arch/powerpc/kernel/signal_64.c

   1 /*
   2  *  linux/arch/ppc64/kernel/signal.c
   3  *
   4  *  PowerPC version
   5  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   6  *
   7  *  Derived from "arch/i386/kernel/signal.c"
   8  *    Copyright (C) 1991, 1992 Linus Torvalds
   9  *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
  10  *
  11  *  This program is free software; you can redistribute it and/or
  12  *  modify it under the terms of the GNU General Public License
  13  *  as published by the Free Software Foundation; either version
  14  *  2 of the License, or (at your option) any later version.
  15  */
  16
  17 #include <linux/config.h>
  18 #include <linux/sched.h>
  19 #include <linux/mm.h>
  20 #include <linux/smp.h>
  21 #include <linux/smp_lock.h>
  22 #include <linux/kernel.h>
  23 #include <linux/signal.h>
  24 #include <linux/errno.h>
  25 #include <linux/wait.h>
  26 #include <linux/unistd.h>
  27 #include <linux/stddef.h>
  28 #include <linux/elf.h>
  29 #include <linux/ptrace.h>
  30 #include <linux/module.h>
  31
  32 #include <asm/sigcontext.h>
  33 #include <asm/ucontext.h>
  34 #include <asm/uaccess.h>
  35 #include <asm/pgtable.h>
  36 #include <asm/unistd.h>
  37 #include <asm/cacheflush.h>
  38 #include <asm/vdso.h>
  39
  40 #define DEBUG_SIG 0
  41
  42 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  43
  44 #define GP_REGS_SIZE    min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
  45 #define FP_REGS_SIZE    sizeof(elf_fpregset_t)
  46
  47 #define TRAMP_TRACEBACK 3
  48 #define TRAMP_SIZE      6
  49
  50 /*
  51  * When we have signals to deliver, we set up on the user stack,
  52  * going down from the original stack pointer:
  53  *      1) a rt_sigframe struct which contains the ucontext
  54  *      2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
  55  *         frame for the signal handler.
  56  */
  57
  58 struct rt_sigframe {
  59         /* sys_rt_sigreturn requires the ucontext be the first field */
  60         struct ucontext uc;
  61         unsigned long _unused[2];
  62         unsigned int tramp[TRAMP_SIZE];
  63         struct siginfo __user *pinfo;
  64         void __user *puc;
  65         struct siginfo info;
  66         /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
  67         char abigap[288];
  68 } __attribute__ ((aligned (16)));
  69
  70 long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss, unsigned long r5,
  71                      unsigned long r6, unsigned long r7, unsigned long r8,
  72                      struct pt_regs *regs)
  73 {
  74         return do_sigaltstack(uss, uoss, regs->gpr[1]);
  75 }
  76
  77
  78 /*
  79  * Set up the sigcontext for the signal frame.
  80  */
  81
  82 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  83                  int signr, sigset_t *set, unsigned long handler)
  84 {
  85         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  86          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  87          * the context). This is very important because we must ensure we
  88          * don't lose the VRSAVE content that may have been set prior to
  89          * the process doing its first vector operation
  90          * Userland shall check AT_HWCAP to know wether it can rely on the
  91          * v_regs pointer or not
  92          */
  93 #ifdef CONFIG_ALTIVEC
  94         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  95 #endif
  96         long err = 0;
  97
  98         flush_fp_to_thread(current);
  99
 100 #ifdef CONFIG_ALTIVEC
 101         err |= __put_user(v_regs, &sc->v_regs);
 102
 103         /* save altivec registers */
 104         if (current->thread.used_vr) {
 105                 flush_altivec_to_thread(current);
 106                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 107                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 108                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 109                  * contains valid data.
 110                  */
 111                 regs->msr |= MSR_VEC;
 112         }
 113         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 114          * use altivec.
 115          */
 116         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 117 #else /* CONFIG_ALTIVEC */
 118         err |= __put_user(0, &sc->v_regs);
 119 #endif /* CONFIG_ALTIVEC */
 120         err |= __put_user(&sc->gp_regs, &sc->regs);
 121         if (!FULL_REGS(regs)) {
 122                 /* Zero out the unsaved GPRs to avoid information
 123                    leak, and set TIF_SAVE_NVGPRS to ensure that the
 124                    registers do actually get saved later. */
 125                 memset(&regs->gpr[14], 0, 18 * sizeof(unsigned long));
 126                 set_thread_flag(TIF_SAVE_NVGPRS);
 127                 current_thread_info()->nvgprs_frame = &sc->gp_regs;
 128         }
 129         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 130         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
 131         err |= __put_user(signr, &sc->signal);
 132         err |= __put_user(handler, &sc->handler);
 133         if (set != NULL)
 134                 err |=  __put_user(set->sig[0], &sc->oldmask);
 135
 136         return err;
 137 }
 138
 139 /*
 140  * Restore the sigcontext from the signal frame.
