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         /* restore the regs from &sc->regs (same as sc, since regs is first)
  60          * (sc is already checked for VERIFY_READ since the sigframe was
  61          *  checked in sys_sigreturn previously)
  62          */
  63         if (__copy_from_user(regs, sc->regs.gpr, 33*sizeof(unsigned long)))
  64                 goto badframe;
  65         if (__copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long)))
  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         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  72          * after this completes, but we don't use that mechanism. maybe we can
  73          * use it now ?
  74          */
  75
  76         return err;
  77
  78 badframe:
  79         return 1;
  80 }
  81
  82 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  83 {
  84         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  85         sigset_t set;
  86         stack_t st;
  87
  88         /*
  89          * Since we stacked the signal on a dword boundary,
  90          * then frame should be dword aligned here.  If it's
  91          * not, then the user is trying to mess with us.
  92          */
  93         if (((long)frame) & 3)
  94                 goto badframe;
  95
  96         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  97                 goto badframe;
  98         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  99                 goto badframe;
 100
 101         sigdelsetmask(&set, ~_BLOCKABLE);
 102         set_current_blocked(&set);
 103
 104         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 105                 goto badframe;
 106
 107         if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
 108                 goto badframe;
 109         /* It is more difficult to avoid calling this function than to
 110            call it and ignore errors.  */
 111         do_sigaltstack(&st, NULL, regs->sp);
 112
 113         return regs->gpr[11];
 114
 115 badframe:
 116         force_sig(SIGSEGV, current);
 117         return 0;
 118 }
 119
 120 /*
 121  * Set up a signal frame.
 122  */
 123
 124 static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
 125                             unsigned long mask)
 126 {
 127         int err = 0;
 128
 129         /* copy the regs. they are first in sc so we can use sc directly */
 130
 131         err |= __copy_to_user(sc->regs.gpr, regs, 33*sizeof(unsigned long));
 132         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 133
 134         /* then some other stuff */
 135
 136         err |= __put_user(mask, &sc->oldmask);
 137
 138         return err;
 139 }
 140
 141 static inline unsigned long align_sigframe(unsigned long sp)
 142 {
 143         return sp & ~3UL;
 144 }
 145
 146 /*
 147  * Work out where the signal frame should go.  It's either on the user stack
 148  * or the alternate stack.
 149  */
 150
 151 static inline void __user *get_sigframe(struct k_sigaction *ka,
 152                                         struct pt_regs *regs, size_t frame_size)
 153 {
 154         unsigned long sp = regs->sp;
 155         int onsigstack = on_sig_stack(sp);
 156
 157         /* redzone */
 158         sp -= STACK_FRAME_OVERHEAD;
 159
 160         /* This is the X/Open sanctioned signal stack switching.  */
 161         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 162                 if (current->sas_ss_size)
 163                         sp = current->sas_ss_sp + current->sas_ss_size;
 164         }
 165
 166         sp = align_sigframe(sp - frame_size);
 167
 168         /*
 169          * If we are on the alternate signal stack and would overflow it, don't.
 170          * Return an always-bogus address instead so we will die with SIGSEGV.
 171          */
 172         if (onsigstack && !likely(on_sig_stack(sp)))
 173                 return (void __user *)-1L;
 174
 175         return (void __user *)sp;
 176 }
 177
 178 /* grab and setup a signal frame.
 179  *
 180  * basically we stack a lot of state info, and arrange for the
 181  * user-mode program to return to the kernel using either a
 182  * trampoline which performs the syscall sigreturn, or a provided
 183  * user-mode trampoline.
 184  */
 185 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 186                           sigset_t *set, struct pt_regs *regs)
 187 {
 188         struct rt_sigframe *frame;
 189         unsigned long return_ip;
 190         int err = 0;
 191
 192         frame = get_sigframe(ka, regs, sizeof(*frame));
 193
 194         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 195                 goto give_sigsegv;
 196
 197         err |= __put_user(&frame->info, &frame->pinfo);
 198         err |= __put_user(&frame->uc, &frame->puc);
 199
 200         if (ka->sa.sa_flags & SA_SIGINFO)
 201                 err |= copy_siginfo_to_user(&frame->info, info);
 202         if (err)
 203                 goto give_sigsegv;
 204
 205         /* Clear all the bits of the ucontext we don't use.  */
 206         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 207         err |= __put_user(0, &frame->uc.uc_flags);
 208         err |= __put_user(NULL, &frame->uc.uc_link);
 209         err |= __put_user((void *)current->sas_ss_sp,
 210                           &frame->uc.uc_stack.ss_sp);
 211         err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
 212         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 213         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 214
 215         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 216
 217         if (err)
 218                 goto give_sigsegv;
 219
 220         /* trampoline - the desired return ip is the retcode itself */
 221         return_ip = (unsigned long)&frame->retcode;
 222         /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
 223         err |= __put_user(0xa960, (short *)(frame->retcode + 0));
 224         err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
 225         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 226         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 227
 228         if (err)
 229                 goto give_sigsegv;
 230
 231         /* TODO what is the current->exec_domain stuff and invmap ? */
 232
 233         /* Set up registers for signal handler */
 234         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 235         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 236         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 237         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 238         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 239
 240         /* actually move the usp to reflect the stacked frame */
 241         regs->sp = (unsigned long)frame;
 242
 243         return 0;
 244
 245 give_sigsegv:
 246         force_sigsegv(sig, current);
 247         return -EFAULT;
 248 }
 249
 250 static inline int
 251 handle_signal(unsigned long sig,
 252               siginfo_t *info, struct k_sigaction *ka,
 253               sigset_t *oldset, struct pt_regs *regs)
 254 {
 255         int ret;
 256
 257         ret = setup_rt_frame(sig, ka, info, oldset, regs);
 258         if (ret)
 259                 return ret;
 260
 261         block_sigmask(ka, sig);
 262
 263         return 0;
 264 }
 265
 266 /*
 267  * Note that 'init' is a special process: it doesn't get signals it doesn't
 268  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 269  * mistake.
