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/resume_user_mode.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/processor.h>
  30 #include <asm/syscall.h>
  31 #include <asm/unistd.h>
  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 #if defined(USER_SUPPORT_WINDOWED)
  51 /*
  52  * Flush register windows stored in pt_regs to stack.
  53  * Returns 1 for errors.
  54  */
  55
  56 static int
  57 flush_window_regs_user(struct pt_regs *regs)
  58 {
  59         const unsigned long ws = regs->windowstart;
  60         const unsigned long wb = regs->windowbase;
  61         unsigned long sp = 0;
  62         unsigned long wm;
  63         int err = 1;
  64         int base;
  65
  66         /* Return if no other frames. */
  67
  68         if (regs->wmask == 1)
  69                 return 0;
  70
  71         /* Rotate windowmask and skip empty frames. */
  72
  73         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
  74         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
  75
  76         /* For call8 or call12 frames, we need the previous stack pointer. */
  77
  78         if ((regs->wmask & 2) == 0)
  79                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
  80                         goto errout;
  81
  82         /* Spill frames to stack. */
  83
  84         while (base < XCHAL_NUM_AREGS / 4) {
  85
  86                 int m = (wm >> base);
  87                 int inc = 0;
  88
  89                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
  90
  91                 if (m & 2) {                    /* call4 */
  92                         inc = 1;
  93
  94                 } else if (m & 4) {             /* call8 */
  95                         if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4),
  96                                          &regs->areg[(base + 1) * 4], 16))
  97                                 goto errout;
  98                         inc = 2;
  99
 100                 } else if (m & 8) {     /* call12 */
 101                         if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
 102                                          &regs->areg[(base + 1) * 4], 32))
 103                                 goto errout;
 104                         inc = 3;
 105                 }
 106
 107                 /* Save current frame a0..a3 under next SP */
 108
 109                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
 110                 if (copy_to_user(&SPILL_SLOT(sp, 0), &regs->areg[base * 4], 16))
 111                         goto errout;
 112
 113                 /* Get current stack pointer for next loop iteration. */
 114
 115                 sp = regs->areg[base * 4 + 1];
 116                 base += inc;
 117         }
 118
 119         regs->wmask = 1;
 120         regs->windowstart = 1 << wb;
 121
 122         return 0;
 123
 124 errout:
 125         return err;
 126 }
 127 #else
 128 static int
 129 flush_window_regs_user(struct pt_regs *regs)
 130 {
 131         return 0;
 132 }
 133 #endif
 134
 135 /*
 136  * Note: We don't copy double exception 'regs', we have to finish double exc.
 137  * first before we return to signal handler! This dbl.exc.handler might cause
 138  * another double exception, but I think we are fine as the situation is the
 139  * same as if we had returned to the signal handerl and got an interrupt
 140  * immediately...
 141  */
 142
 143 static int
 144 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
 145 {
 146         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 147         struct thread_info *ti = current_thread_info();
 148         int err = 0;
 149
 150 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
 151         COPY(pc);
 152         COPY(ps);
 153         COPY(lbeg);
 154         COPY(lend);
 155         COPY(lcount);
 156         COPY(sar);
 157 #undef COPY
 158
 159         err |= flush_window_regs_user(regs);
 160         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
 161         err |= __put_user(0, &sc->sc_xtregs);
 162
 163         if (err)
 164                 return err;
 165
 166 #if XTENSA_HAVE_COPROCESSORS
 167         coprocessor_flush_release_all(ti);
 168         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
 169                               sizeof (frame->xtregs.cp));
 170 #endif
 171         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
 172                               sizeof (xtregs_opt_t));
 173         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
 174                               sizeof (xtregs_user_t));
 175
 176         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
 177
 178         return err;
 179 }
 180
 181 static int
 182 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
 183 {
 184         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 185         struct thread_info *ti = current_thread_info();
 186         unsigned int err = 0;
 187         unsigned long ps;
 188
 189 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
 190         COPY(pc);
 191         COPY(lbeg);
 192         COPY(lend);
 193         COPY(lcount);
 194         COPY(sar);
 195 #undef COPY
 196
 197         /* All registers were flushed to stack. Start with a pristine frame. */
 198
 199         regs->wmask = 1;
 200         regs->windowbase = 0;
 201         regs->windowstart = 1;
 202
 203         regs->syscall = NO_SYSCALL;     /* disable syscall checks */
 204
 205         /* For PS, restore only PS.CALLINC.
 206          * Assume that all other bits are either the same as for the signal
 207          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
 208          */
 209         err |= __get_user(ps, &sc->sc_ps);
 210         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
 211
 212         /* Additional corruption checks */
 213
 214         if ((regs->lcount > 0)
 215             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
 216                 err = 1;
 217
 218         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
 219
 220         if (err)
 221                 return err;
 222
 223         /* The signal handler may have used coprocessors in which
 224          * case they are still enabled.  We disable them to force a
 225          * reloading of the original task's CP state by the lazy
 226          * context-switching mechanisms of CP exception handling.
