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linux/arch/x86/kernel/vm86_32.c
Linus Torvalds 96d4f267e4 Remove 'type' argument from access_ok() function 
Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument
of the user address range verification function since we got rid of the
old racy i386-only code to walk page tables by hand.

It existed because the original 80386 would not honor the write protect
bit when in kernel mode, so you had to do COW by hand before doing any
user access.  But we haven't supported that in a long time, and these
days the 'type' argument is a purely historical artifact.

A discussion about extending 'user_access_begin()' to do the range
checking resulted this patch, because there is no way we're going to
move the old VERIFY_xyz interface to that model.  And it's best done at
the end of the merge window when I've done most of my merges, so let's
just get this done once and for all.

This patch was mostly done with a sed-script, with manual fix-ups for
the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form.

There were a couple of notable cases:

 - csky still had the old "verify_area()" name as an alias.

 - the iter_iov code had magical hardcoded knowledge of the actual
   values of VERIFY_{READ,WRITE} (not that they mattered, since nothing
   really used it)

 - microblaze used the type argument for a debug printout

but other than those oddities this should be a total no-op patch.

I tried to fix up all architectures, did fairly extensive grepping for
access_ok() uses, and the changes are trivial, but I may have missed
something.  Any missed conversion should be trivially fixable, though.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-03 18:57:57 -08:00

