/*
* 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.
*/
/*
* 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)
{
unsigned long tmp;
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);
tmp = current->tss.esp0;
current->tss.esp0 = current->saved_kernel_stack;
current->saved_kernel_stack = 0;
return (struct pt_regs *) tmp;
}
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();
}
asmlinkage int sys_vm86(struct vm86_struct * v86)
{
struct vm86_struct info;
struct pt_regs * pt_regs = (struct pt_regs *) &v86;
int error;
if (current->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(info));
/*
* 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 |= pt_regs->eflags & ~SAFE_MASK;
info.regs.eflags |= VM_MASK;
switch (info.cpu_type) {
case CPU_286:
current->tss.v86mask = 0;
break;
case CPU_386:
current->tss.v86mask = NT_MASK | IOPL_MASK;
break;
case CPU_486:
current->tss.v86mask = AC_MASK | NT_MASK | IOPL_MASK;
break;
default:
current->tss.v86mask = ID_MASK | AC_MASK | NT_MASK | IOPL_MASK;
break;
}
/*
* Save old state, set default return value (%eax) to 0
*/
pt_regs->eax = 0;
current->saved_kernel_stack = current->tss.esp0;
current->tss.esp0 = (unsigned long) pt_regs;
current->tss.vm86_info = v86;
current->tss.screen_bitmap = info.screen_bitmap;
if (info.flags & VM86_SCREEN_BITMAP)
mark_screen_rdonly(current);
__asm__ __volatile__("movl %0,%%esp\n\t"
"jmp ret_from_sys_call"
: /* no outputs */
:"r" (&info.regs));
return 0;
}
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)
{
if (verify_area(VERIFY_READ, bitmap, 256/8) < 0)
return 1;
__asm__ __volatile__("btl %2,%%fs:%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 short *intr_ptr, seg;
if (regs->cs == BIOSSEG)
goto cannot_handle;
if (is_revectored(i, ¤t->tss.vm86_info->int_revectored))
goto cannot_handle;
if (i==0x21 && is_revectored(AH(regs),¤t->tss.vm86_info->int21_revectored))
goto cannot_handle;
intr_ptr = (unsigned short *) (i << 2);
if (verify_area(VERIFY_READ, intr_ptr, 4) < 0)
goto cannot_handle;
seg = get_fs_word(intr_ptr+1);
if (seg == BIOSSEG)
goto cannot_handle;
pushw(ssp, sp, get_vflags(regs));
pushw(ssp, sp, regs->cs);
pushw(ssp, sp, IP(regs));
regs->cs = seg;
SP(regs) -= 6;
IP(regs) = get_fs_word(intr_ptr+0);
clear_TF(regs);
clear_IF(regs);
return;
cannot_handle:
return_to_32bit(regs, VM86_INTx + (i << 8));
}
void handle_vm86_debug(struct vm86_regs * regs, long error_code)
{
#if 0
do_int(regs, 1, (unsigned char *) (regs->ss << 4), SP(regs));
#else
if (current->flags & PF_PTRACED)
current->blocked &= ~(1 << (SIGTRAP-1));
send_sig(SIGTRAP, current, 1);
current->tss.trap_no = 1;
current->tss.error_code = error_code;
#endif
}
void handle_vm86_fault(struct vm86_regs * regs, long error_code)
{
unsigned char *csp, *ssp;
unsigned long ip, sp;
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));
return;
/* popfd */
case 0x9d:
SP(regs) += 4;
IP(regs) += 2;
set_vflags_long(popl(ssp, sp), regs);
return;
/* iretd */
case 0xcf:
SP(regs) += 12;
IP(regs) = (unsigned short)popl(ssp, sp);
regs->cs = (unsigned short)popl(ssp, sp);
set_vflags_long(popl(ssp, sp), regs);
return;
}
break;
/* pushf */
case 0x9c:
SP(regs) -= 2;
IP(regs)++;
pushw(ssp, sp, get_vflags(regs));
return;
/* popf */
case 0x9d:
SP(regs) += 2;
IP(regs)++;
set_vflags_short(popw(ssp, sp), regs);
return;
/* int xx */
case 0xcd:
IP(regs) += 2;
do_int(regs, popb(csp, ip), ssp, sp);
return;
/* iret */
case 0xcf:
SP(regs) += 6;
IP(regs) = popw(ssp, sp);
regs->cs = popw(ssp, sp);
set_vflags_short(popw(ssp, sp), regs);
return;
/* cli */
case 0xfa:
IP(regs)++;
clear_IF(regs);
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);
return;
}
/*
* We didn't recognize it, let the emulator take care of it..
*/
return_to_32bit(regs, VM86_UNKNOWN);
}