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 <linux/key.h>
  15 #include <asm/hw_breakpoint.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/unistd.h>
  18 #include <asm/debug.h>
  19
  20 #include "signal.h"
  21
  22 /* Log an error when sending an unhandled signal to a process. Controlled
  23  * through debug.exception-trace sysctl.
  24  */
  25
  26 int show_unhandled_signals = 0;
  27
  28 /*
  29  * Allocate space for the signal frame
  30  */
  31 void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
  32                            size_t frame_size, int is_32)
  33 {
  34         unsigned long oldsp, newsp;
  35
  36         /* Default to using normal stack */
  37         oldsp = get_clean_sp(regs, is_32);
  38
  39         /* Check for alt stack */
  40         if ((ka->sa.sa_flags & SA_ONSTACK) &&
  41             current->sas_ss_size && !on_sig_stack(oldsp))
  42                 oldsp = (current->sas_ss_sp + current->sas_ss_size);
  43
  44         /* Get aligned frame */
  45         newsp = (oldsp - frame_size) & ~0xFUL;
  46
  47         /* Check access */
  48         if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
  49                 return NULL;
  50
  51         return (void __user *)newsp;
  52 }
  53
  54 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  55                                   int has_handler)
  56 {
  57         unsigned long ret = regs->gpr[3];
  58         int restart = 1;
  59
  60         /* syscall ? */
  61         if (TRAP(regs) != 0x0C00)
  62                 return;
  63
  64         /* error signalled ? */
  65         if (!(regs->ccr & 0x10000000))
  66                 return;
  67
  68         switch (ret) {
  69         case ERESTART_RESTARTBLOCK:
  70         case ERESTARTNOHAND:
  71                 /* ERESTARTNOHAND means that the syscall should only be
  72                  * restarted if there was no handler for the signal, and since
  73                  * we only get here if there is a handler, we dont restart.
  74                  */
  75                 restart = !has_handler;
  76                 break;
  77         case ERESTARTSYS:
  78                 /* ERESTARTSYS means to restart the syscall if there is no
  79                  * handler or the handler was registered with SA_RESTART
  80                  */
  81                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  82                 break;
  83         case ERESTARTNOINTR:
  84                 /* ERESTARTNOINTR means that the syscall should be
  85                  * called again after the signal handler returns.
  86                  */
  87                 break;
  88         default:
  89                 return;
  90         }
  91         if (restart) {
  92                 if (ret == ERESTART_RESTARTBLOCK)
  93                         regs->gpr[0] = __NR_restart_syscall;
  94                 else
  95                         regs->gpr[3] = regs->orig_gpr3;
  96                 regs->nip -= 4;
  97                 regs->result = 0;
  98         } else {
  99                 regs->result = -EINTR;
 100                 regs->gpr[3] = EINTR;
 101                 regs->ccr |= 0x10000000;
 102         }
 103 }
 104
 105 static int do_signal(struct pt_regs *regs)
 106 {
 107         sigset_t *oldset = sigmask_to_save();
 108         siginfo_t info;
 109         int signr;
 110         struct k_sigaction ka;
 111         int ret;
 112         int is32 = is_32bit_task();
 113
 114         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 115
 116         /* Is there any syscall restart business here ? */
 117         check_syscall_restart(regs, &ka, signr > 0);
 118
 119         if (signr <= 0) {
 120                 /* No signal to deliver -- put the saved sigmask back */
 121                 restore_saved_sigmask();
 122                 regs->trap = 0;
 123                 return 0;               /* no signals delivered */
 124         }
 125
 126 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 127         /*
 128          * Reenable the DABR before delivering the signal to
 129          * user space. The DABR will have been cleared if it
 130          * triggered inside the kernel.
 131          */
 132         if (current->thread.dabr)
 133                 set_dabr(current->thread.dabr);
 134 #endif
 135         /* Re-enable the breakpoints for the signal stack */
 136         thread_change_pc(current, regs);
 137
 138         if (is32) {
 139                 if (ka.sa.sa_flags & SA_SIGINFO)
 140                         ret = handle_rt_signal32(signr, &ka, &info, oldset,
 141                                         regs);
 142                 else
 143                         ret = handle_signal32(signr, &ka, &info, oldset,
 144                                         regs);
 145         } else {
 146                 ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);
 147         }
 148
 149         regs->trap = 0;
 150         if (ret) {
 151                 block_sigmask(&ka, signr);
 152                 /*
 153                  * Let tracing know that we've done the handler setup.
 154                  */
 155                 tracehook_signal_handler(signr, &info, &ka, regs,
 156                                          test_thread_flag(TIF_SINGLESTEP));
 157         }
 158
 159         return ret;
 160 }
 161
 162 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 163 {
 164         if (thread_info_flags & _TIF_SIGPENDING)
 165                 do_signal(regs);
 166
 167         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 168                 clear_thread_flag(TIF_NOTIFY_RESUME);
 169                 tracehook_notify_resume(regs);
 170         }
 171 }
 172
 173 long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
 174                 unsigned long r5, unsigned long r6, unsigned long r7,
 175                 unsigned long r8, struct pt_regs *regs)
 176 {
 177         return do_sigaltstack(uss, uoss, regs->gpr[1]);
 178 }