// SPDX-License-Identifier: GPL-2.0
/*
 *    Copyright IBM Corp. 1999, 2006
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
 *
 *    Based on Intel version
 * 
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 */

#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/rseq.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/entry-common.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/syscalls.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/vdso-symbols.h>
#include <asm/access-regs.h>
#include <asm/lowcore.h>
#include "entry.h"

/*
 * Layout of an old-style signal-frame:
 *      -----------------------------------------
 *      | save area (_SIGNAL_FRAMESIZE)         |
 *      -----------------------------------------
 *      | struct sigcontext                     |
 *      |       oldmask                         |
 *      |       _sigregs *                      |
 *      -----------------------------------------
 *      | _sigregs with                         |
 *      |       _s390_regs_common               |
 *      |       _s390_fp_regs                   |
 *      -----------------------------------------
 *      | int signo                             |
 *      -----------------------------------------
 *      | _sigregs_ext with                     |
 *      |       gprs_high 64 byte (opt)         |
 *      |       vxrs_low 128 byte (opt)         |
 *      |       vxrs_high 256 byte (opt)        |
 *      |       reserved 128 byte (opt)         |
 *      -----------------------------------------
 *      | __u16 svc_insn                        |
 *      -----------------------------------------
 * The svc_insn entry with the sigreturn system call opcode does not
 * have a fixed position and moves if gprs_high or vxrs exist.
 * Future extensions will be added to _sigregs_ext.
 */
struct sigframe
{
        __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
        struct sigcontext sc;
        _sigregs sregs;
        int signo;
        _sigregs_ext sregs_ext;
        __u16 svc_insn;         /* Offset of svc_insn is NOT fixed! */
};

/*
 * Layout of an rt signal-frame:
 *      -----------------------------------------
 *      | save area (_SIGNAL_FRAMESIZE)         |
 *      -----------------------------------------
 *      | svc __NR_rt_sigreturn 2 byte          |
 *      -----------------------------------------
 *      | struct siginfo                        |
 *      -----------------------------------------
 *      | struct ucontext_extended with         |
 *      |       unsigned long uc_flags          |
 *      |       struct ucontext *uc_link        |
 *      |       stack_t uc_stack                |
 *      |       _sigregs uc_mcontext with       |
 *      |               _s390_regs_common       |
 *      |               _s390_fp_regs           |
 *      |       sigset_t uc_sigmask             |
 *      |       _sigregs_ext uc_mcontext_ext    |
 *      |               gprs_high 64 byte (opt) |
 *      |               vxrs_low 128 byte (opt) |
 *      |               vxrs_high 256 byte (opt)|
 *      |               reserved 128 byte (opt) |
 *      -----------------------------------------
 * Future extensions will be added to _sigregs_ext.
 */
struct rt_sigframe
{
        __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
        __u16 svc_insn;
        struct siginfo info;
        struct ucontext_extended uc;
};

/* Store registers needed to create the signal frame */
static void store_sigregs(void)
{
        save_access_regs(current->thread.acrs);
        save_user_fpu_regs();
}

/* Load registers after signal return */
static void load_sigregs(void)
{
        restore_access_regs(current->thread.acrs);
}

/* Returns non-zero on fault. */
static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
        _sigregs user_sregs;

        /* Copy a 'clean' PSW mask to the user to avoid leaking
           information about whether PER is currently on.  */
        user_sregs.regs.psw.mask = PSW_USER_BITS |
                (regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
        user_sregs.regs.psw.addr = regs->psw.addr;
        memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
        memcpy(&user_sregs.regs.acrs, current->thread.acrs,
               sizeof(user_sregs.regs.acrs));
        fpregs_store(&user_sregs.fpregs, &current->thread.ufpu);
        if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
                return -EFAULT;
        return 0;
}

static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
        _sigregs user_sregs;

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

        if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
                return -EFAULT;

        if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI))
                return -EINVAL;

        /* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
        regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) |
                (user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
        /* Check for invalid user address space control. */
        if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME)
                regs->psw.mask = PSW_ASC_PRIMARY |
                        (regs->psw.mask & ~PSW_MASK_ASC);
        /* Check for invalid amode */
        if (regs->psw.mask & PSW_MASK_EA)
                regs->psw.mask |= PSW_MASK_BA;
        regs->psw.addr = user_sregs.regs.psw.addr;
        memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
        memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
               sizeof(current->thread.acrs));

        fpregs_load(&user_sregs.fpregs, &current->thread.ufpu);

        clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */
        return 0;
}

/* Returns non-zero on fault. */
static int save_sigregs_ext(struct pt_regs *regs,
                            _sigregs_ext __user *sregs_ext)
{
        __u64 vxrs[__NUM_VXRS_LOW];
        int i;

