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/sched/task_stack.h>
  18 #include <linux/mm.h>
  19 #include <linux/smp.h>
  20 #include <linux/kernel.h>
  21 #include <linux/signal.h>
  22 #include <linux/errno.h>
  23 #include <linux/wait.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/unistd.h>
  26 #include <linux/stddef.h>
  27
  28 #include <asm/processor.h>
  29 #include <asm/ucontext.h>
  30 #include <linux/uaccess.h>
  31 #include <arch/system.h>
  32
  33 #define DEBUG_SIG 0
  34
  35 /* a syscall in Linux/CRIS is a break 13 instruction which is 2 bytes */
  36 /* manipulate regs so that upon return, it will be re-executed */
  37
  38 /* We rely on that pc points to the instruction after "break 13", so the
  39  * library must never do strange things like putting it in a delay slot.
  40  */
  41 #define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->irp -= 2;
  42
  43 void do_signal(int canrestart, struct pt_regs *regs);
  44
  45 /*
  46  * Do a signal return; undo the signal stack.
  47  */
  48
  49 struct sigframe {
  50         struct sigcontext sc;
  51         unsigned long extramask[_NSIG_WORDS-1];
  52         unsigned char retcode[8];  /* trampoline code */
  53 };
  54
  55 struct rt_sigframe {
  56         struct siginfo *pinfo;
  57         void *puc;
  58         struct siginfo info;
  59         struct ucontext uc;
  60         unsigned char retcode[8];  /* trampoline code */
  61 };
  62
  63
  64 static int
  65 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
  66 {
  67         unsigned int err = 0;
  68         unsigned long old_usp;
  69
  70         /* Always make any pending restarted system calls return -EINTR */
  71         current->restart_block.fn = do_no_restart_syscall;
  72
  73         /* restore the regs from &sc->regs (same as sc, since regs is first)
  74          * (sc is already checked for VERIFY_READ since the sigframe was
  75          *  checked in sys_sigreturn previously)
  76          */
  77
  78         if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
  79                 goto badframe;
  80
  81         /* make sure the U-flag is set so user-mode cannot fool us */
  82
  83         regs->dccr |= 1 << 8;
  84
  85         /* restore the old USP as it was before we stacked the sc etc.
  86          * (we cannot just pop the sigcontext since we aligned the sp and
  87          *  stuff after pushing it)
  88          */
  89
  90         err |= __get_user(old_usp, &sc->usp);
  91
  92         wrusp(old_usp);
  93
  94         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  95          * after this completes, but we don't use that mechanism. maybe we can
  96          * use it now ?
  97          */
  98
  99         return err;
 100
 101 badframe:
 102         return 1;
 103 }
 104
 105 asmlinkage int sys_sigreturn(void)
 106 {
 107         struct pt_regs *regs = current_pt_regs();
 108         struct sigframe __user *frame = (struct sigframe *)rdusp();
 109         sigset_t set;
 110
 111         /*
 112          * Since we stacked the signal on a dword boundary,
 113          * then frame should be dword aligned here.  If it's
 114          * not, then the user is trying to mess with us.
 115          */
 116         if (((long)frame) & 3)
 117                 goto badframe;
 118
 119         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 120                 goto badframe;
 121         if (__get_user(set.sig[0], &frame->sc.oldmask)
 122             || (_NSIG_WORDS > 1
 123                 && __copy_from_user(&set.sig[1], frame->extramask,
 124                                     sizeof(frame->extramask))))
 125                 goto badframe;
 126
 127         set_current_blocked(&set);
 128
 129         if (restore_sigcontext(regs, &frame->sc))
 130                 goto badframe;
 131
 132         /* TODO: SIGTRAP when single-stepping as in arm ? */
 133
 134         return regs->r10;
 135
 136 badframe:
 137         force_sig(SIGSEGV, current);
 138         return 0;
 139 }
 140
 141 asmlinkage int sys_rt_sigreturn(void)
 142 {
 143         struct pt_regs *regs = current_pt_regs();
 144         struct rt_sigframe __user *frame = (struct rt_sigframe *)rdusp();
 145         sigset_t set;
 146
 147         /*
 148          * Since we stacked the signal on a dword boundary,
 149          * then frame should be dword aligned here.  If it's
 150          * not, then the user is trying to mess with us.
