// SPDX-License-Identifier: GPL-2.0
/*
 * This file handles the architecture dependent parts of process handling.
 *
 *    Copyright IBM Corp. 1999, 2009
 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
 *               Hartmut Penner <hp@de.ibm.com>,
 *               Denis Joseph Barrow,
 */

#include <linux/elf-randomize.h>
#include <linux/compiler.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/smp.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
#include <linux/personality.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/kprobes.h>
#include <linux/random.h>
#include <linux/export.h>
#include <linux/init_task.h>
#include <asm/cpu_mf.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/vtimer.h>
#include <asm/exec.h>
#include <asm/irq.h>
#include <asm/nmi.h>
#include <asm/smp.h>
#include <asm/stacktrace.h>
#include <asm/switch_to.h>
#include <asm/runtime_instr.h>
#include "entry.h"

asmlinkage void ret_from_fork(void) asm ("ret_from_fork");

extern void kernel_thread_starter(void);

void flush_thread(void)
{
}

void arch_setup_new_exec(void)
{
        if (S390_lowcore.current_pid != current->pid) {
                S390_lowcore.current_pid = current->pid;
                if (test_facility(40))
                        lpp(&S390_lowcore.lpp);
        }
}

void arch_release_task_struct(struct task_struct *tsk)
{
        runtime_instr_release(tsk);
        guarded_storage_release(tsk);
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
        /*
         * Save the floating-point or vector register state of the current
         * task and set the CIF_FPU flag to lazy restore the FPU register
         * state when returning to user space.
         */
        save_fpu_regs();

        memcpy(dst, src, arch_task_struct_size);
        dst->thread.fpu.regs = dst->thread.fpu.fprs;
        return 0;
}

int copy_thread_tls(unsigned long clone_flags, unsigned long new_stackp,
                    unsigned long arg, struct task_struct *p, unsigned long tls)
{
        struct fake_frame
        {
                struct stack_frame sf;
                struct pt_regs childregs;
        } *frame;

        frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
        p->thread.ksp = (unsigned long) frame;
        /* Save access registers to new thread structure. */
        save_access_regs(&p->thread.acrs[0]);
        /* start new process with ar4 pointing to the correct address space */
        p->thread.mm_segment = get_fs();
        /* Don't copy debug registers */
        memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
        memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
        clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
        p->thread.per_flags = 0;
        /* Initialize per thread user and system timer values */
        p->thread.user_timer = 0;
        p->thread.guest_timer = 0;
        p->thread.system_timer = 0;
        p->thread.hardirq_timer = 0;
        p->thread.softirq_timer = 0;

        frame->sf.back_chain = 0;
        /* new return point is ret_from_fork */
        frame->sf.gprs[8] = (unsigned long) ret_from_fork;
        /* fake return stack for resume(), don't go back to schedule */
        frame->sf.gprs[9] = (unsigned long) frame;

        /* Store access registers to kernel stack of new process. */
        if (unlikely(p->flags & PF_KTHREAD)) {
                /* kernel thread */
                memset(&frame->childregs, 0, sizeof(struct pt_regs));
                frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_DAT |
                                PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
                frame->childregs.psw.addr =
                                (unsigned long) kernel_thread_starter;
                frame->childregs.gprs[9] = new_stackp; /* function */
                frame->childregs.gprs[10] = arg;
                frame->childregs.gprs[11] = (unsigned long) do_exit;
                frame->childregs.orig_gpr2 = -1;

                return 0;
        }
        frame->childregs = *current_pt_regs();
        frame->childregs.gprs[2] = 0;   /* child returns 0 on fork. */
        frame->childregs.flags = 0;
        if (new_stackp)
                frame->childregs.gprs[15] = new_stackp;

        /* Don't copy runtime instrumentation info */
        p->thread.ri_cb = NULL;
        frame->childregs.psw.mask &= ~PSW_MASK_RI;
        /* Don't copy guarded storage control block */
        p->thread.gs_cb = NULL;
        p->thread.gs_bc_cb = NULL;

        /* Set a new TLS ?  */
        if (clone_flags & CLONE_SETTLS) {
                if (is_compat_task()) {
                        p->thread.acrs[0] = (unsigned int)tls;
                } else {
                        p->thread.acrs[0] = (unsigned int)(tls >> 32);
                        p->thread.acrs[1] = (unsigned int)tls;
                }
        }
        return 0;
}

asmlinkage void execve_tail(void)
{
        current->thread.fpu.fpc = 0;
        asm volatile("sfpc %0" : : "d" (0));
}

/*
 * fill in the FPU structure for a core dump.
 */
int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
{
        save_fpu_regs();
        fpregs->fpc = current->thread.fpu.fpc;
        fpregs->pad = 0;
        if (MACHINE_HAS_VX)
                convert_vx_to_fp((freg_t *)&fpregs->fprs,
                                 current->thread.fpu.vxrs);
        else
                memcpy(&fpregs->fprs, current->thread.fpu.fprs,
                       sizeof(fpregs->fprs));
        return 1;
}
EXPORT_SYMBOL(dump_fpu);

unsigned long get_wchan(struct task_struct *p)
{
        struct stack_frame *sf, *low, *high;
        unsigned long return_address;
        int count;

        if (!p || p == current || p->state == TASK_RUNNING || !task_stack_page(p))
                return 0;

        if (!try_get_task_stack(p))
                return 0;

        low = task_stack_page(p);
        high = (struct stack_frame *) task_pt_regs(p);
        sf = (struct stack_frame *) p->thread.ksp;
        if (sf <= low || sf > high) {
                return_address = 0;
                goto out;
        }
        for (count = 0; count < 16; count++) {
                sf = (struct stack_frame *)READ_ONCE_NOCHECK(sf->back_chain);
                if (sf <= low || sf > high) {
                        return_address = 0;
                        goto out;
                }
                return_address = READ_ONCE_NOCHECK(sf->gprs[8]);
                if (!in_sched_functions(return_address))
                        goto out;
        }
out:
        put_task_stack(p);
        return return_address;
}

unsigned long arch_align_stack(unsigned long sp)
{
        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
                sp -= get_random_int() & ~PAGE_MASK;
        return sp & ~0xf;
}

static inline unsigned long brk_rnd(void)
{
        return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
        unsigned long ret;

        ret = PAGE_ALIGN(mm->brk + brk_rnd());
        return (ret > mm->brk) ? ret : mm->brk;
}

void set_fs_fixup(void)
{
        struct pt_regs *regs = current_pt_regs();
        static bool warned;

        set_fs(USER_DS);
        if (warned)
                return;
        WARN(1, "Unbalanced set_fs - int code: 0x%x\n", regs->int_code);
        show_registers(regs);
        warned = true;
}