arch/cris/arch-v10/kernel/signal.c

   1 /*
   2  *  linux/arch/cris/kernel/signal.c
   3  *
   4  *  Based on arch/i386/kernel/signal.c by
   5  *     Copyright (C) 1991, 1992  Linus Torvalds
   6  *     1997-11-28  Modified for POSIX.1b signals by Richard Henderson *
   7  *
   8  *  Ideas also taken from arch/arm.
   9  *
  10  *  Copyright (C) 2000-2007 Axis Communications AB
  11  *
  12  *  Authors:  Bjorn Wesen (bjornw@axis.com)
  13  *
  14  */
  15
  16 #include <linux/sched.h>
  17 #include <linux/mm.h>
  18 #include <linux/smp.h>
  19 #include <linux/kernel.h>
  20 #include <linux/signal.h>
  21 #include <linux/errno.h>
  22 #include <linux/wait.h>
  23 #include <linux/ptrace.h>
  24 #include <linux/unistd.h>
  25 #include <linux/stddef.h>
  26
  27 #include <asm/processor.h>
  28 #include <asm/ucontext.h>
  29 #include <asm/uaccess.h>
  30 #include <arch/system.h>
  31
  32 #define DEBUG_SIG 0
  33
  34 /* a syscall in Linux/CRIS is a break 13 instruction which is 2 bytes */
  35 /* manipulate regs so that upon return, it will be re-executed */
  36
  37 /* We rely on that pc points to the instruction after "break 13", so the
  38  * library must never do strange things like putting it in a delay slot.
  39  */
  40 #define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->irp -= 2;
  41
  42 void do_signal(int canrestart, struct pt_regs *regs);
  43
  44 /*
  45  * Do a signal return; undo the signal stack.
  46  */
  47
  48 struct sigframe {
  49         struct sigcontext sc;
  50         unsigned long extramask[_NSIG_WORDS-1];
  51         unsigned char retcode[8];  /* trampoline code */
  52 };
  53
  54 struct rt_sigframe {
  55         struct siginfo *pinfo;
  56         void *puc;
  57         struct siginfo info;
  58         struct ucontext uc;
  59         unsigned char retcode[8];  /* trampoline code */
  60 };
  61
  62
  63 static int
  64 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
  65 {
  66         unsigned int err = 0;
  67         unsigned long old_usp;
  68
  69         /* Always make any pending restarted system calls return -EINTR */
  70         current->restart_block.fn = do_no_restart_syscall;
  71
  72         /* restore the regs from &sc->regs (same as sc, since regs is first)
  73          * (sc is already checked for VERIFY_READ since the sigframe was
  74          *  checked in sys_sigreturn previously)
  75          */
  76
  77         if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
  78                 goto badframe;
  79
  80         /* make sure the U-flag is set so user-mode cannot fool us */
  81
  82         regs->dccr |= 1 << 8;
  83
  84         /* restore the old USP as it was before we stacked the sc etc.
  85          * (we cannot just pop the sigcontext since we aligned the sp and
  86          *  stuff after pushing it)
  87          */
  88
  89         err |= __get_user(old_usp, &sc->usp);
  90
  91         wrusp(old_usp);
  92
  93         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  94          * after this completes, but we don't use that mechanism. maybe we can
  95          * use it now ?
  96          */
  97
  98         return err;
  99
 100 badframe:
 101         return 1;
 102 }
 103
 104 asmlinkage int sys_sigreturn(void)
 105 {
 106         struct pt_regs *regs = current_pt_regs();
 107         struct sigframe __user *frame = (struct sigframe *)rdusp();
 108         sigset_t set;
 109
 110         /*
 111          * Since we stacked the signal on a dword boundary,
 112          * then frame should be dword aligned here.  If it's
 113          * not, then the user is trying to mess with us.
 114          */
 115         if (((long)frame) & 3)
 116                 goto badframe;
 117
 118         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 119                 goto badframe;
 120         if (__get_user(set.sig[0], &frame->sc.oldmask)
 121             || (_NSIG_WORDS > 1
 122                 && __copy_from_user(&set.sig[1], frame->extramask,
 123                                     sizeof(frame->extramask))))
 124                 goto badframe;
 125
 126         set_current_blocked(&set);
 127
 128         if (restore_sigcontext(regs, &frame->sc))
 129                 goto badframe;
 130
 131         /* TODO: SIGTRAP when single-stepping as in arm ? */
 132
 133         return regs->r10;
 134
 135 badframe:
 136         force_sig(SIGSEGV, current);
 137         return 0;
 138 }
 139
 140 asmlinkage int sys_rt_sigreturn(void)
 141 {
 142         struct pt_regs *regs = current_pt_regs();
 143         struct rt_sigframe __user *frame = (struct rt_sigframe *)rdusp();
 144         sigset_t set;
 145
 146         /*
 147          * Since we stacked the signal on a dword boundary,
 148          * then frame should be dword aligned here.  If it's
 149          * not, then the user is trying to mess with us.
