/*
 * Common signal handling code for both 32 and 64 bits
 *
 *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Corporation
 *    Extracted from signal_32.c and signal_64.c
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file README.legal in the main directory of
 * this archive for more details.
 */

#include <linux/tracehook.h>
#include <linux/signal.h>
#include <linux/uprobes.h>
#include <linux/key.h>
#include <linux/context_tracking.h>
#include <linux/livepatch.h>
#include <linux/syscalls.h>
#include <asm/hw_breakpoint.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <asm/debug.h>
#include <asm/tm.h>

#include "signal.h"

/* Log an error when sending an unhandled signal to a process. Controlled
 * through debug.exception-trace sysctl.
 */

int show_unhandled_signals = 1;

/*
 * Allocate space for the signal frame
 */
void __user *get_sigframe(struct ksignal *ksig, unsigned long sp,
                           size_t frame_size, int is_32)
{
        unsigned long oldsp, newsp;

        /* Default to using normal stack */
        oldsp = get_clean_sp(sp, is_32);
        oldsp = sigsp(oldsp, ksig);
        newsp = (oldsp - frame_size) & ~0xFUL;

        /* Check access */
        if (!access_ok((void __user *)newsp, oldsp - newsp))
                return NULL;

        return (void __user *)newsp;
}

static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
                                  int has_handler)
{
        unsigned long ret = regs->gpr[3];
        int restart = 1;

        /* syscall ? */
        if (TRAP(regs) != 0x0C00)
                return;

        /* error signalled ? */
        if (!(regs->ccr & 0x10000000))
                return;

        switch (ret) {
        case ERESTART_RESTARTBLOCK:
        case ERESTARTNOHAND:
                /* ERESTARTNOHAND means that the syscall should only be
                 * restarted if there was no handler for the signal, and since
                 * we only get here if there is a handler, we dont restart.
                 */
                restart = !has_handler;
                break;
        case ERESTARTSYS:
                /* ERESTARTSYS means to restart the syscall if there is no
                 * handler or the handler was registered with SA_RESTART
                 */
                restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
                break;
        case ERESTARTNOINTR:
                /* ERESTARTNOINTR means that the syscall should be
                 * called again after the signal handler returns.
                 */
                break;
        default:
                return;
        }
        if (restart) {
                if (ret == ERESTART_RESTARTBLOCK)
                        regs->gpr[0] = __NR_restart_syscall;
                else
                        regs->gpr[3] = regs->orig_gpr3;
                regs->nip -= 4;
                regs->result = 0;
        } else {
                regs->result = -EINTR;
                regs->gpr[3] = EINTR;
                regs->ccr |= 0x10000000;
        }
}

static void do_signal(struct task_struct *tsk)
{
        sigset_t *oldset = sigmask_to_save();
        struct ksignal ksig = { .sig = 0 };
        int ret;
        int is32 = is_32bit_task();

        BUG_ON(tsk != current);

        get_signal(&ksig);

        /* Is there any syscall restart business here ? */
        check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);

        if (ksig.sig <= 0) {
                /* No signal to deliver -- put the saved sigmask back */
                restore_saved_sigmask();
                tsk->thread.regs->trap = 0;
                return;               /* no signals delivered */
        }

#ifndef CONFIG_PPC_ADV_DEBUG_REGS
        /*
         * Reenable the DABR before delivering the signal to
         * user space. The DABR will have been cleared if it
         * triggered inside the kernel.
         */
        if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
                __set_breakpoint(&tsk->thread.hw_brk);
#endif
        /* Re-enable the breakpoints for the signal stack */
        thread_change_pc(tsk, tsk->thread.regs);

        rseq_signal_deliver(&ksig, tsk->thread.regs);

        if (is32) {
                if (ksig.ka.sa.sa_flags & SA_SIGINFO)
                        ret = handle_rt_signal32(&ksig, oldset, tsk);
                else
                        ret = handle_signal32(&ksig, oldset, tsk);
        } else {
                ret = handle_rt_signal64(&ksig, oldset, tsk);
        }

        tsk->thread.regs->trap = 0;
        signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
}

void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
{
        user_exit();

        /* Check valid addr_limit, TIF check is done there */
        addr_limit_user_check();

        if (thread_info_flags & _TIF_UPROBE)
                uprobe_notify_resume(regs);

        if (thread_info_flags & _TIF_PATCH_PENDING)
                klp_update_patch_state(current);

        if (thread_info_flags & _TIF_SIGPENDING) {
                BUG_ON(regs != current->thread.regs);
                do_signal(current);
        }

        if (thread_info_flags & _TIF_NOTIFY_RESUME) {
                clear_thread_flag(TIF_NOTIFY_RESUME);
                tracehook_notify_resume(regs);
                rseq_handle_notify_resume(NULL, regs);
        }

        user_enter();
}

unsigned long get_tm_stackpointer(struct task_struct *tsk)
{
        /* When in an active transaction that takes a signal, we need to be
         * careful with the stack.  It's possible that the stack has moved back
         * up after the tbegin.  The obvious case here is when the tbegin is
         * called inside a function that returns before a tend.  In this case,
         * the stack is part of the checkpointed transactional memory state.
         * If we write over this non transactionally or in suspend, we are in
         * trouble because if we get a tm abort, the program counter and stack
         * pointer will be back at the tbegin but our in memory stack won't be
         * valid anymore.
         *
         * To avoid this, when taking a signal in an active transaction, we
         * need to use the stack pointer from the checkpointed state, rather
         * than the speculated state.  This ensures that the signal context
         * (written tm suspended) will be written below the stack required for
         * the rollback.  The transaction is aborted because of the treclaim,
         * so any memory written between the tbegin and the signal will be
         * rolled back anyway.
         *
         * For signals taken in non-TM or suspended mode, we use the
         * normal/non-checkpointed stack pointer.
         */

        unsigned long ret = tsk->thread.regs->gpr[1];

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        BUG_ON(tsk != current);

        if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
                preempt_disable();
                tm_reclaim_current(TM_CAUSE_SIGNAL);
                if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
                        ret = tsk->thread.ckpt_regs.gpr[1];

                /*
                 * If we treclaim, we must clear the current thread's TM bits
                 * before re-enabling preemption. Otherwise we might be
                 * preempted and have the live MSR[TS] changed behind our back
                 * (tm_recheckpoint_new_task() would recheckpoint). Besides, we
                 * enter the signal handler in non-transactional state.
                 */
                tsk->thread.regs->msr &= ~MSR_TS_MASK;
                preempt_enable();
        }
#endif
        return ret;
}