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 #ifdef CONFIG_VSX
  93         double buf[FP_REGS_SIZE];
  94         int i;
  95 #endif
  96
  97         flush_fp_to_thread(current);
  98
  99 #ifdef CONFIG_ALTIVEC
 100         err |= __put_user(v_regs, &sc->v_regs);
 101
 102         /* save altivec registers */
 103         if (current->thread.used_vr) {
 104                 flush_altivec_to_thread(current);
 105                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 106                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 107                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 108                  * contains valid data.
 109                  */
 110                 msr |= MSR_VEC;
 111         }
 112         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 113          * use altivec.
 114          */
 115         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 116 #else /* CONFIG_ALTIVEC */
 117         err |= __put_user(0, &sc->v_regs);
 118 #endif /* CONFIG_ALTIVEC */
 119         flush_fp_to_thread(current);
 120 #ifdef CONFIG_VSX
 121         /* Copy FP to local buffer then write that out */
 122         for (i = 0; i < 32 ; i++)
 123                 buf[i] = current->thread.TS_FPR(i);
 124         memcpy(&buf[i], &current->thread.fpscr, sizeof(double));
 125         err |= __copy_to_user(&sc->fp_regs, buf, FP_REGS_SIZE);
 126         /*
 127          * Copy VSX low doubleword to local buffer for formatting,
 128          * then out to userspace.  Update v_regs to point after the
 129          * VMX data.
 130          */
 131         if (current->thread.used_vsr) {
 132                 flush_vsx_to_thread(current);
 133                 v_regs += ELF_NVRREG;
 134                 for (i = 0; i < 32 ; i++)
 135                         buf[i] = current->thread.fpr[i][TS_VSRLOWOFFSET];
 136                 err |= __copy_to_user(v_regs, buf, 32 * sizeof(double));
 137                 /* set MSR_VSX in the MSR value in the frame to
 138                  * indicate that sc->vs_reg) contains valid data.
 139                  */
 140                 msr |= MSR_VSX;
 141         }
 142 #else /* CONFIG_VSX */
 143         /* copy fpr regs and fpscr */
 144         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
 145 #endif /* CONFIG_VSX */
 146         err |= __put_user(&sc->gp_regs, &sc->regs);
 147         WARN_ON(!FULL_REGS(regs));
 148         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 149         err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
 150         err |= __put_user(signr, &sc->signal);
 151         err |= __put_user(handler, &sc->handler);
 152         if (set != NULL)
 153                 err |=  __put_user(set->sig[0], &sc->oldmask);
 154
 155         return err;
 156 }
 157
 158 /*
 159  * Restore the sigcontext from the signal frame.
 160  */
 161
 162 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 163                               struct sigcontext __user *sc)
 164 {
 165 #ifdef CONFIG_ALTIVEC
 166         elf_vrreg_t __user *v_regs;
 167 #endif
 168 #ifdef CONFIG_VSX
 169         double buf[FP_REGS_SIZE];
 170 #endif
 171         unsigned long err = 0;
 172         unsigned long save_r13 = 0;
 173         elf_greg_t *gregs = (elf_greg_t *)regs;
 174         unsigned long msr;
 175         int i;
 176
 177         /* If this is not a signal return, we preserve the TLS in r13 */
 178         if (!sig)
 179                 save_r13 = regs->gpr[13];
 180
 181         /* copy everything before MSR */
 182         err |= __copy_from_user(regs, &sc->gp_regs,
 183                                 PT_MSR*sizeof(unsigned long));
 184
 185         /* get MSR separately, transfer the LE bit if doing signal return */
 186         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 187         if (sig)
 188                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 189
 190         /* skip SOFTE */
 191         for (i = PT_MSR+1; i <= PT_RESULT; i++) {
 192                 if (i == PT_SOFTE)
 193                         continue;
 194                 err |= __get_user(gregs[i], &sc->gp_regs[i]);
 195         }
 196
 197         if (!sig)
 198                 regs->gpr[13] = save_r13;
 199         if (set != NULL)
 200                 err |=  __get_user(set->sig[0], &sc->oldmask);
 201
 202         /*
 203          * Do this before updating the thread state in
 204          * current->thread.fpr/vr.  That way, if we get preempted
 205          * and another task grabs the FPU/Altivec, it won't be
 206          * tempted to save the current CPU state into the thread_struct
 207          * and corrupt what we are writing there.