        /* Save vector registers to signal stack */
        if (cpu_has_vx()) {
                for (i = 0; i < __NUM_VXRS_LOW; i++)
                        vxrs[i] = current->thread.ufpu.vxrs[i].low;
                if (__copy_to_user(&sregs_ext->vxrs_low, vxrs,
                                   sizeof(sregs_ext->vxrs_low)) ||
                    __copy_to_user(&sregs_ext->vxrs_high,
                                   current->thread.ufpu.vxrs + __NUM_VXRS_LOW,
                                   sizeof(sregs_ext->vxrs_high)))
                        return -EFAULT;
        }
        return 0;
}

static int restore_sigregs_ext(struct pt_regs *regs,
                               _sigregs_ext __user *sregs_ext)
{
        __u64 vxrs[__NUM_VXRS_LOW];
        int i;

        /* Restore vector registers from signal stack */
        if (cpu_has_vx()) {
                if (__copy_from_user(vxrs, &sregs_ext->vxrs_low,
                                     sizeof(sregs_ext->vxrs_low)) ||
                    __copy_from_user(current->thread.ufpu.vxrs + __NUM_VXRS_LOW,
                                     &sregs_ext->vxrs_high,
                                     sizeof(sregs_ext->vxrs_high)))
                        return -EFAULT;
                for (i = 0; i < __NUM_VXRS_LOW; i++)
                        current->thread.ufpu.vxrs[i].low = vxrs[i];
        }
        return 0;
}

SYSCALL_DEFINE0(sigreturn)
{
        struct pt_regs *regs = task_pt_regs(current);
        struct sigframe __user *frame =
                (struct sigframe __user *) regs->gprs[15];
        sigset_t set;

        if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
                goto badframe;
        set_current_blocked(&set);
        save_user_fpu_regs();
        if (restore_sigregs(regs, &frame->sregs))
                goto badframe;
        if (restore_sigregs_ext(regs, &frame->sregs_ext))
                goto badframe;
        load_sigregs();
        return regs->gprs[2];
badframe:
        force_sig(SIGSEGV);
        return 0;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = task_pt_regs(current);
        struct rt_sigframe __user *frame =
                (struct rt_sigframe __user *)regs->gprs[15];
        sigset_t set;

        if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;
        set_current_blocked(&set);
        if (restore_altstack(&frame->uc.uc_stack))
                goto badframe;
        save_user_fpu_regs();
        if (restore_sigregs(regs, &frame->uc.uc_mcontext))
                goto badframe;
        if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
                goto badframe;
        load_sigregs();
        return regs->gprs[2];
badframe:
        force_sig(SIGSEGV);
        return 0;
}

/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
{
        unsigned long sp;

        /* Default to using normal stack */
        sp = regs->gprs[15];

        /* Overflow on alternate signal stack gives SIGSEGV. */
        if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
                return (void __user *) -1UL;

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
                if (! sas_ss_flags(sp))
                        sp = current->sas_ss_sp + current->sas_ss_size;
        }

        return (void __user *)((sp - frame_size) & -8ul);
}

static int setup_frame(int sig, struct k_sigaction *ka,
                       sigset_t *set, struct pt_regs * regs)
{
        struct sigframe __user *frame;
        struct sigcontext sc;
        unsigned long restorer;
        size_t frame_size;

        frame_size = sizeof(*frame) - sizeof(frame->sregs_ext);
        if (cpu_has_vx())
                frame_size += sizeof(frame->sregs_ext);
        frame = get_sigframe(ka, regs, frame_size);
        if (frame == (void __user *) -1UL)
                return -EFAULT;

        /* Set up backchain. */
        if (__put_user(regs->gprs[15], (addr_t __user *) frame))
                return -EFAULT;

        /* Create struct sigcontext on the signal stack */
        memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE);
        sc.sregs = (_sigregs __user __force *) &frame->sregs;
        if (__copy_to_user(&frame->sc, &sc, sizeof(frame->sc)))
                return -EFAULT;

        /* Store registers needed to create the signal frame */
        store_sigregs();

        /* Create _sigregs on the signal stack */
        if (save_sigregs(regs, &frame->sregs))
                return -EFAULT;

        /* Place signal number on stack to allow backtrace from handler.  */
        if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
                return -EFAULT;

        /* Create _sigregs_ext on the signal stack */
        if (save_sigregs_ext(regs, &frame->sregs_ext))
                return -EFAULT;

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER)
                restorer = (unsigned long) ka->sa.sa_restorer;
        else
                restorer = VDSO_SYMBOL(current, sigreturn);

        /* Set up registers for signal handler */
        regs->gprs[14] = restorer;
        regs->gprs[15] = (unsigned long) frame;
        /* Force default amode and default user address space control. */
        regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
                (PSW_USER_BITS & PSW_MASK_ASC) |
                (regs->psw.mask & ~PSW_MASK_ASC);
        regs->psw.addr = (unsigned long) ka->sa.sa_handler;

        regs->gprs[2] = sig;
        regs->gprs[3] = (unsigned long) &frame->sc;

