arch/openrisc/kernel/signal.c

   1 /*
   2  * OpenRISC signal.c
   3  *
   4  * Linux architectural port borrowing liberally from similar works of
   5  * others.  All original copyrights apply as per the original source
   6  * declaration.
   7  *
   8  * Modifications for the OpenRISC architecture:
   9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  11  *
  12  *      This program is free software; you can redistribute it and/or
  13  *      modify it under the terms of the GNU General Public License
  14  *      as published by the Free Software Foundation; either version
  15  *      2 of the License, or (at your option) any later version.
  16  */
  17
  18 #include <linux/sched.h>
  19 #include <linux/mm.h>
  20 #include <linux/smp.h>
  21 #include <linux/kernel.h>
  22 #include <linux/signal.h>
  23 #include <linux/errno.h>
  24 #include <linux/wait.h>
  25 #include <linux/ptrace.h>
  26 #include <linux/unistd.h>
  27 #include <linux/stddef.h>
  28 #include <linux/tracehook.h>
  29
  30 #include <asm/processor.h>
  31 #include <asm/ucontext.h>
  32 #include <asm/uaccess.h>
  33
  34 #define DEBUG_SIG 0
  35
  36 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  37
  38 asmlinkage long
  39 _sys_sigaltstack(const stack_t *uss, stack_t *uoss, struct pt_regs *regs)
  40 {
  41         return do_sigaltstack(uss, uoss, regs->sp);
  42 }
  43
  44 struct rt_sigframe {
  45         struct siginfo *pinfo;
  46         void *puc;
  47         struct siginfo info;
  48         struct ucontext uc;
  49         unsigned char retcode[16];      /* trampoline code */
  50 };
  51
  52 static int restore_sigcontext(struct pt_regs *regs, struct sigcontext *sc)
  53 {
  54         unsigned int err = 0;
  55
  56         /* Alwys make any pending restarted system call return -EINTR */
  57         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  58
  59         /*
  60          * Restore the regs from &sc->regs.
  61          * (sc is already checked for VERIFY_READ since the sigframe was
  62          *  checked in sys_sigreturn previously)
  63          */
  64         if (__copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)))
  65                 goto badframe;
  66         if (__copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long)))
  67                 goto badframe;
  68         if (__copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long)))
  69                 goto badframe;
  70
  71         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  72         regs->sr &= ~SPR_SR_SM;
  73
  74         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  75          * after this completes, but we don't use that mechanism. maybe we can
  76          * use it now ?
  77          */
  78
  79         return err;
  80
  81 badframe:
  82         return 1;
  83 }
  84
  85 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  86 {
  87         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  88         sigset_t set;
  89         stack_t st;
  90
  91         /*
  92          * Since we stacked the signal on a dword boundary,
  93          * then frame should be dword aligned here.  If it's
  94          * not, then the user is trying to mess with us.
  95          */
  96         if (((long)frame) & 3)
  97                 goto badframe;
  98
  99         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 100                 goto badframe;
 101         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 102                 goto badframe;
 103
 104         sigdelsetmask(&set, ~_BLOCKABLE);
 105         spin_lock_irq(&current->sighand->siglock);
 106         current->blocked = set;
 107         recalc_sigpending();
 108         spin_unlock_irq(&current->sighand->siglock);
 109
 110         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 111                 goto badframe;
 112
 113         if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
 114                 goto badframe;
 115         /* It is more difficult to avoid calling this function than to
 116            call it and ignore errors.  */
 117         do_sigaltstack(&st, NULL, regs->sp);
 118
 119         return regs->gpr[11];
 120
 121 badframe:
 122         force_sig(SIGSEGV, current);
 123         return 0;
 124 }
 125
 126 /*
 127  * Set up a signal frame.
 128  */
 129
 130 static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
 131                             unsigned long mask)
 132 {
 133         int err = 0;
 134
 135         /* copy the regs */
 136
 137         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 138         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 139         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 140
 141         /* then some other stuff */
 142
 143         err |= __put_user(mask, &sc->oldmask);
 144
 145         return err;
 146 }
 147
 148 static inline unsigned long align_sigframe(unsigned long sp)
 149 {
 150         return sp & ~3UL;
 151 }
 152
 153 /*
 154  * Work out where the signal frame should go.  It's either on the user stack
 155  * or the alternate stack.
