linux/arch/xtensa/kernel/signal.c
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   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 <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
  32extern struct task_struct *coproc_owners[];
  33
  34struct 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
  54int
  55flush_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
 122errout:
 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
 134static int
 135setup_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
 173static int
 174restore_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
 240asmlinkage 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_thread_info()->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
 273badframe:
 274        force_sig(SIGSEGV, current);
 275        return 0;
 276}
 277
 278
 279
 280/*
 281 * Set up a signal frame.
 282 */
 283
 284static int
 285gen_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
 334static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 335                       sigset_t *set, struct pt_regs *regs)
 336{
 337        struct rt_sigframe *frame;
 338        int err = 0;
 339        int signal;
 340        unsigned long sp, ra, tp;
 341
 342        sp = regs->areg[1];
 343
 344        if ((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                goto give_sigsegv;
 355        }
 356
 357        signal = current_thread_info()->exec_domain
 358                && current_thread_info()->exec_domain->signal_invmap
 359                && sig < 32
 360                ? current_thread_info()->exec_domain->signal_invmap[sig]
 361                : sig;
 362
 363        if (ka->sa.sa_flags & SA_SIGINFO) {
 364                err |= copy_siginfo_to_user(&frame->info, info);
 365        }
 366
 367        /* Create the user context.  */
 368
 369        err |= __put_user(0, &frame->uc.uc_flags);
 370        err |= __put_user(0, &frame->uc.uc_link);
 371        err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
 372        err |= setup_sigcontext(frame, regs);
 373        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 374
 375        if (ka->sa.sa_flags & SA_RESTORER) {
 376                ra = (unsigned long)ka->sa.sa_restorer;
 377        } else {
 378
 379                /* Create sys_rt_sigreturn syscall in stack frame */
 380
 381                err |= gen_return_code(frame->retcode);
 382
 383                if (err) {
 384                        goto give_sigsegv;
 385                }
 386                ra = (unsigned long) frame->retcode;
 387        }
 388
 389        /* 
 390         * Create signal handler execution context.
 391         * Return context not modified until this point.
 392         */
 393
 394        /* Set up registers for signal handler; preserve the threadptr */
 395        tp = regs->threadptr;
 396        start_thread(regs, (unsigned long) ka->sa.sa_handler,
 397                     (unsigned long) frame);
 398
 399        /* Set up a stack frame for a call4
 400         * Note: PS.CALLINC is set to one by start_thread
 401         */
 402        regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
 403        regs->areg[6] = (unsigned long) signal;
 404        regs->areg[7] = (unsigned long) &frame->info;
 405        regs->areg[8] = (unsigned long) &frame->uc;
 406        regs->threadptr = tp;
 407
 408        /* Set access mode to USER_DS.  Nomenclature is outdated, but
 409         * functionality is used in uaccess.h
 410         */
 411        set_fs(USER_DS);
 412
 413#if DEBUG_SIG
 414        printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
 415                current->comm, current->pid, signal, frame, regs->pc);
 416#endif
 417
 418        return 0;
 419
 420give_sigsegv:
 421        force_sigsegv(sig, current);
 422        return -EFAULT;
 423}
 424
 425/*
 426 * Note that 'init' is a special process: it doesn't get signals it doesn't
 427 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 428 * mistake.
 429 *
 430 * Note that we go through the signals twice: once to check the signals that
 431 * the kernel can handle, and then we build all the user-level signal handling
 432 * stack-frames in one go after that.
 433 */
 434static void do_signal(struct pt_regs *regs)
 435{
 436        siginfo_t info;
 437        int signr;
 438        struct k_sigaction ka;
 439
 440        task_pt_regs(current)->icountlevel = 0;
 441
 442        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 443
 444        if (signr > 0) {
 445                int ret;
 446
 447                /* Are we from a system call? */
 448
 449                if ((signed)regs->syscall >= 0) {
 450
 451                        /* If so, check system call restarting.. */
 452
 453                        switch (regs->areg[2]) {
 454                                case -ERESTARTNOHAND:
 455                                case -ERESTART_RESTARTBLOCK:
 456                                        regs->areg[2] = -EINTR;
 457                                        break;
 458
 459                                case -ERESTARTSYS:
 460                                        if (!(ka.sa.sa_flags & SA_RESTART)) {
 461                                                regs->areg[2] = -EINTR;
 462                                                break;
 463                                        }
 464                                        /* fallthrough */
 465                                case -ERESTARTNOINTR:
 466                                        regs->areg[2] = regs->syscall;
 467                                        regs->pc -= 3;
 468                                        break;
 469
 470                                default:
 471                                        /* nothing to do */
 472                                        if (regs->areg[2] != 0)
 473                                        break;
 474                        }
 475                }
 476
 477                /* Whee!  Actually deliver the signal.  */
 478                /* Set up the stack frame */
 479                ret = setup_frame(signr, &ka, &info, sigmask_to_save(), regs);
 480                if (ret)
 481                        return;
 482
 483                signal_delivered(signr, &info, &ka, regs, 0);
 484                if (current->ptrace & PT_SINGLESTEP)
 485                        task_pt_regs(current)->icountlevel = 1;
 486
 487                return;
 488        }
 489
 490        /* Did we come from a system call? */
 491        if ((signed) regs->syscall >= 0) {
 492                /* Restart the system call - no handlers present */
 493                switch (regs->areg[2]) {
 494                case -ERESTARTNOHAND:
 495                case -ERESTARTSYS:
 496                case -ERESTARTNOINTR:
 497                        regs->areg[2] = regs->syscall;
 498                        regs->pc -= 3;
 499                        break;
 500                case -ERESTART_RESTARTBLOCK:
 501                        regs->areg[2] = __NR_restart_syscall;
 502                        regs->pc -= 3;
 503                        break;
 504                }
 505        }
 506
 507        /* If there's no signal to deliver, we just restore the saved mask.  */
 508        restore_saved_sigmask();
 509
 510        if (current->ptrace & PT_SINGLESTEP)
 511                task_pt_regs(current)->icountlevel = 1;
 512        return;
 513}
 514
 515void do_notify_resume(struct pt_regs *regs)
 516{
 517        if (test_thread_flag(TIF_SIGPENDING))
 518                do_signal(regs);
 519
 520        if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
 521                tracehook_notify_resume(regs);
 522}
 523