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 #include <linux/ratelimit.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 #include "signal.h"
  39
  40 #define DEBUG_SIG 0
  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 static const char fmt32[] = KERN_INFO \
  69         "%s[%d]: bad frame in %s: %08lx nip %08lx lr %08lx\n";
  70 static const char fmt64[] = KERN_INFO \
  71         "%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";
  72
  73 /*
  74  * Set up the sigcontext for the signal frame.
  75  */
  76
  77 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  78                  int signr, sigset_t *set, unsigned long handler,
  79                  int ctx_has_vsx_region)
  80 {
  81         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  82          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  83          * the context). This is very important because we must ensure we
  84          * don't lose the VRSAVE content that may have been set prior to
  85          * the process doing its first vector operation
  86          * Userland shall check AT_HWCAP to know wether it can rely on the
  87          * v_regs pointer or not
  88          */
  89 #ifdef CONFIG_ALTIVEC
  90         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  91 #endif
  92         unsigned long msr = regs->msr;
  93         long err = 0;
  94
  95         flush_fp_to_thread(current);
  96
  97 #ifdef CONFIG_ALTIVEC
  98         err |= __put_user(v_regs, &sc->v_regs);
  99
 100         /* save altivec registers */
 101         if (current->thread.used_vr) {
 102                 flush_altivec_to_thread(current);
 103                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 104                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 105                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 106                  * contains valid data.
 107                  */
 108                 msr |= MSR_VEC;
 109         }
 110         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 111          * use altivec.
 112          */
 113         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 114 #else /* CONFIG_ALTIVEC */
 115         err |= __put_user(0, &sc->v_regs);
 116 #endif /* CONFIG_ALTIVEC */
 117         flush_fp_to_thread(current);
 118         /* copy fpr regs and fpscr */
 119         err |= copy_fpr_to_user(&sc->fp_regs, current);
 120 #ifdef CONFIG_VSX
 121         /*
 122          * Copy VSX low doubleword to local buffer for formatting,
 123          * then out to userspace.  Update v_regs to point after the
 124          * VMX data.
 125          */
 126         if (current->thread.used_vsr && ctx_has_vsx_region) {
 127                 __giveup_vsx(current);
 128                 v_regs += ELF_NVRREG;
 129                 err |= copy_vsx_to_user(v_regs, current);
 130                 /* set MSR_VSX in the MSR value in the frame to
 131                  * indicate that sc->vs_reg) contains valid data.
 132                  */
 133                 msr |= MSR_VSX;
 134         }
 135 #endif /* CONFIG_VSX */
 136         err |= __put_user(&sc->gp_regs, &sc->regs);
 137         WARN_ON(!FULL_REGS(regs));
 138         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 139         err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
 140         err |= __put_user(signr, &sc->signal);
 141         err |= __put_user(handler, &sc->handler);
 142         if (set != NULL)
 143                 err |=  __put_user(set->sig[0], &sc->oldmask);
 144
 145         return err;
 146 }
 147
 148 /*
 149  * Restore the sigcontext from the signal frame.
 150  */
 151
 152 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 153                               struct sigcontext __user *sc)
 154 {
 155 #ifdef CONFIG_ALTIVEC
 156         elf_vrreg_t __user *v_regs;
 157 #endif
 158         unsigned long err = 0;
 159         unsigned long save_r13 = 0;
 160         unsigned long msr;
 161 #ifdef CONFIG_VSX
 162         int i;
 163 #endif
 164
 165         /* If this is not a signal return, we preserve the TLS in r13 */
 166         if (!sig)
 167                 save_r13 = regs->gpr[13];
 168
 169         /* copy the GPRs */
 170         err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
 171         err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
 172         /* get MSR separately, transfer the LE bit if doing signal return */
 173         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 174         if (sig)
 175                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 176         err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
 177         err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
 178         err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
 179         err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
 180         err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
 181         /* skip SOFTE */
 182         regs->trap = 0;
 183         err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
 184         err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
 185         err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);
 186
 187         if (!sig)
 188                 regs->gpr[13] = save_r13;
 189         if (set != NULL)
 190                 err |=  __get_user(set->sig[0], &sc->oldmask);
 191
 192         /*
 193          * Do this before updating the thread state in
 194          * current->thread.fpr/vr.  That way, if we get preempted
 195          * and another task grabs the FPU/Altivec, it won't be
 196          * tempted to save the current CPU state into the thread_struct
 197          * and corrupt what we are writing there.