 270  *
 271  * Also note that the regs structure given here as an argument, is the latest
 272  * pushed pt_regs. It may or may not be the same as the first pushed registers
 273  * when the initial usermode->kernelmode transition took place. Therefore
 274  * we can use user_mode(regs) to see if we came directly from kernel or user
 275  * mode below.
 276  */
 277
 278 void do_signal(struct pt_regs *regs)
 279 {
 280         siginfo_t info;
 281         int signr;
 282         struct k_sigaction ka;
 283
 284         /*
 285          * We want the common case to go fast, which
 286          * is why we may in certain cases get here from
 287          * kernel mode. Just return without doing anything
 288          * if so.
 289          */
 290         if (!user_mode(regs))
 291                 return;
 292
 293         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 294
 295         /* If we are coming out of a syscall then we need
 296          * to check if the syscall was interrupted and wants to be
 297          * restarted after handling the signal.  If so, the original
 298          * syscall number is put back into r11 and the PC rewound to
 299          * point at the l.sys instruction that resulted in the
 300          * original syscall.  Syscall results other than the four
 301          * below mean that the syscall executed to completion and no
 302          * restart is necessary.
 303          */
 304         if (regs->syscallno) {
 305                 int restart = 0;
 306
 307                 switch (regs->gpr[11]) {
 308                 case -ERESTART_RESTARTBLOCK:
 309                 case -ERESTARTNOHAND:
 310                         /* Restart if there is no signal handler */
 311                         restart = (signr <= 0);
 312                         break;
 313                 case -ERESTARTSYS:
 314                         /* Restart if there no signal handler or
 315                          * SA_RESTART flag is set */
 316                         restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
 317                         break;
 318                 case -ERESTARTNOINTR:
 319                         /* Always restart */
 320                         restart = 1;
 321                         break;
 322                 }
 323
 324                 if (restart) {
 325                         if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
 326                                 regs->gpr[11] = __NR_restart_syscall;
 327                         else
 328                                 regs->gpr[11] = regs->orig_gpr11;
 329                         regs->pc -= 4;
 330                 } else {
 331                         regs->gpr[11] = -EINTR;
 332                 }
 333         }
 334
 335         if (signr <= 0) {
 336                 /* no signal to deliver so we just put the saved sigmask
 337                  * back */
 338                 if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 339                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 340                         sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 341                 }
 342
 343         } else {                /* signr > 0 */
 344                 sigset_t *oldset;
 345
 346                 if (current_thread_info()->flags & _TIF_RESTORE_SIGMASK)
 347                         oldset = &current->saved_sigmask;
 348                 else
 349                         oldset = &current->blocked;
 350
 351                 /* Whee!  Actually deliver the signal.  */
 352                 if (!handle_signal(signr, &info, &ka, oldset, regs)) {
 353                         /* a signal was successfully delivered; the saved
 354                          * sigmask will have been stored in the signal frame,
 355                          * and will be restored by sigreturn, so we can simply
 356                          * clear the TIF_RESTORE_SIGMASK flag */
 357                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 358                 }
 359
 360                 tracehook_signal_handler(signr, &info, &ka, regs,
 361                                          test_thread_flag(TIF_SINGLESTEP));
 362         }
 363
 364         return;
 365 }
 366
 367 asmlinkage void do_notify_resume(struct pt_regs *regs)
 368 {
 369         if (current_thread_info()->flags & _TIF_SIGPENDING)
 370                 do_signal(regs);
 371
 372         if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
 373                 clear_thread_flag(TIF_NOTIFY_RESUME);
 374                 tracehook_notify_resume(regs);
 375                 if (current->replacement_session_keyring)
 376                         key_replace_session_keyring();
 377         }
 378 }