arch/powerpc/kernel/signal_64.c

   1 /*
   2  *  PowerPC version
   3  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   4  *
   5  *  Derived from "arch/i386/kernel/signal.c"
   6  *    Copyright (C) 1991, 1992 Linus Torvalds
   7  *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   8  *
   9  *  This program is free software; you can redistribute it and/or
  10  *  modify it under the terms of the GNU General Public License
  11  *  as published by the Free Software Foundation; either version
  12  *  2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/sched.h>
  16 #include <linux/mm.h>
  17 #include <linux/smp.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/kernel.h>
  20 #include <linux/signal.h>
  21 #include <linux/errno.h>
  22 #include <linux/wait.h>
  23 #include <linux/unistd.h>
  24 #include <linux/stddef.h>
  25 #include <linux/elf.h>
  26 #include <linux/ptrace.h>
  27 #include <linux/module.h>
  28
  29 #include <asm/sigcontext.h>
  30 #include <asm/ucontext.h>
  31 #include <asm/uaccess.h>
  32 #include <asm/pgtable.h>
  33 #include <asm/unistd.h>
  34 #include <asm/cacheflush.h>
  35 #include <asm/syscalls.h>
  36 #include <asm/vdso.h>
  37
  38 #define DEBUG_SIG 0
  39
  40 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  41
  42 #define GP_REGS_SIZE    min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
  43 #define FP_REGS_SIZE    sizeof(elf_fpregset_t)
  44
  45 #define TRAMP_TRACEBACK 3
  46 #define TRAMP_SIZE      6
  47
  48 /*
  49  * When we have signals to deliver, we set up on the user stack,
  50  * going down from the original stack pointer:
  51  *      1) a rt_sigframe struct which contains the ucontext
  52  *      2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
  53  *         frame for the signal handler.
  54  */
  55
  56 struct rt_sigframe {
  57         /* sys_rt_sigreturn requires the ucontext be the first field */
  58         struct ucontext uc;
  59         unsigned long _unused[2];
  60         unsigned int tramp[TRAMP_SIZE];
  61         struct siginfo __user *pinfo;
  62         void __user *puc;
  63         struct siginfo info;
  64         /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
  65         char abigap[288];
  66 } __attribute__ ((aligned (16)));
  67
  68 long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss, unsigned long r5,
  69                      unsigned long r6, unsigned long r7, unsigned long r8,
  70                      struct pt_regs *regs)
  71 {
  72         return do_sigaltstack(uss, uoss, regs->gpr[1]);
  73 }
  74
  75
  76 /*
  77  * Set up the sigcontext for the signal frame.
  78  */
  79
  80 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  81                  int signr, sigset_t *set, unsigned long handler)
  82 {
  83         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  84          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  85          * the context). This is very important because we must ensure we
  86          * don't lose the VRSAVE content that may have been set prior to
  87          * the process doing its first vector operation
  88          * Userland shall check AT_HWCAP to know wether it can rely on the
  89          * v_regs pointer or not
  90          */
  91 #ifdef CONFIG_ALTIVEC
  92         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  93 #endif
  94         long err = 0;
  95
  96         flush_fp_to_thread(current);
  97
  98 #ifdef CONFIG_ALTIVEC
  99         err |= __put_user(v_regs, &sc->v_regs);
 100
 101         /* save altivec registers */
 102         if (current->thread.used_vr) {
 103                 flush_altivec_to_thread(current);
 104                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 105                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 106                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 107                  * contains valid data.
 108                  */
 109                 regs->msr |= MSR_VEC;
 110         }
 111         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 112          * use altivec.
 113          */
 114         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 115 #else /* CONFIG_ALTIVEC */
 116         err |= __put_user(0, &sc->v_regs);
 117 #endif /* CONFIG_ALTIVEC */
 118         err |= __put_user(&sc->gp_regs, &sc->regs);
 119         WARN_ON(!FULL_REGS(regs));
 120         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 121         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
 122         err |= __put_user(signr, &sc->signal);
 123         err |= __put_user(handler, &sc->handler);
 124         if (set != NULL)
 125                 err |=  __put_user(set->sig[0], &sc->oldmask);
 126
 127         return err;
 128 }
 129
 130 /*
 131  * Restore the sigcontext from the signal frame.
