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         long err = 0;
  91
  92         flush_fp_to_thread(current);
  93
  94 #ifdef CONFIG_ALTIVEC
  95         err |= __put_user(v_regs, &sc->v_regs);
  96
  97         /* save altivec registers */
  98         if (current->thread.used_vr) {
  99                 flush_altivec_to_thread(current);
 100                 /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
 101                 err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
 102                 /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
 103                  * contains valid data.
 104                  */
 105                 regs->msr |= MSR_VEC;
 106         }
 107         /* We always copy to/from vrsave, it's 0 if we don't have or don't
 108          * use altivec.
 109          */
 110         err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 111 #else /* CONFIG_ALTIVEC */
 112         err |= __put_user(0, &sc->v_regs);
 113 #endif /* CONFIG_ALTIVEC */
 114         err |= __put_user(&sc->gp_regs, &sc->regs);
 115         WARN_ON(!FULL_REGS(regs));
 116         err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
 117         err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
 118         err |= __put_user(signr, &sc->signal);
 119         err |= __put_user(handler, &sc->handler);
 120         if (set != NULL)
 121                 err |=  __put_user(set->sig[0], &sc->oldmask);
 122
 123         return err;
 124 }
 125
 126 /*
 127  * Restore the sigcontext from the signal frame.
 128  */
 129
 130 static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 131                               struct sigcontext __user *sc)
 132 {
 133 #ifdef CONFIG_ALTIVEC
 134         elf_vrreg_t __user *v_regs;
 135 #endif
 136         unsigned long err = 0;
 137         unsigned long save_r13 = 0;
 138         elf_greg_t *gregs = (elf_greg_t *)regs;
 139         unsigned long msr;
 140         int i;
 141
 142         /* If this is not a signal return, we preserve the TLS in r13 */
 143         if (!sig)
 144                 save_r13 = regs->gpr[13];
 145
 146         /* copy everything before MSR */
 147         err |= __copy_from_user(regs, &sc->gp_regs,
 148                                 PT_MSR*sizeof(unsigned long));
 149
 150         /* get MSR separately, transfer the LE bit if doing signal return */
 151         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
 152         if (sig)
 153                 regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
 154
 155         /* skip SOFTE */
 156         for (i = PT_MSR+1; i <= PT_RESULT; i++) {
 157                 if (i == PT_SOFTE)
 158                         continue;
 159                 err |= __get_user(gregs[i], &sc->gp_regs[i]);
 160         }
 161
 162         if (!sig)
 163                 regs->gpr[13] = save_r13;
 164         if (set != NULL)
 165                 err |=  __get_user(set->sig[0], &sc->oldmask);
 166
 167         /*
 168          * Do this before updating the thread state in
 169          * current->thread.fpr/vr.  That way, if we get preempted
 170          * and another task grabs the FPU/Altivec, it won't be
 171          * tempted to save the current CPU state into the thread_struct
 172          * and corrupt what we are writing there.
 173          */
 174         discard_lazy_cpu_state();
 175
 176         /*
 177          * Force reload of FP/VEC.
 178          * This has to be done before copying stuff into current->thread.fpr/vr
 179          * for the reasons explained in the previous comment.
 180          */
 181         regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
 182
 183         err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
 184
 185 #ifdef CONFIG_ALTIVEC
 186         err |= __get_user(v_regs, &sc->v_regs);
 187         if (err)
 188                 return err;
 189         if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 190                 return -EFAULT;
 191         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
 192         if (v_regs != 0 && (msr & MSR_VEC) != 0)
 193                 err |= __copy_from_user(current->thread.vr, v_regs,
 194                                         33 * sizeof(vector128));
 195         else if (current->thread.used_vr)
 196                 memset(current->thread.vr, 0, 33 * sizeof(vector128));
 197         /* Always get VRSAVE back */
 198         if (v_regs != 0)
 199                 err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
 200         else
 201                 current->thread.vrsave = 0;
 202 #endif /* CONFIG_ALTIVEC */
 203
 204         return err;
 205 }
 206
 207 /*
 208  * Setup the trampoline code on the stack
 209  */
 210 static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 211 {
 212         int i;
 213         long err = 0;
 214
 215         /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
 216         err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
 217         /* li r0, __NR_[rt_]sigreturn| */
 218         err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
 219         /* sc */
 220         err |= __put_user(0x44000002UL, &tramp[2]);
 221
 222         /* Minimal traceback info */
 223         for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
 224                 err |= __put_user(0, &tramp[i]);
 225
 226         if (!err)
 227                 flush_icache_range((unsigned long) &tramp[0],
 228                            (unsigned long) &tramp[TRAMP_SIZE]);
 229
 230         return err;
 231 }
 232
 233 /*
 234  * Handle {get,set,swap}_context operations
 235  */
 236 int sys_swapcontext(struct ucontext __user *old_ctx,
 237                     struct ucontext __user *new_ctx,
 238                     long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
 239 {
 240         unsigned char tmp;
 241         sigset_t set;
 242
 243         /* Context size is for future use. Right now, we only make sure
 244          * we are passed something we understand
 245          */
 246         if (ctx_size < sizeof(struct ucontext))
 247                 return -EINVAL;
 248
 249         if (old_ctx != NULL) {
 250                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
 251                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
 252                     || __copy_to_user(&old_ctx->uc_sigmask,
 253                                       &current->blocked, sizeof(sigset_t)))
 254                         return -EFAULT;
 255         }
 256         if (new_ctx == NULL)
 257                 return 0;
 258         if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
 259             || __get_user(tmp, (u8 __user *) new_ctx)
 260             || __get_user(tmp, (u8 __user *) (new_ctx + 1) - 1))
 261                 return -EFAULT;
 262
 263         /*
 264          * If we get a fault copying the context into the kernel's
 265          * image of the user's registers, we can't just return -EFAULT
 266          * because the user's registers will be corrupted.  For instance
 267          * the NIP value may have been updated but not some of the
 268          * other registers.  Given that we have done the access_ok
 269          * and successfully read the first and last bytes of the region
 270          * above, this should only happen in an out-of-memory situation
 271          * or if another thread unmaps the region containing the context.
