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/kernel.h>
  19 #include <linux/signal.h>
  20 #include <linux/errno.h>
  21 #include <linux/wait.h>
  22 #include <linux/unistd.h>
  23 #include <linux/stddef.h>
  24 #include <linux/elf.h>
  25 #include <linux/ptrace.h>
  26 #include <linux/module.h>
  27
  28 #include <asm/sigcontext.h>
  29 #include <asm/ucontext.h>
  30 #include <asm/uaccess.h>
  31 #include <asm/pgtable.h>
  32 #include <asm/unistd.h>
  33 #include <asm/cacheflush.h>
  34 #include <asm/syscalls.h>
  35 #include <asm/vdso.h>
  36
  37 #include "signal.h"
  38
  39 #define DEBUG_SIG 0
  40
  41 #define GP_REGS_SIZE    min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
  42 #define FP_REGS_SIZE    sizeof(elf_fpregset_t)
  43
  44 #define TRAMP_TRACEBACK 3
  45 #define TRAMP_SIZE      6
  46
  47 /*
  48  * When we have signals to deliver, we set up on the user stack,
  49  * going down from the original stack pointer:
  50  *      1) a rt_sigframe struct which contains the ucontext
  51  *      2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
  52  *         frame for the signal handler.
  53  */
  54
  55 struct rt_sigframe {
  56         /* sys_rt_sigreturn requires the ucontext be the first field */
  57         struct ucontext uc;
  58         unsigned long _unused[2];
  59         unsigned int tramp[TRAMP_SIZE];
  60         struct siginfo __user *pinfo;
  61         void __user *puc;
  62         struct siginfo info;
  63         /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
  64         char abigap[288];
  65 } __attribute__ ((aligned (16)));
  66
  67 static const char fmt32[] = KERN_INFO \
  68         "%s[%d]: bad frame in %s: %08lx nip %08lx lr %08lx\n";
  69 static const char fmt64[] = KERN_INFO \
  70         "%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";
  71
  72 /*
  73  * Set up the sigcontext for the signal frame.
  74  */
  75
  76 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  77                  int signr, sigset_t *set, unsigned long handler)
  78 {
  79         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  80          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  81          * the context). This is very important because we must ensure we
  82          * don't lose the VRSAVE content that may have been set prior to
  83          * the process doing its first vector operation
  84          * Userland shall check AT_HWCAP to know wether it can rely on the
  85          * v_regs pointer or not
  86          */
  87 #ifdef CONFIG_ALTIVEC
  88         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  89 #endif
  90         unsigned long msr = regs->msr;
  91         long err = 0;
  92
  93         flush_fp_to_thread(current);
  94
  95 #ifdef CONFIG_ALTIVEC
  96         err |= __put_user(v_regs, &sc->v_regs);
  97
  98         /* save altivec registers */
  99         if (current->thread.used_vr) {
 100                 flush_altivec_to_thread(current);
 101                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 102                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 103                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 104                  * contains valid data.
 105                  */
 106                 msr |= MSR_VEC;
 107         }
 108         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 109          * use altivec.
 110          */
 111         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 112 #else /* CONFIG_ALTIVEC */
 113         err |= __put_user(0, &sc->v_regs);
 114 #endif /* CONFIG_ALTIVEC */
 115         flush_fp_to_thread(current);
 116         /* copy fpr regs and fpscr */
 117         err |= copy_fpr_to_user(&sc->fp_regs, current);
 118 #ifdef CONFIG_VSX
 119         /*
 120          * Copy VSX low doubleword to local buffer for formatting,
 121          * then out to userspace.  Update v_regs to point after the
 122          * VMX data.
 123          */
 124         if (current->thread.used_vsr) {
 125                 __giveup_vsx(current);
 126                 v_regs += ELF_NVRREG;
 127                 err |= copy_vsx_to_user(v_regs, current);
 128                 /* set MSR_VSX in the MSR value in the frame to
 129                  * indicate that sc->vs_reg) contains valid data.
 130                  */
 131                 msr |= MSR_VSX;
 132         }
 133 #endif /* CONFIG_VSX */
 134         err |= __put_user(&sc->gp_regs, &sc->regs);
 135         WARN_ON(!FULL_REGS(regs));
 136         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 137         err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
 138         err |= __put_user(signr, &sc->signal);
 139         err |= __put_user(handler, &sc->handler);
 140         if (set != NULL)
 141                 err |=  __put_user(set->sig[0], &sc->oldmask);
 142
 143         return err;
 144 }
 145
 146 /*
 147  * Restore the sigcontext from the signal frame.
