/*
 * arch/xtensa/kernel/signal.c
 *
 * Default platform functions.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005, 2006 Tensilica Inc.
 * Copyright (C) 1991, 1992  Linus Torvalds
 * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 * Chris Zankel <chris@zankel.net>
 * Joe Taylor <joe@tensilica.com>
 */

#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/tracehook.h>
#include <linux/sched/task_stack.h>

#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/coprocessor.h>
#include <asm/unistd.h>

extern struct task_struct *coproc_owners[];

struct rt_sigframe
{
        struct siginfo info;
        struct ucontext uc;
        struct {
                xtregs_opt_t opt;
                xtregs_user_t user;
#if XTENSA_HAVE_COPROCESSORS
                xtregs_coprocessor_t cp;
#endif
        } xtregs;
        unsigned char retcode[6];
        unsigned int window[4];
};

/* 
 * Flush register windows stored in pt_regs to stack.
 * Returns 1 for errors.
 */

int
flush_window_regs_user(struct pt_regs *regs)
{
        const unsigned long ws = regs->windowstart;
        const unsigned long wb = regs->windowbase;
        unsigned long sp = 0;
        unsigned long wm;
        int err = 1;
        int base;

        /* Return if no other frames. */

        if (regs->wmask == 1)
                return 0;

        /* Rotate windowmask and skip empty frames. */

        wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
        base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
                
        /* For call8 or call12 frames, we need the previous stack pointer. */

        if ((regs->wmask & 2) == 0)
                if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
                        goto errout;

        /* Spill frames to stack. */

        while (base < XCHAL_NUM_AREGS / 4) {

                int m = (wm >> base);
                int inc = 0;

                /* Save registers a4..a7 (call8) or a4...a11 (call12) */

                if (m & 2) {                    /* call4 */
                        inc = 1;

                } else if (m & 4) {             /* call8 */
                        if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4),
                                         &regs->areg[(base + 1) * 4], 16))
                                goto errout;
                        inc = 2;

                } else if (m & 8) {     /* call12 */
                        if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
                                         &regs->areg[(base + 1) * 4], 32))
                                goto errout;
                        inc = 3;
                }

                /* Save current frame a0..a3 under next SP */

                sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
                if (copy_to_user(&SPILL_SLOT(sp, 0), &regs->areg[base * 4], 16))
                        goto errout;

                /* Get current stack pointer for next loop iteration. */

                sp = regs->areg[base * 4 + 1];
                base += inc;
        }

        regs->wmask = 1;
        regs->windowstart = 1 << wb;

        return 0;

errout:
        return err;
}

/*
 * Note: We don't copy double exception 'regs', we have to finish double exc. 
 * first before we return to signal handler! This dbl.exc.handler might cause 
 * another double exception, but I think we are fine as the situation is the 
 * same as if we had returned to the signal handerl and got an interrupt 
 * immediately...
 */

static int
setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
{
        struct sigcontext __user *sc = &frame->uc.uc_mcontext;
        struct thread_info *ti = current_thread_info();
        int err = 0;

#define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
        COPY(pc);
        COPY(ps);
        COPY(lbeg);
        COPY(lend);
        COPY(lcount);
        COPY(sar);
#undef COPY

        err |= flush_window_regs_user(regs);
        err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
        err |= __put_user(0, &sc->sc_xtregs);

        if (err)
                return err;

#if XTENSA_HAVE_COPROCESSORS
        coprocessor_flush_all(ti);
        coprocessor_release_all(ti);
        err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
                              sizeof (frame->xtregs.cp));
#endif
        err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
                              sizeof (xtregs_opt_t));
        err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
                              sizeof (xtregs_user_t));

        err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);

        return err;
}

static int
restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
{
        struct sigcontext __user *sc = &frame->uc.uc_mcontext;
        struct thread_info *ti = current_thread_info();
        unsigned int err = 0;
        unsigned long ps;

