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 <linux/syscalls.h>
  19 #include <asm/hw_breakpoint.h>
  20 #include <linux/uaccess.h>
  21 #include <asm/unistd.h>
  22 #include <asm/debug.h>
  23 #include <asm/tm.h>
  24
  25 #include "signal.h"
  26
  27 /* Log an error when sending an unhandled signal to a process. Controlled
  28  * through debug.exception-trace sysctl.
  29  */
  30
  31 int show_unhandled_signals = 1;
  32
  33 /*
  34  * Allocate space for the signal frame
  35  */
  36 void __user *get_sigframe(struct ksignal *ksig, unsigned long sp,
  37                            size_t frame_size, int is_32)
  38 {
  39         unsigned long oldsp, newsp;
  40
  41         /* Default to using normal stack */
  42         oldsp = get_clean_sp(sp, is_32);
  43         oldsp = sigsp(oldsp, ksig);
  44         newsp = (oldsp - frame_size) & ~0xFUL;
  45
  46         /* Check access */
  47         if (!access_ok((void __user *)newsp, oldsp - newsp))
  48                 return NULL;
  49
  50         return (void __user *)newsp;
  51 }
  52
  53 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
  54                                   int has_handler)
  55 {
  56         unsigned long ret = regs->gpr[3];
  57         int restart = 1;
  58
  59         /* syscall ? */
  60         if (TRAP(regs) != 0x0C00)
  61                 return;
  62
  63         /* error signalled ? */
  64         if (!(regs->ccr & 0x10000000))
  65                 return;
  66
  67         switch (ret) {
  68         case ERESTART_RESTARTBLOCK:
  69         case ERESTARTNOHAND:
  70                 /* ERESTARTNOHAND means that the syscall should only be
  71                  * restarted if there was no handler for the signal, and since
  72                  * we only get here if there is a handler, we dont restart.
  73                  */
  74                 restart = !has_handler;
  75                 break;
  76         case ERESTARTSYS:
  77                 /* ERESTARTSYS means to restart the syscall if there is no
  78                  * handler or the handler was registered with SA_RESTART
  79                  */
  80                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
  81                 break;
  82         case ERESTARTNOINTR:
  83                 /* ERESTARTNOINTR means that the syscall should be
  84                  * called again after the signal handler returns.
  85                  */
  86                 break;
  87         default:
  88                 return;
  89         }
  90         if (restart) {
  91                 if (ret == ERESTART_RESTARTBLOCK)
  92                         regs->gpr[0] = __NR_restart_syscall;
  93                 else
  94                         regs->gpr[3] = regs->orig_gpr3;
  95                 regs->nip -= 4;
  96                 regs->result = 0;
  97         } else {
  98                 regs->result = -EINTR;
  99                 regs->gpr[3] = EINTR;
 100                 regs->ccr |= 0x10000000;
 101         }
 102 }
 103
 104 static void do_signal(struct task_struct *tsk)
 105 {
 106         sigset_t *oldset = sigmask_to_save();
 107         struct ksignal ksig = { .sig = 0 };
 108         int ret;
 109         int is32 = is_32bit_task();
 110
 111         BUG_ON(tsk != current);
 112
 113         get_signal(&ksig);
 114
 115         /* Is there any syscall restart business here ? */
 116         check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);
 117
 118         if (ksig.sig <= 0) {
 119                 /* No signal to deliver -- put the saved sigmask back */
 120                 restore_saved_sigmask();
 121                 tsk->thread.regs->trap = 0;
 122                 return;               /* no signals delivered */
 123         }
 124
 125 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 126         /*
 127          * Reenable the DABR before delivering the signal to
 128          * user space. The DABR will have been cleared if it
 129          * triggered inside the kernel.
 130          */
 131         if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
 132                 __set_breakpoint(&tsk->thread.hw_brk);
 133 #endif
 134         /* Re-enable the breakpoints for the signal stack */
 135         thread_change_pc(tsk, tsk->thread.regs);
 136
 137         rseq_signal_deliver(&ksig, tsk->thread.regs);
 138
 139         if (is32) {
 140                 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 141                         ret = handle_rt_signal32(&ksig, oldset, tsk);
 142                 else
 143                         ret = handle_signal32(&ksig, oldset, tsk);
 144         } else {
 145                 ret = handle_rt_signal64(&ksig, oldset, tsk);
 146         }
 147
 148         tsk->thread.regs->trap = 0;
 149         signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
 150 }
 151
 152 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 153 {
 154         user_exit();
 155
 156         /* Check valid addr_limit, TIF check is done there */
 157         addr_limit_user_check();
 158
 159         if (thread_info_flags & _TIF_UPROBE)
 160                 uprobe_notify_resume(regs);
 161
 162         if (thread_info_flags & _TIF_PATCH_PENDING)
 163                 klp_update_patch_state(current);
 164
 165         if (thread_info_flags & _TIF_SIGPENDING) {
 166                 BUG_ON(regs != current->thread.regs);
 167                 do_signal(current);
 168         }
 169
 170         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 171                 clear_thread_flag(TIF_NOTIFY_RESUME);
 172                 tracehook_notify_resume(regs);
 173                 rseq_handle_notify_resume(NULL, regs);
 174         }
 175
 176         user_enter();
 177 }
 178
 179 unsigned long get_tm_stackpointer(struct task_struct *tsk)
 180 {
 181         /* When in an active transaction that takes a signal, we need to be
 182          * careful with the stack.  It's possible that the stack has moved back
 183          * up after the tbegin.  The obvious case here is when the tbegin is
 184          * called inside a function that returns before a tend.  In this case,
 185          * the stack is part of the checkpointed transactional memory state.
 186          * If we write over this non transactionally or in suspend, we are in
 187          * trouble because if we get a tm abort, the program counter and stack
 188          * pointer will be back at the tbegin but our in memory stack won't be
 189          * valid anymore.
 190          *
 191          * To avoid this, when taking a signal in an active transaction, we
 192          * need to use the stack pointer from the checkpointed state, rather
 193          * than the speculated state.  This ensures that the signal context
 194          * (written tm suspended) will be written below the stack required for
 195          * the rollback.  The transaction is aborted because of the treclaim,
 196          * so any memory written between the tbegin and the signal will be
 197          * rolled back anyway.
 198          *
 199          * For signals taken in non-TM or suspended mode, we use the
 200          * normal/non-checkpointed stack pointer.
 201          */
 202
 203         unsigned long ret = tsk->thread.regs->gpr[1];
 204
 205 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 206         BUG_ON(tsk != current);
 207
 208         if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
 209                 preempt_disable();
 210                 tm_reclaim_current(TM_CAUSE_SIGNAL);
 211                 if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
 212                         ret = tsk->thread.ckpt_regs.gpr[1];
 213
 214                 /*
 215                  * If we treclaim, we must clear the current thread's TM bits
 216                  * before re-enabling preemption. Otherwise we might be
 217                  * preempted and have the live MSR[TS] changed behind our back
 218                  * (tm_recheckpoint_new_task() would recheckpoint). Besides, we
 219                  * enter the signal handler in non-transactional state.
 220                  */
 221                 tsk->thread.regs->msr &= ~MSR_TS_MASK;
 222                 preempt_enable();
 223         }
 224 #endif
 225         return ret;
 226 }