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/syscall.h>
  32 #include <asm/ucontext.h>
  33 #include <asm/uaccess.h>
  34
  35 #define DEBUG_SIG 0
  36
  37 struct rt_sigframe {
  38         struct siginfo info;
  39         struct ucontext uc;
  40         unsigned char retcode[16];      /* trampoline code */
  41 };
  42
  43 static int restore_sigcontext(struct pt_regs *regs,
  44                               struct sigcontext __user *sc)
  45 {
  46         int err = 0;
  47
  48         /* Always make any pending restarted system calls 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         err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
  57         err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
  58         err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
  59
  60         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  61         regs->sr &= ~SPR_SR_SM;
  62
  63         regs->orig_gpr11 = -1;  /* Avoid syscall restart checks */
  64
  65         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  66          * after this completes, but we don't use that mechanism. maybe we can
  67          * use it now ?
  68          */
  69
  70         return err;
  71 }
  72
  73 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
  74 {
  75         struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
  76         sigset_t set;
  77
  78         /*
  79          * Since we stacked the signal on a dword boundary,
  80          * then frame should be dword aligned here.  If it's
  81          * not, then the user is trying to mess with us.
  82          */
  83         if (((long)frame) & 3)
  84                 goto badframe;
  85
  86         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  87                 goto badframe;
  88         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  89                 goto badframe;
  90
  91         set_current_blocked(&set);
  92
  93         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
  94                 goto badframe;
  95
  96         if (restore_altstack(&frame->uc.uc_stack))
  97                 goto badframe;
  98
  99         return regs->gpr[11];
 100
 101 badframe:
 102         force_sig(SIGSEGV, current);
 103         return 0;
 104 }
 105
 106 /*
 107  * Set up a signal frame.
 108  */
 109
 110 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 111 {
 112         int err = 0;
 113
 114         /* copy the regs */
 115         /* There should be no need to save callee-saved registers here...
 116          * ...but we save them anyway.  Revisit this
 117          */
 118         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 119         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 120         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 121
 122         return err;
 123 }
 124
 125 static inline unsigned long align_sigframe(unsigned long sp)
 126 {
 127         return sp & ~3UL;
 128 }
 129
 130 /*
 131  * Work out where the signal frame should go.  It's either on the user stack
 132  * or the alternate stack.
 133  */
 134
 135 static inline void __user *get_sigframe(struct k_sigaction *ka,
 136                                         struct pt_regs *regs, size_t frame_size)
 137 {
 138         unsigned long sp = regs->sp;
 139         int onsigstack = on_sig_stack(sp);
 140
 141         /* redzone */
 142         sp -= STACK_FRAME_OVERHEAD;
 143
 144         /* This is the X/Open sanctioned signal stack switching.  */
 145         if ((ka->sa.sa_flags & SA_ONSTACK) && !onsigstack) {
 146                 if (current->sas_ss_size)
 147                         sp = current->sas_ss_sp + current->sas_ss_size;
 148         }
 149
 150         sp = align_sigframe(sp - frame_size);
 151
 152         /*
 153          * If we are on the alternate signal stack and would overflow it, don't.
 154          * Return an always-bogus address instead so we will die with SIGSEGV.
 155          */
 156         if (onsigstack && !likely(on_sig_stack(sp)))
 157                 return (void __user *)-1L;
 158
 159         return (void __user *)sp;
 160 }
 161
 162 /* grab and setup a signal frame.
 163  *
 164  * basically we stack a lot of state info, and arrange for the
 165  * user-mode program to return to the kernel using either a
 166  * trampoline which performs the syscall sigreturn, or a provided
 167  * user-mode trampoline.
 168  */
 169 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 170                           sigset_t *set, struct pt_regs *regs)
 171 {
 172         struct rt_sigframe *frame;
 173         unsigned long return_ip;
 174         int err = 0;
 175
 176         frame = get_sigframe(ka, regs, sizeof(*frame));
 177         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 178                 goto give_sigsegv;
 179
 180         /* Create siginfo.  */
 181         if (ka->sa.sa_flags & SA_SIGINFO)
 182                 err |= copy_siginfo_to_user(&frame->info, info);
 183
 184         /* Create the ucontext.  */
 185         err |= __put_user(0, &frame->uc.uc_flags);
 186         err |= __put_user(NULL, &frame->uc.uc_link);
 187         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 188         err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
 189
 190         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 191
 192         if (err)
 193                 goto give_sigsegv;
 194
 195         /* trampoline - the desired return ip is the retcode itself */
 196         return_ip = (unsigned long)&frame->retcode;
 197         /* This is:
 198                 l.ori r11,r0,__NR_sigreturn
 199                 l.sys 1
 200          */
 201         err |= __put_user(0xa960,             (short *)(frame->retcode + 0));
 202         err |= __put_user(__NR_rt_sigreturn,  (short *)(frame->retcode + 2));
 203         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 204         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 205
 206         if (err)
 207                 goto give_sigsegv;
 208
 209         /* TODO what is the current->exec_domain stuff and invmap ? */
 210
 211         /* Set up registers for signal handler */
 212         regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
 213         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 214         regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
 215         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 216         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 217
 218         /* actually move the usp to reflect the stacked frame */
 219         regs->sp = (unsigned long)frame;
 220
 221         return 0;
 222
 223 give_sigsegv:
 224         force_sigsegv(sig, current);
 225         return -EFAULT;
 226 }
 227
 228 static inline void
 229 handle_signal(unsigned long sig,
 230               siginfo_t *info, struct k_sigaction *ka,
 231               struct pt_regs *regs)
 232 {
 233         int ret;
 234
 235         ret = setup_rt_frame(sig, ka, info, sigmask_to_save(), regs);
 236         if (ret)
 237                 return;
 238
 239         signal_delivered(sig, info, ka, regs,
 240                                  test_thread_flag(TIF_SINGLESTEP));
 241 }
 242
 243 /*
 244  * Note that 'init' is a special process: it doesn't get signals it doesn't
 245  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 246  * mistake.