 132  */
 133
 134 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 135                               struct sigcontext __user *sc)
 136 {
 137 #ifdef CONFIG_ALTIVEC
 138         elf_vrreg_t __user *v_regs;
 139 #endif
 140         unsigned long err = 0;
 141         unsigned long save_r13 = 0;
 142         elf_greg_t *gregs = (elf_greg_t *)regs;
 143         unsigned long msr;
 144         int i;
 145
 146         /* If this is not a signal return, we preserve the TLS in r13 */
 147         if (!sig)
 148                 save_r13 = regs->gpr[13];
 149
 150         /* copy everything before MSR */
 151         err |= __copy_from_user(regs, &sc->gp_regs,
 152                                 PT_MSR*sizeof(unsigned long));
 153
 154         /* get MSR separately, transfer the LE bit if doing signal return */
 155         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 156         if (sig)
 157                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 158
 159         /* skip SOFTE */
 160         for (i = PT_MSR+1; i <= PT_RESULT; i++) {
 161                 if (i == PT_SOFTE)
 162                         continue;
 163                 err |= __get_user(gregs[i], &sc->gp_regs[i]);
 164         }
 165
 166         if (!sig)
 167                 regs->gpr[13] = save_r13;
 168         if (set != NULL)
 169                 err |=  __get_user(set->sig[0], &sc->oldmask);
 170
 171         /*
 172          * Do this before updating the thread state in
 173          * current->thread.fpr/vr.  That way, if we get preempted
 174          * and another task grabs the FPU/Altivec, it won't be
 175          * tempted to save the current CPU state into the thread_struct
 176          * and corrupt what we are writing there.
 177          */
 178         discard_lazy_cpu_state();
 179
 180         err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
 181
 182 #ifdef CONFIG_ALTIVEC
 183         err |= __get_user(v_regs, &sc->v_regs);
 184         if (err)
 185                 return err;
 186         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 187                 return -EFAULT;
 188         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 189         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 190                 err |= __copy_from_user(current->thread.vr, v_regs,
 191                                         33 * sizeof(vector128));
 192         else if (current->thread.used_vr)
 193                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 194         /* Always get VRSAVE back */
 195         if (v_regs != 0)
 196                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 197         else
 198                 current->thread.vrsave = 0;
 199 #endif /* CONFIG_ALTIVEC */
 200
 201         /* Force reload of FP/VEC */
 202         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
 203
 204         return err;
 205 }
 206
 207 /*
 208  * Allocate space for the signal frame
 209  */
 210 static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 211                                   size_t frame_size)
 212 {
 213         unsigned long newsp;
 214
 215         /* Default to using normal stack */
 216         newsp = regs->gpr[1];
 217
 218         if ((ka->sa.sa_flags & SA_ONSTACK) && current->sas_ss_size) {
 219                 if (! on_sig_stack(regs->gpr[1]))
 220                         newsp = (current->sas_ss_sp + current->sas_ss_size);
 221         }
 222
 223         return (void __user *)((newsp - frame_size) & -16ul);
 224 }
 225
 226 /*
 227  * Setup the trampoline code on the stack
 228  */
 229 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 230 {
 231         int i;
 232         long err = 0;
 233
 234         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 235         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 236         /* li r0, __NR_[rt_]sigreturn| */
 237         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 238         /* sc */
 239         err |= __put_user(0x44000002UL, &tramp[2]);
 240
 241         /* Minimal traceback info */
 242         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 243                 err |= __put_user(0, &tramp[i]);
 244
 245         if (!err)
 246                 flush_icache_range((unsigned long) &tramp[0],
 247                            (unsigned long) &tramp[TRAMP_SIZE]);
 248
 249         return err;
 250 }
 251
 252 /*
 253  * Restore the user process's signal mask (also used by signal32.c)
 254  */
 255 void restore_sigmask(sigset_t *set)
 256 {
 257         sigdelsetmask(set, ~_BLOCKABLE);
 258         spin_lock_irq(&current->sighand->siglock);
 259         current->blocked = *set;
 260         recalc_sigpending();
 261         spin_unlock_irq(&current->sighand->siglock);
 262 }
 263
 264
 265 /*
 266  * Handle {get,set,swap}_context operations
 267  */
 268 int sys_swapcontext(struct ucontext __user *old_ctx,
 269                     struct ucontext __user *new_ctx,
 270                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 271 {
 272         unsigned char tmp;
 273         sigset_t set;
 274
 275         /* Context size is for future use. Right now, we only make sure
 276          * we are passed something we understand
 277          */
 278         if (ctx_size < sizeof(struct ucontext))
 279                 return -EINVAL;
 280
 281         if (old_ctx != NULL) {
 282                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 283                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 284                     || __copy_to_user(&old_ctx->uc_sigmask,
 285                                       &current->blocked, sizeof(sigset_t)))
 286                         return -EFAULT;
 287         }
 288         if (new_ctx == NULL)
 289                 return 0;
 290         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 291             || __get_user(tmp, (u8 __user *) new_ctx)
 292             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 293                 return -EFAULT;
 294
 295         /*
 296          * If we get a fault copying the context into the kernel's
 297          * image of the user's registers, we can't just return -EFAULT
 298          * because the user's registers will be corrupted.  For instance
 299          * the NIP value may have been updated but not some of the
 300          * other registers.  Given that we have done the access_ok
 301          * and successfully read the first and last bytes of the region
 302          * above, this should only happen in an out-of-memory situation
 303          * or if another thread unmaps the region containing the context.