 198          */
 199         discard_lazy_cpu_state();
 200
 201         /*
 202          * Force reload of FP/VEC.
 203          * This has to be done before copying stuff into current->thread.fpr/vr
 204          * for the reasons explained in the previous comment.
 205          */
 206         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
 207
 208 #ifdef CONFIG_ALTIVEC
 209         err |= __get_user(v_regs, &sc->v_regs);
 210         if (err)
 211                 return err;
 212         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 213                 return -EFAULT;
 214         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 215         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 216                 err |= __copy_from_user(current->thread.vr, v_regs,
 217                                         33 * sizeof(vector128));
 218         else if (current->thread.used_vr)
 219                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 220         /* Always get VRSAVE back */
 221         if (v_regs != 0)
 222                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 223         else
 224                 current->thread.vrsave = 0;
 225 #endif /* CONFIG_ALTIVEC */
 226         /* restore floating point */
 227         err |= copy_fpr_from_user(current, &sc->fp_regs);
 228 #ifdef CONFIG_VSX
 229         /*
 230          * Get additional VSX data. Update v_regs to point after the
 231          * VMX data.  Copy VSX low doubleword from userspace to local
 232          * buffer for formatting, then into the taskstruct.
 233          */
 234         v_regs += ELF_NVRREG;
 235         if ((msr & MSR_VSX) != 0)
 236                 err |= copy_vsx_from_user(current, v_regs);
 237         else
 238                 for (i = 0; i < 32 ; i++)
 239                         current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
 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         int ctx_has_vsx_region = 0;
 288
 289         if (new_ctx &&
 290             get_user(new_msr, &new_ctx->uc_mcontext.gp_regs[PT_MSR]))
 291                 return -EFAULT;
 292         /*
 293          * Check that the context is not smaller than the original
 294          * size (with VMX but without VSX)
 295          */
 296         if (ctx_size < UCONTEXTSIZEWITHOUTVSX)
 297                 return -EINVAL;
 298         /*
 299          * If the new context state sets the MSR VSX bits but
 300          * it doesn't provide VSX state.
 301          */
 302         if ((ctx_size < sizeof(struct ucontext)) &&
 303             (new_msr & MSR_VSX))
 304                 return -EINVAL;
 305         /* Does the context have enough room to store VSX data? */
 306         if (ctx_size >= sizeof(struct ucontext))
 307                 ctx_has_vsx_region = 1;
 308
 309         if (old_ctx != NULL) {
 310                 if (!access_ok(VERIFY_WRITE, old_ctx, ctx_size)
 311                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0,
 312                                         ctx_has_vsx_region)
 313                     || __copy_to_user(&old_ctx->uc_sigmask,
 314                                       &current->blocked, sizeof(sigset_t)))
 315                         return -EFAULT;
 316         }
 317         if (new_ctx == NULL)
 318                 return 0;
 319         if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
 320             || __get_user(tmp, (u8 __user *) new_ctx)
 321             || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
 322                 return -EFAULT;
 323
 324         /*
 325          * If we get a fault copying the context into the kernel's
 326          * image of the user's registers, we can't just return -EFAULT
 327          * because the user's registers will be corrupted.  For instance
 328          * the NIP value may have been updated but not some of the
 329          * other registers.  Given that we have done the access_ok
 330          * and successfully read the first and last bytes of the region
 331          * above, this should only happen in an out-of-memory situation
 332          * or if another thread unmaps the region containing the context.
 333          * We kill the task with a SIGSEGV in this situation.
