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 struct rt_sigframe {
  37         struct siginfo *pinfo;
  38         void *puc;
  39         struct siginfo info;
  40         struct ucontext uc;
  41         unsigned char retcode[16];      /* trampoline code */
  42 };
  43
  44 static int restore_sigcontext(struct pt_regs *regs, struct sigcontext *sc)
  45 {
  46         unsigned int err = 0;
  47
  48         /* Alwys make any pending restarted system call return -EINTR */
  49         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  50
  51         /*
  52          * Restore the regs from &sc->regs.
  53          * (sc is already checked for VERIFY_READ since the sigframe was
  54          *  checked in sys_sigreturn previously)
  55          */
  56         if (__copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)))
  57                 goto badframe;
  58         if (__copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long)))
  59                 goto badframe;
  60         if (__copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long)))
  61                 goto badframe;
  62
  63         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  64         regs->sr &= ~SPR_SR_SM;
  65
  66         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  67          * after this completes, but we don't use that mechanism. maybe we can
  68          * use it now ?
  69          */
  70
  71         return err;
  72
  73 badframe:
  74         return 1;
  75 }
  76
  77 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  78 {
  79         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  80         sigset_t set;
  81
  82         /*
  83          * Since we stacked the signal on a dword boundary,
  84          * then frame should be dword aligned here.  If it's
  85          * not, then the user is trying to mess with us.
  86          */
  87         if (((long)frame) & 3)
  88                 goto badframe;
  89
  90         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  91                 goto badframe;
  92         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  93                 goto badframe;
  94
  95         set_current_blocked(&set);
  96
  97         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
  98                 goto badframe;
  99
 100         if (restore_altstack(&frame->uc.uc_stack))
 101                 goto badframe;
 102
 103         return regs->gpr[11];
 104
 105 badframe:
 106         force_sig(SIGSEGV, current);
 107         return 0;
 108 }
 109
 110 /*
 111  * Set up a signal frame.
 112  */
 113
 114 static int setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
 115                             unsigned long mask)
 116 {
 117         int err = 0;
 118
 119         /* copy the regs */
 120
 121         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 122         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 123         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 124
 125         /* then some other stuff */
 126
 127         err |= __put_user(mask, &sc->oldmask);
 128
 129         return err;
 130 }
 131
 132 static inline unsigned long align_sigframe(unsigned long sp)
 133 {
 134         return sp & ~3UL;
 135 }
 136
 137 /*
 138  * Work out where the signal frame should go.  It's either on the user stack
 139  * or the alternate stack.
 140  */
 141
 142 static inline void __user *get_sigframe(struct k_sigaction *ka,
 143                                         struct pt_regs *regs, size_t frame_size)
 144 {
 145         unsigned long sp = regs->sp;
 146         int onsigstack = on_sig_stack(sp);
 147
 148         /* redzone */
 149         sp -= STACK_FRAME_OVERHEAD;
 150
 151         /* This is the X/Open sanctioned signal stack switching.  */
 152         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 153                 if (current->sas_ss_size)
 154                         sp = current->sas_ss_sp + current->sas_ss_size;
 155         }
 156
 157         sp = align_sigframe(sp - frame_size);
 158
 159         /*
 160          * If we are on the alternate signal stack and would overflow it, don't.
 161          * Return an always-bogus address instead so we will die with SIGSEGV.
 162          */
 163         if (onsigstack && !likely(on_sig_stack(sp)))
 164                 return (void __user *)-1L;
 165
 166         return (void __user *)sp;
 167 }
 168
 169 /* grab and setup a signal frame.
 170  *
 171  * basically we stack a lot of state info, and arrange for the
 172  * user-mode program to return to the kernel using either a
 173  * trampoline which performs the syscall sigreturn, or a provided
 174  * user-mode trampoline.