 304          * We kill the task with a SIGSEGV in this situation.
 305          */
 306
 307         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 308                 do_exit(SIGSEGV);
 309         restore_sigmask(&set);
 310         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 311                 do_exit(SIGSEGV);
 312
 313         /* This returns like rt_sigreturn */
 314         set_thread_flag(TIF_RESTOREALL);
 315         return 0;
 316 }
 317
 318
 319 /*
 320  * Do a signal return; undo the signal stack.
 321  */
 322
 323 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 324                      unsigned long r6, unsigned long r7, unsigned long r8,
 325                      struct pt_regs *regs)
 326 {
 327         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 328         sigset_t set;
 329
 330         /* Always make any pending restarted system calls return -EINTR */
 331         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 332
 333         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 334                 goto badframe;
 335
 336         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 337                 goto badframe;
 338         restore_sigmask(&set);
 339         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 340                 goto badframe;
 341
 342         /* do_sigaltstack expects a __user pointer and won't modify
 343          * what's in there anyway
 344          */
 345         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 346
 347         set_thread_flag(TIF_RESTOREALL);
 348         return 0;
 349
 350 badframe:
 351 #if DEBUG_SIG
 352         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 353                regs, uc, &uc->uc_mcontext);
 354 #endif
 355         force_sig(SIGSEGV, current);
 356         return 0;
 357 }
 358
 359 static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
 360                 sigset_t *set, struct pt_regs *regs)
 361 {
 362         /* Handler is *really* a pointer to the function descriptor for
 363          * the signal routine.  The first entry in the function
 364          * descriptor is the entry address of signal and the second
 365          * entry is the TOC value we need to use.
 366          */
 367         func_descr_t __user *funct_desc_ptr;
 368         struct rt_sigframe __user *frame;
 369         unsigned long newsp = 0;
 370         long err = 0;
 371
 372         frame = get_sigframe(ka, regs, sizeof(*frame));
 373
 374         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 375                 goto badframe;
 376
 377         err |= __put_user(&frame->info, &frame->pinfo);
 378         err |= __put_user(&frame->uc, &frame->puc);
 379         err |= copy_siginfo_to_user(&frame->info, info);
 380         if (err)
 381                 goto badframe;
 382
 383         /* Create the ucontext.  */
 384         err |= __put_user(0, &frame->uc.uc_flags);
 385         err |= __put_user(0, &frame->uc.uc_link);
 386         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 387         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 388                           &frame->uc.uc_stack.ss_flags);
 389         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 390         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 391                                 (unsigned long)ka->sa.sa_handler);
 392         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 393         if (err)
 394                 goto badframe;
 395
 396         /* Make sure signal handler doesn't get spurious FP exceptions */
 397         current->thread.fpscr.val = 0;
 398
 399         /* Set up to return from userspace. */
 400         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 401                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 402         } else {
 403                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 404                 if (err)
 405                         goto badframe;
 406                 regs->link = (unsigned long) &frame->tramp[0];
 407         }
 408         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 409
 410         /* Allocate a dummy caller frame for the signal handler. */
 411         newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
 412         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 413
 414         /* Set up "regs" so we "return" to the signal handler. */
 415         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 416         /* enter the signal handler in big-endian mode */
 417         regs->msr &= ~MSR_LE;
 418         regs->gpr[1] = newsp;
 419         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 420         regs->gpr[3] = signr;
 421         regs->result = 0;
 422         if (ka->sa.sa_flags & SA_SIGINFO) {
 423                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 424                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 425                 regs->gpr[6] = (unsigned long) frame;
 426         } else {
 427                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 428         }
 429         if (err)
 430                 goto badframe;
 431
 432         return 1;
 433
 434 badframe:
 435 #if DEBUG_SIG
 436         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 437                regs, frame, newsp);
 438 #endif
 439         force_sigsegv(signr, current);
 440         return 0;
 441 }
 442
 443
 444 /*
 445  * OK, we're invoking a handler
 446  */
 447 static int handle_signal(unsigned long sig, struct k_sigaction *ka,
 448                          siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
 449 {
 450         int ret;
 451
 452         /* Set up Signal Frame */
 453         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 454
 455         if (ret) {
 456                 spin_lock_irq(&current->sighand->siglock);
 457                 sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 458                 if (!(ka->sa.sa_flags & SA_NODEFER))
 459                         sigaddset(&current->blocked,sig);
 460                 recalc_sigpending();
 461                 spin_unlock_irq(&current->sighand->siglock);
 462         }
 463
 464         return ret;
 465 }
 466
 467 static inline void syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
 468 {
 469         switch ((int)regs->result) {
 470         case -ERESTART_RESTARTBLOCK:
 471         case -ERESTARTNOHAND:
 472                 /* ERESTARTNOHAND means that the syscall should only be
 473                  * restarted if there was no handler for the signal, and since
 474                  * we only get here if there is a handler, we dont restart.
