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 <linux/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->restart_block.fn = do_no_restart_syscall;
  50
  51         /*
  52          * Restore the regs from &sc->regs.
  53          * (sc is already checked 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(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 ksignal *ksig,
 136                                         struct pt_regs *regs, size_t frame_size)
 137 {
 138         unsigned long sp = regs->sp;
 139
 140         /* redzone */
 141         sp -= STACK_FRAME_OVERHEAD;
 142         sp = sigsp(sp, ksig);
 143         sp = align_sigframe(sp - frame_size);
 144
 145         return (void __user *)sp;
 146 }
 147
 148 /* grab and setup a signal frame.
 149  *
 150  * basically we stack a lot of state info, and arrange for the
 151  * user-mode program to return to the kernel using either a
 152  * trampoline which performs the syscall sigreturn, or a provided
 153  * user-mode trampoline.
 154  */
 155 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 156                           struct pt_regs *regs)
 157 {
 158         struct rt_sigframe *frame;
 159         unsigned long return_ip;
 160         int err = 0;
 161
 162         frame = get_sigframe(ksig, regs, sizeof(*frame));
 163
 164         if (!access_ok(frame, sizeof(*frame)))
 165                 return -EFAULT;
 166
 167         /* Create siginfo.  */
 168         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 169                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 170
 171         /* Create the ucontext.  */
 172         err |= __put_user(0, &frame->uc.uc_flags);
 173         err |= __put_user(NULL, &frame->uc.uc_link);
 174         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 175         err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
 176
 177         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 178
 179         if (err)
 180                 return -EFAULT;
 181
 182         /* trampoline - the desired return ip is the retcode itself */
 183         return_ip = (unsigned long)&frame->retcode;
 184         /* This is:
 185                 l.ori r11,r0,__NR_sigreturn
 186                 l.sys 1
 187          */
 188         err |= __put_user(0xa960,             (short *)(frame->retcode + 0));
 189         err |= __put_user(__NR_rt_sigreturn,  (short *)(frame->retcode + 2));
 190         err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
 191         err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));
 192
 193         if (err)
 194                 return -EFAULT;
 195
 196         /* Set up registers for signal handler */
 197         regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
 198         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 199         regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
 200         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 201         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 202
 203         /* actually move the usp to reflect the stacked frame */
 204         regs->sp = (unsigned long)frame;
 205
 206         return 0;
 207 }
 208
 209 static inline void
 210 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 211 {
 212         int ret;
 213
 214         ret = setup_rt_frame(ksig, sigmask_to_save(), regs);
 215
 216         signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
 217 }
 218
 219 /*
 220  * Note that 'init' is a special process: it doesn't get signals it doesn't
 221  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 222  * mistake.
 223  *
 224  * Also note that the regs structure given here as an argument, is the latest
 225  * pushed pt_regs. It may or may not be the same as the first pushed registers
 226  * when the initial usermode->kernelmode transition took place. Therefore
 227  * we can use user_mode(regs) to see if we came directly from kernel or user
 228  * mode below.
 229  */
 230
 231 int do_signal(struct pt_regs *regs, int syscall)
 232 {
 233         struct ksignal ksig;
 234         unsigned long continue_addr = 0;
 235         unsigned long restart_addr = 0;
 236         unsigned long retval = 0;
 237         int restart = 0;
 238
 239         if (syscall) {
 240                 continue_addr = regs->pc;
 241                 restart_addr = continue_addr - 4;
 242                 retval = regs->gpr[11];
 243
 244                 /*
 245                  * Setup syscall restart here so that a debugger will
 246                  * see the already changed PC.
 247                  */
 248                 switch (retval) {
 249                 case -ERESTART_RESTARTBLOCK:
 250                         restart = -2;
 251                         /* Fall through */
 252                 case -ERESTARTNOHAND:
 253                 case -ERESTARTSYS:
 254                 case -ERESTARTNOINTR:
 255                         restart++;
 256                         regs->gpr[11] = regs->orig_gpr11;
 257                         regs->pc = restart_addr;
 258                         break;
 259                 }
 260         }
 261
 262         /*
 263          * Get the signal to deliver.  During the call to get_signal the
 264          * debugger may change all our registers so we may need to revert
 265          * the decision to restart the syscall; specifically, if the PC is
 266          * changed, don't restart the syscall.
 267          */
 268         if (get_signal(&ksig)) {
 269                 if (unlikely(restart) && regs->pc == restart_addr) {
 270                         if (retval == -ERESTARTNOHAND ||
 271                             retval == -ERESTART_RESTARTBLOCK
 272                             || (retval == -ERESTARTSYS
 273                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 274                                 /* No automatic restart */
 275                                 regs->gpr[11] = -EINTR;
 276                                 regs->pc = continue_addr;
 277                         }
 278                 }
 279                 handle_signal(&ksig, regs);
 280         } else {
 281                 /* no handler */
 282                 restore_saved_sigmask();
 283                 /*
 284                  * Restore pt_regs PC as syscall restart will be handled by
 285                  * kernel without return to userspace
 286                  */
 287                 if (unlikely(restart) && regs->pc == restart_addr) {
 288                         regs->pc = continue_addr;
 289                         return restart;
 290                 }
 291         }
 292
 293         return 0;
 294 }
 295
 296 asmlinkage int
 297 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 298 {
 299         do {
 300                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 301                         schedule();
 302                 } else {
 303                         if (unlikely(!user_mode(regs)))
 304                                 return 0;
 305                         local_irq_enable();
 306                         if (thread_flags & _TIF_SIGPENDING) {
 307                                 int restart = do_signal(regs, syscall);
 308                                 if (unlikely(restart)) {
 309                                         /*
 310                                          * Restart without handlers.
 311                                          * Deal with it without leaving
 312                                          * the kernel space.
 313                                          */
 314                                         return restart;
 315                                 }
 316                                 syscall = 0;
 317                         } else {
 318                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 319                                 tracehook_notify_resume(regs);
 320                         }
 321                 }
 322                 local_irq_disable();
 323                 thread_flags = current_thread_info()->flags;
 324         } while (thread_flags & _TIF_WORK_MASK);
 325         return 0;
 326 }