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linux/arch/i386/kernel/vm86.c

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/*
* linux/kernel/vm86.c
*
* Copyright (C) 1994 Linus Torvalds
*
* 29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
* stack - Manfred Spraul <manfreds@colorfullife.com>
*
* 22 mar 2002 - Manfred detected the stackfaults, but didn't handle
* them correctly. Now the emulation will be in a
* consistent state after stackfaults - Kasper Dupont
* <kasperd@daimi.au.dk>
*
* 22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
* <kasperd@daimi.au.dk>
*
* ?? ??? 2002 - Fixed premature returns from handle_vm86_fault
* caused by Kasper Dupont's changes - Stas Sergeev
*
* 4 apr 2002 - Fixed CHECK_IF_IN_TRAP broken by Stas' changes.
* Kasper Dupont <kasperd@daimi.au.dk>
*
* 9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
* Kasper Dupont <kasperd@daimi.au.dk>
*
* 9 apr 2002 - Changed stack access macros to jump to a label
* instead of returning to userspace. This simplifies
* do_int, and is needed by handle_vm6_fault. Kasper
* Dupont <kasperd@daimi.au.dk>
*
*/
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/tlbflush.h>
#include <asm/irq.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.
*
* Let's hope 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->thread.v86flags))
#define VEFLAGS (current->thread.v86flags)
#define set_flags(X,new,mask) \
((X) = ((X) & ~(mask)) | ((new) & (mask)))
#define SAFE_MASK (0xDD5)
#define RETURN_MASK (0xDFF)
#define VM86_REGS_PART2 orig_eax
#define VM86_REGS_SIZE1 \
( (unsigned)( & (((struct kernel_vm86_regs *)0)->VM86_REGS_PART2) ) )
#define VM86_REGS_SIZE2 (sizeof(struct kernel_vm86_regs) - VM86_REGS_SIZE1)
struct pt_regs * FASTCALL(save_v86_state(struct kernel_vm86_regs * regs));
struct pt_regs * fastcall save_v86_state(struct kernel_vm86_regs * regs)
{
struct tss_struct *tss;
struct pt_regs *ret;
unsigned long tmp;
/*
* This gets called from entry.S with interrupts disabled, but
* from process context. Enable interrupts here, before trying
* to access user space.
*/
local_irq_enable();
if (!current->thread.vm86_info) {
printk("no vm86_info: BAD\n");
do_exit(SIGSEGV);
}
set_flags(regs->eflags, VEFLAGS, VIF_MASK | current->thread.v86mask);
tmp = copy_to_user(&current->thread.vm86_info->regs,regs, VM86_REGS_SIZE1);
tmp += copy_to_user(&current->thread.vm86_info->regs.VM86_REGS_PART2,
&regs->VM86_REGS_PART2, VM86_REGS_SIZE2);
tmp += put_user(current->thread.screen_bitmap,&current->thread.vm86_info->screen_bitmap);
if (tmp) {
printk("vm86: could not access userspace vm86_info\n");
do_exit(SIGSEGV);
}
tss = &per_cpu(init_tss, get_cpu());
current->thread.esp0 = current->thread.saved_esp0;
current->thread.sysenter_cs = __KERNEL_CS;
load_esp0(tss, &current->thread);
current->thread.saved_esp0 = 0;
put_cpu();
loadsegment(fs, current->thread.saved_fs);
loadsegment(gs, current->thread.saved_gs);
ret = KVM86->regs32;
return ret;
}
static void mark_screen_rdonly(struct task_struct * tsk)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte, *mapped;
int i;
preempt_disable();
spin_lock(&tsk->mm->page_table_lock);
pgd = pgd_offset(tsk->mm, 0xA0000);
if (pgd_none_or_clear_bad(pgd))
goto out;
pud = pud_offset(pgd, 0xA0000);
if (pud_none_or_clear_bad(pud))
goto out;
pmd = pmd_offset(pud, 0xA0000);
if (pmd_none_or_clear_bad(pmd))
goto out;
pte = mapped = pte_offset_map(pmd, 0xA0000);
for (i = 0; i < 32; i++) {
if (pte_present(*pte))
set_pte(pte, pte_wrprotect(*pte));
pte++;
}
pte_unmap(mapped);
out:
spin_unlock(&tsk->mm->page_table_lock);
preempt_enable();
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 pt_regs regs)
{
struct vm86_struct __user *v86 = (struct vm86_struct __user *)regs.ebx;
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;