 334          */
 335
 336         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 337                 do_exit(SIGSEGV);
 338         restore_sigmask(&set);
 339         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 340                 do_exit(SIGSEGV);
 341
 342         /* This returns like rt_sigreturn */
 343         set_thread_flag(TIF_RESTOREALL);
 344         return 0;
 345 }
 346
 347
 348 /*
 349  * Do a signal return; undo the signal stack.
 350  */
 351
 352 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 353                      unsigned long r6, unsigned long r7, unsigned long r8,
 354                      struct pt_regs *regs)
 355 {
 356         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 357         sigset_t set;
 358
 359         /* Always make any pending restarted system calls return -EINTR */
 360         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 361
 362         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 363                 goto badframe;
 364
 365         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 366                 goto badframe;
 367         restore_sigmask(&set);
 368         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 369                 goto badframe;
 370
 371         /* do_sigaltstack expects a __user pointer and won't modify
 372          * what's in there anyway
 373          */
 374         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 375
 376         set_thread_flag(TIF_RESTOREALL);
 377         return 0;
 378
 379 badframe:
 380 #if DEBUG_SIG
 381         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 382                regs, uc, &uc->uc_mcontext);
 383 #endif
 384         if (show_unhandled_signals)
 385                 printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
 386                                    current->comm, current->pid, "rt_sigreturn",
 387                                    (long)uc, regs->nip, regs->link);
 388
 389         force_sig(SIGSEGV, current);
 390         return 0;
 391 }
 392
 393 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 394                 sigset_t *set, struct pt_regs *regs)
 395 {
 396         /* Handler is *really* a pointer to the function descriptor for
 397          * the signal routine.  The first entry in the function
 398          * descriptor is the entry address of signal and the second
 399          * entry is the TOC value we need to use.
 400          */
 401         func_descr_t __user *funct_desc_ptr;
 402         struct rt_sigframe __user *frame;
 403         unsigned long newsp = 0;
 404         long err = 0;
 405
 406         frame = get_sigframe(ka, regs, sizeof(*frame), 0);
 407         if (unlikely(frame == NULL))
 408                 goto badframe;
 409
 410         err |= __put_user(&frame->info, &frame->pinfo);
 411         err |= __put_user(&frame->uc, &frame->puc);
 412         err |= copy_siginfo_to_user(&frame->info, info);
 413         if (err)
 414                 goto badframe;
 415
 416         /* Create the ucontext.  */
 417         err |= __put_user(0, &frame->uc.uc_flags);
 418         err |= __put_user(0, &frame->uc.uc_link);
 419         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 420         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 421                           &frame->uc.uc_stack.ss_flags);
 422         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 423         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 424                                 (unsigned long)ka->sa.sa_handler, 1);
 425         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 426         if (err)
 427                 goto badframe;
 428
 429         /* Make sure signal handler doesn't get spurious FP exceptions */
 430         current->thread.fpscr.val = 0;
 431
 432         /* Set up to return from userspace. */
 433         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 434                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 435         } else {
 436                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 437                 if (err)
 438                         goto badframe;
 439                 regs->link = (unsigned long) &frame->tramp[0];
 440         }
 441         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 442
 443         /* Allocate a dummy caller frame for the signal handler. */
 444         newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 445         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 446
 447         /* Set up "regs" so we "return" to the signal handler. */
 448         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 449         /* enter the signal handler in big-endian mode */
 450         regs->msr &= ~MSR_LE;
 451         regs->gpr[1] = newsp;
 452         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 453         regs->gpr[3] = signr;
 454         regs->result = 0;
 455         if (ka->sa.sa_flags & SA_SIGINFO) {
 456                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 457                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 458                 regs->gpr[6] = (unsigned long) frame;
 459         } else {
 460                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 461         }
 462         if (err)
 463                 goto badframe;
 464
 465         return 1;
 466
 467 badframe:
 468 #if DEBUG_SIG
 469         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 470                regs, frame, newsp);
 471 #endif
 472         if (show_unhandled_signals)
 473                 printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
 474                                    current->comm, current->pid, "setup_rt_frame",
 475                                    (long)frame, regs->nip, regs->link);
 476
 477         force_sigsegv(signr, current);
 478         return 0;
 479 }