 141  */
 142
 143 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 144                               struct sigcontext __user *sc)
 145 {
 146 #ifdef CONFIG_ALTIVEC
 147         elf_vrreg_t __user *v_regs;
 148 #endif
 149         unsigned long err = 0;
 150         unsigned long save_r13 = 0;
 151         elf_greg_t *gregs = (elf_greg_t *)regs;
 152 #ifdef CONFIG_ALTIVEC
 153         unsigned long msr;
 154 #endif
 155         int i;
 156
 157         /* If this is not a signal return, we preserve the TLS in r13 */
 158         if (!sig)
 159                 save_r13 = regs->gpr[13];
 160
 161         /* copy everything before MSR */
 162         err |= __copy_from_user(regs, &sc->gp_regs,
 163                                 PT_MSR*sizeof(unsigned long));
 164
 165         /* skip MSR and SOFTE */
 166         for (i = PT_MSR+1; i <= PT_RESULT; i++) {
 167                 if (i == PT_SOFTE)
 168                         continue;
 169                 err |= __get_user(gregs[i], &sc->gp_regs[i]);
 170         }
 171
 172         if (!sig)
 173                 regs->gpr[13] = save_r13;
 174         if (set != NULL)
 175                 err |=  __get_user(set->sig[0], &sc->oldmask);
 176
 177         /*
 178          * Do this before updating the thread state in
 179          * current->thread.fpr/vr.  That way, if we get preempted
 180          * and another task grabs the FPU/Altivec, it won't be
 181          * tempted to save the current CPU state into the thread_struct
 182          * and corrupt what we are writing there.
 183          */
 184         discard_lazy_cpu_state();
 185
 186         err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
 187
 188 #ifdef CONFIG_ALTIVEC
 189         err |= __get_user(v_regs, &sc->v_regs);
 190         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 191         if (err)
 192                 return err;
 193         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 194         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 195                 err |= __copy_from_user(current->thread.vr, v_regs,
 196                                         33 * sizeof(vector128));
 197         else if (current->thread.used_vr)
 198                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 199         /* Always get VRSAVE back */
 200         if (v_regs != 0)
 201                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 202         else
 203                 current->thread.vrsave = 0;
 204 #endif /* CONFIG_ALTIVEC */
 205
 206         /* Force reload of FP/VEC */
 207         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
 208
 209         return err;
 210 }
 211
 212 /*
 213  * Allocate space for the signal frame
 214  */
 215 static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 216                                   size_t frame_size)
 217 {
 218         unsigned long newsp;
 219
 220         /* Default to using normal stack */
 221         newsp = regs->gpr[1];
 222
 223         if (ka->sa.sa_flags & SA_ONSTACK) {
 224                 if (! on_sig_stack(regs->gpr[1]))
 225                         newsp = (current->sas_ss_sp + current->sas_ss_size);
 226         }
 227
 228         return (void __user *)((newsp - frame_size) & -16ul);
 229 }
 230
 231 /*
 232  * Setup the trampoline code on the stack
 233  */
 234 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 235 {
 236         int i;
 237         long err = 0;
 238
 239         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 240         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 241         /* li r0, __NR_[rt_]sigreturn| */
 242         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 243         /* sc */
 244         err |= __put_user(0x44000002UL, &tramp[2]);
 245
 246         /* Minimal traceback info */
 247         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 248                 err |= __put_user(0, &tramp[i]);
 249
 250         if (!err)
 251                 flush_icache_range((unsigned long) &tramp[0],
 252                            (unsigned long) &tramp[TRAMP_SIZE]);
 253
 254         return err;
 255 }
 256
 257 /*
 258  * Restore the user process's signal mask (also used by signal32.c)
 259  */
 260 void restore_sigmask(sigset_t *set)
 261 {
 262         sigdelsetmask(set, ~_BLOCKABLE);
 263         spin_lock_irq(&current->sighand->siglock);
 264         current->blocked = *set;
 265         recalc_sigpending();
 266         spin_unlock_irq(&current->sighand->siglock);
 267 }
 268
 269
 270 /*
 271  * Handle {get,set,swap}_context operations
 272  */
 273 int sys_swapcontext(struct ucontext __user *old_ctx,
 274                     struct ucontext __user *new_ctx,
 275                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 276 {
 277         unsigned char tmp;
 278         sigset_t set;
 279
 280         /* Context size is for future use. Right now, we only make sure
 281          * we are passed something we understand
 282          */
 283         if (ctx_size < sizeof(struct ucontext))
 284                 return -EINVAL;
 285
 286         if (old_ctx != NULL) {
 287                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 288                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 289                     || __copy_to_user(&old_ctx->uc_sigmask,
 290                                       &current->blocked, sizeof(sigset_t)))
 291                         return -EFAULT;
 292         }
 293         if (new_ctx == NULL)
 294                 return 0;
 295         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 296             || __get_user(tmp, (u8 __user *) new_ctx)
 297             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 298                 return -EFAULT;
 299
 300         /*
 301          * If we get a fault copying the context into the kernel's
 302          * image of the user's registers, we can't just return -EFAULT
 303          * because the user's registers will be corrupted.  For instance
 304          * the NIP value may have been updated but not some of the
 305          * other registers.  Given that we have done the access_ok
 306          * and successfully read the first and last bytes of the region
 307          * above, this should only happen in an out-of-memory situation
 308          * or if another thread unmaps the region containing the context.