 227          * Also, we essentially discard any coprocessor state that the
 228          * signal handler created. */
 229
 230 #if XTENSA_HAVE_COPROCESSORS
 231         coprocessor_release_all(ti);
 232         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
 233                                 sizeof (frame->xtregs.cp));
 234 #endif
 235         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
 236                                 sizeof (xtregs_user_t));
 237         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
 238                                 sizeof (xtregs_opt_t));
 239
 240         return err;
 241 }
 242
 243
 244 /*
 245  * Do a signal return; undo the signal stack.
 246  */
 247
 248 asmlinkage long xtensa_rt_sigreturn(void)
 249 {
 250         struct pt_regs *regs = current_pt_regs();
 251         struct rt_sigframe __user *frame;
 252         sigset_t set;
 253         int ret;
 254
 255         /* Always make any pending restarted system calls return -EINTR */
 256         current->restart_block.fn = do_no_restart_syscall;
 257
 258         if (regs->depc > 64)
 259                 panic("rt_sigreturn in double exception!\n");
 260
 261         frame = (struct rt_sigframe __user *) regs->areg[1];
 262
 263         if (!access_ok(frame, sizeof(*frame)))
 264                 goto badframe;
 265
 266         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 267                 goto badframe;
 268
 269         set_current_blocked(&set);
 270
 271         if (restore_sigcontext(regs, frame))
 272                 goto badframe;
 273
 274         ret = regs->areg[2];
 275
 276         if (restore_altstack(&frame->uc.uc_stack))
 277                 goto badframe;
 278
 279         return ret;
 280
 281 badframe:
 282         force_sig(SIGSEGV);
 283         return 0;
 284 }
 285
 286
 287
 288 /*
 289  * Set up a signal frame.
 290  */
 291
 292 static int
 293 gen_return_code(unsigned char *codemem)
 294 {
 295         int err = 0;
 296
 297         /*
 298          * The 12-bit immediate is really split up within the 24-bit MOVI
 299          * instruction.  As long as the above system call numbers fit within
 300          * 8-bits, the following code works fine. See the Xtensa ISA for
 301          * details.
 302          */
 303
 304 #if __NR_rt_sigreturn > 255
 305 # error Generating the MOVI instruction below breaks!
 306 #endif
 307
 308 #ifdef __XTENSA_EB__   /* Big Endian version */
 309         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 310         err |= __put_user(0x22, &codemem[0]);
 311         err |= __put_user(0x0a, &codemem[1]);
 312         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 313         /* Generate instruction:  SYSCALL */
 314         err |= __put_user(0x00, &codemem[3]);
 315         err |= __put_user(0x05, &codemem[4]);
 316         err |= __put_user(0x00, &codemem[5]);
 317
 318 #elif defined __XTENSA_EL__   /* Little Endian version */
 319         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
 320         err |= __put_user(0x22, &codemem[0]);
 321         err |= __put_user(0xa0, &codemem[1]);
 322         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
 323         /* Generate instruction:  SYSCALL */
 324         err |= __put_user(0x00, &codemem[3]);
 325         err |= __put_user(0x50, &codemem[4]);
 326         err |= __put_user(0x00, &codemem[5]);
 327 #else
 328 # error Must use compiler for Xtensa processors.
 329 #endif
 330
 331         /* Flush generated code out of the data cache */
 332
 333         if (err == 0) {
 334                 __invalidate_icache_range((unsigned long)codemem, 6UL);
 335                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
 336         }
 337
 338         return err;
 339 }
 340
 341
 342 static int setup_frame(struct ksignal *ksig, sigset_t *set,
 343                        struct pt_regs *regs)
 344 {
 345         struct rt_sigframe *frame;
 346         int err = 0, sig = ksig->sig;
 347         unsigned long sp, ra, tp, ps;
 348         unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
 349         unsigned long handler_fdpic_GOT = 0;
 350         unsigned int base;
 351         bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
 352                 (current->personality & FDPIC_FUNCPTRS);
 353
 354         if (fdpic) {
 355                 unsigned long __user *fdpic_func_desc =
 356                         (unsigned long __user *)handler;
 357                 if (__get_user(handler, &fdpic_func_desc[0]) ||
 358                     __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
 359                         return -EFAULT;
 360         }
 361
 362         sp = regs->areg[1];
 363
 364         if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
 365                 sp = current->sas_ss_sp + current->sas_ss_size;
 366         }
 367
 368         frame = (void *)((sp - sizeof(*frame)) & -16ul);
 369
 370         if (regs->depc > 64)
 371                 panic ("Double exception sys_sigreturn\n");
 372
 373         if (!access_ok(frame, sizeof(*frame))) {
 374                 return -EFAULT;
 375         }
 376
 377         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 378                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 379         }
 380
 381         /* Create the user context.  */
 382
 383         err |= __put_user(0, &frame->uc.uc_flags);
 384         err |= __put_user(0, &frame->uc.uc_link);
 385         err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
 386         err |= setup_sigcontext(frame, regs);
 387         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 388
 389         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 390                 if (fdpic) {
 391                         unsigned long __user *fdpic_func_desc =
 392                                 (unsigned long __user *)ksig->ka.sa.sa_restorer;
 393
 394                         err |= __get_user(ra, fdpic_func_desc);
 395                 } else {
 396                         ra = (unsigned long)ksig->ka.sa.sa_restorer;
 397                 }
 398         } else {
 399
 400                 /* Create sys_rt_sigreturn syscall in stack frame */
 401
 402                 err |= gen_return_code(frame->retcode);
 403                 ra = (unsigned long) frame->retcode;
 404         }
 405
 406         if (err)
 407                 return -EFAULT;
 408
 409         /*
 410          * Create signal handler execution context.