 156  */
 157
 158 static inline void __user *get_sigframe(struct k_sigaction *ka,
 159                                         struct pt_regs *regs, size_t frame_size)
 160 {
 161         unsigned long sp = regs->sp;
 162         int onsigstack = on_sig_stack(sp);
 163
 164         /* redzone */
 165         sp -= STACK_FRAME_OVERHEAD;
 166
 167         /* This is the X/Open sanctioned signal stack switching.  */
 168         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 169                 if (current->sas_ss_size)
 170                         sp = current->sas_ss_sp + current->sas_ss_size;
 171         }
 172
 173         sp = align_sigframe(sp - frame_size);
 174
 175         /*
 176          * If we are on the alternate signal stack and would overflow it, don't.
 177          * Return an always-bogus address instead so we will die with SIGSEGV.
 178          */
 179         if (onsigstack && !likely(on_sig_stack(sp)))
 180                 return (void __user *)-1L;
 181
 182         return (void __user *)sp;
 183 }
 184
 185 /* grab and setup a signal frame.
 186  *
 187  * basically we stack a lot of state info, and arrange for the
 188  * user-mode program to return to the kernel using either a
 189  * trampoline which performs the syscall sigreturn, or a provided
 190  * user-mode trampoline.
 191  */
 192 static void setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 193                            sigset_t *set, struct pt_regs *regs)
 194 {
 195         struct rt_sigframe *frame;
 196         unsigned long return_ip;
 197         int err = 0;
 198
 199         frame = get_sigframe(ka, regs, sizeof(*frame));
 200
 201         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 202                 goto give_sigsegv;
 203
 204         err |= __put_user(&frame->info, &frame->pinfo);
 205         err |= __put_user(&frame->uc, &frame->puc);
 206
 207         if (ka->sa.sa_flags & SA_SIGINFO)
 208                 err |= copy_siginfo_to_user(&frame->info, info);
 209         if (err)
 210                 goto give_sigsegv;
 211
 212         /* Clear all the bits of the ucontext we don't use.  */
 213         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 214         err |= __put_user(0, &frame->uc.uc_flags);
 215         err |= __put_user(NULL, &frame->uc.uc_link);
 216         err |= __put_user((void *)current->sas_ss_sp,
 217                           &frame->uc.uc_stack.ss_sp);
 218         err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
 219         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 220         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 221
 222         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 223
 224         if (err)
 225                 goto give_sigsegv;
 226
 227         /* trampoline - the desired return ip is the retcode itself */
 228         return_ip = (unsigned long)&frame->retcode;
 229         /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
 230         err |= __put_user(0xa960, (short *)(frame->retcode + 0));
 231         err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
 232         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 233         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 234
 235         if (err)
 236                 goto give_sigsegv;
 237
 238         /* TODO what is the current->exec_domain stuff and invmap ? */
 239
 240         /* Set up registers for signal handler */
 241         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 242         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 243         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 244         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 245         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 246
 247         /* actually move the usp to reflect the stacked frame */
 248         regs->sp = (unsigned long)frame;
 249
 250         return;
 251
 252 give_sigsegv:
 253         if (sig == SIGSEGV)
 254                 ka->sa.sa_handler = SIG_DFL;
 255         force_sig(SIGSEGV, current);
 256 }
 257
 258 static inline void
 259 handle_signal(unsigned long sig,
 260               siginfo_t *info, struct k_sigaction *ka,
 261               sigset_t *oldset, struct pt_regs *regs)
 262 {
 263         setup_rt_frame(sig, ka, info, oldset, regs);
 264
 265         if (ka->sa.sa_flags & SA_ONESHOT)
 266                 ka->sa.sa_handler = SIG_DFL;
 267
 268         spin_lock_irq(&current->sighand->siglock);
 269         sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 270         if (!(ka->sa.sa_flags & SA_NODEFER))
 271                 sigaddset(&current->blocked, sig);
 272         recalc_sigpending();
 273
 274         spin_unlock_irq(&current->sighand->siglock);
 275 }
 276
 277 /*
 278  * Note that 'init' is a special process: it doesn't get signals it doesn't
 279  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 280  * mistake.