 309          * We kill the task with a SIGSEGV in this situation.
 310          */
 311
 312         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 313                 do_exit(SIGSEGV);
 314         restore_sigmask(&set);
 315         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 316                 do_exit(SIGSEGV);
 317
 318         /* This returns like rt_sigreturn */
 319         set_thread_flag(TIF_RESTOREALL);
 320         return 0;
 321 }
 322
 323
 324 /*
 325  * Do a signal return; undo the signal stack.
 326  */
 327
 328 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 329                      unsigned long r6, unsigned long r7, unsigned long r8,
 330                      struct pt_regs *regs)
 331 {
 332         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 333         sigset_t set;
 334
 335         /* Always make any pending restarted system calls return -EINTR */
 336         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 337
 338         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 339                 goto badframe;
 340
 341         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 342                 goto badframe;
 343         restore_sigmask(&set);
 344         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 345                 goto badframe;
 346
 347         /* do_sigaltstack expects a __user pointer and won't modify
 348          * what's in there anyway
 349          */
 350         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 351
 352         set_thread_flag(TIF_RESTOREALL);
 353         return 0;
 354
 355 badframe:
 356 #if DEBUG_SIG
 357         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 358                regs, uc, &uc->uc_mcontext);
 359 #endif
 360         force_sig(SIGSEGV, current);
 361         return 0;
 362 }
 363
 364 static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
 365                 sigset_t *set, struct pt_regs *regs)
 366 {
 367         /* Handler is *really* a pointer to the function descriptor for
 368          * the signal routine.  The first entry in the function
 369          * descriptor is the entry address of signal and the second
 370          * entry is the TOC value we need to use.
 371          */
 372         func_descr_t __user *funct_desc_ptr;
 373         struct rt_sigframe __user *frame;
 374         unsigned long newsp = 0;
 375         long err = 0;
 376
 377         frame = get_sigframe(ka, regs, sizeof(*frame));
 378
 379         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 380                 goto badframe;
 381
 382         err |= __put_user(&frame->info, &frame->pinfo);
 383         err |= __put_user(&frame->uc, &frame->puc);
 384         err |= copy_siginfo_to_user(&frame->info, info);
 385         if (err)
 386                 goto badframe;
 387
 388         /* Create the ucontext.  */
 389         err |= __put_user(0, &frame->uc.uc_flags);
 390         err |= __put_user(0, &frame->uc.uc_link);
 391         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 392         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 393                           &frame->uc.uc_stack.ss_flags);
 394         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 395         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 396                                 (unsigned long)ka->sa.sa_handler);
 397         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 398         if (err)
 399                 goto badframe;
 400
 401         /* Make sure signal handler doesn't get spurious FP exceptions */
 402         current->thread.fpscr.val = 0;
 403
 404         /* Set up to return from userspace. */
 405         if (vdso64_rt_sigtramp && current->thread.vdso_base) {
 406                 regs->link = current->thread.vdso_base + vdso64_rt_sigtramp;
 407         } else {
 408                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 409                 if (err)
 410                         goto badframe;
 411                 regs->link = (unsigned long) &frame->tramp[0];
 412         }
 413         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 414
 415         /* Allocate a dummy caller frame for the signal handler. */
 416         newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
 417         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 418
 419         /* Set up "regs" so we "return" to the signal handler. */
 420         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 421         regs->gpr[1] = newsp;
 422         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 423         regs->gpr[3] = signr;
 424         regs->result = 0;
 425         if (ka->sa.sa_flags & SA_SIGINFO) {
 426                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 427                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 428                 regs->gpr[6] = (unsigned long) frame;
 429         } else {
 430                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 431         }
 432         if (err)
 433                 goto badframe;
 434
 435         return 1;
 436
 437 badframe:
 438 #if DEBUG_SIG
 439         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 440                regs, frame, newsp);
 441 #endif
 442         force_sigsegv(signr, current);
 443         return 0;
 444 }
 445
 446
 447 /*
 448  * OK, we're invoking a handler
 449  */
 450 static int handle_signal(unsigned long sig, struct k_sigaction *ka,
 451                          siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
 452 {
 453         int ret;
 454
 455         /* Set up Signal Frame */
 456         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 457
 458         if (ret) {
 459                 spin_lock_irq(&current->sighand->siglock);
 460                 sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 461                 if (!(ka->sa.sa_flags & SA_NODEFER))
 462                         sigaddset(&current->blocked,sig);
 463                 recalc_sigpending();
 464                 spin_unlock_irq(&current->sighand->siglock);
 465         }
 466
 467         return ret;
 468 }
 469
 470 static inline void syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
 471 {
 472         switch ((int)regs->result) {
 473         case -ERESTART_RESTARTBLOCK:
 474         case -ERESTARTNOHAND:
 475                 /* ERESTARTNOHAND means that the syscall should only be
 476                  * restarted if there was no handler for the signal, and since
 477                  * we only get here if there is a handler, we dont restart.
