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 Corporation
   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 <linux/livepatch.h>
  18 #include <asm/hw_breakpoint.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/unistd.h>
  21 #include <asm/debug.h>
  22 #include <asm/tm.h>
  23
  24 #include "signal.h"
  25
  26 /* Log an error when sending an unhandled signal to a process. Controlled
  27  * through debug.exception-trace sysctl.
  28  */
  29
  30 int show_unhandled_signals = 1;
  31
  32 /*
  33  * Allocate space for the signal frame
  34  */
  35 void __user *get_sigframe(struct ksignal *ksig, unsigned long sp,
  36                            size_t frame_size, int is_32)
  37 {
  38         unsigned long oldsp, newsp;
  39
  40         /* Default to using normal stack */
  41         oldsp = get_clean_sp(sp, is_32);
  42         oldsp = sigsp(oldsp, ksig);
  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 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  53                                   int has_handler)
  54 {
  55         unsigned long ret = regs->gpr[3];
  56         int restart = 1;
  57
  58         /* syscall ? */
  59         if (TRAP(regs) != 0x0C00)
  60                 return;
  61
  62         /* error signalled ? */
  63         if (!(regs->ccr & 0x10000000))
  64                 return;
  65
  66         switch (ret) {
  67         case ERESTART_RESTARTBLOCK:
  68         case ERESTARTNOHAND:
  69                 /* ERESTARTNOHAND means that the syscall should only be
  70                  * restarted if there was no handler for the signal, and since
  71                  * we only get here if there is a handler, we dont restart.
  72                  */
  73                 restart = !has_handler;
  74                 break;
  75         case ERESTARTSYS:
  76                 /* ERESTARTSYS means to restart the syscall if there is no
  77                  * handler or the handler was registered with SA_RESTART
  78                  */
  79                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  80                 break;
  81         case ERESTARTNOINTR:
  82                 /* ERESTARTNOINTR means that the syscall should be
  83                  * called again after the signal handler returns.
  84                  */
  85                 break;
  86         default:
  87                 return;
  88         }
  89         if (restart) {
  90                 if (ret == ERESTART_RESTARTBLOCK)
  91                         regs->gpr[0] = __NR_restart_syscall;
  92                 else
  93                         regs->gpr[3] = regs->orig_gpr3;
  94                 regs->nip -= 4;
  95                 regs->result = 0;
  96         } else {
  97                 regs->result = -EINTR;
  98                 regs->gpr[3] = EINTR;
  99                 regs->ccr |= 0x10000000;
 100         }
 101 }
 102
 103 static void do_signal(struct task_struct *tsk)
 104 {
 105         sigset_t *oldset = sigmask_to_save();
 106         struct ksignal ksig;
 107         int ret;
 108         int is32 = is_32bit_task();
 109
 110         BUG_ON(tsk != current);
 111
 112         get_signal(&ksig);
 113
 114         /* Is there any syscall restart business here ? */
 115         check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);
 116
 117         if (ksig.sig <= 0) {
 118                 /* No signal to deliver -- put the saved sigmask back */
 119                 restore_saved_sigmask();
 120                 tsk->thread.regs->trap = 0;
 121                 return;               /* no signals delivered */
 122         }
 123
 124 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 125         /*
 126          * Reenable the DABR before delivering the signal to
 127          * user space. The DABR will have been cleared if it
 128          * triggered inside the kernel.
 129          */
 130         if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
 131                 __set_breakpoint(&tsk->thread.hw_brk);
 132 #endif
 133         /* Re-enable the breakpoints for the signal stack */
 134         thread_change_pc(tsk, tsk->thread.regs);
 135
 136         if (is32) {
 137                 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 138                         ret = handle_rt_signal32(&ksig, oldset, tsk);
 139                 else
 140                         ret = handle_signal32(&ksig, oldset, tsk);
 141         } else {
 142                 ret = handle_rt_signal64(&ksig, oldset, tsk);
 143         }
 144
 145         tsk->thread.regs->trap = 0;
 146         signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
 147 }
 148
 149 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 150 {
 151         user_exit();
 152
 153         if (thread_info_flags & _TIF_UPROBE)
 154                 uprobe_notify_resume(regs);
 155
 156         if (thread_info_flags & _TIF_SIGPENDING) {
 157                 BUG_ON(regs != current->thread.regs);
 158                 do_signal(current);
 159         }
 160
 161         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 162                 clear_thread_flag(TIF_NOTIFY_RESUME);
 163                 tracehook_notify_resume(regs);
 164         }
 165
 166         if (thread_info_flags & _TIF_PATCH_PENDING)
 167                 klp_update_patch_state(current);
 168
 169         user_enter();
 170 }
 171
 172 unsigned long get_tm_stackpointer(struct task_struct *tsk)
 173 {
 174         /* When in an active transaction that takes a signal, we need to be
 175          * careful with the stack.  It's possible that the stack has moved back
 176          * up after the tbegin.  The obvious case here is when the tbegin is
 177          * called inside a function that returns before a tend.  In this case,
 178          * the stack is part of the checkpointed transactional memory state.
 179          * If we write over this non transactionally or in suspend, we are in
 180          * trouble because if we get a tm abort, the program counter and stack
 181          * pointer will be back at the tbegin but our in memory stack won't be
 182          * valid anymore.
 183          *
 184          * To avoid this, when taking a signal in an active transaction, we
 185          * need to use the stack pointer from the checkpointed state, rather
 186          * than the speculated state.  This ensures that the signal context
 187          * (written tm suspended) will be written below the stack required for
 188          * the rollback.  The transaction is aborted because of the treclaim,
 189          * so any memory written between the tbegin and the signal will be
 190          * rolled back anyway.
 191          *
 192          * For signals taken in non-TM or suspended mode, we use the
 193          * normal/non-checkpointed stack pointer.
 194          */
 195
 196 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 197         BUG_ON(tsk != current);
 198
 199         if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
 200                 tm_reclaim_current(TM_CAUSE_SIGNAL);
 201                 if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
 202                         return tsk->thread.ckpt_regs.gpr[1];
 203         }
 204 #endif
 205         return tsk->thread.regs->gpr[1];
 206 }