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 asmlinkage long
  37 _sys_sigaltstack(const stack_t *uss, stack_t *uoss, struct pt_regs *regs)
  38 {
  39         return do_sigaltstack(uss, uoss, regs->sp);
  40 }
  41
  42 struct rt_sigframe {
  43         struct siginfo *pinfo;
  44         void *puc;
  45         struct siginfo info;
  46         struct ucontext uc;
  47         unsigned char retcode[16];      /* trampoline code */
  48 };
  49
  50 static int restore_sigcontext(struct pt_regs *regs, struct sigcontext *sc)
  51 {
  52         unsigned int err = 0;
  53
  54         /* Alwys make any pending restarted system call return -EINTR */
  55         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  56
  57         /*
  58          * Restore the regs from &sc->regs.
  59          * (sc is already checked for VERIFY_READ since the sigframe was
  60          *  checked in sys_sigreturn previously)
  61          */
  62         if (__copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)))
  63                 goto badframe;
  64         if (__copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long)))
  65                 goto badframe;
  66         if (__copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long)))
  67                 goto badframe;
  68
  69         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  70         regs->sr &= ~SPR_SR_SM;
  71
  72         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  73          * after this completes, but we don't use that mechanism. maybe we can
  74          * use it now ?
  75          */
  76
  77         return err;
  78
  79 badframe:
  80         return 1;
  81 }
  82
  83 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  84 {
  85         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  86         sigset_t set;
  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         set_current_blocked(&set);
 102
 103         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 104                 goto badframe;
 105
 106         /* It is more difficult to avoid calling this function than to
 107            call it and ignore errors.  */
 108         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 109                 goto badframe;
 110
 111         return regs->gpr[11];
 112
 113 badframe:
 114         force_sig(SIGSEGV, current);
 115         return 0;
 116 }
 117
 118 /*
 119  * Set up a signal frame.
 120  */
 121
 122 static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
 123                             unsigned long mask)
 124 {
 125         int err = 0;
 126
 127         /* copy the regs */
 128
 129         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 130         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 131         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 132
 133         /* then some other stuff */
 134
 135         err |= __put_user(mask, &sc->oldmask);
 136
 137         return err;
 138 }
 139
 140 static inline unsigned long align_sigframe(unsigned long sp)
 141 {
 142         return sp & ~3UL;
 143 }
 144
 145 /*
 146  * Work out where the signal frame should go.  It's either on the user stack
 147  * or the alternate stack.
 148  */
 149
 150 static inline void __user *get_sigframe(struct k_sigaction *ka,
 151                                         struct pt_regs *regs, size_t frame_size)
 152 {
 153         unsigned long sp = regs->sp;
 154         int onsigstack = on_sig_stack(sp);
 155
 156         /* redzone */
 157         sp -= STACK_FRAME_OVERHEAD;
 158
 159         /* This is the X/Open sanctioned signal stack switching.  */
 160         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 161                 if (current->sas_ss_size)
 162                         sp = current->sas_ss_sp + current->sas_ss_size;
 163         }
 164
 165         sp = align_sigframe(sp - frame_size);
 166
 167         /*
 168          * If we are on the alternate signal stack and would overflow it, don't.
 169          * Return an always-bogus address instead so we will die with SIGSEGV.
 170          */
 171         if (onsigstack && !likely(on_sig_stack(sp)))
 172                 return (void __user *)-1L;
 173
 174         return (void __user *)sp;
 175 }
 176
 177 /* grab and setup a signal frame.
 178  *
 179  * basically we stack a lot of state info, and arrange for the
 180  * user-mode program to return to the kernel using either a
 181  * trampoline which performs the syscall sigreturn, or a provided
 182  * user-mode trampoline.