 247  *
 248  * Also note that the regs structure given here as an argument, is the latest
 249  * pushed pt_regs. It may or may not be the same as the first pushed registers
 250  * when the initial usermode->kernelmode transition took place. Therefore
 251  * we can use user_mode(regs) to see if we came directly from kernel or user
 252  * mode below.
 253  */
 254
 255 int do_signal(struct pt_regs *regs, int syscall)
 256 {
 257         siginfo_t info;
 258         int signr;
 259         struct k_sigaction ka;
 260         unsigned long continue_addr = 0;
 261         unsigned long restart_addr = 0;
 262         unsigned long retval = 0;
 263         int restart = 0;
 264
 265         if (syscall) {
 266                 continue_addr = regs->pc;
 267                 restart_addr = continue_addr - 4;
 268                 retval = regs->gpr[11];
 269
 270                 /*
 271                  * Setup syscall restart here so that a debugger will
 272                  * see the already changed PC.
 273                  */
 274                 switch (retval) {
 275                 case -ERESTART_RESTARTBLOCK:
 276                         restart = -2;
 277                         /* Fall through */
 278                 case -ERESTARTNOHAND:
 279                 case -ERESTARTSYS:
 280                 case -ERESTARTNOINTR:
 281                         restart++;
 282                         regs->gpr[11] = regs->orig_gpr11;
 283                         regs->pc = restart_addr;
 284                         break;
 285                 }
 286         }
 287
 288         /*
 289          * Get the signal to deliver.  When running under ptrace, at this
 290          * point the debugger may change all our registers ...
 291          */
 292         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 293         /*
 294          * Depending on the signal settings we may need to revert the
 295          * decision to restart the system call.  But skip this if a
 296          * debugger has chosen to restart at a different PC.
 297          */
 298         if (signr > 0) {
 299                 if (unlikely(restart) && regs->pc == restart_addr) {
 300                         if (retval == -ERESTARTNOHAND ||
 301                             retval == -ERESTART_RESTARTBLOCK
 302                             || (retval == -ERESTARTSYS
 303                                 && !(ka.sa.sa_flags & SA_RESTART))) {
 304                                 /* No automatic restart */
 305                                 regs->gpr[11] = -EINTR;
 306                                 regs->pc = continue_addr;
 307                         }
 308                 }
 309
 310                 handle_signal(signr, &info, &ka, regs);
 311         } else {
 312                 /* no handler */
 313                 restore_saved_sigmask();
 314                 /*
 315                  * Restore pt_regs PC as syscall restart will be handled by
 316                  * kernel without return to userspace
 317                  */
 318                 if (unlikely(restart) && regs->pc == restart_addr) {
 319                         regs->pc = continue_addr;
 320                         return restart;
 321                 }
 322         }
 323
 324         return 0;
 325 }
 326
 327 asmlinkage int
 328 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 329 {
 330         do {
 331                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 332                         schedule();
 333                 } else {
 334                         if (unlikely(!user_mode(regs)))
 335                                 return 0;
 336                         local_irq_enable();
 337                         if (thread_flags & _TIF_SIGPENDING) {
 338                                 int restart = do_signal(regs, syscall);
 339                                 if (unlikely(restart)) {
 340                                         /*
 341                                          * Restart without handlers.
 342                                          * Deal with it without leaving
 343                                          * the kernel space.
 344                                          */
 345                                         return restart;
 346                                 }
 347                                 syscall = 0;
 348                         } else {
 349                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 350                                 tracehook_notify_resume(regs);
 351                         }
 352                 }
 353                 local_irq_disable();
 354                 thread_flags = current_thread_info()->flags;
 355         } while (thread_flags & _TIF_WORK_MASK);
 356         return 0;
 357 }