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