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/*

 *  linux/kernel/vm86.c

 *

 *  Copyright (C) 1994  Linus Torvalds

 */

#include <linux/errno.h>

#include <linux/sched.h>

#include <linux/kernel.h>

#include <linux/signal.h>

#include <linux/string.h>

#include <linux/ptrace.h>

#include <linux/mm.h>

#include <asm/segment.h>

#include <asm/pgtable.h>

#include <asm/io.h>

/*

 * Known problems:

 *

 * Interrupt handling is not guaranteed:

 * - a real x86 will disable all interrupts for one instruction

 *   after a "mov ss,xx" to make stack handling atomic even without

 *   the 'lss' instruction. We can't guarantee this in v86 mode,

 *   as the next instruction might result in a page fault or similar.

 * - a real x86 will have interrupts disabled for one instruction

 *   past the 'sti' that enables them. We don't bother with all the

 *   details yet..

 *

 * Hopefully these problems do not actually matter for anything.

 */

#define KVM86   ((struct kernel_vm86_struct *)regs)

#define VMPI    KVM86->vm86plus

/*

 * 8- and 16-bit register defines..

 */

#define AL(regs)        (((unsigned char *)&((regs)->eax))[0])

#define AH(regs)        (((unsigned char *)&((regs)->eax))[1])

#define IP(regs)        (*(unsigned short *)&((regs)->eip))

#define SP(regs)        (*(unsigned short *)&((regs)->esp))

/*

 * virtual flags (16 and 32-bit versions)

 */

#define VFLAGS  (*(unsigned short *)&(current->tss.v86flags))

#define VEFLAGS (current->tss.v86flags)

#define set_flags(X,new,mask) \

((X) = ((X) & ~(mask)) | ((new) & (mask)))

#define SAFE_MASK       (0xDD5)

#define RETURN_MASK     (0xDFF)

asmlinkage struct pt_regs * save_v86_state(struct vm86_regs * regs)

{

        if (!current->tss.vm86_info) {

                printk("no vm86_info: BAD\n");

                do_exit(SIGSEGV);

        }

        set_flags(regs->eflags, VEFLAGS, VIF_MASK | current->tss.v86mask);

        memcpy_tofs(&current->tss.vm86_info->regs,regs,sizeof(*regs));

        put_fs_long(current->tss.screen_bitmap,&current->tss.vm86_info->screen_bitmap);

        current->tss.esp0 = current->saved_kernel_stack;

        current->saved_kernel_stack = 0;

        return KVM86->regs32;

}

static void mark_screen_rdonly(struct task_struct * tsk)

{

        pgd_t *pgd;

        pmd_t *pmd;

        pte_t *pte;

        int i;

        pgd = pgd_offset(tsk->mm, 0xA0000);

        if (pgd_none(*pgd))

                return;

        if (pgd_bad(*pgd)) {

                printk("vm86: bad pgd entry [%p]:%08lx\n", pgd, pgd_val(*pgd));

                pgd_clear(pgd);

                return;

        }

        pmd = pmd_offset(pgd, 0xA0000);

        if (pmd_none(*pmd))

                return;

        if (pmd_bad(*pmd)) {

                printk("vm86: bad pmd entry [%p]:%08lx\n", pmd, pmd_val(*pmd));

                pmd_clear(pmd);

                return;

        }

        pte = pte_offset(pmd, 0xA0000);

        for (i = 0; i < 32; i++) {

                if (pte_present(*pte))

                        set_pte(pte, pte_wrprotect(*pte));

                pte++;

        }

        flush_tlb();

}

static int do_vm86_irq_handling(int subfunction, int irqnumber);

static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);

asmlinkage int sys_vm86old(struct vm86_struct * v86)

{

        struct kernel_vm86_struct info; /* declare this _on top_,

                                         * this avoids wasting of stack space.

                                         * This remains on the stack until we

                                         * return to 32 bit user space.

