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/uprobes.h>
  15 #include <linux/key.h>
  16 #include <linux/context_tracking.h>
  17 #include <asm/hw_breakpoint.h>
  18 #include <asm/uaccess.h>
  19 #include <asm/unistd.h>
  20 #include <asm/debug.h>
  21 #include <asm/tm.h>
  22
  23 #include "signal.h"
  24
  25 /* Log an error when sending an unhandled signal to a process. Controlled
  26  * through debug.exception-trace sysctl.
  27  */
  28
  29 int show_unhandled_signals = 1;
  30
  31 /*
  32  * Allocate space for the signal frame
  33  */
  34 void __user * get_sigframe(struct k_sigaction *ka, unsigned long sp,
  35                            size_t frame_size, int is_32)
  36 {
  37         unsigned long oldsp, newsp;
  38
  39         /* Default to using normal stack */
  40         oldsp = get_clean_sp(sp, is_32);
  41
  42         /* Check for alt stack */
  43         if ((ka->sa.sa_flags & SA_ONSTACK) &&
  44             current->sas_ss_size && !on_sig_stack(oldsp))
  45                 oldsp = (current->sas_ss_sp + current->sas_ss_size);
  46
  47         /* Get aligned frame */
  48         newsp = (oldsp - frame_size) & ~0xFUL;
  49
  50         /* Check access */
  51         if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
  52                 return NULL;
  53
  54         return (void __user *)newsp;
  55 }
  56
  57 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  58                                   int has_handler)
  59 {
  60         unsigned long ret = regs->gpr[3];
  61         int restart = 1;
  62
  63         /* syscall ? */
  64         if (TRAP(regs) != 0x0C00)
  65                 return;
  66
  67         /* error signalled ? */
  68         if (!(regs->ccr & 0x10000000))
  69                 return;
  70
  71         switch (ret) {
  72         case ERESTART_RESTARTBLOCK:
  73         case ERESTARTNOHAND:
  74                 /* ERESTARTNOHAND means that the syscall should only be
  75                  * restarted if there was no handler for the signal, and since
  76                  * we only get here if there is a handler, we dont restart.
  77                  */
  78                 restart = !has_handler;
  79                 break;
  80         case ERESTARTSYS:
  81                 /* ERESTARTSYS means to restart the syscall if there is no
  82                  * handler or the handler was registered with SA_RESTART
  83                  */
  84                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  85                 break;
  86         case ERESTARTNOINTR:
  87                 /* ERESTARTNOINTR means that the syscall should be
  88                  * called again after the signal handler returns.
  89                  */
  90                 break;
  91         default:
  92                 return;
  93         }
  94         if (restart) {
  95                 if (ret == ERESTART_RESTARTBLOCK)
  96                         regs->gpr[0] = __NR_restart_syscall;
  97                 else
  98                         regs->gpr[3] = regs->orig_gpr3;
  99                 regs->nip -= 4;
 100                 regs->result = 0;
 101         } else {
 102                 regs->result = -EINTR;
 103                 regs->gpr[3] = EINTR;
 104                 regs->ccr |= 0x10000000;
 105         }
 106 }
 107
 108 static int do_signal(struct pt_regs *regs)
 109 {
 110         sigset_t *oldset = sigmask_to_save();
 111         siginfo_t info;
 112         int signr;
 113         struct k_sigaction ka;
 114         int ret;
 115         int is32 = is_32bit_task();
 116
 117         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 118
 119         /* Is there any syscall restart business here ? */
 120         check_syscall_restart(regs, &ka, signr > 0);
 121
 122         if (signr <= 0) {
 123                 /* No signal to deliver -- put the saved sigmask back */
 124                 restore_saved_sigmask();
 125                 regs->trap = 0;
 126                 return 0;               /* no signals delivered */
 127         }
 128
 129 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 130         /*
 131          * Reenable the DABR before delivering the signal to
 132          * user space. The DABR will have been cleared if it
 133          * triggered inside the kernel.
 134          */
 135         if (current->thread.hw_brk.address &&
 136                 current->thread.hw_brk.type)
 137                 set_breakpoint(&current->thread.hw_brk);
 138 #endif
 139         /* Re-enable the breakpoints for the signal stack */
 140         thread_change_pc(current, regs);
 141
 142         if (is32) {
 143                 if (ka.sa.sa_flags & SA_SIGINFO)
 144                         ret = handle_rt_signal32(signr, &ka, &info, oldset,
 145                                         regs);
 146                 else
 147                         ret = handle_signal32(signr, &ka, &info, oldset,
 148                                         regs);
 149         } else {
 150                 ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);
 151         }
 152
 153         regs->trap = 0;
 154         if (ret) {
 155                 signal_delivered(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         user_exit();
 165
 166         if (thread_info_flags & _TIF_UPROBE)
 167                 uprobe_notify_resume(regs);
 168
 169         if (thread_info_flags & _TIF_SIGPENDING)
 170                 do_signal(regs);
 171
 172         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 173                 clear_thread_flag(TIF_NOTIFY_RESUME);
 174                 tracehook_notify_resume(regs);
 175         }
 176
 177         user_enter();
 178 }
 179
 180 unsigned long get_tm_stackpointer(struct pt_regs *regs)
 181 {
 182         /* When in an active transaction that takes a signal, we need to be
 183          * careful with the stack.  It's possible that the stack has moved back
 184          * up after the tbegin.  The obvious case here is when the tbegin is
 185          * called inside a function that returns before a tend.  In this case,
 186          * the stack is part of the checkpointed transactional memory state.
 187          * If we write over this non transactionally or in suspend, we are in
 188          * trouble because if we get a tm abort, the program counter and stack
 189          * pointer will be back at the tbegin but our in memory stack won't be
 190          * valid anymore.
 191          *
 192          * To avoid this, when taking a signal in an active transaction, we
 193          * need to use the stack pointer from the checkpointed state, rather
 194          * than the speculated state.  This ensures that the signal context
 195          * (written tm suspended) will be written below the stack required for
 196          * the rollback.  The transaction is aborted becuase of the treclaim,
 197          * so any memory written between the tbegin and the signal will be
 198          * rolled back anyway.
 199          *
 200          * For signals taken in non-TM or suspended mode, we use the
 201          * normal/non-checkpointed stack pointer.
 202          */
 203
 204 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 205         if (MSR_TM_ACTIVE(regs->msr)) {
 206                 tm_enable();
 207                 tm_reclaim(&current->thread, regs->msr, TM_CAUSE_SIGNAL);
 208                 if (MSR_TM_TRANSACTIONAL(regs->msr))
 209                         return current->thread.ckpt_regs.gpr[1];
 210         }
 211 #endif
 212         return regs->gpr[1];
 213 }