875 lines
23 KiB
C
Raw Blame History

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1994 Linus Torvalds
*
* 29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
* stack - Manfred Spraul <manfred@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>
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/syscalls.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/audit.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <asm/io.h>
#include <asm/tlbflush.h>
#include <asm/irq.h>
#include <asm/traps.h>
#include <asm/vm86.h>
#include <asm/switch_to.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.
*/
/*
* 8- and 16-bit register defines..
*/
#define AL(regs) (((unsigned char *)&((regs)->pt.ax))[0])
#define AH(regs) (((unsigned char *)&((regs)->pt.ax))[1])
#define IP(regs) (*(unsigned short *)&((regs)->pt.ip))
#define SP(regs) (*(unsigned short *)&((regs)->pt.sp))
/*
* virtual flags (16 and 32-bit versions)
*/
#define VFLAGS (*(unsigned short *)&(current->thread.vm86->veflags))
#define VEFLAGS (current->thread.vm86->veflags)
#define set_flags(X, new, mask) \
((X) = ((X) & ~(mask)) | ((new) & (mask)))
#define SAFE_MASK (0xDD5)
#define RETURN_MASK (0xDFF)
void save_v86_state(struct kernel_vm86_regs *regs, int retval)
{
struct task_struct *tsk = current;
struct vm86plus_struct __user *user;
struct vm86 *vm86 = current->thread.vm86;
long err = 0;
/*
* 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 (!vm86 || !vm86->user_vm86) {
pr_alert("no user_vm86: BAD\n");
do_exit(SIGSEGV);
}
set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->veflags_mask);
user = vm86->user_vm86;
if (!access_ok(user, vm86->vm86plus.is_vm86pus ?
sizeof(struct vm86plus_struct) :
sizeof(struct vm86_struct))) {
pr_alert("could not access userspace vm86 info\n");
do_exit(SIGSEGV);
}
put_user_try {
put_user_ex(regs->pt.bx, &user->regs.ebx);
put_user_ex(regs->pt.cx, &user->regs.ecx);
put_user_ex(regs->pt.dx, &user->regs.edx);
put_user_ex(regs->pt.si, &user->regs.esi);
put_user_ex(regs->pt.di, &user->regs.edi);
put_user_ex(regs->pt.bp, &user->regs.ebp);
put_user_ex(regs->pt.ax, &user->regs.eax);
put_user_ex(regs->pt.ip, &user->regs.eip);
put_user_ex(regs->pt.cs, &user->regs.cs);
put_user_ex(regs->pt.flags, &user->regs.eflags);
put_user_ex(regs->pt.sp, &user->regs.esp);
put_user_ex(regs->pt.ss, &user->regs.ss);
put_user_ex(regs->es, &user->regs.es);
put_user_ex(regs->ds, &user->regs.ds);
put_user_ex(regs->fs, &user->regs.fs);
put_user_ex(regs->gs, &user->regs.gs);
put_user_ex(vm86->screen_bitmap, &user->screen_bitmap);
} put_user_catch(err);
if (err) {
pr_alert("could not access userspace vm86 info\n");
do_exit(SIGSEGV);
}
preempt_disable();
tsk->thread.sp0 = vm86->saved_sp0;
tsk->thread.sysenter_cs = __KERNEL_CS;
update_task_stack(tsk);
refresh_sysenter_cs(&tsk->thread);
vm86->saved_sp0 = 0;
preempt_enable();
memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
lazy_load_gs(vm86->regs32.gs);
regs->pt.ax = retval;
}
static void mark_screen_rdonly(struct mm_struct *mm)
{
struct vm_area_struct *vma;
spinlock_t *ptl;
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
int i;
down_write(&mm->mmap_sem);
pgd = pgd_offset(mm, 0xA0000);
if (pgd_none_or_clear_bad(pgd))
goto out;
p4d = p4d_offset(pgd, 0xA0000);
if (p4d_none_or_clear_bad(p4d))
goto out;
pud = pud_offset(p4d, 0xA0000);
if (pud_none_or_clear_bad(pud))
goto out;
pmd = pmd_offset(pud, 0xA0000);
if (pmd_trans_huge(*pmd)) {
vma = find_vma(mm, 0xA0000);
split_huge_pmd(vma, pmd, 0xA0000);
}
if (pmd_none_or_clear_bad(pmd))
goto out;
pte = pte_offset_map_lock(mm, pmd, 0xA0000, &ptl);
for (i = 0; i < 32; i++) {
if (pte_present(*pte))
set_pte(pte, pte_wrprotect(*pte));
pte++;
}
pte_unmap_unlock(pte, ptl);
out:
up_write(&mm->mmap_sem);
flush_tlb_mm_range(mm, 0xA0000, 0xA0000 + 32*PAGE_SIZE, PAGE_SHIFT, false);
}
static int do_vm86_irq_handling(int subfunction, int irqnumber);
static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus);
SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, user_vm86)
{
return do_sys_vm86((struct vm86plus_struct __user *) user_vm86, false);
}
SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
{
switch (cmd) {
case VM86_REQUEST_IRQ:
case VM86_FREE_IRQ:
