linux/arch/powerpc/kernel/signal.c
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   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
  29int show_unhandled_signals = 1;
  30
  31/*
  32 * Allocate space for the signal frame
  33 */
  34void __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
  51static 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
 102static 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
 147void 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
 165unsigned 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}
 198