 208          */
 209         discard_lazy_cpu_state();
 210
 211         /*
 212          * Force reload of FP/VEC.
 213          * This has to be done before copying stuff into current->thread.fpr/vr
 214          * for the reasons explained in the previous comment.
 215          */
 216         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);
 217
 218 #ifdef CONFIG_ALTIVEC
 219         err |= __get_user(v_regs, &sc->v_regs);
 220         if (err)
 221                 return err;
 222         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 223                 return -EFAULT;
 224         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 225         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 226                 err |= __copy_from_user(current->thread.vr, v_regs,
 227                                         33 * sizeof(vector128));
 228         else if (current->thread.used_vr)
 229                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 230         /* Always get VRSAVE back */
 231         if (v_regs != 0)
 232                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 233         else
 234                 current->thread.vrsave = 0;
 235 #endif /* CONFIG_ALTIVEC */
 236 #ifdef CONFIG_VSX
 237         /* restore floating point */
 238         err |= __copy_from_user(buf, &sc->fp_regs, FP_REGS_SIZE);
 239         if (err)
 240                 return err;
 241         for (i = 0; i < 32 ; i++)
 242                 current->thread.TS_FPR(i) = buf[i];
 243         memcpy(&current->thread.fpscr, &buf[i], sizeof(double));
 244
 245         /*
 246          * Get additional VSX data. Update v_regs to point after the
 247          * VMX data.  Copy VSX low doubleword from userspace to local
 248          * buffer for formatting, then into the taskstruct.
 249          */
 250         v_regs += ELF_NVRREG;
 251         if ((msr & MSR_VSX) != 0)
 252                 err |= __copy_from_user(buf, v_regs, 32 * sizeof(double));
 253         else
 254                 memset(buf, 0, 32 * sizeof(double));
 255
 256         for (i = 0; i < 32 ; i++)
 257                 current->thread.fpr[i][TS_VSRLOWOFFSET] = buf[i];
 258 #else
 259         err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
 260 #endif
 261         return err;
 262 }
 263
 264 /*
 265  * Setup the trampoline code on the stack
 266  */
 267 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 268 {
 269         int i;
 270         long err = 0;
 271
 272         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 273         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 274         /* li r0, __NR_[rt_]sigreturn| */
 275         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 276         /* sc */
 277         err |= __put_user(0x44000002UL, &tramp[2]);
 278
 279         /* Minimal traceback info */
 280         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 281                 err |= __put_user(0, &tramp[i]);
 282
 283         if (!err)
 284                 flush_icache_range((unsigned long) &tramp[0],
 285                            (unsigned long) &tramp[TRAMP_SIZE]);
 286
 287         return err;
 288 }
 289
 290 /*
 291  * Handle {get,set,swap}_context operations
 292  */
 293 int sys_swapcontext(struct ucontext __user *old_ctx,
 294                     struct ucontext __user *new_ctx,
 295                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 296 {
 297         unsigned char tmp;
 298         sigset_t set;
 299
 300         /* Context size is for future use. Right now, we only make sure
 301          * we are passed something we understand
 302          */
 303         if (ctx_size < sizeof(struct ucontext))
 304                 return -EINVAL;
 305
 306         if (old_ctx != NULL) {
 307                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 308                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 309                     || __copy_to_user(&old_ctx->uc_sigmask,
 310                                       &current->blocked, sizeof(sigset_t)))
 311                         return -EFAULT;
 312         }
 313         if (new_ctx == NULL)
 314                 return 0;
 315         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 316             || __get_user(tmp, (u8 __user *) new_ctx)
 317             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 318                 return -EFAULT;
 319
 320         /*
 321          * If we get a fault copying the context into the kernel's
 322          * image of the user's registers, we can't just return -EFAULT
 323          * because the user's registers will be corrupted.  For instance
 324          * the NIP value may have been updated but not some of the
 325          * other registers.  Given that we have done the access_ok
 326          * and successfully read the first and last bytes of the region
 327          * above, this should only happen in an out-of-memory situation
 328          * or if another thread unmaps the region containing the context.
 329          * We kill the task with a SIGSEGV in this situation.
