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/ratelimit.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                  int ctx_has_vsx_region)
  79 {
  80         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  81          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  82          * the context). This is very important because we must ensure we
  83          * don't lose the VRSAVE content that may have been set prior to
  84          * the process doing its first vector operation
  85          * Userland shall check AT_HWCAP to know wether it can rely on the
  86          * v_regs pointer or not
  87          */
  88 #ifdef CONFIG_ALTIVEC
  89         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  90 #endif
  91         unsigned long msr = regs->msr;
  92         long err = 0;
  93
  94         flush_fp_to_thread(current);
  95
  96 #ifdef CONFIG_ALTIVEC
  97         err |= __put_user(v_regs, &sc->v_regs);
  98
  99         /* save altivec registers */
 100         if (current->thread.used_vr) {
 101                 flush_altivec_to_thread(current);
 102                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 103                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 104                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 105                  * contains valid data.
 106                  */
 107                 msr |= MSR_VEC;
 108         }
 109         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 110          * use altivec.
 111          */
 112         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 113 #else /* CONFIG_ALTIVEC */
 114         err |= __put_user(0, &sc->v_regs);
 115 #endif /* CONFIG_ALTIVEC */
 116         flush_fp_to_thread(current);
 117         /* copy fpr regs and fpscr */
 118         err |= copy_fpr_to_user(&sc->fp_regs, current);
 119 #ifdef CONFIG_VSX
 120         /*
 121          * Copy VSX low doubleword to local buffer for formatting,
 122          * then out to userspace.  Update v_regs to point after the
 123          * VMX data.
 124          */
 125         if (current->thread.used_vsr && ctx_has_vsx_region) {
 126                 __giveup_vsx(current);
 127                 v_regs += ELF_NVRREG;
 128                 err |= copy_vsx_to_user(v_regs, current);
 129                 /* set MSR_VSX in the MSR value in the frame to
 130                  * indicate that sc->vs_reg) contains valid data.
 131                  */
 132                 msr |= MSR_VSX;
 133         }
 134 #endif /* CONFIG_VSX */
 135         err |= __put_user(&sc->gp_regs, &sc->regs);
 136         WARN_ON(!FULL_REGS(regs));
 137         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 138         err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
 139         err |= __put_user(signr, &sc->signal);
 140         err |= __put_user(handler, &sc->handler);
 141         if (set != NULL)
 142                 err |=  __put_user(set->sig[0], &sc->oldmask);
 143
 144         return err;
 145 }
 146
 147 /*
 148  * Restore the sigcontext from the signal frame.
 149  */
 150
 151 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 152                               struct sigcontext __user *sc)
 153 {
 154 #ifdef CONFIG_ALTIVEC
 155         elf_vrreg_t __user *v_regs;
 156 #endif
 157         unsigned long err = 0;
 158         unsigned long save_r13 = 0;
 159         unsigned long msr;
 160 #ifdef CONFIG_VSX
 161         int i;
 162 #endif
 163
 164         /* If this is not a signal return, we preserve the TLS in r13 */
 165         if (!sig)
 166                 save_r13 = regs->gpr[13];
 167
 168         /* copy the GPRs */
 169         err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
 170         err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
 171         /* get MSR separately, transfer the LE bit if doing signal return */
 172         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 173         if (sig)
 174                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 175         err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
 176         err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
 177         err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
 178         err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
 179         err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
 180         /* skip SOFTE */
 181         regs->trap = 0;
 182         err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
 183         err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
 184         err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);
 185
 186         if (!sig)
 187                 regs->gpr[13] = save_r13;
 188         if (set != NULL)
 189                 err |=  __get_user(set->sig[0], &sc->oldmask);
 190
 191         /*
 192          * Do this before updating the thread state in
 193          * current->thread.fpr/vr.  That way, if we get preempted
 194          * and another task grabs the FPU/Altivec, it won't be
 195          * tempted to save the current CPU state into the thread_struct
 196          * and corrupt what we are writing there.
 197          */
 198         discard_lazy_cpu_state();
 199
 200         /*
 201          * Force reload of FP/VEC.
