arch/powerpc/kernel/signal.c

   1 /*
   2  * Common signal handling code for both 32 and 64 bits
   3  *
   4  *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
   5  *    Extracted from signal_32.c and signal_64.c
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file README.legal in the main directory of
   9  * this archive for more details.
  10  */
  11
  12 #include <linux/tracehook.h>
  13 #include <linux/signal.h>
  14 #include <asm/hw_breakpoint.h>
  15 #include <asm/uaccess.h>
  16 #include <asm/unistd.h>
  17
  18 #include "signal.h"
  19
  20 /* Log an error when sending an unhandled signal to a process. Controlled
  21  * through debug.exception-trace sysctl.
  22  */
  23
  24 int show_unhandled_signals = 0;
  25
  26 /*
  27  * Allocate space for the signal frame
  28  */
  29 void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
  30                            size_t frame_size, int is_32)
  31 {
  32         unsigned long oldsp, newsp;
  33
  34         /* Default to using normal stack */
  35         oldsp = get_clean_sp(regs, is_32);
  36
  37         /* Check for alt stack */
  38         if ((ka->sa.sa_flags & SA_ONSTACK) &&
  39             current->sas_ss_size && !on_sig_stack(oldsp))
  40                 oldsp = (current->sas_ss_sp + current->sas_ss_size);
  41
  42         /* Get aligned frame */
  43         newsp = (oldsp - frame_size) & ~0xFUL;
  44
  45         /* Check access */
  46         if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
  47                 return NULL;
  48
  49         return (void __user *)newsp;
  50 }
  51
  52
  53 /*
  54  * Restore the user process's signal mask
  55  */
  56 void restore_sigmask(sigset_t *set)
  57 {
  58         sigdelsetmask(set, ~_BLOCKABLE);
  59         set_current_blocked(set);
  60 }
  61
  62 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  63                                   int has_handler)
  64 {
  65         unsigned long ret = regs->gpr[3];
  66         int restart = 1;
  67
  68         /* syscall ? */
  69         if (TRAP(regs) != 0x0C00)
  70                 return;
  71
  72         /* error signalled ? */
  73         if (!(regs->ccr & 0x10000000))
  74                 return;
  75
  76         switch (ret) {
  77         case ERESTART_RESTARTBLOCK:
  78         case ERESTARTNOHAND:
  79                 /* ERESTARTNOHAND means that the syscall should only be
  80                  * restarted if there was no handler for the signal, and since
  81                  * we only get here if there is a handler, we dont restart.
  82                  */
  83                 restart = !has_handler;
  84                 break;
  85         case ERESTARTSYS:
  86                 /* ERESTARTSYS means to restart the syscall if there is no
  87                  * handler or the handler was registered with SA_RESTART
  88                  */
  89                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  90                 break;
  91         case ERESTARTNOINTR:
  92                 /* ERESTARTNOINTR means that the syscall should be
  93                  * called again after the signal handler returns.
  94                  */
  95                 break;
  96         default:
  97                 return;
  98         }
  99         if (restart) {
 100                 if (ret == ERESTART_RESTARTBLOCK)
 101                         regs->gpr[0] = __NR_restart_syscall;
 102                 else
 103                         regs->gpr[3] = regs->orig_gpr3;
 104                 regs->nip -= 4;
 105                 regs->result = 0;
 106         } else {
 107                 regs->result = -EINTR;
 108                 regs->gpr[3] = EINTR;
 109                 regs->ccr |= 0x10000000;
 110         }
 111 }
 112
 113 static int do_signal_pending(sigset_t *oldset, struct pt_regs *regs)
 114 {
 115         siginfo_t info;
 116         int signr;
 117         struct k_sigaction ka;
 118         int ret;
 119         int is32 = is_32bit_task();
 120
 121         if (current_thread_info()->local_flags & _TLF_RESTORE_SIGMASK)
 122                 oldset = &current->saved_sigmask;
 123         else if (!oldset)
 124                 oldset = &current->blocked;
 125
 126         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 127
 128         /* Is there any syscall restart business here ? */
 129         check_syscall_restart(regs, &ka, signr > 0);
 130
 131         if (signr <= 0) {
 132                 struct thread_info *ti = current_thread_info();
 133                 /* No signal to deliver -- put the saved sigmask back */
 134                 if (ti->local_flags & _TLF_RESTORE_SIGMASK) {
 135                         ti->local_flags &= ~_TLF_RESTORE_SIGMASK;
 136                         sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 137                 }
 138                 regs->trap = 0;
 139                 return 0;               /* no signals delivered */
 140         }
 141
 142 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 143         /*
 144          * Reenable the DABR before delivering the signal to
 145          * user space. The DABR will have been cleared if it
 146          * triggered inside the kernel.
 147          */
 148         if (current->thread.dabr)
 149                 set_dabr(current->thread.dabr);
 150 #endif
 151         /* Re-enable the breakpoints for the signal stack */
 152         thread_change_pc(current, regs);
 153
 154         if (is32) {
 155                 if (ka.sa.sa_flags & SA_SIGINFO)
 156                         ret = handle_rt_signal32(signr, &ka, &info, oldset,
 157                                         regs);
 158                 else
 159                         ret = handle_signal32(signr, &ka, &info, oldset,
 160                                         regs);
 161         } else {
 162                 ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);
 163         }
 164
 165         regs->trap = 0;
 166         if (ret) {
 167                 block_sigmask(&ka, signr);
 168
 169                 /*
 170                  * A signal was successfully delivered; the saved sigmask is in
 171                  * its frame, and we can clear the TLF_RESTORE_SIGMASK flag.
 172                  */
 173                 current_thread_info()->local_flags &= ~_TLF_RESTORE_SIGMASK;
 174
 175                 /*
 176                  * Let tracing know that we've done the handler setup.
 177                  */
 178                 tracehook_signal_handler(signr, &info, &ka, regs,
 179                                          test_thread_flag(TIF_SINGLESTEP));
 180         }
 181
 182         return ret;
 183 }
 184
 185 void do_signal(struct pt_regs *regs, unsigned long thread_info_flags)
 186 {
 187         if (thread_info_flags & _TIF_SIGPENDING)
 188                 do_signal_pending(NULL, regs);
 189
 190         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 191                 clear_thread_flag(TIF_NOTIFY_RESUME);
 192                 tracehook_notify_resume(regs);
 193         }
 194 }
 195
 196 long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
 197                 unsigned long r5, unsigned long r6, unsigned long r7,
 198                 unsigned long r8, struct pt_regs *regs)
 199 {
 200         return do_sigaltstack(uss, uoss, regs->gpr[1]);
 201 }