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 ksignal *ksig, 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         oldsp = sigsp(oldsp, ksig);
  42         newsp = (oldsp - frame_size) & ~0xFUL;
  43
  44         /* Check access */
  45         if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
  46                 return NULL;
  47
  48         return (void __user *)newsp;
  49 }
  50
  51 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  52                                   int has_handler)
  53 {
  54         unsigned long ret = regs->gpr[3];
  55         int restart = 1;
  56
  57         /* syscall ? */
  58         if (TRAP(regs) != 0x0C00)
  59                 return;
  60
  61         /* error signalled ? */
  62         if (!(regs->ccr & 0x10000000))
  63                 return;
  64
  65         switch (ret) {
  66         case ERESTART_RESTARTBLOCK:
  67         case ERESTARTNOHAND:
  68                 /* ERESTARTNOHAND means that the syscall should only be
  69                  * restarted if there was no handler for the signal, and since
  70                  * we only get here if there is a handler, we dont restart.
  71                  */
  72                 restart = !has_handler;
  73                 break;
  74         case ERESTARTSYS:
  75                 /* ERESTARTSYS means to restart the syscall if there is no
  76                  * handler or the handler was registered with SA_RESTART
  77                  */
  78                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  79                 break;
  80         case ERESTARTNOINTR:
  81                 /* ERESTARTNOINTR means that the syscall should be
  82                  * called again after the signal handler returns.
  83                  */
  84                 break;
  85         default:
  86                 return;
  87         }
  88         if (restart) {
  89                 if (ret == ERESTART_RESTARTBLOCK)
  90                         regs->gpr[0] = __NR_restart_syscall;
  91                 else
  92                         regs->gpr[3] = regs->orig_gpr3;
  93                 regs->nip -= 4;
  94                 regs->result = 0;
  95         } else {
  96                 regs->result = -EINTR;
  97                 regs->gpr[3] = EINTR;
  98                 regs->ccr |= 0x10000000;
  99         }
 100 }
 101
 102 static void do_signal(struct pt_regs *regs)
 103 {
 104         sigset_t *oldset = sigmask_to_save();
 105         struct ksignal ksig;
 106         int ret;
 107         int is32 = is_32bit_task();
 108
 109         get_signal(&ksig);
 110
 111         /* Is there any syscall restart business here ? */
 112         check_syscall_restart(regs, &ksig.ka, ksig.sig > 0);
 113
 114         if (ksig.sig <= 0) {
 115                 /* No signal to deliver -- put the saved sigmask back */
 116                 restore_saved_sigmask();
 117                 regs->trap = 0;
 118                 return;               /* no signals delivered */
 119         }
 120
 121 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 122         /*
 123          * Reenable the DABR before delivering the signal to
 124          * user space. The DABR will have been cleared if it
 125          * triggered inside the kernel.
 126          */
 127         if (current->thread.hw_brk.address &&
 128                 current->thread.hw_brk.type)
 129                 __set_breakpoint(&current->thread.hw_brk);
 130 #endif
 131         /* Re-enable the breakpoints for the signal stack */
 132         thread_change_pc(current, regs);
 133
 134         if (is32) {
 135                 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 136                         ret = handle_rt_signal32(&ksig, oldset, regs);
 137                 else
 138                         ret = handle_signal32(&ksig, oldset, regs);
 139         } else {
 140                 ret = handle_rt_signal64(&ksig, oldset, regs);
 141         }
 142
 143         regs->trap = 0;
 144         signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
 145 }
 146
 147 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 148 {
 149         user_exit();
 150
 151         if (thread_info_flags & _TIF_UPROBE)
 152                 uprobe_notify_resume(regs);
 153
 154         if (thread_info_flags & _TIF_SIGPENDING)
 155                 do_signal(regs);
 156
 157         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 158                 clear_thread_flag(TIF_NOTIFY_RESUME);
 159                 tracehook_notify_resume(regs);
 160         }
 161
 162         user_enter();
 163 }
 164
 165 unsigned long get_tm_stackpointer(struct pt_regs *regs)
 166 {
 167         /* When in an active transaction that takes a signal, we need to be
 168          * careful with the stack.  It's possible that the stack has moved back
 169          * up after the tbegin.  The obvious case here is when the tbegin is
 170          * called inside a function that returns before a tend.  In this case,
 171          * the stack is part of the checkpointed transactional memory state.
 172          * If we write over this non transactionally or in suspend, we are in
 173          * trouble because if we get a tm abort, the program counter and stack
 174          * pointer will be back at the tbegin but our in memory stack won't be
 175          * valid anymore.
 176          *
 177          * To avoid this, when taking a signal in an active transaction, we
 178          * need to use the stack pointer from the checkpointed state, rather
 179          * than the speculated state.  This ensures that the signal context
 180          * (written tm suspended) will be written below the stack required for
 181          * the rollback.  The transaction is aborted becuase of the treclaim,
 182          * so any memory written between the tbegin and the signal will be
 183          * rolled back anyway.
 184          *
 185          * For signals taken in non-TM or suspended mode, we use the
 186          * normal/non-checkpointed stack pointer.
 187          */
 188
 189 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 190         if (MSR_TM_ACTIVE(regs->msr)) {
 191                 tm_reclaim_current(TM_CAUSE_SIGNAL);
 192                 if (MSR_TM_TRANSACTIONAL(regs->msr))
 193                         return current->thread.ckpt_regs.gpr[1];
 194         }
 195 #endif
 196         return regs->gpr[1];
 197 }