 202          * This has to be done before copying stuff into current->thread.fpr/vr
 203          * for the reasons explained in the previous comment.
 204          */
 205         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
 206
 207 #ifdef CONFIG_ALTIVEC
 208         err |= __get_user(v_regs, &sc->v_regs);
 209         if (err)
 210                 return err;
 211         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 212                 return -EFAULT;
 213         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 214         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 215                 err |= __copy_from_user(current->thread.vr, v_regs,
 216                                         33 * sizeof(vector128));
 217         else if (current->thread.used_vr)
 218                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 219         /* Always get VRSAVE back */
 220         if (v_regs != 0)
 221                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 222         else
 223                 current->thread.vrsave = 0;
 224 #endif /* CONFIG_ALTIVEC */
 225         /* restore floating point */
 226         err |= copy_fpr_from_user(current, &sc->fp_regs);
 227 #ifdef CONFIG_VSX
 228         /*
 229          * Get additional VSX data. Update v_regs to point after the
 230          * VMX data.  Copy VSX low doubleword from userspace to local
 231          * buffer for formatting, then into the taskstruct.
 232          */
 233         v_regs += ELF_NVRREG;
 234         if ((msr & MSR_VSX) != 0)
 235                 err |= copy_vsx_from_user(current, v_regs);
 236         else
 237                 for (i = 0; i < 32 ; i++)
 238                         current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
 239 #endif
 240         return err;
 241 }
 242
 243 /*
 244  * Setup the trampoline code on the stack
 245  */
 246 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 247 {
 248         int i;
 249         long err = 0;
 250
 251         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 252         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 253         /* li r0, __NR_[rt_]sigreturn| */
 254         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 255         /* sc */
 256         err |= __put_user(0x44000002UL, &tramp[2]);
 257
 258         /* Minimal traceback info */
 259         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 260                 err |= __put_user(0, &tramp[i]);
 261
 262         if (!err)
 263                 flush_icache_range((unsigned long) &tramp[0],
 264                            (unsigned long) &tramp[TRAMP_SIZE]);
 265
 266         return err;
 267 }
 268
 269 /*
 270  * Userspace code may pass a ucontext which doesn't include VSX added
 271  * at the end.  We need to check for this case.
 272  */
 273 #define UCONTEXTSIZEWITHOUTVSX \
 274                 (sizeof(struct ucontext) - 32*sizeof(long))
 275
 276 /*
 277  * Handle {get,set,swap}_context operations
 278  */
 279 int sys_swapcontext(struct ucontext __user *old_ctx,
 280                     struct ucontext __user *new_ctx,
 281                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 282 {
 283         unsigned char tmp;
 284         sigset_t set;
 285         unsigned long new_msr = 0;
 286         int ctx_has_vsx_region = 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         /* Does the context have enough room to store VSX data? */
 305         if (ctx_size >= sizeof(struct ucontext))
 306                 ctx_has_vsx_region = 1;
 307
 308         if (old_ctx != NULL) {
 309                 if (!access_ok(VERIFY_WRITE, old_ctx, ctx_size)
 310                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0,
 311                                         ctx_has_vsx_region)
 312                     || __copy_to_user(&old_ctx->uc_sigmask,
 313                                       &current->blocked, sizeof(sigset_t)))
 314                         return -EFAULT;
 315         }
 316         if (new_ctx == NULL)
 317                 return 0;
 318         if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
 319             || __get_user(tmp, (u8 __user *) new_ctx)
 320             || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
 321                 return -EFAULT;
 322
 323         /*
 324          * If we get a fault copying the context into the kernel's
 325          * image of the user's registers, we can't just return -EFAULT
 326          * because the user's registers will be corrupted.  For instance
 327          * the NIP value may have been updated but not some of the
 328          * other registers.  Given that we have done the access_ok
 329          * and successfully read the first and last bytes of the region
 330          * above, this should only happen in an out-of-memory situation
 331          * or if another thread unmaps the region containing the context.
 332          * We kill the task with a SIGSEGV in this situation.