 148  */
 149
 150 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 151                               struct sigcontext __user *sc)
 152 {
 153 #ifdef CONFIG_ALTIVEC
 154         elf_vrreg_t __user *v_regs;
 155 #endif
 156         unsigned long err = 0;
 157         unsigned long save_r13 = 0;
 158         unsigned long msr;
 159 #ifdef CONFIG_VSX
 160         int i;
 161 #endif
 162
 163         /* If this is not a signal return, we preserve the TLS in r13 */
 164         if (!sig)
 165                 save_r13 = regs->gpr[13];
 166
 167         /* copy the GPRs */
 168         err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
 169         err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
 170         /* get MSR separately, transfer the LE bit if doing signal return */
 171         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 172         if (sig)
 173                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 174         err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
 175         err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
 176         err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
 177         err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
 178         err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
 179         /* skip SOFTE */
 180         err |= __get_user(regs->trap, &sc->gp_regs[PT_TRAP]);
 181         err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
 182         err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
 183         err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);
 184
 185         if (!sig)
 186                 regs->gpr[13] = save_r13;
 187         if (set != NULL)
 188                 err |=  __get_user(set->sig[0], &sc->oldmask);
 189
 190         /*
 191          * Do this before updating the thread state in
 192          * current->thread.fpr/vr.  That way, if we get preempted
 193          * and another task grabs the FPU/Altivec, it won't be
 194          * tempted to save the current CPU state into the thread_struct
 195          * and corrupt what we are writing there.
 196          */
 197         discard_lazy_cpu_state();
 198
 199         /*
 200          * Force reload of FP/VEC.
 201          * This has to be done before copying stuff into current->thread.fpr/vr
 202          * for the reasons explained in the previous comment.
 203          */
 204         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
 205
 206 #ifdef CONFIG_ALTIVEC
 207         err |= __get_user(v_regs, &sc->v_regs);
 208         if (err)
 209                 return err;
 210         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 211                 return -EFAULT;
 212         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 213         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 214                 err |= __copy_from_user(current->thread.vr, v_regs,
 215                                         33 * sizeof(vector128));
 216         else if (current->thread.used_vr)
 217                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 218         /* Always get VRSAVE back */
 219         if (v_regs != 0)
 220                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 221         else
 222                 current->thread.vrsave = 0;
 223 #endif /* CONFIG_ALTIVEC */
 224         /* restore floating point */
 225         err |= copy_fpr_from_user(current, &sc->fp_regs);
 226 #ifdef CONFIG_VSX
 227         /*
 228          * Get additional VSX data. Update v_regs to point after the
 229          * VMX data.  Copy VSX low doubleword from userspace to local
 230          * buffer for formatting, then into the taskstruct.
 231          */
 232         v_regs += ELF_NVRREG;
 233         if ((msr & MSR_VSX) != 0)
 234                 err |= copy_vsx_from_user(current, v_regs);
 235         else
 236                 for (i = 0; i < 32 ; i++)
 237                         current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
 238
 239 #else
 240 #endif
 241         return err;
 242 }
 243
 244 /*
 245  * Setup the trampoline code on the stack
 246  */
 247 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 248 {
 249         int i;
 250         long err = 0;
 251
 252         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 253         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 254         /* li r0, __NR_[rt_]sigreturn| */
 255         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 256         /* sc */
 257         err |= __put_user(0x44000002UL, &tramp[2]);
 258
 259         /* Minimal traceback info */
 260         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 261                 err |= __put_user(0, &tramp[i]);
 262
 263         if (!err)
 264                 flush_icache_range((unsigned long) &tramp[0],
 265                            (unsigned long) &tramp[TRAMP_SIZE]);
 266
 267         return err;
 268 }
 269
 270 /*
 271  * Userspace code may pass a ucontext which doesn't include VSX added
 272  * at the end.  We need to check for this case.
 273  */
 274 #define UCONTEXTSIZEWITHOUTVSX \
 275                 (sizeof(struct ucontext) - 32*sizeof(long))
 276
 277 /*
 278  * Handle {get,set,swap}_context operations
 279  */
 280 int sys_swapcontext(struct ucontext __user *old_ctx,
 281                     struct ucontext __user *new_ctx,
 282                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 283 {
 284         unsigned char tmp;
 285         sigset_t set;
 286         unsigned long new_msr = 0;
 287
 288         if (new_ctx &&
 289             __get_user(new_msr, &new_ctx->uc_mcontext.gp_regs[PT_MSR]))
 290                 return -EFAULT;
 291         /*
 292          * Check that the context is not smaller than the original
 293          * size (with VMX but without VSX)
 294          */
 295         if (ctx_size < UCONTEXTSIZEWITHOUTVSX)
 296                 return -EINVAL;
 297         /*
 298          * If the new context state sets the MSR VSX bits but
 299          * it doesn't provide VSX state.
 300          */
 301         if ((ctx_size < sizeof(struct ucontext)) &&
 302             (new_msr & MSR_VSX))
 303                 return -EINVAL;
 304 #ifdef CONFIG_VSX
 305         /*
 306          * If userspace doesn't provide enough room for VSX data,
 307          * but current thread has used VSX, we don't have anywhere
 308          * to store the full context back into.
