// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * OpenRISC signal.c
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tracehook.h>

#include <asm/processor.h>
#include <asm/syscall.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>

struct rt_sigframe {
        struct siginfo info;
        struct ucontext uc;
        unsigned char retcode[16];      /* trampoline code */
};

static int restore_sigcontext(struct pt_regs *regs,
                              struct sigcontext __user *sc)
{
        int err = 0;

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

        /*
         * Restore the regs from &sc->regs.
         * (sc is already checked since the sigframe was
         *  checked in sys_sigreturn previously)
         */
        err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
        err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
        err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));

        /* make sure the SM-bit is cleared so user-mode cannot fool us */
        regs->sr &= ~SPR_SR_SM;

        regs->orig_gpr11 = -1;  /* Avoid syscall restart checks */

        /* TODO: the other ports use regs->orig_XX to disable syscall checks
         * after this completes, but we don't use that mechanism. maybe we can
         * use it now ?
         */

        return err;
}

asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
{
        struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->sp;
        sigset_t set;

        /*
         * Since we stacked the signal on a dword boundary,
         * then frame should be dword aligned here.  If it's
         * not, then the user is trying to mess with us.
         */
        if (((unsigned long)frame) & 3)
                goto badframe;

        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->uc.uc_mcontext))
                goto badframe;

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

        return regs->gpr[11];

badframe:
        force_sig(SIGSEGV);
        return 0;
}

/*
 * Set up a signal frame.
 */

static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
        int err = 0;

        /* copy the regs */
        /* There should be no need to save callee-saved registers here...
         * ...but we save them anyway.  Revisit this
         */
        err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
        err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
        err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));

        return err;
}

static inline unsigned long align_sigframe(unsigned long sp)
{
        return sp & ~3UL;
}

/*
 * Work out where the signal frame should go.  It's either on the user stack
 * or the alternate stack.
 */

static inline void __user *get_sigframe(struct ksignal *ksig,
                                        struct pt_regs *regs, size_t frame_size)
{
        unsigned long sp = regs->sp;

        /* redzone */
        sp -= STACK_FRAME_OVERHEAD;
        sp = sigsp(sp, ksig);
        sp = align_sigframe(sp - frame_size);

        return (void __user *)sp;
}

/* grab and setup a signal frame.
 *
 * basically we stack a lot of state info, and arrange for the
 * user-mode program to return to the kernel using either a
 * trampoline which performs the syscall sigreturn, or a provided
 * user-mode trampoline.
 */
static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        unsigned long return_ip;
        int err = 0;

        frame = get_sigframe(ksig, regs, sizeof(*frame));

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

        /* Create siginfo.  */
        if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                err |= copy_siginfo_to_user(&frame->info, &ksig->info);

        /* Create the ucontext.  */
        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(NULL, &frame->uc.uc_link);
        err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
        err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);

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

        if (err)
                return -EFAULT;

        /* trampoline - the desired return ip is the retcode itself */
        return_ip = (unsigned long)&frame->retcode;
        /* This is:
                l.ori r11,r0,__NR_sigreturn
                l.sys 1
         */
        err |= __put_user(0xa960,             (short __user *)(frame->retcode + 0));
        err |= __put_user(__NR_rt_sigreturn,  (short __user *)(frame->retcode + 2));
        err |= __put_user(0x20000001, (unsigned long __user *)(frame->retcode + 4));
        err |= __put_user(0x15000000, (unsigned long __user *)(frame->retcode + 8));

        if (err)
                return -EFAULT;

        /* Set up registers for signal handler */
        regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
        regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
        regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
        regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
        regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */

        /* actually move the usp to reflect the stacked frame */
        regs->sp = (unsigned long)frame;

        return 0;
}

static inline void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        int ret;

        ret = setup_rt_frame(ksig, sigmask_to_save(), regs);

        signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
}

/*
 * 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.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */

int do_signal(struct pt_regs *regs, int syscall)
{
        struct ksignal ksig;
        unsigned long continue_addr = 0;
        unsigned long restart_addr = 0;
        unsigned long retval = 0;
        int restart = 0;

        if (syscall) {
                continue_addr = regs->pc;
                restart_addr = continue_addr - 4;
                retval = regs->gpr[11];

                /*
                 * Setup syscall restart here so that a debugger will
                 * see the already changed PC.
                 */
                switch (retval) {
                case -ERESTART_RESTARTBLOCK:
                        restart = -2;
                        fallthrough;
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        restart++;
                        regs->gpr[11] = regs->orig_gpr11;
                        regs->pc = restart_addr;
                        break;
                }
        }

        /*
         * Get the signal to deliver.  During the call to get_signal the
         * debugger may change all our registers so we may need to revert
         * the decision to restart the syscall; specifically, if the PC is
         * changed, don't restart the syscall.
         */
        if (get_signal(&ksig)) {
                if (unlikely(restart) && regs->pc == restart_addr) {
                        if (retval == -ERESTARTNOHAND ||
                            retval == -ERESTART_RESTARTBLOCK
                            || (retval == -ERESTARTSYS
                                && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
                                /* No automatic restart */
                                regs->gpr[11] = -EINTR;
                                regs->pc = continue_addr;
                        }
                }
                handle_signal(&ksig, regs);
        } else {
                /* no handler */
                restore_saved_sigmask();
                /*
                 * Restore pt_regs PC as syscall restart will be handled by
                 * kernel without return to userspace
                 */
                if (unlikely(restart) && regs->pc == restart_addr) {
                        regs->pc = continue_addr;
                        return restart;
                }
        }

        return 0;
}

asmlinkage int
do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
{
        do {
                if (likely(thread_flags & _TIF_NEED_RESCHED)) {
                        schedule();
                } else {
                        if (unlikely(!user_mode(regs)))
                                return 0;
                        local_irq_enable();
                        if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) {
                                int restart = do_signal(regs, syscall);
                                if (unlikely(restart)) {
                                        /*
                                         * Restart without handlers.
                                         * Deal with it without leaving
                                         * the kernel space.
                                         */
                                        return restart;
                                }
                                syscall = 0;
                        } else {
                                tracehook_notify_resume(regs);
                        }
                }
                local_irq_disable();
                thread_flags = current_thread_info()->flags;
        } while (thread_flags & _TIF_WORK_MASK);
        return 0;
}