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         unsigned long old_usp;
  56
  57         /* Alwys make any pending restarted system call return -EINTR */
  58         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  59
  60         /* restore the regs from &sc->regs (same as sc, since regs is first)
  61          * (sc is already checked for VERIFY_READ since the sigframe was
  62          *  checked in sys_sigreturn previously)
  63          */
  64
  65         if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
  66                 goto badframe;
  67
  68         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  69         regs->sr &= ~SPR_SR_SM;
  70
  71         /* restore the old USP as it was before we stacked the sc etc.
  72          * (we cannot just pop the sigcontext since we aligned the sp and
  73          *  stuff after pushing it)
  74          */
  75
  76         err |= __get_user(old_usp, &sc->usp);
  77
  78         regs->sp = old_usp;
  79
  80         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  81          * after this completes, but we don't use that mechanism. maybe we can
  82          * use it now ?
  83          */
  84
  85         return err;
  86
  87 badframe:
  88         return 1;
  89 }
  90
  91 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  92 {
  93         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  94         sigset_t set;
  95         stack_t st;
  96
  97         /*
  98          * Since we stacked the signal on a dword boundary,
  99          * then frame should be dword aligned here.  If it's
 100          * not, then the user is trying to mess with us.
 101          */
 102         if (((long)frame) & 3)
 103                 goto badframe;
 104
 105         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 106                 goto badframe;
 107         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 108                 goto badframe;
 109
 110         sigdelsetmask(&set, ~_BLOCKABLE);
 111         spin_lock_irq(&current->sighand->siglock);
 112         current->blocked = set;
 113         recalc_sigpending();
 114         spin_unlock_irq(&current->sighand->siglock);
 115
 116         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 117                 goto badframe;
 118
 119         if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
 120                 goto badframe;
 121         /* It is more difficult to avoid calling this function than to
 122            call it and ignore errors.  */
 123         do_sigaltstack(&st, NULL, regs->sp);
 124
 125         return regs->gpr[11];
 126
 127 badframe:
 128         force_sig(SIGSEGV, current);
 129         return 0;
 130 }
 131
 132 /*
 133  * Set up a signal frame.
 134  */
 135
 136 static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
 137                             unsigned long mask)
 138 {
 139         int err = 0;
 140         unsigned long usp = regs->sp;
 141
 142         /* copy the regs. they are first in sc so we can use sc directly */
 143
 144         err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
 145
 146         /* then some other stuff */
 147
 148         err |= __put_user(mask, &sc->oldmask);
 149
 150         err |= __put_user(usp, &sc->usp);
 151
 152         return err;
 153 }
 154
 155 static inline unsigned long align_sigframe(unsigned long sp)
 156 {
 157         return sp & ~3UL;
 158 }
 159
 160 /*
 161  * Work out where the signal frame should go.  It's either on the user stack
 162  * or the alternate stack.
 163  */
 164
 165 static inline void __user *get_sigframe(struct k_sigaction *ka,
 166                                         struct pt_regs *regs, size_t frame_size)
 167 {
 168         unsigned long sp = regs->sp;
 169         int onsigstack = on_sig_stack(sp);
 170
 171         /* redzone */
 172         sp -= STACK_FRAME_OVERHEAD;
 173
 174         /* This is the X/Open sanctioned signal stack switching.  */
 175         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 176                 if (current->sas_ss_size)
 177                         sp = current->sas_ss_sp + current->sas_ss_size;
 178         }
 179
 180         sp = align_sigframe(sp - frame_size);
 181
 182         /*
 183          * If we are on the alternate signal stack and would overflow it, don't.
 184          * Return an always-bogus address instead so we will die with SIGSEGV.
 185          */
 186         if (onsigstack && !likely(on_sig_stack(sp)))
 187                 return (void __user *)-1L;
 188
 189         return (void __user *)sp;
 190 }
 191
 192 /* grab and setup a signal frame.
 193  *
 194  * basically we stack a lot of state info, and arrange for the
 195  * user-mode program to return to the kernel using either a
 196  * trampoline which performs the syscall sigreturn, or a provided
 197  * user-mode trampoline.