 183  */
 184 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 185                           sigset_t *set, struct pt_regs *regs)
 186 {
 187         struct rt_sigframe *frame;
 188         unsigned long return_ip;
 189         int err = 0;
 190
 191         frame = get_sigframe(ka, regs, sizeof(*frame));
 192
 193         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 194                 goto give_sigsegv;
 195
 196         err |= __put_user(&frame->info, &frame->pinfo);
 197         err |= __put_user(&frame->uc, &frame->puc);
 198
 199         if (ka->sa.sa_flags & SA_SIGINFO)
 200                 err |= copy_siginfo_to_user(&frame->info, info);
 201         if (err)
 202                 goto give_sigsegv;
 203
 204         /* Clear all the bits of the ucontext we don't use.  */
 205         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 206         err |= __put_user(0, &frame->uc.uc_flags);
 207         err |= __put_user(NULL, &frame->uc.uc_link);
 208         err |= __put_user((void *)current->sas_ss_sp,
 209                           &frame->uc.uc_stack.ss_sp);
 210         err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
 211         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 212         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 213
 214         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 215
 216         if (err)
 217                 goto give_sigsegv;
 218
 219         /* trampoline - the desired return ip is the retcode itself */
 220         return_ip = (unsigned long)&frame->retcode;
 221         /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
 222         err |= __put_user(0xa960, (short *)(frame->retcode + 0));
 223         err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
 224         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 225         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 226
 227         if (err)
 228                 goto give_sigsegv;
 229
 230         /* TODO what is the current->exec_domain stuff and invmap ? */
 231
 232         /* Set up registers for signal handler */
 233         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 234         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 235         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 236         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 237         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 238
 239         /* actually move the usp to reflect the stacked frame */
 240         regs->sp = (unsigned long)frame;
 241
 242         return 0;
 243
 244 give_sigsegv:
 245         force_sigsegv(sig, current);
 246         return -EFAULT;
 247 }
 248
 249 static inline void
 250 handle_signal(unsigned long sig,
 251               siginfo_t *info, struct k_sigaction *ka,
 252               struct pt_regs *regs)
 253 {
 254         int ret;
 255
 256         ret = setup_rt_frame(sig, ka, info, sigmask_to_save(), regs);
 257         if (ret)
 258                 return;
 259
 260         signal_delivered(sig, info, ka, regs,
 261                                  test_thread_flag(TIF_SINGLESTEP));
 262 }
 263
 264 /*
 265  * Note that 'init' is a special process: it doesn't get signals it doesn't
 266  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 267  * mistake.
 268  *
 269  * Also note that the regs structure given here as an argument, is the latest
 270  * pushed pt_regs. It may or may not be the same as the first pushed registers
 271  * when the initial usermode->kernelmode transition took place. Therefore
 272  * we can use user_mode(regs) to see if we came directly from kernel or user
 273  * mode below.
 274  */
 275
 276 void do_signal(struct pt_regs *regs)
 277 {
 278         siginfo_t info;
 279         int signr;
 280         struct k_sigaction ka;
 281
 282         /*
 283          * We want the common case to go fast, which
 284          * is why we may in certain cases get here from
 285          * kernel mode. Just return without doing anything
 286          * if so.
 287          */
 288         if (!user_mode(regs))
 289                 return;
 290
 291         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 292
 293         /* If we are coming out of a syscall then we need
 294          * to check if the syscall was interrupted and wants to be
 295          * restarted after handling the signal.  If so, the original
 296          * syscall number is put back into r11 and the PC rewound to
 297          * point at the l.sys instruction that resulted in the
 298          * original syscall.  Syscall results other than the four
 299          * below mean that the syscall executed to completion and no
 300          * restart is necessary.
 301          */
 302         if (regs->orig_gpr11) {
 303                 int restart = 0;
 304
 305                 switch (regs->gpr[11]) {
 306                 case -ERESTART_RESTARTBLOCK:
 307                 case -ERESTARTNOHAND:
 308                         /* Restart if there is no signal handler */
 309                         restart = (signr <= 0);
 310                         break;
 311                 case -ERESTARTSYS:
 312                         /* Restart if there no signal handler or
 313                          * SA_RESTART flag is set */
 314                         restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
 315                         break;
 316                 case -ERESTARTNOINTR:
 317                         /* Always restart */
 318                         restart = 1;
 319                         break;
 320                 }
 321
 322                 if (restart) {
 323                         if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
 324                                 regs->gpr[11] = __NR_restart_syscall;
 325                         else
 326                                 regs->gpr[11] = regs->orig_gpr11;
 327                         regs->pc -= 4;
 328                 } else {
 329                         regs->gpr[11] = -EINTR;
 330                 }
 331         }
 332
 333         if (signr <= 0) {
 334                 /* no signal to deliver so we just put the saved sigmask
 335                  * back */
 336                 restore_saved_sigmask();
 337         } else {                /* signr > 0 */
 338                 /* Whee!  Actually deliver the signal.  */
 339                 handle_signal(signr, &info, &ka, regs);
 340         }
 341
 342         return;
 343 }
 344
 345 asmlinkage void do_notify_resume(struct pt_regs *regs)
 346 {
 347         if (current_thread_info()->flags & _TIF_SIGPENDING)
 348                 do_signal(regs);
 349
 350         if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
 351                 clear_thread_flag(TIF_NOTIFY_RESUME);
 352                 tracehook_notify_resume(regs);
 353         }
 354 }