 150          */
 151         if (((long)frame) & 3)
 152                 goto badframe;
 153
 154         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 155                 goto badframe;
 156         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 157                 goto badframe;
 158
 159         set_current_blocked(&set);
 160
 161         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 162                 goto badframe;
 163
 164         if (restore_altstack(&frame->uc.uc_stack))
 165                 goto badframe;
 166
 167         return regs->r10;
 168
 169 badframe:
 170         force_sig(SIGSEGV, current);
 171         return 0;
 172 }
 173
 174 /*
 175  * Set up a signal frame.
 176  */
 177
 178 static int setup_sigcontext(struct sigcontext __user *sc,
 179         struct pt_regs *regs, unsigned long mask)
 180 {
 181         int err = 0;
 182         unsigned long usp = rdusp();
 183
 184         /* copy the regs. they are first in sc so we can use sc directly */
 185
 186         err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
 187
 188         /* Set the frametype to CRIS_FRAME_NORMAL for the execution of
 189            the signal handler. The frametype will be restored to its previous
 190            value in restore_sigcontext. */
 191         regs->frametype = CRIS_FRAME_NORMAL;
 192
 193         /* then some other stuff */
 194
 195         err |= __put_user(mask, &sc->oldmask);
 196
 197         err |= __put_user(usp, &sc->usp);
 198
 199         return err;
 200 }
 201
 202 /* Figure out where we want to put the new signal frame
 203  * - usually on the stack. */
 204
 205 static inline void __user *
 206 get_sigframe(struct ksignal *ksig, size_t frame_size)
 207 {
 208         unsigned long sp = sigsp(rdusp(), ksig);
 209
 210         /* make sure the frame is dword-aligned */
 211
 212         sp &= ~3;
 213
 214         return (void __user*)(sp - frame_size);
 215 }
 216
 217 /* grab and setup a signal frame.
 218  *
 219  * basically we stack a lot of state info, and arrange for the
 220  * user-mode program to return to the kernel using either a
 221  * trampoline which performs the syscall sigreturn, or a provided
 222  * user-mode trampoline.
 223  */
 224
 225 static int setup_frame(struct ksignal *ksig, sigset_t *set,
 226                        struct pt_regs *regs)
 227 {
 228         struct sigframe __user *frame;
 229         unsigned long return_ip;
 230         int err = 0;
 231
 232         frame = get_sigframe(ksig, sizeof(*frame));
 233
 234         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 235                 return -EFAULT;
 236
 237         err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
 238         if (err)
 239                 return -EFAULT;
 240
 241         if (_NSIG_WORDS > 1) {
 242                 err |= __copy_to_user(frame->extramask, &set->sig[1],
 243                                       sizeof(frame->extramask));
 244         }
 245         if (err)
 246                 return -EFAULT;
 247
 248         /* Set up to return from userspace.  If provided, use a stub
 249            already in userspace.  */
 250         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 251                 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
 252         } else {
 253                 /* trampoline - the desired return ip is the retcode itself */
 254                 return_ip = (unsigned long)&frame->retcode;
 255                 /* This is movu.w __NR_sigreturn, r9; break 13; */
 256                 err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
 257                 err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
 258                 err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
 259         }
 260
 261         if (err)
 262                 return -EFAULT;
 263
 264         /* Set up registers for signal handler */
 265
 266         regs->irp = (unsigned long) ksig->ka.sa.sa_handler;  /* what we enter NOW   */
 267         regs->srp = return_ip;                          /* what we enter LATER */
 268         regs->r10 = ksig->sig;                                /* first argument is signo */
 269
 270         /* actually move the usp to reflect the stacked frame */
 271
 272         wrusp((unsigned long)frame);
 273
 274         return 0;
 275 }
 276
 277 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 278                           struct pt_regs *regs)
 279 {
 280         struct rt_sigframe __user *frame;
 281         unsigned long return_ip;
 282         int err = 0;
 283
 284         frame = get_sigframe(ksig, sizeof(*frame));
 285
 286         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 287                 return -EFAULT;
 288
 289         err |= __put_user(&frame->info, &frame->pinfo);
 290         err |= __put_user(&frame->uc, &frame->puc);
 291         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 292         if (err)
 293                 return -EFAULT;
 294
 295         /* Clear all the bits of the ucontext we don't use.  */
 296         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 297
 298         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 299
 300         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 301
 302         err |= __save_altstack(&frame->uc.uc_stack, rdusp());
 303
 304         if (err)
 305                 return -EFAULT;
 306