 309          */
 310         if ((ctx_size < sizeof(struct ucontext)) &&
 311             (current->thread.used_vsr && old_ctx))
 312                 return -EINVAL;
 313 #endif
 314         if (old_ctx != NULL) {
 315                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 316                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 317                     || __copy_to_user(&old_ctx->uc_sigmask,
 318                                       &current->blocked, sizeof(sigset_t)))
 319                         return -EFAULT;
 320         }
 321         if (new_ctx == NULL)
 322                 return 0;
 323         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 324             || __get_user(tmp, (u8 __user *) new_ctx)
 325             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 326                 return -EFAULT;
 327
 328         /*
 329          * If we get a fault copying the context into the kernel's
 330          * image of the user's registers, we can't just return -EFAULT
 331          * because the user's registers will be corrupted.  For instance
 332          * the NIP value may have been updated but not some of the
 333          * other registers.  Given that we have done the access_ok
 334          * and successfully read the first and last bytes of the region
 335          * above, this should only happen in an out-of-memory situation
 336          * or if another thread unmaps the region containing the context.
 337          * We kill the task with a SIGSEGV in this situation.
 338          */
 339
 340         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 341                 do_exit(SIGSEGV);
 342         restore_sigmask(&set);
 343         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 344                 do_exit(SIGSEGV);
 345
 346         /* This returns like rt_sigreturn */
 347         set_thread_flag(TIF_RESTOREALL);
 348         return 0;
 349 }
 350
 351
 352 /*
 353  * Do a signal return; undo the signal stack.
 354  */
 355
 356 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 357                      unsigned long r6, unsigned long r7, unsigned long r8,
 358                      struct pt_regs *regs)
 359 {
 360         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 361         sigset_t set;
 362
 363         /* Always make any pending restarted system calls return -EINTR */
 364         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 365
 366         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 367                 goto badframe;
 368
 369         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 370                 goto badframe;
 371         restore_sigmask(&set);
 372         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 373                 goto badframe;
 374
 375         /* do_sigaltstack expects a __user pointer and won't modify
 376          * what's in there anyway
 377          */
 378         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 379
 380         set_thread_flag(TIF_RESTOREALL);
 381         return 0;
 382
 383 badframe:
 384 #if DEBUG_SIG
 385         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 386                regs, uc, &uc->uc_mcontext);
 387 #endif
 388         if (show_unhandled_signals && printk_ratelimit())
 389                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 390                         current->comm, current->pid, "rt_sigreturn",
 391                         (long)uc, regs->nip, regs->link);
 392
 393         force_sig(SIGSEGV, current);
 394         return 0;
 395 }
 396
 397 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 398                 sigset_t *set, struct pt_regs *regs)
 399 {
 400         /* Handler is *really* a pointer to the function descriptor for
 401          * the signal routine.  The first entry in the function
 402          * descriptor is the entry address of signal and the second
 403          * entry is the TOC value we need to use.
 404          */
 405         func_descr_t __user *funct_desc_ptr;
 406         struct rt_sigframe __user *frame;
 407         unsigned long newsp = 0;
 408         long err = 0;
 409
 410         frame = get_sigframe(ka, regs, sizeof(*frame));
 411         if (unlikely(frame == NULL))
 412                 goto badframe;
 413
 414         err |= __put_user(&frame->info, &frame->pinfo);
 415         err |= __put_user(&frame->uc, &frame->puc);
 416         err |= copy_siginfo_to_user(&frame->info, info);
 417         if (err)
 418                 goto badframe;
 419
 420         /* Create the ucontext.  */
 421         err |= __put_user(0, &frame->uc.uc_flags);
 422         err |= __put_user(0, &frame->uc.uc_link);
 423         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 424         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 425                           &frame->uc.uc_stack.ss_flags);
 426         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 427         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 428                                 (unsigned long)ka->sa.sa_handler);
 429         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 430         if (err)
 431                 goto badframe;
 432
 433         /* Make sure signal handler doesn't get spurious FP exceptions */
 434         current->thread.fpscr.val = 0;
 435
 436         /* Set up to return from userspace. */
 437         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 438                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 439         } else {
 440                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 441                 if (err)
 442                         goto badframe;
 443                 regs->link = (unsigned long) &frame->tramp[0];
 444         }
 445         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 446
 447         /* Allocate a dummy caller frame for the signal handler. */
 448         newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 449         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 450
 451         /* Set up "regs" so we "return" to the signal handler. */
 452         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 453         /* enter the signal handler in big-endian mode */
 454         regs->msr &= ~MSR_LE;
 455         regs->gpr[1] = newsp;
 456         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 457         regs->gpr[3] = signr;
 458         regs->result = 0;
 459         if (ka->sa.sa_flags & SA_SIGINFO) {
 460                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 461                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 462                 regs->gpr[6] = (unsigned long) frame;
 463         } else {
 464                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 465         }
 466         if (err)
 467                 goto badframe;
 468
 469         return 1;
 470
 471 badframe:
 472 #if DEBUG_SIG
 473         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 474                regs, frame, newsp);
 475 #endif
 476         if (show_unhandled_signals && printk_ratelimit())
 477                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 478                         current->comm, current->pid, "setup_rt_frame",
 479                         (long)frame, regs->nip, regs->link);
 480
 481         force_sigsegv(signr, current);
 482         return 0;
 483 }