&ksig)) {
 426                 int ret;
 427
 428                 /* Are we from a system call? */
 429
 430                 if ((signed)regs->syscall >= 0) {
 431
 432                         /* If so, check system call restarting.. */
 433
 434                         switch (regs->areg[2]) {
 435                                 case -ERESTARTNOHAND:
 436                                 case -ERESTART_RESTARTBLOCK:
 437                                         regs->areg[2] = -EINTR;
 438                                         break;
 439
 440                                 case -ERESTARTSYS:
 441                                         if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
 442                                                 regs->areg[2] = -EINTR;
 443                                                 break;
 444                                         }
 445                                         /* fallthrough */
 446                                 case -ERESTARTNOINTR:
 447                                         regs->areg[2] = regs->syscall;
 448                                         regs->pc -= 3;
 449                                         break;
 450
 451                                 default:
 452                                         /* nothing to do */
 453                                         if (regs->areg[2] != 0)
 454                                         break;
 455                         }
 456                 }
 457
 458                 /* Whee!  Actually deliver the signal.  */
 459                 /* Set up the stack frame */
 460                 ret = setup_frame(&ksig, sigmask_to_save(), regs);
 461                 signal_setup_done(ret, &ksig, 0);
 462                 if (current->ptrace & PT_SINGLESTEP)
 463                         task_pt_regs(current)->icountlevel = 1;
 464
 465                 return;
 466         }
 467
 468         /* Did we come from a system call? */
 469         if ((signed) regs->syscall >= 0) {
 470                 /* Restart the system call - no handlers present */
 471                 switch (regs->areg[2]) {
 472                 case -ERESTARTNOHAND:
 473                 case -ERESTARTSYS:
 474                 case -ERESTARTNOINTR:
 475                         regs->areg[2] = regs->syscall;
 476                         regs->pc -= 3;
 477                         break;
 478                 case -ERESTART_RESTARTBLOCK:
 479                         regs->areg[2] = __NR_restart_syscall;
 480                         regs->pc -= 3;
 481                         break;
 482                 }
 483         }
 484
 485         /* If there's no signal to deliver, we just restore the saved mask.  */
 486         restore_saved_sigmask();
 487
 488         if (current->ptrace & PT_SINGLESTEP)
 489                 task_pt_regs(current)->icountlevel = 1;
 490         return;
 491 }
 492
 493 void do_notify_resume(struct pt_regs *regs)
 494 {
 495         if (test_thread_flag(TIF_SIGPENDING))
 496                 do_signal(regs);
 497
 498         if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
 499                 tracehook_notify_resume(regs);
 500 }