        /* We forgot to include these in the sigcontext.
           To avoid breaking binary compatibility, they are passed as args. */
        if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
            sig == SIGTRAP || sig == SIGFPE) {
                /* set extra registers only for synchronous signals */
                regs->gprs[4] = regs->int_code & 127;
                regs->gprs[5] = regs->int_parm_long;
                regs->gprs[6] = current->thread.last_break;
        }
        return 0;
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        unsigned long uc_flags, restorer;
        size_t frame_size;

        frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext);
        uc_flags = 0;
        if (cpu_has_vx()) {
                frame_size += sizeof(_sigregs_ext);
                uc_flags |= UC_VXRS;
        }
        frame = get_sigframe(&ksig->ka, regs, frame_size);
        if (frame == (void __user *) -1UL)
                return -EFAULT;

        /* Set up backchain. */
        if (__put_user(regs->gprs[15], (addr_t __user *) frame))
                return -EFAULT;

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        if (ksig->ka.sa.sa_flags & SA_RESTORER)
                restorer = (unsigned long) ksig->ka.sa.sa_restorer;
        else
                restorer = VDSO_SYMBOL(current, rt_sigreturn);

        /* Create siginfo on the signal stack */
        if (copy_siginfo_to_user(&frame->info, &ksig->info))
                return -EFAULT;

        /* Store registers needed to create the signal frame */
        store_sigregs();

        /* Create ucontext on the signal stack. */
        if (__put_user(uc_flags, &frame->uc.uc_flags) ||
            __put_user(NULL, &frame->uc.uc_link) ||
            __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) ||
            save_sigregs(regs, &frame->uc.uc_mcontext) ||
            __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)) ||
            save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
                return -EFAULT;

        /* Set up registers for signal handler */
        regs->gprs[14] = restorer;
        regs->gprs[15] = (unsigned long) frame;
        /* Force default amode and default user address space control. */
        regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
                (PSW_USER_BITS & PSW_MASK_ASC) |
                (regs->psw.mask & ~PSW_MASK_ASC);
        regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler;

        regs->gprs[2] = ksig->sig;
        regs->gprs[3] = (unsigned long) &frame->info;
        regs->gprs[4] = (unsigned long) &frame->uc;
        regs->gprs[5] = current->thread.last_break;
        return 0;
}

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

        /* Set up the stack frame */
        if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                ret = setup_rt_frame(ksig, oldset, regs);
        else
                ret = setup_frame(ksig->sig, &ksig->ka, oldset, regs);

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

/*
 * 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.
 */

void arch_do_signal_or_restart(struct pt_regs *regs)
{
        struct ksignal ksig;
        sigset_t *oldset = sigmask_to_save();

        /*
         * Get signal to deliver. When running under ptrace, at this point
         * the debugger may change all our registers, including the system
         * call information.
         */
        current->thread.system_call =
                test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;

        if (get_signal(&ksig)) {
                /* Whee!  Actually deliver the signal.  */
                if (current->thread.system_call) {
                        regs->int_code = current->thread.system_call;
                        /* Check for system call restarting. */
                        switch (regs->gprs[2]) {
                        case -ERESTART_RESTARTBLOCK:
                        case -ERESTARTNOHAND:
                                regs->gprs[2] = -EINTR;
                                break;
                        case -ERESTARTSYS:
                                if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
                                        regs->gprs[2] = -EINTR;
                                        break;
                                }
                                fallthrough;
                        case -ERESTARTNOINTR:
                                regs->gprs[2] = regs->orig_gpr2;
                                regs->psw.addr =
                                        __rewind_psw(regs->psw,
                                                     regs->int_code >> 16);
                                break;
                        }
                }
                /* No longer in a system call */
                clear_pt_regs_flag(regs, PIF_SYSCALL);

                rseq_signal_deliver(&ksig, regs);
                handle_signal(&ksig, oldset, regs);
                return;
        }

        /* No handlers present - check for system call restart */
        clear_pt_regs_flag(regs, PIF_SYSCALL);
        if (current->thread.system_call) {
                regs->int_code = current->thread.system_call;
                switch (regs->gprs[2]) {
                case -ERESTART_RESTARTBLOCK:
                        /* Restart with sys_restart_syscall */
                        regs->gprs[2] = regs->orig_gpr2;
                        current->restart_block.arch_data = regs->psw.addr;
                        regs->psw.addr = VDSO_SYMBOL(current, restart_syscall);
                        if (test_thread_flag(TIF_SINGLE_STEP))
                                clear_thread_flag(TIF_PER_TRAP);
                        break;
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->gprs[2] = regs->orig_gpr2;
                        regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
                        if (test_thread_flag(TIF_SINGLE_STEP))
                                clear_thread_flag(TIF_PER_TRAP);
                        break;
                }
        }

        /*
         * If there's no signal to deliver, we just put the saved sigmask back.
         */
        restore_saved_sigmask();
}