 478                  */
 479                 regs->result = -EINTR;
 480                 regs->gpr[3] = EINTR;
 481                 regs->ccr |= 0x10000000;
 482                 break;
 483         case -ERESTARTSYS:
 484                 /* ERESTARTSYS means to restart the syscall if there is no
 485                  * handler or the handler was registered with SA_RESTART
 486                  */
 487                 if (!(ka->sa.sa_flags & SA_RESTART)) {
 488                         regs->result = -EINTR;
 489                         regs->gpr[3] = EINTR;
 490                         regs->ccr |= 0x10000000;
 491                         break;
 492                 }
 493                 /* fallthrough */
 494         case -ERESTARTNOINTR:
 495                 /* ERESTARTNOINTR means that the syscall should be
 496                  * called again after the signal handler returns.
 497                  */
 498                 regs->gpr[3] = regs->orig_gpr3;
 499                 regs->nip -= 4;
 500                 regs->result = 0;
 501                 break;
 502         }
 503 }
 504
 505 /*
 506  * Note that 'init' is a special process: it doesn't get signals it doesn't
 507  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 508  * mistake.
 509  */
 510 int do_signal(sigset_t *oldset, struct pt_regs *regs)
 511 {
 512         siginfo_t info;
 513         int signr;
 514         struct k_sigaction ka;
 515
 516         /*
 517          * If the current thread is 32 bit - invoke the
 518          * 32 bit signal handling code
 519          */
 520         if (test_thread_flag(TIF_32BIT))
 521                 return do_signal32(oldset, regs);
 522
 523         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 524                 oldset = &current->saved_sigmask;
 525         else if (!oldset)
 526                 oldset = &current->blocked;
 527
 528         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 529         if (signr > 0) {
 530                 int ret;
 531
 532                 /* Whee!  Actually deliver the signal.  */
 533                 if (TRAP(regs) == 0x0C00)
 534                         syscall_restart(regs, &ka);
 535
 536                 /*
 537                  * Reenable the DABR before delivering the signal to
 538                  * user space. The DABR will have been cleared if it
 539                  * triggered inside the kernel.
 540                  */
 541                 if (current->thread.dabr)
 542                         set_dabr(current->thread.dabr);
 543
 544                 ret = handle_signal(signr, &ka, &info, oldset, regs);
 545
 546                 /* If a signal was successfully delivered, the saved sigmask is in
 547                    its frame, and we can clear the TIF_RESTORE_SIGMASK flag */
 548                 if (ret && test_thread_flag(TIF_RESTORE_SIGMASK))
 549                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 550
 551                 return ret;
 552         }
 553
 554         if (TRAP(regs) == 0x0C00) {     /* System Call! */
 555                 if ((int)regs->result == -ERESTARTNOHAND ||
 556                     (int)regs->result == -ERESTARTSYS ||
 557                     (int)regs->result == -ERESTARTNOINTR) {
 558                         regs->gpr[3] = regs->orig_gpr3;
 559                         regs->nip -= 4; /* Back up & retry system call */
 560                         regs->result = 0;
 561                 } else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
 562                         regs->gpr[0] = __NR_restart_syscall;
 563                         regs->nip -= 4;
 564                         regs->result = 0;
 565                 }
 566         }
 567         /* No signal to deliver -- put the saved sigmask back */
 568         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 569                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 570                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 571         }
 572
 573         return 0;
 574 }
 575 EXPORT_SYMBOL(do_signal);