/*
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 */

/*
 * This file handles the architecture-dependent parts of process handling..
 */

#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/user.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/mc146818rtc.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/percpu.h>
#include <linux/prctl.h>
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/kdebug.h>

#include <asm/pgtable.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/fpu/internal.h>
#include <asm/desc.h>
#ifdef CONFIG_MATH_EMULATION
#include <asm/math_emu.h>
#endif

#include <linux/err.h>

#include <asm/tlbflush.h>
#include <asm/cpu.h>
#include <asm/idle.h>
#include <asm/syscalls.h>
#include <asm/debugreg.h>
#include <asm/switch_to.h>

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
        return ((unsigned long *)tsk->thread.sp)[3];
}

void __show_regs(struct pt_regs *regs, int all)
{
        unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
        unsigned long d0, d1, d2, d3, d6, d7;
        unsigned long sp;
        unsigned short ss, gs;

        if (user_mode(regs)) {
                sp = regs->sp;
                ss = regs->ss & 0xffff;
                gs = get_user_gs(regs);
        } else {
                sp = kernel_stack_pointer(regs);
                savesegment(ss, ss);
                savesegment(gs, gs);
        }

        printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
                        (u16)regs->cs, regs->ip, regs->flags,
                        smp_processor_id());
        print_symbol("EIP is at %s\n", regs->ip);

        printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
                regs->ax, regs->bx, regs->cx, regs->dx);
        printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
                regs->si, regs->di, regs->bp, sp);
        printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
               (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);

        if (!all)
                return;

        cr0 = read_cr0();
        cr2 = read_cr2();
        cr3 = read_cr3();
        cr4 = __read_cr4_safe();
        printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
                        cr0, cr2, cr3, cr4);

        get_debugreg(d0, 0);
        get_debugreg(d1, 1);
        get_debugreg(d2, 2);
        get_debugreg(d3, 3);
        get_debugreg(d6, 6);
        get_debugreg(d7, 7);

        /* Only print out debug registers if they are in their non-default state. */
        if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
            (d6 == DR6_RESERVED) && (d7 == 0x400))
                return;

        printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
                        d0, d1, d2, d3);
        printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
                        d6, d7);
}

void release_thread(struct task_struct *dead_task)
{
        BUG_ON(dead_task->mm);
        release_vm86_irqs(dead_task);
}

int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
        unsigned long arg, struct task_struct *p, unsigned long tls)
{
        struct pt_regs *childregs = task_pt_regs(p);
        struct task_struct *tsk;
        int err;

        p->thread.sp = (unsigned long) childregs;
        p->thread.sp0 = (unsigned long) (childregs+1);
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));

        if (unlikely(p->flags & PF_KTHREAD)) {
                /* kernel thread */
                memset(childregs, 0, sizeof(struct pt_regs));
                p->thread.ip = (unsigned long) ret_from_kernel_thread;
                task_user_gs(p) = __KERNEL_STACK_CANARY;
                childregs->ds = __USER_DS;
                childregs->es = __USER_DS;
                childregs->fs = __KERNEL_PERCPU;
                childregs->bx = sp;     /* function */
                childregs->bp = arg;
                childregs->orig_ax = -1;
                childregs->cs = __KERNEL_CS | get_kernel_rpl();
                childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
                p->thread.io_bitmap_ptr = NULL;
                return 0;
        }
        *childregs = *current_pt_regs();
        childregs->ax = 0;
        if (sp)
                childregs->sp = sp;

        p->thread.ip = (unsigned long) ret_from_fork;
        task_user_gs(p) = get_user_gs(current_pt_regs());

        p->thread.io_bitmap_ptr = NULL;
        tsk = current;
        err = -ENOMEM;

        if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
                p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
                                                IO_BITMAP_BYTES, GFP_KERNEL);
                if (!p->thread.io_bitmap_ptr) {
                        p->thread.io_bitmap_max = 0;
                        return -ENOMEM;
                }
                set_tsk_thread_flag(p, TIF_IO_BITMAP);
        }

        err = 0;

        /*
         * Set a new TLS for the child thread?
         */
        if (clone_flags & CLONE_SETTLS)
                err = do_set_thread_area(p, -1,
                        (struct user_desc __user *)tls, 0);

        if (err && p->thread.io_bitmap_ptr) {
                kfree(p->thread.io_bitmap_ptr);
                p->thread.io_bitmap_max = 0;
        }
        return err;
}

void
start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
{
        set_user_gs(regs, 0);
        regs->fs                = 0;
        regs->ds                = __USER_DS;
        regs->es                = __USER_DS;
        regs->ss                = __USER_DS;
        regs->cs                = __USER_CS;
        regs->ip                = new_ip;
        regs->sp                = new_sp;
        regs->flags             = X86_EFLAGS_IF;
        force_iret();
}
EXPORT_SYMBOL_GPL(start_thread);


