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 /*
  68  * Set up the sigcontext for the signal frame.
  69  */
  70
  71 static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
  72                  int signr, sigset_t *set, unsigned long handler)
  73 {
  74         /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
  75          * process never used altivec yet (MSR_VEC is zero in pt_regs of
  76          * the context). This is very important because we must ensure we
  77          * don't lose the VRSAVE content that may have been set prior to
  78          * the process doing its first vector operation
  79          * Userland shall check AT_HWCAP to know wether it can rely on the
  80          * v_regs pointer or not
  81          */
  82 #ifdef CONFIG_ALTIVEC
  83         elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
  84 #endif
  85         long err = 0;
  86
  87         flush_fp_to_thread(current);
  88
  89 #ifdef CONFIG_ALTIVEC
  90         err |= __put_user(v_regs, &sc->v_regs);
  91
  92         /* save altivec registers */
  93         if (current->thread.used_vr) {
  94                 flush_altivec_to_thread(current);
  95                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
  96                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
  97                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
  98                  * contains valid data.
  99                  */
 100                 regs->msr |= MSR_VEC;
 101         }
 102         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 103          * use altivec.
 104          */
 105         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 106 #else /* CONFIG_ALTIVEC */
 107         err |= __put_user(0, &sc->v_regs);
 108 #endif /* CONFIG_ALTIVEC */
 109         err |= __put_user(&sc->gp_regs, &sc->regs);
 110         WARN_ON(!FULL_REGS(regs));
 111         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 112         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
 113         err |= __put_user(signr, &sc->signal);
 114         err |= __put_user(handler, &sc->handler);
 115         if (set != NULL)
 116                 err |=  __put_user(set->sig[0], &sc->oldmask);
 117
 118         return err;
 119 }
 120
 121 /*
 122  * Restore the sigcontext from the signal frame.
 123  */
 124
 125 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 126                               struct sigcontext __user *sc)
 127 {
 128 #ifdef CONFIG_ALTIVEC
 129         elf_vrreg_t __user *v_regs;
 130 #endif
 131         unsigned long err = 0;
 132         unsigned long save_r13 = 0;
 133         elf_greg_t *gregs = (elf_greg_t *)regs;
 134         unsigned long msr;
 135         int i;
 136
 137         /* If this is not a signal return, we preserve the TLS in r13 */
 138         if (!sig)
 139                 save_r13 = regs->gpr[13];
 140
 141         /* copy everything before MSR */
 142         err |= __copy_from_user(regs, &sc->gp_regs,
 143                                 PT_MSR*sizeof(unsigned long));
 144
 145         /* get MSR separately, transfer the LE bit if doing signal return */
 146         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 147         if (sig)
 148                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 149
 150         /* skip SOFTE */
 151         for (i = PT_MSR+1; i <= PT_RESULT; i++) {
 152                 if (i == PT_SOFTE)
 153                         continue;
 154                 err |= __get_user(gregs[i], &sc->gp_regs[i]);
 155         }
 156
 157         if (!sig)
 158                 regs->gpr[13] = save_r13;
 159         if (set != NULL)
 160                 err |=  __get_user(set->sig[0], &sc->oldmask);
 161
 162         /*
 163          * Do this before updating the thread state in
 164          * current->thread.fpr/vr.  That way, if we get preempted
 165          * and another task grabs the FPU/Altivec, it won't be
 166          * tempted to save the current CPU state into the thread_struct
 167          * and corrupt what we are writing there.
 168          */
 169         discard_lazy_cpu_state();
 170
 171         err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
 172
 173 #ifdef CONFIG_ALTIVEC
 174         err |= __get_user(v_regs, &sc->v_regs);
 175         if (err)
 176                 return err;
 177         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 178                 return -EFAULT;
 179         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 180         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 181                 err |= __copy_from_user(current->thread.vr, v_regs,
 182                                         33 * sizeof(vector128));
 183         else if (current->thread.used_vr)
 184                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 185         /* Always get VRSAVE back */
 186         if (v_regs != 0)
 187                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 188         else
 189                 current->thread.vrsave = 0;
 190 #endif /* CONFIG_ALTIVEC */
 191
 192         /* Force reload of FP/VEC */
 193         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
 194
 195         return err;
 196 }
 197
 198 /*
 199  * Allocate space for the signal frame
 200  */
 201 static inline void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 202                                   size_t frame_size)
 203 {
 204         unsigned long newsp;
 205
 206         /* Default to using normal stack */
 207         newsp = regs->gpr[1];
 208
 209         if ((ka->sa.sa_flags & SA_ONSTACK) && current->sas_ss_size) {
 210                 if (! on_sig_stack(regs->gpr[1]))
 211                         newsp = (current->sas_ss_sp + current->sas_ss_size);
 212         }
 213
 214         return (void __user *)((newsp - frame_size) & -16ul);
 215 }
 216
 217 /*
 218  * Setup the trampoline code on the stack
 219  */
 220 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 221 {
 222         int i;
 223         long err = 0;
 224
 225         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 226         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 227         /* li r0, __NR_[rt_]sigreturn| */
 228         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 229         /* sc */
 230         err |= __put_user(0x44000002UL, &tramp[2]);
 231
 232         /* Minimal traceback info */
 233         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 234                 err |= __put_user(0, &tramp[i]);
 235
 236         if (!err)
 237                 flush_icache_range((unsigned long) &tramp[0],
 238                            (unsigned long) &tramp[TRAMP_SIZE]);
 239
 240         return err;
 241 }
 242
 243 /*
 244  * Handle {get,set,swap}_context operations
 245  */
 246 int sys_swapcontext(struct ucontext __user *old_ctx,
 247                     struct ucontext __user *new_ctx,
 248                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 249 {
 250         unsigned char tmp;
 251         sigset_t set;
 252
 253         /* Context size is for future use. Right now, we only make sure
 254          * we are passed something we understand
 255          */
 256         if (ctx_size < sizeof(struct ucontext))
 257                 return -EINVAL;
 258
 259         if (old_ctx != NULL) {
 260                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 261                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 262                     || __copy_to_user(&old_ctx->uc_sigmask,
 263                                       &current->blocked, sizeof(sigset_t)))
 264                         return -EFAULT;
 265         }
 266         if (new_ctx == NULL)
 267                 return 0;
 268         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 269             || __get_user(tmp, (u8 __user *) new_ctx)
 270             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 271                 return -EFAULT;
 272
 273         /*
 274          * If we get a fault copying the context into the kernel's
 275          * image of the user's registers, we can't just return -EFAULT
 276          * because the user's registers will be corrupted.  For instance
 277          * the NIP value may have been updated but not some of the
 278          * other registers.  Given that we have done the access_ok
 279          * and successfully read the first and last bytes of the region
 280          * above, this should only happen in an out-of-memory situation
 281          * or if another thread unmaps the region containing the context.