 281  *
 282  * Also note that the regs structure given here as an argument, is the latest
 283  * pushed pt_regs. It may or may not be the same as the first pushed registers
 284  * when the initial usermode->kernelmode transition took place. Therefore
 285  * we can use user_mode(regs) to see if we came directly from kernel or user
 286  * mode below.
 287  */
 288
 289 void do_signal(struct pt_regs *regs)
 290 {
 291         siginfo_t info;
 292         int signr;
 293         struct k_sigaction ka;
 294
 295         /*
 296          * We want the common case to go fast, which
 297          * is why we may in certain cases get here from
 298          * kernel mode. Just return without doing anything
 299          * if so.
 300          */
 301         if (!user_mode(regs))
 302                 return;
 303
 304         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 305
 306         /* If we are coming out of a syscall then we need
 307          * to check if the syscall was interrupted and wants to be
 308          * restarted after handling the signal.  If so, the original
 309          * syscall number is put back into r11 and the PC rewound to
 310          * point at the l.sys instruction that resulted in the
 311          * original syscall.  Syscall results other than the four
 312          * below mean that the syscall executed to completion and no
 313          * restart is necessary.
 314          */
 315         if (regs->syscallno) {
 316                 int restart = 0;
 317
 318                 switch (regs->gpr[11]) {
 319                 case -ERESTART_RESTARTBLOCK:
 320                 case -ERESTARTNOHAND:
 321                         /* Restart if there is no signal handler */
 322                         restart = (signr <= 0);
 323                         break;
 324                 case -ERESTARTSYS:
 325                         /* Restart if there no signal handler or
 326                          * SA_RESTART flag is set */
 327                         restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
 328                         break;
 329                 case -ERESTARTNOINTR:
 330                         /* Always restart */
 331                         restart = 1;
 332                         break;
 333                 }
 334
 335                 if (restart) {
 336                         if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
 337                                 regs->gpr[11] = __NR_restart_syscall;
 338                         else
 339                                 regs->gpr[11] = regs->orig_gpr11;
 340                         regs->pc -= 4;
 341                 } else {
 342                         regs->gpr[11] = -EINTR;
 343                 }
 344         }
 345
 346         if (signr <= 0) {
 347                 /* no signal to deliver so we just put the saved sigmask
 348                  * back */
 349                 if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 350                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 351                         sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 352                 }
 353
 354         } else {                /* signr > 0 */
 355                 sigset_t *oldset;
 356
 357                 if (current_thread_info()->flags & _TIF_RESTORE_SIGMASK)
 358                         oldset = &current->saved_sigmask;
 359                 else
 360                         oldset = &current->blocked;
 361
 362                 /* Whee!  Actually deliver the signal.  */
 363                 handle_signal(signr, &info, &ka, oldset, regs);
 364                 /* a signal was successfully delivered; the saved
 365                  * sigmask will have been stored in the signal frame,
 366                  * and will be restored by sigreturn, so we can simply
 367                  * clear the TIF_RESTORE_SIGMASK flag */
 368                 if (test_thread_flag(TIF_RESTORE_SIGMASK))
 369                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 370
 371                 tracehook_signal_handler(signr, &info, &ka, regs,
 372                                          test_thread_flag(TIF_SINGLESTEP));
 373         }
 374
 375         return;
 376 }
 377
 378 asmlinkage void do_notify_resume(struct pt_regs *regs)
 379 {
 380         if (current_thread_info()->flags & _TIF_SIGPENDING)
 381                 do_signal(regs);
 382
 383         if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
 384                 clear_thread_flag(TIF_NOTIFY_RESUME);
 385                 tracehook_notify_resume(regs);
 386                 if (current->replacement_session_keyring)
 387                         key_replace_session_keyring();
 388         }
 389 }