int tmp, ret = -EPERM;
tsk = current;
if (tsk->thread.saved_esp0)
goto out;
tmp = copy_from_user(&info, v86, VM86_REGS_SIZE1);
tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2,
(long)&info.vm86plus - (long)&info.regs.VM86_REGS_PART2);
ret = -EFAULT;
if (tmp)
goto out;
memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);
info.regs32 = &regs;
tsk->thread.vm86_info = v86;
do_sys_vm86(&info, tsk);
ret = 0; /* we never return here */
out:
return ret;
}
asmlinkage int sys_vm86(struct pt_regs regs)
{
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;
int tmp, ret;
struct vm86plus_struct __user *v86;
tsk = current;
switch (regs.ebx) {
case VM86_REQUEST_IRQ:
case VM86_FREE_IRQ:
case VM86_GET_IRQ_BITS:
case VM86_GET_AND_RESET_IRQ:
ret = do_vm86_irq_handling(regs.ebx, (int)regs.ecx);
goto out;
case VM86_PLUS_INSTALL_CHECK:
/* NOTE: on old vm86 stuff this will return the error
from access_ok(), because the subfunction is
interpreted as (invalid) address to vm86_struct.
So the installation check works.
*/
ret = 0;
goto out;
}
/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
ret = -EPERM;
if (tsk->thread.saved_esp0)
goto out;
v86 = (struct vm86plus_struct __user *)regs.ecx;
tmp = copy_from_user(&info, v86, VM86_REGS_SIZE1);
tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2,
(long)&info.regs32 - (long)&info.regs.VM86_REGS_PART2);
ret = -EFAULT;
if (tmp)
goto out;
info.regs32 = &regs;
info.vm86plus.is_vm86pus = 1;
tsk->thread.vm86_info = (struct vm86_struct __user *)v86;
do_sys_vm86(&info, tsk);
ret = 0; /* we never return here */
out:
return ret;
}
static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
{
struct tss_struct *tss;
/*
* make sure the vm86() system call doesn't try to do anything silly
*/
info->regs.__null_ds = 0;
info->regs.__null_es = 0;
/* we are clearing fs,gs later just before "jmp resume_userspace",
* because starting with Linux 2.1.x they aren't no longer saved/restored
*/
/*
* 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->thread.v86mask = 0;
break;
case CPU_386:
tsk->thread.v86mask = NT_MASK | IOPL_MASK;
break;
case CPU_486:
tsk->thread.v86mask = AC_MASK | NT_MASK | IOPL_MASK;
break;
default:
tsk->thread.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->thread.saved_esp0 = tsk->thread.esp0;
savesegment(fs, tsk->thread.saved_fs);
savesegment(gs, tsk->thread.saved_gs);
tss = &per_cpu(init_tss, get_cpu());
tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
if (cpu_has_sep)
tsk->thread.sysenter_cs = 0;
load_esp0(tss, &tsk->thread);
put_cpu();
tsk->thread.screen_bitmap = info->screen_bitmap;
if (info->flags & VM86_SCREEN_BITMAP)
mark_screen_rdonly(tsk);
__asm__ __volatile__(
"xorl %%eax,%%eax; movl %%eax,%%fs; movl %%eax,%%gs\n\t"
"movl %0,%%esp\n\t"
"movl %1,%%ebp\n\t"
"jmp resume_userspace"
: /* no outputs */
:"r" (&info->regs), "r" (tsk->thread_info) : "ax");
/* we never return here */
}
static inline void return_to_32bit(struct kernel_vm86_regs * regs16, int retval)
{
struct pt_regs * regs32;
regs32 = save_v86_state(regs16);
regs32->eax = retval;
__asm__ __volatile__("movl %0,%%esp\n\t"
"movl %1,%%ebp\n\t"
"jmp resume_userspace"
: : "r" (regs32), "r" (current_thread_info()));
}
static inline void set_IF(struct kernel_vm86_regs * regs)
{
VEFLAGS |= VIF_MASK;
if (VEFLAGS & VIP_MASK)
return_to_32bit(regs, VM86_STI);
}
static inline void clear_IF(struct kernel_vm86_regs * regs)
{
VEFLAGS &= ~VIF_MASK;
}
static inline void clear_TF(struct kernel_vm86_regs * regs)
{
regs->eflags &= ~TF_MASK;
}
static inline void clear_AC(struct kernel_vm86_regs * regs)
{
regs->eflags &= ~AC_MASK;
}
/* It is correct to call set_IF(regs) from the set_vflags_*
* functions. However someone forgot to call clear_IF(regs)
* in the opposite case.