 151          */
 152         if (((long)frame) & 3)
 153                 goto badframe;
 154
 155         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 156                 goto badframe;
 157         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 158                 goto badframe;
 159
 160         set_current_blocked(&set);
 161
 162         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 163                 goto badframe;
 164
 165         if (restore_altstack(&frame->uc.uc_stack))
 166                 goto badframe;
 167
 168         return regs->r10;
 169
 170 badframe:
 171         force_sig(SIGSEGV, current);
 172         return 0;
 173 }
 174
 175 /*
 176  * Set up a signal frame.
 177  */
 178
 179 static int setup_sigcontext(struct sigcontext __user *sc,
 180         struct pt_regs *regs, unsigned long mask)
 181 {
 182         int err = 0;
 183         unsigned long usp = rdusp();
 184
 185         /* copy the regs. they are first in sc so we can use sc directly */
 186
 187         err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
 188
 189         /* Set the frametype to CRIS_FRAME_NORMAL for the execution of
 190            the signal handler. The frametype will be restored to its previous
 191            value in restore_sigcontext. */
 192         regs->frametype = CRIS_FRAME_NORMAL;
 193
 194         /* then some other stuff */
 195
 196         err |= __put_user(mask, &sc->oldmask);
 197
 198         err |= __put_user(usp, &sc->usp);
 199
 200         return err;
 201 }
 202
 203 /* Figure out where we want to put the new signal frame
 204  * - usually on the stack. */
 205
 206 static inline void __user *
 207 get_sigframe(struct ksignal *ksig, size_t frame_size)
 208 {
 209         unsigned long sp = sigsp(rdusp(), ksig);
 210
 211         /* make sure the frame is dword-aligned */
 212
 213         sp &= ~3;
 214
 215         return (void __user*)(sp - frame_size);
 216 }
 217
 218 /* grab and setup a signal frame.
 219  *
 220  * basically we stack a lot of state info, and arrange for the
 221  * user-mode program to return to the kernel using either a
 222  * trampoline which performs the syscall sigreturn, or a provided
 223  * user-mode trampoline.
 224  */
 225
 226 static int setup_frame(struct ksignal *ksig, sigset_t *set,
 227                        struct pt_regs *regs)
 228 {
 229         struct sigframe __user *frame;
 230         unsigned long return_ip;
 231         int err = 0;
 232
 233         frame = get_sigframe(ksig, sizeof(*frame));
 234
 235         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 236                 return -EFAULT;
 237
 238         err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
 239         if (err)
 240                 return -EFAULT;
 241
 242         if (_NSIG_WORDS > 1) {
 243                 err |= __copy_to_user(frame->extramask, &set->sig[1],
 244                                       sizeof(frame->extramask));
 245         }
 246         if (err)
 247                 return -EFAULT;
 248
 249         /* Set up to return from userspace.  If provided, use a stub
 250            already in userspace.  */
 251         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 252                 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
 253         } else {
 254                 /* trampoline - the desired return ip is the retcode itself */
 255                 return_ip = (unsigned long)&frame->retcode;
 256                 /* This is movu.w __NR_sigreturn, r9; break 13; */
 257                 err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
 258                 err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
 259                 err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
 260         }
 261
 262         if (err)
 263                 return -EFAULT;
 264
 265         /* Set up registers for signal handler */
 266
 267         regs->irp = (unsigned long) ksig->ka.sa.sa_handler;  /* what we enter NOW   */
 268         regs->srp = return_ip;                          /* what we enter LATER */
 269         regs->r10 = ksig->sig;                                /* first argument is signo */
 270
 271         /* actually move the usp to reflect the stacked frame */
 272
 273         wrusp((unsigned long)frame);
 274
 275         return 0;
 276 }
 277
 278 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 279                           struct pt_regs *regs)
 280 {
 281         struct rt_sigframe __user *frame;
 282         unsigned long return_ip;
 283         int err = 0;
 284
 285         frame = get_sigframe(ksig, sizeof(*frame));
 286
 287         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 288                 return -EFAULT;
 289
 290         err |= __put_user(&frame->info, &frame->pinfo);
 291         err |= __put_user(&frame->uc, &frame->puc);
 292         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 293         if (err)
 294                 return -EFAULT;
 295
 296         /* Clear all the bits of the ucontext we don't use.  */
 297         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 298
 299         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 300
 301         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 302
 303         err |= __save_altstack(&frame->uc.uc_stack, rdusp());
 304
 305         if (err)
 306                 return -EFAULT;
 307