                                         */

        struct task_struct *tsk = current;

        int error;

        if (tsk->saved_kernel_stack)

                return -EPERM;

        /* v86 must be readable (now) and writable (for save_v86_state) */

        error = verify_area(VERIFY_WRITE,v86,sizeof(*v86));

        if (error)

                return error;

        memcpy_fromfs(&info,v86,sizeof(struct vm86_struct));

        memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);

        info.regs32 = (struct pt_regs *) &v86;

        tsk->tss.vm86_info = v86;

        do_sys_vm86(&info, tsk);

        return 0;        /* we never return here */

}

asmlinkage int sys_vm86(unsigned long subfunction, struct vm86plus_struct * v86)

{

        struct kernel_vm86_struct info; /* declare this _on top_,

                                         * this avoids wasting of stack space.

                                         * This remains on the stack until we

                                         * return to 32 bit user space.

                                         */

        struct task_struct *tsk = current;

        int error;

        switch (subfunction) {

                case VM86_REQUEST_IRQ:

                case VM86_FREE_IRQ:

                case VM86_GET_IRQ_BITS:

                case VM86_GET_AND_RESET_IRQ:

                        return do_vm86_irq_handling(subfunction,(int)v86);

                case VM86_PLUS_INSTALL_CHECK:

                        /* NOTE: on old vm86 stuff this will return the error

                           from verify_area(), because the subfunction is

                           interpreted as (invalid) address to vm86_struct.

                           So the installation check works.

                         */

                        return 0;

        }

        /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */

        if (tsk->saved_kernel_stack)

                return -EPERM;

        /* v86 must be readable (now) and writable (for save_v86_state) */

        error = verify_area(VERIFY_WRITE,v86,sizeof(struct vm86plus_struct));

        if (error)

                return error;

        memcpy_fromfs(&info,v86,sizeof(struct vm86plus_struct));

        info.regs32 = (struct pt_regs *) &subfunction;

        info.vm86plus.is_vm86pus = 1;

        tsk->tss.vm86_info = (struct vm86_struct *)v86;

        do_sys_vm86(&info, tsk);

        return 0;        /* we never return here */

}

static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)

{

/*

 * make sure the vm86() system call doesn't try to do anything silly

 */

        info->regs.__null_ds = 0;

        info->regs.__null_es = 0;

        info->regs.__null_fs = 0;

        info->regs.__null_gs = 0;

/*

 * The eflags register is also special: we cannot trust that the user

 * has set it up safely, so this makes sure interrupt etc flags are

 * inherited from protected mode.

 */

        VEFLAGS = info->regs.eflags;

        info->regs.eflags &= SAFE_MASK;

        info->regs.eflags |= info->regs32->eflags & ~SAFE_MASK;

        info->regs.eflags |= VM_MASK;

        switch (info->cpu_type) {

                case CPU_286:

                        tsk->tss.v86mask = 0;

                        break;

                case CPU_386:

                        tsk->tss.v86mask = NT_MASK | IOPL_MASK;

                        break;

                case CPU_486:

                        tsk->tss.v86mask = AC_MASK | NT_MASK | IOPL_MASK;

                        break;

                default:

                        tsk->tss.v86mask = ID_MASK | AC_MASK | NT_MASK | IOPL_MASK;

                        break;

        }

/*

 * Save old state, set default return value (%eax) to 0

 */

        info->regs32->eax = 0;

        tsk->saved_kernel_stack = tsk->tss.esp0;

        tsk->tss.esp0 = (unsigned long) &info->VM86_TSS_ESP0;

        tsk->tss.screen_bitmap = info->screen_bitmap;

        if (info->flags & VM86_SCREEN_BITMAP)

                mark_screen_rdonly(tsk);

        __asm__ __volatile__(

                "movl %0,%%esp\n\t"

                "jmp ret_from_sys_call"

                : /* no outputs */

                :"r" (&info->regs));

        /* we never return here */

}

static inline void return_to_32bit(struct vm86_regs * regs16, int retval)

{

        struct pt_regs * regs32;

        regs32 = save_v86_state(regs16);

        regs32->eax = retval;

        __asm__ __volatile__("movl %0,%%esp\n\t"

                "jmp ret_from_sys_call"

                : : "r" (regs32));

}

static inline void set_IF(struct vm86_regs * regs)

{

        VEFLAGS |= VIF_MASK;

        if (VEFLAGS & VIP_MASK)

                return_to_32bit(regs, VM86_STI);

}

static inline void clear_IF(struct vm86_regs * regs)

{

        VEFLAGS &= ~VIF_MASK;

}

static inline void clear_TF(struct vm86_regs * regs)