 198  */
 199 static void setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 200                            sigset_t *set, struct pt_regs *regs)
 201 {
 202         struct rt_sigframe *frame;
 203         unsigned long return_ip;
 204         int err = 0;
 205
 206         frame = get_sigframe(ka, regs, sizeof(*frame));
 207
 208         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 209                 goto give_sigsegv;
 210
 211         err |= __put_user(&frame->info, &frame->pinfo);
 212         err |= __put_user(&frame->uc, &frame->puc);
 213
 214         if (ka->sa.sa_flags & SA_SIGINFO)
 215                 err |= copy_siginfo_to_user(&frame->info, info);
 216         if (err)
 217                 goto give_sigsegv;
 218
 219         /* Clear all the bits of the ucontext we don't use.  */
 220         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 221         err |= __put_user(0, &frame->uc.uc_flags);
 222         err |= __put_user(NULL, &frame->uc.uc_link);
 223         err |= __put_user((void *)current->sas_ss_sp,
 224                           &frame->uc.uc_stack.ss_sp);
 225         err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
 226         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 227         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 228
 229         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 230
 231         if (err)
 232                 goto give_sigsegv;
 233
 234         /* trampoline - the desired return ip is the retcode itself */
 235         return_ip = (unsigned long)&frame->retcode;
 236         /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
 237         err |= __put_user(0xa960, (short *)(frame->retcode + 0));
 238         err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
 239         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 240         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 241
 242         if (err)
 243                 goto give_sigsegv;
 244
 245         /* TODO what is the current->exec_domain stuff and invmap ? */
 246
 247         /* Set up registers for signal handler */
 248         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 249         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 250         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 251         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 252         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 253
 254         /* actually move the usp to reflect the stacked frame */
 255         regs->sp = (unsigned long)frame;
 256
 257         return;
 258
 259 give_sigsegv:
 260         if (sig == SIGSEGV)
 261                 ka->sa.sa_handler = SIG_DFL;
 262         force_sig(SIGSEGV, current);
 263 }
 264
 265 static inline void
 266 handle_signal(unsigned long sig,
 267               siginfo_t *info, struct k_sigaction *ka,
 268               sigset_t *oldset, struct pt_regs *regs)
 269 {
 270         setup_rt_frame(sig, ka, info, oldset, regs);
 271
 272         if (ka->sa.sa_flags & SA_ONESHOT)
 273                 ka->sa.sa_handler = SIG_DFL;
 274
 275         spin_lock_irq(&current->sighand->siglock);
 276         sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
 277         if (!(ka->sa.sa_flags & SA_NODEFER))
 278                 sigaddset(&current->blocked, sig);
 279         recalc_sigpending();
 280
 281         spin_unlock_irq(&current->sighand->siglock);
 282 }
 283
 284 /*
 285  * Note that 'init' is a special process: it doesn't get signals it doesn't
 286  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 287  * mistake.
 288  *
 289  * Also note that the regs structure given here as an argument, is the latest
 290  * pushed pt_regs. It may or may not be the same as the first pushed registers
 291  * when the initial usermode->kernelmode transition took place. Therefore
 292  * we can use user_mode(regs) to see if we came directly from kernel or user
 293  * mode below.
 294  */
 295
 296 void do_signal(struct pt_regs *regs)
 297 {
 298         siginfo_t info;
 299         int signr;
 300         struct k_sigaction ka;
 301
 302         /*
 303          * We want the common case to go fast, which
 304          * is why we may in certain cases get here from
 305          * kernel mode. Just return without doing anything
 306          * if so.
 307          */
 308         if (!user_mode(regs))
 309                 return;
 310
 311         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 312
 313         /* If we are coming out of a syscall then we need
 314          * to check if the syscall was interrupted and wants to be
 315          * restarted after handling the signal.  If so, the original
 316          * syscall number is put back into r11 and the PC rewound to
 317          * point at the l.sys instruction that resulted in the
 318          * original syscall.  Syscall results other than the four
 319          * below mean that the syscall executed to completion and no
 320          * restart is necessary.
 321          */
 322         if (regs->syscallno) {
 323                 int restart = 0;
 324
 325                 switch (regs->gpr[11]) {
 326                 case -ERESTART_RESTARTBLOCK:
 327                 case -ERESTARTNOHAND:
 328                         /* Restart if there is no signal handler */
 329                         restart = (signr <= 0);
 330                         break;
 331                 case -ERESTARTSYS:
 332                         /* Restart if there no signal handler or
 333                          * SA_RESTART flag is set */
 334                         restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
 335                         break;
 336                 case -ERESTARTNOINTR:
 337                         /* Always restart */
 338                         restart = 1;
 339                         break;
 340                 }
 341
 342                 if (restart) {
 343                         if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
 344                                 regs->gpr[11] = __NR_restart_syscall;
 345                         else
 346                                 regs->gpr[11] = regs->orig_gpr11;
 347                         regs->pc -= 4;
 348                 } else {
 349                         regs->gpr[11] = -EINTR;
 350                 }
 351         }
 352
 353         if (signr <= 0) {
 354                 /* no signal to deliver so we just put the saved sigmask
 355                  * back */
 356                 if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 357                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 358                         sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 359                 }
 360
 361         } else {                /* signr > 0 */
 362                 sigset_t *oldset;
 363
 364                 if (current_thread_info()->flags & _TIF_RESTORE_SIGMASK)
 365                         oldset = &current->saved_sigmask;
 366                 else
 367                         oldset = &current->blocked;
 368
 369                 /* Whee!  Actually deliver the signal.  */
 370                 handle_signal(signr, &info, &ka, oldset, regs);
 371                 /* a signal was successfully delivered; the saved
 372                  * sigmask will have been stored in the signal frame,
 373                  * and will be restored by sigreturn, so we can simply
 374                  * clear the TIF_RESTORE_SIGMASK flag */
 375                 if (test_thread_flag(TIF_RESTORE_SIGMASK))
 376                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 377
 378                 tracehook_signal_handler(signr, &info, &ka, regs,
 379                                          test_thread_flag(TIF_SINGLESTEP));
 380         }
 381
 382         return;
 383 }
 384
 385 asmlinkage void do_notify_resume(struct pt_regs *regs)
 386 {
 387         if (current_thread_info()->flags & _TIF_SIGPENDING)
 388                 do_signal(regs);
 389
 390         if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
 391                 clear_thread_flag(TIF_NOTIFY_RESUME);
 392                 tracehook_notify_resume(regs);
 393                 if (current->replacement_session_keyring)
 394                         key_replace_session_keyring();
 395         }
 396 }