* After the command sequence CLI PUSHF STI POPF you should
* end up with interrups disabled, but you ended up with
* interrupts enabled.
* ( I was testing my own changes, but the only bug I
* could find was in a function I had not changed. )
* [KD]
*/
static inline void set_vflags_long(unsigned long eflags, struct kernel_vm86_regs * regs)
{
set_flags(VEFLAGS, eflags, current->thread.v86mask);
set_flags(regs->eflags, eflags, SAFE_MASK);
if (eflags & IF_MASK)
set_IF(regs);
else
clear_IF(regs);
}
static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs * regs)
{
set_flags(VFLAGS, flags, current->thread.v86mask);
set_flags(regs->eflags, flags, SAFE_MASK);
if (flags & IF_MASK)
set_IF(regs);
else
clear_IF(regs);
}
static inline unsigned long get_vflags(struct kernel_vm86_regs * regs)
{
unsigned long flags = regs->eflags & RETURN_MASK;
if (VEFLAGS & VIF_MASK)
flags |= IF_MASK;
flags |= IOPL_MASK;
return flags | (VEFLAGS & current->thread.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;
}
#define val_byte(val, n) (((__u8 *)&val)[n])
#define pushb(base, ptr, val, err_label) \
do { \
__u8 __val = val; \
ptr--; \
if (put_user(__val, base + ptr) < 0) \
goto err_label; \
} while(0)
#define pushw(base, ptr, val, err_label) \
do { \
__u16 __val = val; \
ptr--; \
if (put_user(val_byte(__val, 1), base + ptr) < 0) \
goto err_label; \
ptr--; \
if (put_user(val_byte(__val, 0), base + ptr) < 0) \
goto err_label; \
} while(0)
#define pushl(base, ptr, val, err_label) \
do { \
__u32 __val = val; \
ptr--; \
if (put_user(val_byte(__val, 3), base + ptr) < 0) \
goto err_label; \
ptr--; \
if (put_user(val_byte(__val, 2), base + ptr) < 0) \
goto err_label; \
ptr--; \
if (put_user(val_byte(__val, 1), base + ptr) < 0) \
goto err_label; \
ptr--; \
if (put_user(val_byte(__val, 0), base + ptr) < 0) \
goto err_label; \
} while(0)
#define popb(base, ptr, err_label) \
({ \
__u8 __res; \
if (get_user(__res, base + ptr) < 0) \
goto err_label; \
ptr++; \
__res; \
})
#define popw(base, ptr, err_label) \
({ \
__u16 __res; \
if (get_user(val_byte(__res, 0), base + ptr) < 0) \
goto err_label; \
ptr++; \
if (get_user(val_byte(__res, 1), base + ptr) < 0) \
goto err_label; \
ptr++; \
__res; \
})
#define popl(base, ptr, err_label) \
({ \
__u32 __res; \
if (get_user(val_byte(__res, 0), base + ptr) < 0) \
goto err_label; \
ptr++; \
if (get_user(val_byte(__res, 1), base + ptr) < 0) \
goto err_label; \
ptr++; \
if (get_user(val_byte(__res, 2), base + ptr) < 0) \
goto err_label; \
ptr++; \
if (get_user(val_byte(__res, 3), base + ptr) < 0) \
goto err_label; \
ptr++; \
__res; \
})
/* There are so many possible reasons for this function to return
* VM86_INTx, so adding another doesn't bother me. We can expect
* userspace programs to be able to handle it. (Getting a problem
* in userspace is always better than an Oops anyway.) [KD]
*/
static void do_int(struct kernel_vm86_regs *regs, int i,
unsigned char __user * ssp, unsigned short sp)
{
unsigned long __user *intr_ptr;
unsigned long 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 __user *) (i << 2);
if (get_user(segoffs, intr_ptr))