 475                  */
 476                 regs->result = -EINTR;
 477                 regs->gpr[3] = EINTR;
 478                 regs->ccr |= 0x10000000;
 479                 break;
 480         case -ERESTARTSYS:
 481                 /* ERESTARTSYS means to restart the syscall if there is no
 482                  * handler or the handler was registered with SA_RESTART
 483                  */
 484                 if (!(ka->sa.sa_flags & SA_RESTART)) {
 485                         regs->result = -EINTR;
 486                         regs->gpr[3] = EINTR;
 487                         regs->ccr |= 0x10000000;
 488                         break;
 489                 }
 490                 /* fallthrough */
 491         case -ERESTARTNOINTR:
 492                 /* ERESTARTNOINTR means that the syscall should be
 493                  * called again after the signal handler returns.
 494                  */
 495                 regs->gpr[3] = regs->orig_gpr3;
 496                 regs->nip -= 4;
 497                 regs->result = 0;
 498                 break;
 499         }
 500 }
 501
 502 /*
 503  * Note that 'init' is a special process: it doesn't get signals it doesn't
 504  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 505  * mistake.
 506  */
 507 int do_signal(sigset_t *oldset, struct pt_regs *regs)
 508 {
 509         siginfo_t info;
 510         int signr;
 511         struct k_sigaction ka;
 512
 513         /*
 514          * If the current thread is 32 bit - invoke the
 515          * 32 bit signal handling code
 516          */
 517         if (test_thread_flag(TIF_32BIT))
 518                 return do_signal32(oldset, regs);
 519
 520         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 521                 oldset = &current->saved_sigmask;
 522         else if (!oldset)
 523                 oldset = &current->blocked;
 524
 525         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 526         if (signr > 0) {
 527                 int ret;
 528
 529                 /* Whee!  Actually deliver the signal.  */
 530                 if (TRAP(regs) == 0x0C00)
 531                         syscall_restart(regs, &ka);
 532
 533                 /*
 534                  * Reenable the DABR before delivering the signal to
 535                  * user space. The DABR will have been cleared if it
 536                  * triggered inside the kernel.
 537                  */
 538                 if (current->thread.dabr)
 539                         set_dabr(current->thread.dabr);
 540
 541                 ret = handle_signal(signr, &ka, &info, oldset, regs);
 542
 543                 /* If a signal was successfully delivered, the saved sigmask is in
 544                    its frame, and we can clear the TIF_RESTORE_SIGMASK flag */
 545                 if (ret && test_thread_flag(TIF_RESTORE_SIGMASK))
 546                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 547
 548                 return ret;
 549         }
 550
 551         if (TRAP(regs) == 0x0C00) {     /* System Call! */
 552                 if ((int)regs->result == -ERESTARTNOHAND ||
 553                     (int)regs->result == -ERESTARTSYS ||
 554                     (int)regs->result == -ERESTARTNOINTR) {
 555                         regs->gpr[3] = regs->orig_gpr3;
 556                         regs->nip -= 4; /* Back up & retry system call */
 557                         regs->result = 0;
 558                 } else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
 559                         regs->gpr[0] = __NR_restart_syscall;
 560                         regs->nip -= 4;
 561                         regs->result = 0;
 562                 }
 563         }
 564         /* No signal to deliver -- put the saved sigmask back */
 565         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 566                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 567                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 568         }
 569
 570         return 0;
 571 }
 572 EXPORT_SYMBOL(do_signal);