{

        regs->eflags &= ~TF_MASK;

}

static inline void set_vflags_long(unsigned long eflags, struct vm86_regs * regs)

{

        set_flags(VEFLAGS, eflags, current->tss.v86mask);

        set_flags(regs->eflags, eflags, SAFE_MASK);

        if (eflags & IF_MASK)

                set_IF(regs);

}

static inline void set_vflags_short(unsigned short flags, struct vm86_regs * regs)

{

        set_flags(VFLAGS, flags, current->tss.v86mask);

        set_flags(regs->eflags, flags, SAFE_MASK);

        if (flags & IF_MASK)

                set_IF(regs);

}

static inline unsigned long get_vflags(struct vm86_regs * regs)

{

        unsigned long flags = regs->eflags & RETURN_MASK;

        if (VEFLAGS & VIF_MASK)

                flags |= IF_MASK;

        return flags | (VEFLAGS & current->tss.v86mask);

}

static inline int is_revectored(int nr, struct revectored_struct * bitmap)

{

        __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"

                :"=r" (nr)

                :"m" (*bitmap),"r" (nr));

        return nr;

}

/*

 * Boy are these ugly, but we need to do the correct 16-bit arithmetic.

 * Gcc makes a mess of it, so we do it inline and use non-obvious calling

 * conventions..

 */

#define pushb(base, ptr, val) \

__asm__ __volatile__( \

        "decw %w0\n\t" \

        "movb %2,%%fs:0(%1,%0)" \

        : "=r" (ptr) \

        : "r" (base), "q" (val), "0" (ptr))

#define pushw(base, ptr, val) \

__asm__ __volatile__( \

        "decw %w0\n\t" \

        "movb %h2,%%fs:0(%1,%0)\n\t" \

        "decw %w0\n\t" \

        "movb %b2,%%fs:0(%1,%0)" \

        : "=r" (ptr) \

        : "r" (base), "q" (val), "0" (ptr))

#define pushl(base, ptr, val) \

__asm__ __volatile__( \

        "decw %w0\n\t" \

        "rorl $16,%2\n\t" \

        "movb %h2,%%fs:0(%1,%0)\n\t" \

        "decw %w0\n\t" \

        "movb %b2,%%fs:0(%1,%0)\n\t" \

        "decw %w0\n\t" \

        "rorl $16,%2\n\t" \

        "movb %h2,%%fs:0(%1,%0)\n\t" \

        "decw %w0\n\t" \

        "movb %b2,%%fs:0(%1,%0)" \

        : "=r" (ptr) \

        : "r" (base), "q" (val), "0" (ptr))

#define popb(base, ptr) \

({ unsigned long __res; \

__asm__ __volatile__( \

        "movb %%fs:0(%1,%0),%b2\n\t" \

        "incw %w0" \

        : "=r" (ptr), "=r" (base), "=q" (__res) \

        : "0" (ptr), "1" (base), "2" (0)); \

__res; })

#define popw(base, ptr) \

({ unsigned long __res; \

__asm__ __volatile__( \

        "movb %%fs:0(%1,%0),%b2\n\t" \

        "incw %w0\n\t" \

        "movb %%fs:0(%1,%0),%h2\n\t" \

        "incw %w0" \

        : "=r" (ptr), "=r" (base), "=q" (__res) \

        : "0" (ptr), "1" (base), "2" (0)); \

__res; })

#define popl(base, ptr) \

({ unsigned long __res; \

__asm__ __volatile__( \

        "movb %%fs:0(%1,%0),%b2\n\t" \

        "incw %w0\n\t" \

        "movb %%fs:0(%1,%0),%h2\n\t" \

        "incw %w0\n\t" \

        "rorl $16,%2\n\t" \

        "movb %%fs:0(%1,%0),%b2\n\t" \

        "incw %w0\n\t" \

        "movb %%fs:0(%1,%0),%h2\n\t" \

        "incw %w0\n\t" \

        "rorl $16,%2" \

        : "=r" (ptr), "=r" (base), "=q" (__res) \

        : "0" (ptr), "1" (base)); \

__res; })

static void do_int(struct vm86_regs *regs, int i, unsigned char * ssp, unsigned long sp)