goto cannot_handle;
if ((segoffs >> 16) == BIOSSEG)
goto cannot_handle;
pushw(ssp, sp, get_vflags(regs), cannot_handle);
pushw(ssp, sp, regs->cs, cannot_handle);
pushw(ssp, sp, IP(regs), cannot_handle);
regs->cs = segoffs >> 16;
SP(regs) -= 6;
IP(regs) = segoffs & 0xffff;
clear_TF(regs);
clear_IF(regs);
clear_AC(regs);
return;
cannot_handle:
return_to_32bit(regs, VM86_INTx + (i << 8));
}
int handle_vm86_trap(struct kernel_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 __user *) (regs->ss << 4), SP(regs));
return 0;
}
if (trapno !=1)
return 1; /* we let this handle by the calling routine */
if (current->ptrace & PT_PTRACED) {
unsigned long flags;
spin_lock_irqsave(&current->sighand->siglock, flags);
sigdelset(&current->blocked, SIGTRAP);
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, flags);
}
send_sig(SIGTRAP, current, 1);
current->thread.trap_no = trapno;
current->thread.error_code = error_code;
return 0;
}
void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code)
{
unsigned char opcode;
unsigned char __user *csp;
unsigned char __user *ssp;
unsigned short ip, sp, orig_flags;
int data32, pref_done;
#define CHECK_IF_IN_TRAP \
if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \
newflags |= TF_MASK
#define VM86_FAULT_RETURN do { \
if (VMPI.force_return_for_pic && (VEFLAGS & (IF_MASK | VIF_MASK))) \
return_to_32bit(regs, VM86_PICRETURN); \
if (orig_flags & TF_MASK) \
handle_vm86_trap(regs, 0, 1); \
return; } while (0)
orig_flags = *(unsigned short *)&regs->eflags;
csp = (unsigned char __user *) (regs->cs << 4);
ssp = (unsigned char __user *) (regs->ss << 4);
sp = SP(regs);
ip = IP(regs);
data32 = 0;
pref_done = 0;
do {
switch (opcode = popb(csp, ip, simulate_sigsegv)) {
case 0x66: /* 32-bit data */ data32=1; break;
case 0x67: /* 32-bit address */ break;
case 0x2e: /* CS */ break;
case 0x3e: /* DS */ break;
case 0x26: /* ES */ break;
case 0x36: /* SS */ break;
case 0x65: /* GS */ break;
case 0x64: /* FS */ break;
case 0xf2: /* repnz */ break;
case 0xf3: /* rep */ break;
default: pref_done = 1;
}
} while (!pref_done);
switch (opcode) {
/* pushf */
case 0x9c:
if (data32) {
pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
SP(regs) -= 4;
} else {
pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
SP(regs) -= 2;
}
IP(regs) = ip;
VM86_FAULT_RETURN;
/* popf */
case 0x9d:
{
unsigned long newflags;
if (data32) {
newflags=popl(ssp, sp, simulate_sigsegv);
SP(regs) += 4;
} else {
newflags = popw(ssp, sp, simulate_sigsegv);
SP(regs) += 2;
}
IP(regs) = ip;
CHECK_IF_IN_TRAP;
if (data32) {
set_vflags_long(newflags, regs);
} else {
set_vflags_short(newflags, regs);
}
VM86_FAULT_RETURN;
}
/* int xx */
case 0xcd: {
int intno=popb(csp, ip, simulate_sigsegv);
IP(regs) = ip;
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:
{
unsigned long newip;
unsigned long newcs;
unsigned long newflags;
if (data32) {
newip=popl(ssp, sp, simulate_sigsegv);
newcs=popl(ssp, sp, simulate_sigsegv);
newflags=popl(ssp, sp, simulate_sigsegv);
SP(regs) += 12;
} else {
newip = popw(ssp, sp, simulate_sigsegv);
newcs = popw(ssp, sp, simulate_sigsegv);