/*
 *      switch_to(x,y) should switch tasks from x to y.
 *
 * We fsave/fwait so that an exception goes off at the right time
 * (as a call from the fsave or fwait in effect) rather than to
 * the wrong process. Lazy FP saving no longer makes any sense
 * with modern CPU's, and this simplifies a lot of things (SMP
 * and UP become the same).
 *
 * NOTE! We used to use the x86 hardware context switching. The
 * reason for not using it any more becomes apparent when you
 * try to recover gracefully from saved state that is no longer
 * valid (stale segment register values in particular). With the
 * hardware task-switch, there is no way to fix up bad state in
 * a reasonable manner.
 *
 * The fact that Intel documents the hardware task-switching to
 * be slow is a fairly red herring - this code is not noticeably
 * faster. However, there _is_ some room for improvement here,
 * so the performance issues may eventually be a valid point.
 * More important, however, is the fact that this allows us much
 * more flexibility.
 *
 * The return value (in %ax) will be the "prev" task after
 * the task-switch, and shows up in ret_from_fork in entry.S,
 * for example.
 */
__visible __notrace_funcgraph struct task_struct *
__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
{
        struct thread_struct *prev = &prev_p->thread,
                             *next = &next_p->thread;
        struct fpu *prev_fpu = &prev->fpu;
        struct fpu *next_fpu = &next->fpu;
        int cpu = smp_processor_id();
        struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
        fpu_switch_t fpu_switch;

        /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */

        fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu);

        /*
         * Save away %gs. No need to save %fs, as it was saved on the
         * stack on entry.  No need to save %es and %ds, as those are
         * always kernel segments while inside the kernel.  Doing this
         * before setting the new TLS descriptors avoids the situation
         * where we temporarily have non-reloadable segments in %fs
         * and %gs.  This could be an issue if the NMI handler ever
         * used %fs or %gs (it does not today), or if the kernel is
         * running inside of a hypervisor layer.
         */
        lazy_save_gs(prev->gs);

        /*
         * Load the per-thread Thread-Local Storage descriptor.
         */
        load_TLS(next, cpu);

        /*
         * Restore IOPL if needed.  In normal use, the flags restore
         * in the switch assembly will handle this.  But if the kernel
         * is running virtualized at a non-zero CPL, the popf will
         * not restore flags, so it must be done in a separate step.
         */
        if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
                set_iopl_mask(next->iopl);

        /*
         * If it were not for PREEMPT_ACTIVE we could guarantee that the
         * preempt_count of all tasks was equal here and this would not be
         * needed.
         */
        task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
        this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);

        /*
         * Now maybe handle debug registers and/or IO bitmaps
         */
        if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
                     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
                __switch_to_xtra(prev_p, next_p, tss);

        /*
         * Leave lazy mode, flushing any hypercalls made here.
         * This must be done before restoring TLS segments so
         * the GDT and LDT are properly updated, and must be
         * done before fpu__restore(), so the TS bit is up
         * to date.
         */
        arch_end_context_switch(next_p);

        /*
         * Reload esp0 and cpu_current_top_of_stack.  This changes
         * current_thread_info().
         */
        load_sp0(tss, next);
        this_cpu_write(cpu_current_top_of_stack,
                       (unsigned long)task_stack_page(next_p) +
                       THREAD_SIZE);

        /*
         * Restore %gs if needed (which is common)
         */
        if (prev->gs | next->gs)
                lazy_load_gs(next->gs);

        switch_fpu_finish(next_fpu, fpu_switch);

        this_cpu_write(current_task, next_p);

        return prev_p;
}

#define top_esp                (THREAD_SIZE - sizeof(unsigned long))
#define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))

unsigned long get_wchan(struct task_struct *p)
{
        unsigned long bp, sp, ip;
        unsigned long stack_page;
        int count = 0;
        if (!p || p == current || p->state == TASK_RUNNING)
                return 0;
        stack_page = (unsigned long)task_stack_page(p);
        sp = p->thread.sp;
        if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
                return 0;
        /* include/asm-i386/system.h:switch_to() pushes bp last. */
        bp = *(unsigned long *) sp;
        do {
                if (bp < stack_page || bp > top_ebp+stack_page)
                        return 0;
                ip = *(unsigned long *) (bp+4);
                if (!in_sched_functions(ip))
                        return ip;
                bp = *(unsigned long *) bp;
        } while (count++ < 16);
        return 0;
}