{

        unsigned long *intr_ptr, segoffs;

        if (regs->cs == BIOSSEG)

                goto cannot_handle;

        if (is_revectored(i, &KVM86->int_revectored))

                goto cannot_handle;

        if (i==0x21 && is_revectored(AH(regs),&KVM86->int21_revectored))

                goto cannot_handle;

        intr_ptr = (unsigned long *) (i << 2);

        if (verify_area(VERIFY_READ, intr_ptr, 4) < 0)

                goto cannot_handle;

        segoffs = get_fs_long(intr_ptr);

        if ((segoffs >> 16) == BIOSSEG)

                goto cannot_handle;

        pushw(ssp, sp, get_vflags(regs));

        pushw(ssp, sp, regs->cs);

        pushw(ssp, sp, IP(regs));

        regs->cs = segoffs >> 16;

        SP(regs) -= 6;

        IP(regs) = segoffs & 0xffff;

        clear_TF(regs);

        clear_IF(regs);

        return;

cannot_handle:

        return_to_32bit(regs, VM86_INTx + (i << 8));

}

int handle_vm86_trap(struct vm86_regs * regs, long error_code, int trapno)

{

        if (VMPI.is_vm86pus) {

                if ( (trapno==3) || (trapno==1) )

                        return_to_32bit(regs, VM86_TRAP + (trapno << 8));

                do_int(regs, trapno, (unsigned char *) (regs->ss << 4), SP(regs));

                return 0;

        }

        if (trapno !=1)

                return 1; /* we let this handle by the calling routine */

        if (current->flags & PF_PTRACED)

                current->blocked &= ~(1 << (SIGTRAP-1));

        send_sig(SIGTRAP, current, 1);

        current->tss.trap_no = trapno;

        current->tss.error_code = error_code;

        return 0;

}

void handle_vm86_fault(struct vm86_regs * regs, long error_code)

{

        unsigned char *csp, *ssp;

        unsigned long ip, sp;

#define CHECK_IF_IN_TRAP \

        if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \

                pushw(ssp,sp,popw(ssp,sp) | TF_MASK);

#define VM86_FAULT_RETURN \

        if (VMPI.force_return_for_pic  && (VEFLAGS & IF_MASK)) \

                return_to_32bit(regs, VM86_PICRETURN); \

        return;

        csp = (unsigned char *) (regs->cs << 4);

        ssp = (unsigned char *) (regs->ss << 4);

        sp = SP(regs);

        ip = IP(regs);

        switch (popb(csp, ip)) {

        /* operand size override */

        case 0x66:

                switch (popb(csp, ip)) {

                /* pushfd */

                case 0x9c:

                        SP(regs) -= 4;

                        IP(regs) += 2;

                        pushl(ssp, sp, get_vflags(regs));

                        VM86_FAULT_RETURN;

                /* popfd */

                case 0x9d:

                        SP(regs) += 4;

                        IP(regs) += 2;

                        CHECK_IF_IN_TRAP

                        set_vflags_long(popl(ssp, sp), regs);

                        VM86_FAULT_RETURN;

                /* iretd */

                case 0xcf:

                        SP(regs) += 12;

                        IP(regs) = (unsigned short)popl(ssp, sp);

                        regs->cs = (unsigned short)popl(ssp, sp);

                        CHECK_IF_IN_TRAP

                        set_vflags_long(popl(ssp, sp), regs);

                        VM86_FAULT_RETURN;

                /* need this to avoid a fallthrough */

                default:

                        return_to_32bit(regs, VM86_UNKNOWN);

                }

        /* pushf */

        case 0x9c:

                SP(regs) -= 2;

                IP(regs)++;

                pushw(ssp, sp, get_vflags(regs));

                VM86_FAULT_RETURN;

        /* popf */

        case 0x9d:

                SP(regs) += 2;

                IP(regs)++;

                CHECK_IF_IN_TRAP

                set_vflags_short(popw(ssp, sp), regs);

                VM86_FAULT_RETURN;

        /* int xx */

        case 0xcd: {

                int intno=popb(csp, ip);

                IP(regs) += 2;

                if (VMPI.vm86dbg_active) {

                        if ( (1 << (intno &7)) & VMPI.vm86dbg_intxxtab[intno >> 3] )

                                return_to_32bit(regs, VM86_INTx + (intno << 8));