 333          */
 334
 335         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 336                 do_exit(SIGSEGV);
 337         restore_sigmask(&set);
 338         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 339                 do_exit(SIGSEGV);
 340
 341         /* This returns like rt_sigreturn */
 342         set_thread_flag(TIF_RESTOREALL);
 343         return 0;
 344 }
 345
 346
 347 /*
 348  * Do a signal return; undo the signal stack.
 349  */
 350
 351 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 352                      unsigned long r6, unsigned long r7, unsigned long r8,
 353                      struct pt_regs *regs)
 354 {
 355         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 356         sigset_t set;
 357
 358         /* Always make any pending restarted system calls return -EINTR */
 359         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 360
 361         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 362                 goto badframe;
 363
 364         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 365                 goto badframe;
 366         restore_sigmask(&set);
 367         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 368                 goto badframe;
 369
 370         /* do_sigaltstack expects a __user pointer and won't modify
 371          * what's in there anyway
 372          */
 373         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 374
 375         set_thread_flag(TIF_RESTOREALL);
 376         return 0;
 377
 378 badframe:
 379 #if DEBUG_SIG
 380         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 381                regs, uc, &uc->uc_mcontext);
 382 #endif
 383         if (show_unhandled_signals)
 384                 printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
 385                                    current->comm, current->pid, "rt_sigreturn",
 386                                    (long)uc, regs->nip, regs->link);
 387
 388         force_sig(SIGSEGV, current);
 389         return 0;
 390 }
 391
 392 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 393                 sigset_t *set, struct pt_regs *regs)
 394 {
 395         /* Handler is *really* a pointer to the function descriptor for
 396          * the signal routine.  The first entry in the function
 397          * descriptor is the entry address of signal and the second
 398          * entry is the TOC value we need to use.
 399          */
 400         func_descr_t __user *funct_desc_ptr;
 401         struct rt_sigframe __user *frame;
 402         unsigned long newsp = 0;
 403         long err = 0;
 404
 405         frame = get_sigframe(ka, regs, sizeof(*frame), 0);
 406         if (unlikely(frame == NULL))
 407                 goto badframe;
 408
 409         err |= __put_user(&frame->info, &frame->pinfo);
 410         err |= __put_user(&frame->uc, &frame->puc);
 411         err |= copy_siginfo_to_user(&frame->info, info);
 412         if (err)
 413                 goto badframe;
 414
 415         /* Create the ucontext.  */
 416         err |= __put_user(0, &frame->uc.uc_flags);
 417         err |= __put_user(0, &frame->uc.uc_link);
 418         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 419         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 420                           &frame->uc.uc_stack.ss_flags);
 421         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 422         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 423                                 (unsigned long)ka->sa.sa_handler, 1);
 424         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 425         if (err)
 426                 goto badframe;
 427
 428         /* Make sure signal handler doesn't get spurious FP exceptions */
 429         current->thread.fpscr.val = 0;
 430
 431         /* Set up to return from userspace. */
 432         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 433                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 434         } else {
 435                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 436                 if (err)
 437                         goto badframe;
 438                 regs->link = (unsigned long) &frame->tramp[0];
 439         }
 440         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 441
 442         /* Allocate a dummy caller frame for the signal handler. */
 443         newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 444         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 445
 446         /* Set up "regs" so we "return" to the signal handler. */
 447         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 448         /* enter the signal handler in big-endian mode */
 449         regs->msr &= ~MSR_LE;
 450         regs->gpr[1] = newsp;
 451         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 452         regs->gpr[3] = signr;
 453         regs->result = 0;
 454         if (ka->sa.sa_flags & SA_SIGINFO) {
 455                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 456                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 457                 regs->gpr[6] = (unsigned long) frame;
 458         } else {
 459                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 460         }
 461         if (err)
 462                 goto badframe;
 463
 464         return 1;
 465
 466 badframe:
 467 #if DEBUG_SIG
 468         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 469                regs, frame, newsp);
 470 #endif
 471         if (show_unhandled_signals)
 472                 printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
 473                                    current->comm, current->pid, "setup_rt_frame",
 474                                    (long)frame, regs->nip, regs->link);
 475
 476         force_sigsegv(signr, current);
 477         return 0;
 478 }