case VM86_GET_IRQ_BITS:
case VM86_GET_AND_RESET_IRQ:
return do_vm86_irq_handling(cmd, (int)arg);
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.
*/
return 0;
}
/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
}
static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
{
struct task_struct *tsk = current;
struct vm86 *vm86 = tsk->thread.vm86;
struct kernel_vm86_regs vm86regs;
struct pt_regs *regs = current_pt_regs();
unsigned long err = 0;
err = security_mmap_addr(0);
if (err) {
/*
* vm86 cannot virtualize the address space, so vm86 users
* need to manage the low 1MB themselves using mmap. Given
* that BIOS places important data in the first page, vm86
* is essentially useless if mmap_min_addr != 0. DOSEMU,
* for example, won't even bother trying to use vm86 if it
* can't map a page at virtual address 0.
*
* To reduce the available kernel attack surface, simply
* disallow vm86(old) for users who cannot mmap at va 0.
*
* The implementation of security_mmap_addr will allow
* suitably privileged users to map va 0 even if
* vm.mmap_min_addr is set above 0, and we want this
* behavior for vm86 as well, as it ensures that legacy
* tools like vbetool will not fail just because of
* vm.mmap_min_addr.
*/
pr_info_once("Denied a call to vm86(old) from %s[%d] (uid: %d). Set the vm.mmap_min_addr sysctl to 0 and/or adjust LSM mmap_min_addr policy to enable vm86 if you are using a vm86-based DOS emulator.\n",
current->comm, task_pid_nr(current),
from_kuid_munged(&init_user_ns, current_uid()));
return -EPERM;
}
if (!vm86) {
if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
return -ENOMEM;
tsk->thread.vm86 = vm86;
}
if (vm86->saved_sp0)
return -EPERM;
if (!access_ok(user_vm86, plus ?
sizeof(struct vm86_struct) :
sizeof(struct vm86plus_struct)))
return -EFAULT;
memset(&vm86regs, 0, sizeof(vm86regs));
get_user_try {
unsigned short seg;
get_user_ex(vm86regs.pt.bx, &user_vm86->regs.ebx);
get_user_ex(vm86regs.pt.cx, &user_vm86->regs.ecx);
get_user_ex(vm86regs.pt.dx, &user_vm86->regs.edx);
get_user_ex(vm86regs.pt.si, &user_vm86->regs.esi);
get_user_ex(vm86regs.pt.di, &user_vm86->regs.edi);
get_user_ex(vm86regs.pt.bp, &user_vm86->regs.ebp);
get_user_ex(vm86regs.pt.ax, &user_vm86->regs.eax);
get_user_ex(vm86regs.pt.ip, &user_vm86->regs.eip);
get_user_ex(seg, &user_vm86->regs.cs);
vm86regs.pt.cs = seg;
get_user_ex(vm86regs.pt.flags, &user_vm86->regs.eflags);
get_user_ex(vm86regs.pt.sp, &user_vm86->regs.esp);
get_user_ex(seg, &user_vm86->regs.ss);
vm86regs.pt.ss = seg;
get_user_ex(vm86regs.es, &user_vm86->regs.es);
get_user_ex(vm86regs.ds, &user_vm86->regs.ds);
get_user_ex(vm86regs.fs, &user_vm86->regs.fs);
get_user_ex(vm86regs.gs, &user_vm86->regs.gs);
get_user_ex(vm86->flags, &user_vm86->flags);
get_user_ex(vm86->screen_bitmap, &user_vm86->screen_bitmap);
get_user_ex(vm86->cpu_type, &user_vm86->cpu_type);
} get_user_catch(err);
if (err)
return err;
if (copy_from_user(&vm86->int_revectored,
&user_vm86->int_revectored,
sizeof(struct revectored_struct)))
return -EFAULT;
if (copy_from_user(&vm86->int21_revectored,
&user_vm86->int21_revectored,
sizeof(struct revectored_struct)))
return -EFAULT;
if (plus) {
if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
sizeof(struct vm86plus_info_struct)))
return -EFAULT;
vm86->vm86plus.is_vm86pus = 1;
} else
memset(&vm86->vm86plus, 0,
sizeof(struct vm86plus_info_struct));
memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
vm86->user_vm86 = user_vm86;
/*
* The flags 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 = vm86regs.pt.flags;
vm86regs.pt.flags &= SAFE_MASK;
vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
vm86regs.pt.flags |= X86_VM_MASK;
vm86regs.pt.orig_ax = regs->orig_ax;
switch (vm86->cpu_type) {
case CPU_286:
vm86->veflags_mask = 0;
break;
case CPU_386:
vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
break;
case CPU_486:
vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
break;
default:
vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
break;
}
/*
* Save old state
*/
vm86->saved_sp0 = tsk->thread.sp0;
lazy_save_gs(vm86->regs32.gs);
/* make room for real-mode segments */
preempt_disable();
tsk->thread.sp0 += 16;