 272          * We kill the task with a SIGSEGV in this situation.
 273          */
 274
 275         if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
 276                 do_exit(SIGSEGV);
 277         restore_sigmask(&set);
 278         if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
 279                 do_exit(SIGSEGV);
 280
 281         /* This returns like rt_sigreturn */
 282         set_thread_flag(TIF_RESTOREALL);
 283         return 0;
 284 }
 285
 286
 287 /*
 288  * Do a signal return; undo the signal stack.
 289  */
 290
 291 int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
 292                      unsigned long r6, unsigned long r7, unsigned long r8,
 293                      struct pt_regs *regs)
 294 {
 295         struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
 296         sigset_t set;
 297
 298         /* Always make any pending restarted system calls return -EINTR */
 299         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 300
 301         if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
 302                 goto badframe;
 303
 304         if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
 305                 goto badframe;
 306         restore_sigmask(&set);
 307         if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
 308                 goto badframe;
 309
 310         /* do_sigaltstack expects a __user pointer and won't modify
 311          * what's in there anyway
 312          */
 313         do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);
 314
 315         set_thread_flag(TIF_RESTOREALL);
 316         return 0;
 317
 318 badframe:
 319 #if DEBUG_SIG
 320         printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
 321                regs, uc, &uc->uc_mcontext);
 322 #endif
 323         if (show_unhandled_signals && printk_ratelimit())
 324                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 325                         current->comm, current->pid, "rt_sigreturn",
 326                         (long)uc, regs->nip, regs->link);
 327
 328         force_sig(SIGSEGV, current);
 329         return 0;
 330 }
 331
 332 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 333                 sigset_t *set, struct pt_regs *regs)
 334 {
 335         /* Handler is *really* a pointer to the function descriptor for
 336          * the signal routine.  The first entry in the function
 337          * descriptor is the entry address of signal and the second
 338          * entry is the TOC value we need to use.
 339          */
 340         func_descr_t __user *funct_desc_ptr;
 341         struct rt_sigframe __user *frame;
 342         unsigned long newsp = 0;
 343         long err = 0;
 344
 345         frame = get_sigframe(ka, regs, sizeof(*frame));
 346         if (unlikely(frame == NULL))
 347                 goto badframe;
 348
 349         err |= __put_user(&frame->info, &frame->pinfo);
 350         err |= __put_user(&frame->uc, &frame->puc);
 351         err |= copy_siginfo_to_user(&frame->info, info);
 352         if (err)
 353                 goto badframe;
 354
 355         /* Create the ucontext.  */
 356         err |= __put_user(0, &frame->uc.uc_flags);
 357         err |= __put_user(0, &frame->uc.uc_link);
 358         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 359         err |= __put_user(sas_ss_flags(regs->gpr[1]),
 360                           &frame->uc.uc_stack.ss_flags);
 361         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 362         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
 363                                 (unsigned long)ka->sa.sa_handler);
 364         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 365         if (err)
 366                 goto badframe;
 367
 368         /* Make sure signal handler doesn't get spurious FP exceptions */
 369         current->thread.fpscr.val = 0;
 370
 371         /* Set up to return from userspace. */
 372         if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
 373                 regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
 374         } else {
 375                 err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 376                 if (err)
 377                         goto badframe;
 378                 regs->link = (unsigned long) &frame->tramp[0];
 379         }
 380         funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 381
 382         /* Allocate a dummy caller frame for the signal handler. */
 383         newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 384         err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 385
 386         /* Set up "regs" so we "return" to the signal handler. */
 387         err |= get_user(regs->nip, &funct_desc_ptr->entry);
 388         /* enter the signal handler in big-endian mode */
 389         regs->msr &= ~MSR_LE;
 390         regs->gpr[1] = newsp;
 391         err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 392         regs->gpr[3] = signr;
 393         regs->result = 0;
 394         if (ka->sa.sa_flags & SA_SIGINFO) {
 395                 err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
 396                 err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
 397                 regs->gpr[6] = (unsigned long) frame;
 398         } else {
 399                 regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
 400         }
 401         if (err)
 402                 goto badframe;
 403
 404         return 1;
 405
 406 badframe:
 407 #if DEBUG_SIG
 408         printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
 409                regs, frame, newsp);
 410 #endif
 411         if (show_unhandled_signals && printk_ratelimit())
 412                 printk(regs->msr & MSR_SF ? fmt64 : fmt32,
 413                         current->comm, current->pid, "setup_rt_frame",
 414                         (long)frame, regs->nip, regs->link);
 415
 416         force_sigsegv(signr, current);
 417         return 0;
 418 }