 307         /* Set up to return from userspace.  If provided, use a stub
 308            already in userspace.  */
 309         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 310                 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
 311         } else {
 312                 /* trampoline - the desired return ip is the retcode itself */
 313                 return_ip = (unsigned long)&frame->retcode;
 314                 /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
 315                 err |= __put_user(0x9c5f, (short __user *)(frame->retcode+0));
 316                 err |= __put_user(__NR_rt_sigreturn,
 317                         (short __user *)(frame->retcode+2));
 318                 err |= __put_user(0xe93d, (short __user *)(frame->retcode+4));
 319         }
 320
 321         if (err)
 322                 return -EFAULT;
 323
 324         /* Set up registers for signal handler */
 325
 326         /* What we enter NOW   */
 327         regs->irp = (unsigned long) ksig->ka.sa.sa_handler;
 328         /* What we enter LATER */
 329         regs->srp = return_ip;
 330         /* First argument is signo */
 331         regs->r10 = ksig->sig;
 332         /* Second argument is (siginfo_t *) */
 333         regs->r11 = (unsigned long)&frame->info;
 334         /* Third argument is unused */
 335         regs->r12 = 0;
 336
 337         /* Actually move the usp to reflect the stacked frame */
 338         wrusp((unsigned long)frame);
 339
 340         return 0;
 341 }
 342
 343 /*
 344  * OK, we're invoking a handler
 345  */
 346
 347 static inline void handle_signal(int canrestart, struct ksignal *ksig,
 348                                  struct pt_regs *regs)
 349 {
 350         sigset_t *oldset = sigmask_to_save();
 351         int ret;
 352
 353         /* Are we from a system call? */
 354         if (canrestart) {
 355                 /* If so, check system call restarting.. */
 356                 switch (regs->r10) {
 357                 case -ERESTART_RESTARTBLOCK:
 358                 case -ERESTARTNOHAND:
 359                         /* ERESTARTNOHAND means that the syscall should
 360                          * only be restarted if there was no handler for
 361                          * the signal, and since we only get here if there
 362                          * is a handler, we don't restart */
 363                         regs->r10 = -EINTR;
 364                         break;
 365                 case -ERESTARTSYS:
 366                         /* ERESTARTSYS means to restart the syscall if
 367                          * there is no handler or the handler was
 368                          * registered with SA_RESTART */
 369                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 370                                 regs->r10 = -EINTR;
 371                                 break;
 372                         }
 373                 /* fallthrough */
 374                 case -ERESTARTNOINTR:
 375                         /* ERESTARTNOINTR means that the syscall should
 376                          * be called again after the signal handler returns. */
 377                         RESTART_CRIS_SYS(regs);
 378                 }
 379         }
 380
 381         /* Set up the stack frame */
 382         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 383                 ret = setup_rt_frame(ksig, oldset, regs);
 384         else
 385                 ret = setup_frame(ksig, oldset, regs);
 386
 387         signal_setup_done(ret, ksig, 0);
 388 }
 389
 390 /*
 391  * Note that 'init' is a special process: it doesn't get signals it doesn't
 392  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 393  * mistake.
 394  *
 395  * Also note that the regs structure given here as an argument, is the latest
 396  * pushed pt_regs. It may or may not be the same as the first pushed registers
 397  * when the initial usermode->kernelmode transition took place. Therefore
 398  * we can use user_mode(regs) to see if we came directly from kernel or user
 399  * mode below.
 400  */
 401
 402 void do_signal(int canrestart, struct pt_regs *regs)
 403 {
 404         struct ksignal ksig;
 405
 406         /*
 407          * We want the common case to go fast, which
 408          * is why we may in certain cases get here from
 409          * kernel mode. Just return without doing anything
 410          * if so.
 411          */
 412         if (!user_mode(regs))
 413                 return;
 414
 415         if (get_signal(&ksig)) {
 416                 /* Whee!  Actually deliver the signal.  */
 417                 handle_signal(canrestart, &ksig, regs);
 418                 return;
 419         }
 420
 421         /* Did we come from a system call? */
 422         if (canrestart) {
 423                 /* Restart the system call - no handlers present */
 424                 if (regs->r10 == -ERESTARTNOHAND ||
 425                     regs->r10 == -ERESTARTSYS ||
 426                     regs->r10 == -ERESTARTNOINTR) {
 427                         RESTART_CRIS_SYS(regs);
 428                 }
 429                 if (regs->r10 == -ERESTART_RESTARTBLOCK) {
 430                         regs->r9 = __NR_restart_syscall;
 431                         regs->irp -= 2;
 432                 }
 433         }
 434
 435         /* if there's no signal to deliver, we just put the saved sigmask
 436          * back */
 437         restore_saved_sigmask();
 438 }