#define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
        COPY(pc);
        COPY(lbeg);
        COPY(lend);
        COPY(lcount);
        COPY(sar);
#undef COPY

        /* All registers were flushed to stack. Start with a pristine frame. */

        regs->wmask = 1;
        regs->windowbase = 0;
        regs->windowstart = 1;

        regs->syscall = NO_SYSCALL;     /* disable syscall checks */

        /* For PS, restore only PS.CALLINC.
         * Assume that all other bits are either the same as for the signal
         * handler, or the user mode value doesn't matter (e.g. PS.OWB).
         */
        err |= __get_user(ps, &sc->sc_ps);
        regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);

        /* Additional corruption checks */

        if ((regs->lcount > 0)
            && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
                err = 1;

        err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);

        if (err)
                return err;

        /* The signal handler may have used coprocessors in which
         * case they are still enabled.  We disable them to force a
         * reloading of the original task's CP state by the lazy
         * context-switching mechanisms of CP exception handling.
         * Also, we essentially discard any coprocessor state that the
         * signal handler created. */

#if XTENSA_HAVE_COPROCESSORS
        coprocessor_release_all(ti);
        err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
                                sizeof (frame->xtregs.cp));
#endif
        err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
                                sizeof (xtregs_user_t));
        err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
                                sizeof (xtregs_opt_t));

        return err;
}


/*
 * Do a signal return; undo the signal stack.
 */

asmlinkage long xtensa_rt_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        sigset_t set;
        int ret;

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

        if (regs->depc > 64)
                panic("rt_sigreturn in double exception!\n");

        frame = (struct rt_sigframe __user *) regs->areg[1];

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

        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;

        set_current_blocked(&set);

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

        ret = regs->areg[2];

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

        return ret;

badframe:
        force_sig(SIGSEGV);
        return 0;
}



/*
 * Set up a signal frame.
 */

static int
gen_return_code(unsigned char *codemem)
{
        int err = 0;

        /*
         * The 12-bit immediate is really split up within the 24-bit MOVI
         * instruction.  As long as the above system call numbers fit within
         * 8-bits, the following code works fine. See the Xtensa ISA for
         * details.
         */

#if __NR_rt_sigreturn > 255
# error Generating the MOVI instruction below breaks!
#endif

#ifdef __XTENSA_EB__   /* Big Endian version */
        /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
        err |= __put_user(0x22, &codemem[0]);
        err |= __put_user(0x0a, &codemem[1]);
        err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
        /* Generate instruction:  SYSCALL */
        err |= __put_user(0x00, &codemem[3]);
        err |= __put_user(0x05, &codemem[4]);
        err |= __put_user(0x00, &codemem[5]);

#elif defined __XTENSA_EL__   /* Little Endian version */
        /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
        err |= __put_user(0x22, &codemem[0]);
        err |= __put_user(0xa0, &codemem[1]);
        err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
        /* Generate instruction:  SYSCALL */
        err |= __put_user(0x00, &codemem[3]);
        err |= __put_user(0x50, &codemem[4]);
        err |= __put_user(0x00, &codemem[5]);
#else
# error Must use compiler for Xtensa processors.
#endif

        /* Flush generated code out of the data cache */

        if (err == 0) {
                __invalidate_icache_range((unsigned long)codemem, 6UL);
                __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
        }

        return err;
}


static int setup_frame(struct ksignal *ksig, sigset_t *set,
                       struct pt_regs *regs)
{
        struct rt_sigframe *frame;
        int err = 0, sig = ksig->sig;
        unsigned long sp, ra, tp, ps;
        unsigned int base;

        sp = regs->areg[1];

        if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
                sp = current->sas_ss_sp + current->sas_ss_size;
        }

        frame = (void *)((sp - sizeof(*frame)) & -16ul);

        if (regs->depc > 64)
                panic ("Double exception sys_sigreturn\n");

        if (!access_ok(frame, sizeof(*frame))) {
                return -EFAULT;
        }

        if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                err |= copy_siginfo_to_user(&frame->info, &ksig->info);
        }

