/*
 * Based on arch/arm/kernel/signal.c
 *
 * Copyright (C) 1995-2009 Russell King
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/freezer.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <linux/ratelimit.h>

#include <asm/debug-monitors.h>
#include <asm/elf.h>
#include <asm/cacheflush.h>
#include <asm/ucontext.h>
#include <asm/unistd.h>
#include <asm/fpsimd.h>
#include <asm/signal32.h>
#include <asm/vdso.h>

/*
 * Do a signal return; undo the signal stack. These are aligned to 128-bit.
 */
struct rt_sigframe {
        struct siginfo info;
        struct ucontext uc;
        u64 fp;
        u64 lr;
};

static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
{
        struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
        int err;

        /* dump the hardware registers to the fpsimd_state structure */
        fpsimd_preserve_current_state();

        /* copy the FP and status/control registers */
        err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
        __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
        __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);

        /* copy the magic/size information */
        __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
        __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);

        return err ? -EFAULT : 0;
}

static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
{
        struct fpsimd_state fpsimd;
        __u32 magic, size;
        int err = 0;

        /* check the magic/size information */
        __get_user_error(magic, &ctx->head.magic, err);
        __get_user_error(size, &ctx->head.size, err);
        if (err)
                return -EFAULT;
        if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
                return -EINVAL;

        /* copy the FP and status/control registers */
        err = __copy_from_user(fpsimd.vregs, ctx->vregs,
                               sizeof(fpsimd.vregs));
        __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
        __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);

        /* load the hardware registers from the fpsimd_state structure */
        if (!err)
                fpsimd_update_current_state(&fpsimd);

        return err ? -EFAULT : 0;
}

static int restore_sigframe(struct pt_regs *regs,
                            struct rt_sigframe __user *sf)
{
        sigset_t set;
        int i, err;
        void *aux = sf->uc.uc_mcontext.__reserved;

        err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
        if (err == 0)
                set_current_blocked(&set);

        for (i = 0; i < 31; i++)
                __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
                                 err);
        __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
        __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
        __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

        /*
         * Avoid sys_rt_sigreturn() restarting.
         */
        regs->syscallno = ~0UL;

        err |= !valid_user_regs(&regs->user_regs, current);

        if (err == 0) {
                struct fpsimd_context *fpsimd_ctx =
                        container_of(aux, struct fpsimd_context, head);
                err |= restore_fpsimd_context(fpsimd_ctx);
        }

        return err;
}

asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;

        /* Always make any pending restarted system calls return -EINTR */
        current->restart_block.fn = do_no_restart_syscall;

        /*
         * Since we stacked the signal on a 128-bit boundary, then 'sp' should
         * be word aligned here.
         */
        if (regs->sp & 15)
                goto badframe;

        frame = (struct rt_sigframe __user *)regs->sp;

        if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
                goto badframe;

        if (restore_sigframe(regs, frame))
                goto badframe;

        if (restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        return regs->regs[0];

badframe:
        if (show_unhandled_signals)
                pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
                                    current->comm, task_pid_nr(current), __func__,
                                    regs->pc, regs->sp);
        force_sig(SIGSEGV, current);
        return 0;
}

static int setup_sigframe(struct rt_sigframe __user *sf,
                          struct pt_regs *regs, sigset_t *set)
{
        int i, err = 0;
        void *aux = sf->uc.uc_mcontext.__reserved;
        struct _aarch64_ctx *end;

        /* set up the stack frame for unwinding */
        __put_user_error(regs->regs[29], &sf->fp, err);
        __put_user_error(regs->regs[30], &sf->lr, err);

        for (i = 0; i < 31; i++)
                __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
                                 err);
        __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
        __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
        __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);

        __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);

        err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));

        if (err == 0) {
                struct fpsimd_context *fpsimd_ctx =
                        container_of(aux, struct fpsimd_context, head);
                err |= preserve_fpsimd_context(fpsimd_ctx);
                aux += sizeof(*fpsimd_ctx);
        }

        /* fault information, if valid */
        if (current->thread.fault_code) {
                struct esr_context *esr_ctx =
                        container_of(aux, struct esr_context, head);
                __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
                __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
                __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
                aux += sizeof(*esr_ctx);
        }

        /* set the "end" magic */
        end = aux;
        __put_user_error(0, &end->magic, err);
        __put_user_error(0, &end->size, err);

        return err;
}

static struct rt_sigframe __user *get_sigframe(struct ksignal *ksig,
                                               struct pt_regs *regs)
{
        unsigned long sp, sp_top;
        struct rt_sigframe __user *frame;

        sp = sp_top = sigsp(regs->sp, ksig);

        sp = (sp - sizeof(struct rt_sigframe)) & ~15;
        frame = (struct rt_sigframe __user *)sp;