 330          */
 331
 332         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 333                 do_exit(SIGSEGV);
 334         restore_sigmask(&set);
 335         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 336                 do_exit(SIGSEGV);
 337
 338         /* This returns like rt_sigreturn */
 339         set_thread_flag(TIF_RESTOREALL);
 340         return 0;
 341 }
 342
 343
 344 /*
 345  * Do a signal return; undo the signal stack.
 346  */
 347
 348 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 349                      unsigned long r6, unsigned long r7, unsigned long r8,
 350                      struct pt_regs *regs)
 351 {
 352         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 353         sigset_t set;
 354
 355         /* Always make any pending restarted system calls return -EINTR */
 356         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 357
 358         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 359                 goto badframe;
 360
 361         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 362                 goto badframe;
 363         restore_sigmask(&set);
 364         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 365                 goto badframe;
 366
 367         /* do_sigaltstack expects a __user pointer and won't modify
 368          * what's in there anyway
 369          */
 370         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 371
 372         set_thread_flag(TIF_RESTOREALL);
 373         return 0;
 374
 375 badframe:
 376 #if DEBUG_SIG
 377         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 378                regs, uc, &uc->uc_mcontext);
 379 #endif
 380         if (show_unhandled_signals && printk_ratelimit())
 381                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 382                         current->comm, current->pid, "rt_sigreturn",
 383                         (long)uc, regs->nip, regs->link);
 384
 385         force_sig(SIGSEGV, current);
 386         return 0;
 387 }
 388
 389 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 390                 sigset_t *set, struct pt_regs *regs)
 391 {
 392         /* Handler is *really* a pointer to the function descriptor for
 393          * the signal routine.  The first entry in the function
 394          * descriptor is the entry address of signal and the second
 395          * entry is the TOC value we need to use.
 396          */
 397         func_descr_t __user *funct_desc_ptr;
 398         struct rt_sigframe __user *frame;
 399         unsigned long newsp = 0;
 400         long err = 0;
 401
 402         frame = get_sigframe(ka, regs, sizeof(*frame));
 403         if (unlikely(frame == NULL))
 404                 goto badframe;
 405
 406         err |= __put_user(&frame->info, &frame->pinfo);
 407         err |= __put_user(&frame->uc, &frame->puc);
 408         err |= copy_siginfo_to_user(&frame->info, info);
 409         if (err)
 410                 goto badframe;
 411
 412         /* Create the ucontext.  */
 413         err |= __put_user(0, &frame->uc.uc_flags);
 414         err |= __put_user(0, &frame->uc.uc_link);
 415         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 416         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 417                           &frame->uc.uc_stack.ss_flags);
 418         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 419         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 420                                 (unsigned long)ka->sa.sa_handler);
 421         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 422         if (err)
 423                 goto badframe;
 424
 425         /* Make sure signal handler doesn't get spurious FP exceptions */
 426         current->thread.fpscr.val = 0;
 427
 428         /* Set up to return from userspace. */
 429         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 430                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 431         } else {
 432                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 433                 if (err)
 434                         goto badframe;
 435                 regs->link = (unsigned long) &frame->tramp[0];
 436         }
 437         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 438
 439         /* Allocate a dummy caller frame for the signal handler. */
 440         newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 441         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 442
 443         /* Set up "regs" so we "return" to the signal handler. */
 444         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 445         /* enter the signal handler in big-endian mode */
 446         regs->msr &= ~MSR_LE;
 447         regs->gpr[1] = newsp;
 448         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 449         regs->gpr[3] = signr;
 450         regs->result = 0;
 451         if (ka->sa.sa_flags & SA_SIGINFO) {
 452                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 453                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 454                 regs->gpr[6] = (unsigned long) frame;
 455         } else {
 456                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 457         }
 458         if (err)
 459                 goto badframe;
 460
 461         return 1;
 462
 463 badframe:
 464 #if DEBUG_SIG
 465         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 466                regs, frame, newsp);
 467 #endif
 468         if (show_unhandled_signals && printk_ratelimit())
 469                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 470                         current->comm, current->pid, "setup_rt_frame",
 471                         (long)frame, regs->nip, regs->link);
 472
 473         force_sigsegv(signr, current);
 474         return 0;
 475 }