 308         /* Set up to return from userspace.  If provided, use a stub
 309            already in userspace.  */
 310         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 311                 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
 312         } else {
 313                 /* trampoline - the desired return ip is the retcode itself */
 314                 return_ip = (unsigned long)&frame->retcode;
 315                 /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
 316                 err |= __put_user(0x9c5f, (short __user *)(frame->retcode+0));
 317                 err |= __put_user(__NR_rt_sigreturn,
 318                         (short __user *)(frame->retcode+2));
 319                 err |= __put_user(0xe93d, (short __user *)(frame->retcode+4));
 320         }
 321
 322         if (err)
 323                 return -EFAULT;
 324
 325         /* Set up registers for signal handler */
 326
 327         /* What we enter NOW   */
 328         regs->irp = (unsigned long) ksig->ka.sa.sa_handler;
 329         /* What we enter LATER */
 330         regs->srp = return_ip;
 331         /* First argument is signo */
 332         regs->r10 = ksig->sig;
 333         /* Second argument is (siginfo_t *) */
 334         regs->r11 = (unsigned long)&frame->info;
 335         /* Third argument is unused */
 336         regs->r12 = 0;
 337
 338         /* Actually move the usp to reflect the stacked frame */
 339         wrusp((unsigned long)frame);
 340
 341         return 0;
 342 }
 343
 344 /*
 345  * OK, we're invoking a handler
 346  */
 347
 348 static inline void handle_signal(int canrestart, struct ksignal *ksig,
 349                                  struct pt_regs *regs)
 350 {
 351         sigset_t *oldset = sigmask_to_save();
 352         int ret;
 353
 354         /* Are we from a system call? */
 355         if (canrestart) {
 356                 /* If so, check system call restarting.. */
 357                 switch (regs->r10) {
 358                 case -ERESTART_RESTARTBLOCK:
 359                 case -ERESTARTNOHAND:
 360                         /* ERESTARTNOHAND means that the syscall should
 361                          * only be restarted if there was no handler for
 362                          * the signal, and since we only get here if there
 363                          * is a handler, we don't restart */
 364                         regs->r10 = -EINTR;
 365                         break;
 366                 case -ERESTARTSYS:
 367                         /* ERESTARTSYS means to restart the syscall if
 368                          * there is no handler or the handler was
 369                          * registered with SA_RESTART */
 370                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 371                                 regs->r10 = -EINTR;
 372                                 break;
 373                         }
 374                 /* fallthrough */
 375                 case -ERESTARTNOINTR:
 376                         /* ERESTARTNOINTR means that the syscall should
 377                          * be called again after the signal handler returns. */
 378                         RESTART_CRIS_SYS(regs);
 379                 }
 380         }
 381
 382         /* Set up the stack frame */
 383         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 384                 ret = setup_rt_frame(ksig, oldset, regs);
 385         else
 386                 ret = setup_frame(ksig, oldset, regs);
 387
 388         signal_setup_done(ret, ksig, 0);
 389 }
 390
 391 /*
 392  * Note that 'init' is a special process: it doesn't get signals it doesn't
 393  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 394  * mistake.
 395  *
 396  * Also note that the regs structure given here as an argument, is the latest
 397  * pushed pt_regs. It may or may not be the same as the first pushed registers
 398  * when the initial usermode->kernelmode transition took place. Therefore
 399  * we can use user_mode(regs) to see if we came directly from kernel or user
 400  * mode below.
 401  */
 402
 403 void do_signal(int canrestart, struct pt_regs *regs)
 404 {
 405         struct ksignal ksig;
 406
 407         /*
 408          * We want the common case to go fast, which
 409          * is why we may in certain cases get here from
 410          * kernel mode. Just return without doing anything
 411          * if so.
 412          */
 413         if (!user_mode(regs))
 414                 return;
 415
 416         if (get_signal(&ksig)) {
 417                 /* Whee!  Actually deliver the signal.  */
 418                 handle_signal(canrestart, &ksig, regs);
 419                 return;
 420         }
 421
 422         /* Did we come from a system call? */
 423         if (canrestart) {
 424                 /* Restart the system call - no handlers present */
 425                 if (regs->r10 == -ERESTARTNOHAND ||
 426                     regs->r10 == -ERESTARTSYS ||
 427                     regs->r10 == -ERESTARTNOINTR) {
 428                         RESTART_CRIS_SYS(regs);
 429                 }
 430                 if (regs->r10 == -ERESTART_RESTARTBLOCK) {
 431                         regs->r9 = __NR_restart_syscall;
 432                         regs->irp -= 2;
 433                 }
 434         }
 435
 436         /* if there's no signal to deliver, we just put the saved sigmask
 437          * back */
 438         restore_saved_sigmask();
 439 }