/*
* 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)
/* VFLAGS jsou vlajky používané aplikací reálného režimu, zatímco
* VEFLAGS jsou používané procesorem pro aktuální proces, obsahují
* VFLAGS a jsou uchovávané v TSS procesu
*/
#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(¤t->tss.vm86_info->regs,regs,sizeof(*regs));
put_fs_long(current->tss.screen_bitmap,¤t->tss.vm86_info->screen_bitmap);
current->tss.esp0 = current->saved_kernel_stack;
current->saved_kernel_stack = 0;
return KVM86->regs32;
}
/* Uloží obraz přerušeného procesu do vracené struktury typu
* vm86_structs podle registrů zadaných jako parametr. Také
* provede nastavení vlajky VIF (Virtual Flag Interrupt obraz
* vlajky IF) v ukládaném obrazu.
*/
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();
}
/* provede uzamknutí paměti, kde jsou uchovávány zobrazované pixely */
static int do_vm86_irq_handling(int subfunction, int irqnumber);
/* provede obsluhu hw přerušení */
static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
/* provede vstup do virtuálního režimu */
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 */
}
/* Provede přepnutí do virtuálního režimu podle popisovače procesu v86.
* Tj. připraví popisovač aktuálního procesu a zavolá do_sys_vm86, která
* se postará o přepnutí.
*/
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 */
}
/* Sem přicházejí požadavky pro práci s hw přerušeními, které jsou obslouženy
* funkcí do_vm86_irg_handling. Na závěr se provede přepnutí procesu jako
* sys_v86_call.
*/
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 */
}
/* Provede bezpečnostní nastavení popisovače procesu a uzamkne obrazovou paměť.
* Volající proces je považován za nedůvěryhodný, a proto jsou mu znovu nastaveny
* vlajky a zásobník tak, aby nenastala vyjímka, a je snížena hodnota úrovně
* oprávnění na 3. Na závěr dojde k přepnutí procesu.
*/
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));
}
/* uloží obash 16 bitových registrů, používaných aplikací virtuálního režimu,
* do struktury uchovávající 32 bitové registry a provede návrat do chráněného
*/
static inline void set_IF(struct vm86_regs * regs)
{
VEFLAGS |= VIF_MASK;
if (VEFLAGS & VIP_MASK)
return_to_32bit(regs, VM86_STI);
}
/* nastaví vlajku VIF a pokud je nastavena VIP(Virtual Interrupt Pending Flag)
* provede volání return_to_32bit
*/
static inline void clear_IF(struct vm86_regs * regs)
{
VEFLAGS &= ~VIF_MASK;
}
/* shodí VIF */
static inline void clear_TF(struct vm86_regs * regs)
{
regs->eflags &= ~TF_MASK;
}
/* shodí vlajku TF(pokud je nastavena, procesor je v krokovacím režimu */
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; })
/* tady končí úsek, kdy byl definován náhradní kód pro některé instrukce
* důvod je v použitém compileru gcc
*/
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));
}
/* provede přepnutí na obsluhu sw vyvolaného přerušení */
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;
}
/* obsluha vyjímky generované procesorem v krokovacím režimu */
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);
}
}
/* obsluha vyjímky vygenerovaní ve virtuálním režimu
* není zde správně ošetřena instrukce STI, která se v reálném
* a virtuálním režimu aktivuje až po provedení další instrukce
*/
/* ---------------- 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);
}
/* obsluha hw přerušení */
static inline void free_vm86_irq(int irqnumber)
{
free_irq(irqnumber,0);
vm86_irqs[irqnumber].tsk = 0;
irqbits &= ~(1 << irqnumber);
}
/* odinstaluje obsluhu hw přerušení */
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;
}
/* zkontroluje platnost popisovače procesu */
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);
}
}
}
/* vyvolá se v případě, že bylo generováno hw přerušení,
* ale nemá nainstalovanou obsluhu - default handler
*/
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;
}
/* provádí obsluhu hw přerušení */