 175  */
 176 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 177                           sigset_t *set, struct pt_regs *regs)
 178 {
 179         struct rt_sigframe *frame;
 180         unsigned long return_ip;
 181         int err = 0;
 182
 183         frame = get_sigframe(ka, regs, sizeof(*frame));
 184
 185         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 186                 goto give_sigsegv;
 187
 188         err |= __put_user(&frame->info, &frame->pinfo);
 189         err |= __put_user(&frame->uc, &frame->puc);
 190
 191         if (ka->sa.sa_flags & SA_SIGINFO)
 192                 err |= copy_siginfo_to_user(&frame->info, info);
 193         if (err)
 194                 goto give_sigsegv;
 195
 196         /* Clear all the bits of the ucontext we don't use.  */
 197         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
 198         err |= __put_user(0, &frame->uc.uc_flags);
 199         err |= __put_user(NULL, &frame->uc.uc_link);
 200         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 201         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
 202
 203         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 204
 205         if (err)
 206                 goto give_sigsegv;
 207
 208         /* trampoline - the desired return ip is the retcode itself */
 209         return_ip = (unsigned long)&frame->retcode;
 210         /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
 211         err |= __put_user(0xa960, (short *)(frame->retcode + 0));
 212         err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
 213         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 214         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 215
 216         if (err)
 217                 goto give_sigsegv;
 218
 219         /* TODO what is the current->exec_domain stuff and invmap ? */
 220
 221         /* Set up registers for signal handler */
 222         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 223         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 224         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 225         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 226         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 227
 228         /* actually move the usp to reflect the stacked frame */
 229         regs->sp = (unsigned long)frame;
 230
 231         return 0;
 232
 233 give_sigsegv:
 234         force_sigsegv(sig, current);
 235         return -EFAULT;
 236 }
 237
 238 static inline void
 239 handle_signal(unsigned long sig,
 240               siginfo_t *info, struct k_sigaction *ka,
 241               struct pt_regs *regs)
 242 {
 243         int ret;
 244
 245         ret = setup_rt_frame(sig, ka, info, sigmask_to_save(), regs);
 246         if (ret)
 247                 return;
 248
 249         signal_delivered(sig, info, ka, regs,
 250                                  test_thread_flag(TIF_SINGLESTEP));
 251 }
 252
 253 /*
 254  * Note that 'init' is a special process: it doesn't get signals it doesn't
 255  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 256  * mistake.
 257  *
 258  * Also note that the regs structure given here as an argument, is the latest
 259  * pushed pt_regs. It may or may not be the same as the first pushed registers
 260  * when the initial usermode->kernelmode transition took place. Therefore
 261  * we can use user_mode(regs) to see if we came directly from kernel or user
 262  * mode below.
 263  */
 264
 265 void do_signal(struct pt_regs *regs)
 266 {
 267         siginfo_t info;
 268         int signr;
 269         struct k_sigaction ka;
 270
 271         /*
 272          * We want the common case to go fast, which
 273          * is why we may in certain cases get here from
 274          * kernel mode. Just return without doing anything
 275          * if so.
 276          */
 277         if (!user_mode(regs))
 278                 return;
 279
 280         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 281
 282         /* If we are coming out of a syscall then we need
 283          * to check if the syscall was interrupted and wants to be
 284          * restarted after handling the signal.  If so, the original
 285          * syscall number is put back into r11 and the PC rewound to
 286          * point at the l.sys instruction that resulted in the
 287          * original syscall.  Syscall results other than the four
 288          * below mean that the syscall executed to completion and no
 289          * restart is necessary.
 290          */
 291         if (regs->orig_gpr11) {
 292                 int restart = 0;
 293
 294                 switch (regs->gpr[11]) {
 295                 case -ERESTART_RESTARTBLOCK:
 296                 case -ERESTARTNOHAND:
 297                         /* Restart if there is no signal handler */
 298                         restart = (signr <= 0);
 299                         break;
 300                 case -ERESTARTSYS:
 301                         /* Restart if there no signal handler or
 302                          * SA_RESTART flag is set */
 303                         restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
 304                         break;
 305                 case -ERESTARTNOINTR:
 306                         /* Always restart */
 307                         restart = 1;
 308                         break;
 309                 }
 310
 311                 if (restart) {
 312                         if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
 313                                 regs->gpr[11] = __NR_restart_syscall;
 314                         else
 315                                 regs->gpr[11] = regs->orig_gpr11;
 316                         regs->pc -= 4;
 317                 } else {
 318                         regs->gpr[11] = -EINTR;
 319                 }
 320         }
 321
 322         if (signr <= 0) {
 323                 /* no signal to deliver so we just put the saved sigmask
 324                  * back */
 325                 restore_saved_sigmask();
 326         } else {                /* signr > 0 */
 327                 /* Whee!  Actually deliver the signal.  */
 328                 handle_signal(signr, &info, &ka, regs);
 329         }
 330
 331         return;
 332 }
 333
 334 asmlinkage void do_notify_resume(struct pt_regs *regs)
 335 {
 336         if (current_thread_info()->flags & _TIF_SIGPENDING)
 337                 do_signal(regs);
 338
 339         if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
 340                 clear_thread_flag(TIF_NOTIFY_RESUME);
 341                 tracehook_notify_resume(regs);
 342         }
 343 }