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