if (static_cpu_has(X86_FEATURE_SEP)) {
tsk->thread.sysenter_cs = 0;
refresh_sysenter_cs(&tsk->thread);
}
update_task_stack(tsk);
preempt_enable();
if (vm86->flags & VM86_SCREEN_BITMAP)
mark_screen_rdonly(tsk->mm);
memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
force_iret();
return regs->ax;
}
static inline void set_IF(struct kernel_vm86_regs *regs)
{
VEFLAGS |= X86_EFLAGS_VIF;
}
static inline void clear_IF(struct kernel_vm86_regs *regs)
{
VEFLAGS &= ~X86_EFLAGS_VIF;
}
static inline void clear_TF(struct kernel_vm86_regs *regs)
{
regs->pt.flags &= ~X86_EFLAGS_TF;
}
static inline void clear_AC(struct kernel_vm86_regs *regs)
{
regs->pt.flags &= ~X86_EFLAGS_AC;
}
/*
* 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 interrupts 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 flags, struct kernel_vm86_regs *regs)
{
set_flags(VEFLAGS, flags, current->thread.vm86->veflags_mask);
set_flags(regs->pt.flags, flags, SAFE_MASK);
if (flags & X86_EFLAGS_IF)
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.vm86->veflags_mask);
set_flags(regs->pt.flags, flags, SAFE_MASK);
if (flags & X86_EFLAGS_IF)
set_IF(regs);
else
clear_IF(regs);
}
static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
{
unsigned long flags = regs->pt.flags & RETURN_MASK;
if (VEFLAGS & X86_EFLAGS_VIF)
flags |= X86_EFLAGS_IF;
flags |= X86_EFLAGS_IOPL;
return flags | (VEFLAGS & current->thread.vm86->veflags_mask);
}
static inline int is_revectored(int nr, struct revectored_struct *bitmap)
{
return test_bit(nr, bitmap->__map);
}
#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;
struct vm86 *vm86 = current->thread.vm86;
if (regs->pt.cs == BIOSSEG)
goto cannot_handle;
if (is_revectored(i, &vm86->int_revectored))
goto cannot_handle;
if (i == 0x21 && is_revectored(AH(regs), &vm86->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->pt.cs, cannot_handle);
pushw(ssp, sp, IP(regs), cannot_handle);
regs->pt.cs = segoffs >> 16;
SP(regs) -= 6;
IP(regs) = segoffs & 0xffff;
clear_TF(regs);
clear_IF(regs);
clear_AC(regs);
return;
cannot_handle:
save_v86_state(regs, VM86_INTx + (i << 8));
}
int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
{
struct vm86 *vm86 = current->thread.vm86;
if (vm86->vm86plus.is_vm86pus) {
if ((trapno == 3) || (trapno == 1)) {
save_v86_state(regs, VM86_TRAP + (trapno << 8));
return 0;
}
do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
return 0;
}
if (trapno != 1)
return 1; /* we let this handle by the calling routine */
current->thread.trap_nr = trapno;
current->thread.error_code = error_code;
force_sig(SIGTRAP, current);
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;
struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
#define CHECK_IF_IN_TRAP \
if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
newflags |= X86_EFLAGS_TF
orig_flags = *(unsigned short *)&regs->pt.flags;
csp = (unsigned char __user *) (regs->pt.cs << 4);
ssp = (unsigned char __user *) (regs->pt.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;
goto 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);
goto check_vip;
}
/* 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]) {
save_v86_state(regs, VM86_INTx + (intno << 8));
return;
}
}
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->pt.cs = newcs;
CHECK_IF_IN_TRAP;
if (data32) {
set_vflags_long(newflags, regs);
} else {
set_vflags_short(newflags, regs);
}
goto check_vip;
}
/* cli */
case 0xfa:
IP(regs) = ip;
clear_IF(regs);
goto 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);
goto check_vip;
default:
save_v86_state(regs, VM86_UNKNOWN);
}
return;
check_vip:
if ((VEFLAGS & (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) ==
(X86_EFLAGS_VIP | X86_EFLAGS_VIF)) {
save_v86_state(regs, VM86_STI);
return;
}
vm86_fault_return:
if (vmpi->force_return_for_pic && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
save_v86_state(regs, VM86_PICRETURN);
return;
}
if (orig_flags & X86_EFLAGS_TF)
handle_vm86_trap(regs, 0, X86_TRAP_DB);
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]
*/
save_v86_state(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)
{
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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