        /* Create the user context.  */

        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(0, &frame->uc.uc_link);
        err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
        err |= setup_sigcontext(frame, regs);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

        if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                ra = (unsigned long)ksig->ka.sa.sa_restorer;
        } else {

                /* Create sys_rt_sigreturn syscall in stack frame */

                err |= gen_return_code(frame->retcode);

                if (err) {
                        return -EFAULT;
                }
                ra = (unsigned long) frame->retcode;
        }

        /* 
         * Create signal handler execution context.
         * Return context not modified until this point.
         */

        /* Set up registers for signal handler; preserve the threadptr */
        tp = regs->threadptr;
        ps = regs->ps;
        start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
                     (unsigned long) frame);

        /* Set up a stack frame for a call4 if userspace uses windowed ABI */
        if (ps & PS_WOE_MASK) {
                base = 4;
                regs->areg[base] =
                        (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
                ps = (ps & ~(PS_CALLINC_MASK | PS_OWB_MASK)) |
                        (1 << PS_CALLINC_SHIFT);
        } else {
                base = 0;
                regs->areg[base] = (unsigned long) ra;
        }
        regs->areg[base + 2] = (unsigned long) sig;
        regs->areg[base + 3] = (unsigned long) &frame->info;
        regs->areg[base + 4] = (unsigned long) &frame->uc;
        regs->threadptr = tp;
        regs->ps = ps;

        pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n",
                 current->comm, current->pid, sig, frame, regs->pc);

        return 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)
{
        struct ksignal ksig;

        task_pt_regs(current)->icountlevel = 0;

        if (get_signal(&ksig)) {
                int ret;

                /* Are we from a system call? */

                if (regs->syscall != NO_SYSCALL) {

                        /* If so, check system call restarting.. */

                        switch (regs->areg[2]) {
                                case -ERESTARTNOHAND:
                                case -ERESTART_RESTARTBLOCK:
                                        regs->areg[2] = -EINTR;
                                        break;

                                case -ERESTARTSYS:
                                        if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
                                                regs->areg[2] = -EINTR;
                                                break;
                                        }
                                        fallthrough;
                                case -ERESTARTNOINTR:
                                        regs->areg[2] = regs->syscall;
                                        regs->pc -= 3;
                                        break;

                                default:
                                        /* nothing to do */
                                        if (regs->areg[2] != 0)
                                        break;
                        }
                }

                /* Whee!  Actually deliver the signal.  */
                /* Set up the stack frame */
                ret = setup_frame(&ksig, sigmask_to_save(), regs);
                signal_setup_done(ret, &ksig, 0);
                if (current->ptrace & PT_SINGLESTEP)
                        task_pt_regs(current)->icountlevel = 1;

                return;
        }

        /* Did we come from a system call? */
        if (regs->syscall != NO_SYSCALL) {
                /* Restart the system call - no handlers present */
                switch (regs->areg[2]) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->areg[2] = regs->syscall;
                        regs->pc -= 3;
                        break;
                case -ERESTART_RESTARTBLOCK:
                        regs->areg[2] = __NR_restart_syscall;
                        regs->pc -= 3;
                        break;
                }
        }

        /* If there's no signal to deliver, we just restore the saved mask.  */
        restore_saved_sigmask();

        if (current->ptrace & PT_SINGLESTEP)
                task_pt_regs(current)->icountlevel = 1;
        return;
}

void do_notify_resume(struct pt_regs *regs)
{
        if (test_thread_flag(TIF_SIGPENDING) ||
            test_thread_flag(TIF_NOTIFY_SIGNAL))
                do_signal(regs);

        if (test_thread_flag(TIF_NOTIFY_RESUME))
                tracehook_notify_resume(regs);
}