                }

                do_int(regs, intno, ssp, sp);

                return;

        }

        /* iret */

        case 0xcf:

                SP(regs) += 6;

                IP(regs) = popw(ssp, sp);

                regs->cs = popw(ssp, sp);

                CHECK_IF_IN_TRAP

                set_vflags_short(popw(ssp, sp), regs);

                VM86_FAULT_RETURN;

        /* cli */

        case 0xfa:

                IP(regs)++;

                clear_IF(regs);

                VM86_FAULT_RETURN;

        /* sti */

        /*

         * Damn. This is incorrect: the 'sti' instruction should actually

         * enable interrupts after the /next/ instruction. Not good.

         *

         * Probably needs some horsing around with the TF flag. Aiee..

         */

        case 0xfb:

                IP(regs)++;

                set_IF(regs);

                VM86_FAULT_RETURN;

        default:

                return_to_32bit(regs, VM86_UNKNOWN);

        }

}

/* ---------------- vm86 special IRQ passing stuff ----------------- */

#define VM86_IRQNAME            "vm86irq"

static struct vm86_irqs {

        struct task_struct *tsk;

        int sig;

} vm86_irqs[16] = {{0},};

static int irqbits=0;

#define ALLOWED_SIGS ( 1 /* 0 = don't send a signal */ \

        | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \

        | (1 << SIGUNUSED) )

static void irq_handler(int intno, void *dev_id, struct pt_regs * regs) {

        int irq_bit;

        unsigned long flags;

        save_flags(flags);

        cli();

        irq_bit = 1 << intno;

        if ((irqbits & irq_bit) || ! vm86_irqs[intno].tsk) {

                restore_flags(flags);

                return;

        }

        irqbits |= irq_bit;

        if (vm86_irqs[intno].sig)

                send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);

        /* else user will poll for IRQs */

        restore_flags(flags);

}

static inline void free_vm86_irq(int irqnumber)

{

        free_irq(irqnumber,0);

        vm86_irqs[irqnumber].tsk = 0;

        irqbits &= ~(1 << irqnumber);

}

static inline int task_valid(struct task_struct *tsk)

{

        struct task_struct *p;

        for_each_task(p) {

                if ((p == tsk) && (p->sig)) return 1;

        }

        return 0;

}

static inline void handle_irq_zombies(void)

{

        int i;

        for (i=3; i<16; i++) {

                if (vm86_irqs[i].tsk) {

                        if (task_valid(vm86_irqs[i].tsk)) continue;

                        free_vm86_irq(i);

                }

        }

}

static inline int get_and_reset_irq(int irqnumber)

{

        int bit;

        unsigned long flags;

        if ( (irqnumber<3) || (irqnumber>15) ) return 0;

        if (vm86_irqs[irqnumber].tsk != current) return 0;

        save_flags(flags);

        cli();

        bit = irqbits & (1 << irqnumber);

        irqbits &= ~bit;

        restore_flags(flags);

        return bit;

}

static int do_vm86_irq_handling(int subfunction, int irqnumber)

{

        int ret;

        switch (subfunction) {

                case VM86_GET_AND_RESET_IRQ: {

                        return get_and_reset_irq(irqnumber);

                }

                case VM86_GET_IRQ_BITS: {

                        return irqbits;

                }

                case VM86_REQUEST_IRQ: {

                        int sig = irqnumber >> 8;

                        int irq = irqnumber & 255;

                        handle_irq_zombies();

                        if (!suser() || securelevel > 0) return -EPERM;

                        if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;

                        if ( (irq<3) || (irq>15) ) return -EPERM;

                        if (vm86_irqs[irq].tsk) return -EPERM;

                        ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, 0);

                        if (ret) return ret;

                        vm86_irqs[irq].sig = sig;

                        vm86_irqs[irq].tsk = current;

                        return irq;

                }

                case  VM86_FREE_IRQ: {

                        handle_irq_zombies();

                        if ( (irqnumber<3) || (irqnumber>15) ) return -EPERM;

                        if (!vm86_irqs[irqnumber].tsk) return 0;

                        if (vm86_irqs[irqnumber].tsk != current) return -EPERM;

                        free_vm86_irq(irqnumber);

                        return 0;

                }

        }

        return -EINVAL;

}