        /*
         * Check that we can actually write to the signal frame.
         */
        if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
                frame = NULL;

        return frame;
}

static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
                         void __user *frame, int usig)
{
        __sigrestore_t sigtramp;

        regs->regs[0] = usig;
        regs->sp = (unsigned long)frame;
        regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
        regs->pc = (unsigned long)ka->sa.sa_handler;

        if (ka->sa.sa_flags & SA_RESTORER)
                sigtramp = ka->sa.sa_restorer;
        else
                sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);

        regs->regs[30] = (unsigned long)sigtramp;
}

static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        int err = 0;

        frame = get_sigframe(ksig, regs);
        if (!frame)
                return 1;

        __put_user_error(0, &frame->uc.uc_flags, err);
        __put_user_error(NULL, &frame->uc.uc_link, err);

        err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
        err |= setup_sigframe(frame, regs, set);
        if (err == 0) {
                setup_return(regs, &ksig->ka, frame, usig);
                if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                        err |= copy_siginfo_to_user(&frame->info, &ksig->info);
                        regs->regs[1] = (unsigned long)&frame->info;
                        regs->regs[2] = (unsigned long)&frame->uc;
                }
        }

        return err;
}

static void setup_restart_syscall(struct pt_regs *regs)
{
        if (is_compat_task())
                compat_setup_restart_syscall(regs);
        else
                regs->regs[8] = __NR_restart_syscall;
}

/*
 * OK, we're invoking a handler
 */
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        struct task_struct *tsk = current;
        sigset_t *oldset = sigmask_to_save();
        int usig = ksig->sig;
        int ret;

        /*
         * Set up the stack frame
         */
        if (is_compat_task()) {
                if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                        ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
                else
                        ret = compat_setup_frame(usig, ksig, oldset, regs);
        } else {
                ret = setup_rt_frame(usig, ksig, oldset, regs);
        }

        /*
         * Check that the resulting registers are actually sane.
         */
        ret |= !valid_user_regs(&regs->user_regs, current);

        /*
         * Fast forward the stepping logic so we step into the signal
         * handler.
         */
        if (!ret)
                user_fastforward_single_step(tsk);

        signal_setup_done(ret, ksig, 0);
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 */
static void do_signal(struct pt_regs *regs)
{
        unsigned long continue_addr = 0, restart_addr = 0;
        int retval = 0;
        int syscall = (int)regs->syscallno;
        struct ksignal ksig;

        /*
         * If we were from a system call, check for system call restarting...
         */
        if (syscall >= 0) {
                continue_addr = regs->pc;
                restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
                retval = regs->regs[0];

                /*
                 * Avoid additional syscall restarting via ret_to_user.
                 */
                regs->syscallno = ~0UL;

                /*
                 * Prepare for system call restart. We do this here so that a
                 * debugger will see the already changed PC.
                 */
                switch (retval) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                case -ERESTART_RESTARTBLOCK:
                        regs->regs[0] = regs->orig_x0;
                        regs->pc = restart_addr;
                        break;
                }
        }

        /*
         * Get the signal to deliver. When running under ptrace, at this point
         * the debugger may change all of our registers.
         */
        if (get_signal(&ksig)) {
                /*
                 * Depending on the signal settings, we may need to revert the
                 * decision to restart the system call, but skip this if a
                 * debugger has chosen to restart at a different PC.
                 */
                if (regs->pc == restart_addr &&
                    (retval == -ERESTARTNOHAND ||
                     retval == -ERESTART_RESTARTBLOCK ||
                     (retval == -ERESTARTSYS &&
                      !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
                        regs->regs[0] = -EINTR;
                        regs->pc = continue_addr;
                }

                handle_signal(&ksig, regs);
                return;
        }

        /*
         * Handle restarting a different system call. As above, if a debugger
         * has chosen to restart at a different PC, ignore the restart.
         */
        if (syscall >= 0 && regs->pc == restart_addr) {
                if (retval == -ERESTART_RESTARTBLOCK)
                        setup_restart_syscall(regs);
                user_rewind_single_step(current);
        }

        restore_saved_sigmask();
}

asmlinkage void do_notify_resume(struct pt_regs *regs,
                                 unsigned int thread_flags)
{
        if (thread_flags & _TIF_SIGPENDING)
                do_signal(regs);

        if (thread_flags & _TIF_NOTIFY_RESUME) {
                clear_thread_flag(TIF_NOTIFY_RESUME);
                tracehook_notify_resume(regs);
        }

        if (thread_flags & _TIF_FOREIGN_FPSTATE)
                fpsimd_restore_current_state();

}