newflags = popw(ssp, sp, simulate_sigsegv);
SP(regs) += 6;
}
IP(regs) = newip;
regs->cs = newcs;
CHECK_IF_IN_TRAP;
if (data32) {
set_vflags_long(newflags, regs);
} else {
set_vflags_short(newflags, regs);
}
VM86_FAULT_RETURN;
}
/* cli */
case 0xfa:
IP(regs) = ip;
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) = ip;
set_IF(regs);
VM86_FAULT_RETURN;
default:
return_to_32bit(regs, VM86_UNKNOWN);
}
return;
simulate_sigsegv:
/* FIXME: After a long discussion with Stas we finally
* agreed, that this is wrong. Here we should
* really send a SIGSEGV to the user program.
* But how do we create the correct context? We
* are inside a general protection fault handler
* and has just returned from a page fault handler.
* The correct context for the signal handler
* should be a mixture of the two, but how do we
* get the information? [KD]
*/
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];
static DEFINE_SPINLOCK(irqbits_lock);
static int irqbits;
#define ALLOWED_SIGS ( 1 /* 0 = don't send a signal */ \
| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO) | (1 << SIGURG) \
| (1 << SIGUNUSED) )
static irqreturn_t irq_handler(int intno, void *dev_id, struct pt_regs * regs)
{
int irq_bit;
unsigned long flags;
spin_lock_irqsave(&irqbits_lock, flags);
irq_bit = 1 << intno;
if ((irqbits & irq_bit) || ! vm86_irqs[intno].tsk)
goto out;
irqbits |= irq_bit;
if (vm86_irqs[intno].sig)
send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
/*
* IRQ will be re-enabled when user asks for the irq (whether
* polling or as a result of the signal)
*/
disable_irq_nosync(intno);
spin_unlock_irqrestore(&irqbits_lock, flags);
return IRQ_HANDLED;
out:
spin_unlock_irqrestore(&irqbits_lock, flags);
return IRQ_NONE;
}
static inline void free_vm86_irq(int irqnumber)
{
unsigned long flags;
free_irq(irqnumber, NULL);
vm86_irqs[irqnumber].tsk = NULL;
spin_lock_irqsave(&irqbits_lock, flags);
irqbits &= ~(1 << irqnumber);
spin_unlock_irqrestore(&irqbits_lock, flags);
}
void release_vm86_irqs(struct task_struct *task)
{
int i;
for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
if (vm86_irqs[i].tsk == task)
free_vm86_irq(i);
}
static inline int get_and_reset_irq(int irqnumber)
{
int bit;
unsigned long flags;
int ret = 0;
if (invalid_vm86_irq(irqnumber)) return 0;
if (vm86_irqs[irqnumber].tsk != current) return 0;
spin_lock_irqsave(&irqbits_lock, flags);
bit = irqbits & (1 << irqnumber);
irqbits &= ~bit;
if (bit) {
enable_irq(irqnumber);
ret = 1;
}
spin_unlock_irqrestore(&irqbits_lock, flags);
return ret;
}
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;
if (!capable(CAP_SYS_ADMIN)) return -EPERM;
if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
if (invalid_vm86_irq(irq)) return -EPERM;
if (vm86_irqs[irq].tsk) return -EPERM;
ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
if (ret) return ret;
vm86_irqs[irq].sig = sig;
vm86_irqs[irq].tsk = current;
return irq;
}
case VM86_FREE_IRQ: {
if (invalid_vm86_irq(irqnumber)) 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;
}
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