 282          * We kill the task with a SIGSEGV in this situation.
 283          */
 284
 285         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 286                 do_exit(SIGSEGV);
 287         restore_sigmask(&set);
 288         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 289                 do_exit(SIGSEGV);
 290
 291         /* This returns like rt_sigreturn */
 292         set_thread_flag(TIF_RESTOREALL);
 293         return 0;
 294 }
 295
 296
 297 /*
 298  * Do a signal return; undo the signal stack.
 299  */
 300
 301 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 302                      unsigned long r6, unsigned long r7, unsigned long r8,
 303                      struct pt_regs *regs)
 304 {
 305         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 306         sigset_t set;
 307
 308         /* Always make any pending restarted system calls return -EINTR */
 309         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 310
 311         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 312                 goto badframe;
 313
 314         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 315                 goto badframe;
 316         restore_sigmask(&set);
 317         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 318                 goto badframe;
 319
 320         /* do_sigaltstack expects a __user pointer and won't modify
 321          * what's in there anyway
 322          */
 323         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 324
 325         set_thread_flag(TIF_RESTOREALL);
 326         return 0;
 327
 328 badframe:
 329 #if DEBUG_SIG
 330         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 331                regs, uc, &uc->uc_mcontext);
 332 #endif
 333         force_sig(SIGSEGV, current);
 334         return 0;
 335 }
 336
 337 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 338                 sigset_t *set, struct pt_regs *regs)
 339 {
 340         /* Handler is *really* a pointer to the function descriptor for
 341          * the signal routine.  The first entry in the function
 342          * descriptor is the entry address of signal and the second
 343          * entry is the TOC value we need to use.
 344          */
 345         func_descr_t __user *funct_desc_ptr;
 346         struct rt_sigframe __user *frame;
 347         unsigned long newsp = 0;
 348         long err = 0;
 349
 350         frame = get_sigframe(ka, regs, sizeof(*frame));
 351
 352         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 353                 goto badframe;
 354
 355         err |= __put_user(&frame->info, &frame->pinfo);
 356         err |= __put_user(&frame->uc, &frame->puc);
 357         err |= copy_siginfo_to_user(&frame->info, info);
 358         if (err)
 359                 goto badframe;
 360
 361         /* Create the ucontext.  */
 362         err |= __put_user(0, &frame->uc.uc_flags);
 363         err |= __put_user(0, &frame->uc.uc_link);
 364         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 365         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 366                           &frame->uc.uc_stack.ss_flags);
 367         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 368         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 369                                 (unsigned long)ka->sa.sa_handler);
 370         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 371         if (err)
 372                 goto badframe;
 373
 374         /* Make sure signal handler doesn't get spurious FP exceptions */
 375         current->thread.fpscr.val = 0;
 376
 377         /* Set up to return from userspace. */
 378         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 379                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 380         } else {
 381                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 382                 if (err)
 383                         goto badframe;
 384                 regs->link = (unsigned long) &frame->tramp[0];
 385         }
 386         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 387
 388         /* Allocate a dummy caller frame for the signal handler. */
 389         newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
 390         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 391
 392         /* Set up "regs" so we "return" to the signal handler. */
 393         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 394         /* enter the signal handler in big-endian mode */
 395         regs->msr &= ~MSR_LE;
 396         regs->gpr[1] = newsp;
 397         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 398         regs->gpr[3] = signr;
 399         regs->result = 0;
 400         if (ka->sa.sa_flags & SA_SIGINFO) {
 401                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 402                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 403                 regs->gpr[6] = (unsigned long) frame;
 404         } else {
 405                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 406         }
 407         if (err)
 408                 goto badframe;
 409
 410         return 1;
 411
 412 badframe:
 413 #if DEBUG_SIG
 414         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 415                regs, frame, newsp);
 416 #endif
 417         force_sigsegv(signr, current);
 418         return 0;
 419 }