/*
 * 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/compiler.h>
#include <linux/cpu.h>
#include <linux/sched.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/module.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/irq.h>
#include <asm/timer.h>
#include <asm/nmi.h>
#include <asm/smp.h>
#include <asm/switch_to.h>
#include "entry.h"

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

/*
 * Return saved PC of a blocked thread. used in kernel/sched.
 * resume in entry.S does not create a new stack frame, it
 * just stores the registers %r6-%r15 to the frame given by
 * schedule. We want to return the address of the caller of
 * schedule, so we have to walk the backchain one time to
 * find the frame schedule() store its return address.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
        struct stack_frame *sf, *low, *high;

        if (!tsk || !task_stack_page(tsk))
                return 0;
        low = task_stack_page(tsk);
        high = (struct stack_frame *) task_pt_regs(tsk);
        sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
        if (sf <= low || sf > high)
                return 0;
        sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
        if (sf <= low || sf > high)
                return 0;
        return sf->gprs[8];
}

/*
 * The idle loop on a S390...
 */
static void default_idle(void)
{
        if (cpu_is_offline(smp_processor_id()))
                cpu_die();
        local_irq_disable();
        if (need_resched()) {
                local_irq_enable();
                return;
        }
        local_mcck_disable();
        if (test_thread_flag(TIF_MCCK_PENDING)) {
                local_mcck_enable();
                local_irq_enable();
                return;
        }
        /* Halt the cpu and keep track of cpu time accounting. */
        vtime_stop_cpu();
}

void cpu_idle(void)
{
        for (;;) {
                tick_nohz_idle_enter();
                rcu_idle_enter();
                while (!need_resched() && !test_thread_flag(TIF_MCCK_PENDING))
                        default_idle();
                rcu_idle_exit();
                tick_nohz_idle_exit();
                if (test_thread_flag(TIF_MCCK_PENDING))
                        s390_handle_mcck();
                schedule_preempt_disabled();
        }
}

extern void __kprobes kernel_thread_starter(void);

asm(
        ".section .kprobes.text, \"ax\"\n"
        ".global kernel_thread_starter\n"
        "kernel_thread_starter:\n"
        "    la    2,0(10)\n"
        "    basr  14,9\n"
        "    la    2,0\n"
        "    br    11\n"
        ".previous\n");

int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
        struct pt_regs regs;

        memset(&regs, 0, sizeof(regs));
        regs.psw.mask = psw_kernel_bits |
                PSW_MASK_DAT | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
        regs.psw.addr = (unsigned long) kernel_thread_starter | PSW_ADDR_AMODE;
        regs.gprs[9] = (unsigned long) fn;
        regs.gprs[10] = (unsigned long) arg;
        regs.gprs[11] = (unsigned long) do_exit;
        regs.orig_gpr2 = -1;

        /* Ok, create the new process.. */
        return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
                       0, &regs, 0, NULL, NULL);
}
EXPORT_SYMBOL(kernel_thread);

/*
 * Free current thread data structures etc..
 */
void exit_thread(void)
{
}

void flush_thread(void)
{
}

void release_thread(struct task_struct *dead_task)
{
}

int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
                unsigned long unused,
                struct task_struct *p, struct pt_regs *regs)
{
        struct thread_info *ti;
        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;
        /* Store access registers to kernel stack of new process. */
        frame->childregs = *regs;
        frame->childregs.gprs[2] = 0;   /* child returns 0 on fork. */
        frame->childregs.gprs[15] = new_stackp;
        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;

        /* Save access registers to new thread structure. */
        save_access_regs(&p->thread.acrs[0]);