 411          * Return context not modified until this point.
 412          */
 413
 414         /* Set up registers for signal handler; preserve the threadptr */
 415         tp = regs->threadptr;
 416         ps = regs->ps;
 417         start_thread(regs, handler, (unsigned long)frame);
 418
 419         /* Set up a stack frame for a call4 if userspace uses windowed ABI */
 420         if (ps & PS_WOE_MASK) {
 421                 base = 4;
 422                 regs->areg[base] =
 423                         (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
 424                 ps = (ps & ~(PS_CALLINC_MASK | PS_OWB_MASK)) |
 425                         (1 << PS_CALLINC_SHIFT);
 426         } else {
 427                 base = 0;
 428                 regs->areg[base] = (unsigned long) ra;
 429         }
 430         regs->areg[base + 2] = (unsigned long) sig;
 431         regs->areg[base + 3] = (unsigned long) &frame->info;
 432         regs->areg[base + 4] = (unsigned long) &frame->uc;
 433         regs->threadptr = tp;
 434         regs->ps = ps;
 435         if (fdpic)
 436                 regs->areg[base + 11] = handler_fdpic_GOT;
 437
 438         pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n",
 439                  current->comm, current->pid, sig, frame, regs->pc);
 440
 441         return 0;
 442 }
 443
 444 /*
 445  * Note that 'init' is a special process: it doesn't get signals it doesn't
 446  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 447  * mistake.
 448  *
 449  * Note that we go through the signals twice: once to check the signals that
 450  * the kernel can handle, and then we build all the user-level signal handling
 451  * stack-frames in one go after that.
 452  */
 453 static void do_signal(struct pt_regs *regs)
 454 {
 455         struct ksignal ksig;
 456
 457         task_pt_regs(current)->icountlevel = 0;
 458
 459         if (get_signal(&ksig)) {
 460                 int ret;
 461
 462                 /* Are we from a system call? */
 463
 464                 if (regs->syscall != NO_SYSCALL) {
 465
 466                         /* If so, check system call restarting.. */
 467
 468                         switch (regs->areg[2]) {
 469                                 case -ERESTARTNOHAND:
 470                                 case -ERESTART_RESTARTBLOCK:
 471                                         regs->areg[2] = -EINTR;
 472                                         break;
 473
 474                                 case -ERESTARTSYS:
 475                                         if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
 476                                                 regs->areg[2] = -EINTR;
 477                                                 break;
 478                                         }
 479                                         fallthrough;
 480                                 case -ERESTARTNOINTR:
 481                                         regs->areg[2] = regs->syscall;
 482                                         regs->pc -= 3;
 483                                         break;
 484
 485                                 default:
 486                                         /* nothing to do */
 487                                         if (regs->areg[2] != 0)
 488                                         break;
 489                         }
 490                 }
 491
 492                 /* Whee!  Actually deliver the signal.  */
 493                 /* Set up the stack frame */
 494                 ret = setup_frame(&ksig, sigmask_to_save(), regs);
 495                 signal_setup_done(ret, &ksig, 0);
 496                 if (test_thread_flag(TIF_SINGLESTEP))
 497                         task_pt_regs(current)->icountlevel = 1;
 498
 499                 return;
 500         }
 501
 502         /* Did we come from a system call? */
 503         if (regs->syscall != NO_SYSCALL) {
 504                 /* Restart the system call - no handlers present */
 505                 switch (regs->areg[2]) {
 506                 case -ERESTARTNOHAND:
 507                 case -ERESTARTSYS:
 508                 case -ERESTARTNOINTR:
 509                         regs->areg[2] = regs->syscall;
 510                         regs->pc -= 3;
 511                         break;
 512                 case -ERESTART_RESTARTBLOCK:
 513                         regs->areg[2] = __NR_restart_syscall;
 514                         regs->pc -= 3;
 515                         break;
 516                 }
 517         }
 518
 519         /* If there's no signal to deliver, we just restore the saved mask.  */
 520         restore_saved_sigmask();
 521
 522         if (test_thread_flag(TIF_SINGLESTEP))
 523                 task_pt_regs(current)->icountlevel = 1;
 524         return;
 525 }
 526
 527 void do_notify_resume(struct pt_regs *regs)
 528 {
 529         if (test_thread_flag(TIF_SIGPENDING) ||
 530             test_thread_flag(TIF_NOTIFY_SIGNAL))
 531                 do_signal(regs);
 532
 533         if (test_thread_flag(TIF_NOTIFY_RESUME))
 534                 resume_user_mode_work(regs);
 535 }