#ifndef CONFIG_64BIT
        /*
         * save fprs to current->thread.fp_regs to merge them with
         * the emulated registers and then copy the result to the child.
         */
        save_fp_regs(&current->thread.fp_regs);
        memcpy(&p->thread.fp_regs, &current->thread.fp_regs,
               sizeof(s390_fp_regs));
        /* Set a new TLS ?  */
        if (clone_flags & CLONE_SETTLS)
                p->thread.acrs[0] = regs->gprs[6];
#else /* CONFIG_64BIT */
        /* Save the fpu registers to new thread structure. */
        save_fp_regs(&p->thread.fp_regs);
        /* Set a new TLS ?  */
        if (clone_flags & CLONE_SETTLS) {
                if (is_compat_task()) {
                        p->thread.acrs[0] = (unsigned int) regs->gprs[6];
                } else {
                        p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);
                        p->thread.acrs[1] = (unsigned int) regs->gprs[6];
                }
        }
#endif /* CONFIG_64BIT */
        /* 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);
        clear_tsk_thread_flag(p, TIF_PER_TRAP);
        /* Initialize per thread user and system timer values */
        ti = task_thread_info(p);
        ti->user_timer = 0;
        ti->system_timer = 0;
        return 0;
}

SYSCALL_DEFINE0(fork)
{
        struct pt_regs *regs = task_pt_regs(current);
        return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
}

SYSCALL_DEFINE4(clone, unsigned long, newsp, unsigned long, clone_flags,
                int __user *, parent_tidptr, int __user *, child_tidptr)
{
        struct pt_regs *regs = task_pt_regs(current);

        if (!newsp)
                newsp = regs->gprs[15];
        return do_fork(clone_flags, newsp, regs, 0,
                       parent_tidptr, child_tidptr);
}

/*
 * This is trivial, and on the face of it looks like it
 * could equally well be done in user mode.
 *
 * Not so, for quite unobvious reasons - register pressure.
 * In user mode vfork() cannot have a stack frame, and if
 * done by calling the "clone()" system call directly, you
 * do not have enough call-clobbered registers to hold all
 * the information you need.
 */
SYSCALL_DEFINE0(vfork)
{
        struct pt_regs *regs = task_pt_regs(current);
        return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
                       regs->gprs[15], regs, 0, NULL, NULL);
}

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

/*
 * sys_execve() executes a new program.
 */
SYSCALL_DEFINE3(execve, const char __user *, name,
                const char __user *const __user *, argv,
                const char __user *const __user *, envp)
{
        struct pt_regs *regs = task_pt_regs(current);
        char *filename;
        long rc;

        filename = getname(name);
        rc = PTR_ERR(filename);
        if (IS_ERR(filename))
                return rc;
        rc = do_execve(filename, argv, envp, regs);
        if (rc)
                goto out;
        execve_tail();
        rc = regs->gprs[2];
out:
        putname(filename);
        return rc;
}

/*
 * fill in the FPU structure for a core dump.
 */
int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
{
#ifndef CONFIG_64BIT
        /*
         * save fprs to current->thread.fp_regs to merge them with
         * the emulated registers and then copy the result to the dump.
         */
        save_fp_regs(&current->thread.fp_regs);
        memcpy(fpregs, &current->thread.fp_regs, sizeof(s390_fp_regs));
#else /* CONFIG_64BIT */
        save_fp_regs(fpregs);
#endif /* CONFIG_64BIT */
        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;
        low = task_stack_page(p);
        high = (struct stack_frame *) task_pt_regs(p);
        sf = (struct stack_frame *) (p->thread.ksp & PSW_ADDR_INSN);
        if (sf <= low || sf > high)
                return 0;
        for (count = 0; count < 16; count++) {
                sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
                if (sf <= low || sf > high)
                        return 0;
                return_address = sf->gprs[8] & PSW_ADDR_INSN;
                if (!in_sched_functions(return_address))
                        return return_address;
        }
        return 0;
}

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)
{
        /* 8MB for 32bit, 1GB for 64bit */
        if (is_32bit_task())
                return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
        else
                return (get_random_int() & 0x3ffffUL) << PAGE_SHIFT;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
        unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());

        if (ret < mm->brk)
                return mm->brk;
        return ret;
}

unsigned long randomize_et_dyn(unsigned long base)
{
        unsigned long ret = PAGE_ALIGN(base + brk_rnd());

        if (!(current->flags & PF_RANDOMIZE))
                return base;
        if (ret < base)
                return base;
        return ret;
}