[PATCH 3/8] x86/vm86: Eliminate kernel_vm86_struct
From: Brian Gerst
Date: Wed Jul 29 2015 - 01:42:12 EST
Now there is no vm86-specific data left on the kernel stack while in
userspace, except for the 32-bit regs.
Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
---
arch/x86/include/asm/vm86.h | 25 +-----------
arch/x86/kernel/vm86_32.c | 95 +++++++++++++++++++--------------------------
2 files changed, 42 insertions(+), 78 deletions(-)
diff --git a/arch/x86/include/asm/vm86.h b/arch/x86/include/asm/vm86.h
index 47c7648..226d6c1 100644
--- a/arch/x86/include/asm/vm86.h
+++ b/arch/x86/include/asm/vm86.h
@@ -27,32 +27,9 @@ struct kernel_vm86_regs {
unsigned short gs, __gsh;
};
-struct kernel_vm86_struct {
- struct kernel_vm86_regs regs;
-/*
- * the below part remains on the kernel stack while we are in VM86 mode.
- * 'tss.esp0' then contains the address of VM86_TSS_ESP0 below, and when we
- * get forced back from VM86, the CPU and "SAVE_ALL" will restore the above
- * 'struct kernel_vm86_regs' with the then actual values.
- * Therefore, pt_regs in fact points to a complete 'kernel_vm86_struct'
- * in kernelspace, hence we need not reget the data from userspace.
- */
-#define VM86_TSS_ESP0 regs32
- struct pt_regs *regs32; /* here we save the pointer to the old regs */
-/*
- * The below is not part of the structure, but the stack layout continues
- * this way. In front of 'return-eip' may be some data, depending on
- * compilation, so we don't rely on this and save the pointer to 'oldregs'
- * in 'regs32' above.
- * However, with GCC-2.7.2 and the current CFLAGS you see exactly this:
-
- long return-eip; from call to vm86()
- struct pt_regs oldregs; user space registers as saved by syscall
- */
-};
-
struct vm86 {
struct vm86plus_struct __user *vm86_info;
+ struct pt_regs *regs32;
unsigned long v86flags;
unsigned long v86mask;
unsigned long saved_sp0;
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index f71b4b9..696ef76 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -67,9 +67,6 @@
*/
-#define KVM86 ((struct kernel_vm86_struct *)regs)
-
-
/*
* 8- and 16-bit register defines..
*/
@@ -152,7 +149,7 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
vm86->saved_sp0 = 0;
put_cpu();
- ret = KVM86->regs32;
+ ret = vm86->regs32;
lazy_load_gs(ret->gs);
@@ -194,29 +191,16 @@ out:
static int do_vm86_irq_handling(int subfunction, int irqnumber);
-static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
- struct kernel_vm86_struct *info);
+static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus);
SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, 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.
- */
-
- return do_sys_vm86((struct vm86plus_struct __user *) v86, false, &info);
+ return do_sys_vm86((struct vm86plus_struct __user *) v86, false);
}
SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
{
- 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.
- */
-
switch (cmd) {
case VM86_REQUEST_IRQ:
case VM86_FREE_IRQ:
@@ -234,16 +218,17 @@ SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
}
/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
- return do_sys_vm86((struct vm86plus_struct __user *) arg, true, &info);
+ return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
}
-static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
- struct kernel_vm86_struct *info)
+static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus)
{
struct tss_struct *tss;
struct task_struct *tsk = current;
struct vm86 *vm86 = tsk->thread.vm86;
+ struct kernel_vm86_regs vm86regs;
+ struct pt_regs *regs32 = current_pt_regs();
unsigned long err = 0;
if (!vm86) {
@@ -259,27 +244,27 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
sizeof(struct vm86plus_struct)))
return -EFAULT;
- memset(info, 0, sizeof(*info));
+ memset(&vm86regs, 0, sizeof(vm86regs));
get_user_try {
unsigned short seg;
- get_user_ex(info->regs.pt.bx, &v86->regs.ebx);
- get_user_ex(info->regs.pt.cx, &v86->regs.ecx);
- get_user_ex(info->regs.pt.dx, &v86->regs.edx);
- get_user_ex(info->regs.pt.si, &v86->regs.esi);
- get_user_ex(info->regs.pt.di, &v86->regs.edi);
- get_user_ex(info->regs.pt.bp, &v86->regs.ebp);
- get_user_ex(info->regs.pt.ax, &v86->regs.eax);
- get_user_ex(info->regs.pt.ip, &v86->regs.eip);
+ get_user_ex(vm86regs.pt.bx, &v86->regs.ebx);
+ get_user_ex(vm86regs.pt.cx, &v86->regs.ecx);
+ get_user_ex(vm86regs.pt.dx, &v86->regs.edx);
+ get_user_ex(vm86regs.pt.si, &v86->regs.esi);
+ get_user_ex(vm86regs.pt.di, &v86->regs.edi);
+ get_user_ex(vm86regs.pt.bp, &v86->regs.ebp);
+ get_user_ex(vm86regs.pt.ax, &v86->regs.eax);
+ get_user_ex(vm86regs.pt.ip, &v86->regs.eip);
get_user_ex(seg, &v86->regs.cs);
- info->regs.pt.cs = seg;
- get_user_ex(info->regs.pt.flags, &v86->regs.eflags);
- get_user_ex(info->regs.pt.sp, &v86->regs.esp);
+ vm86regs.pt.cs = seg;
+ get_user_ex(vm86regs.pt.flags, &v86->regs.eflags);
+ get_user_ex(vm86regs.pt.sp, &v86->regs.esp);
get_user_ex(seg, &v86->regs.ss);
- info->regs.pt.ss = seg;
- get_user_ex(info->regs.es, &v86->regs.es);
- get_user_ex(info->regs.ds, &v86->regs.ds);
- get_user_ex(info->regs.fs, &v86->regs.fs);
- get_user_ex(info->regs.gs, &v86->regs.gs);
+ vm86regs.pt.ss = seg;
+ get_user_ex(vm86regs.es, &v86->regs.es);
+ get_user_ex(vm86regs.ds, &v86->regs.ds);
+ get_user_ex(vm86regs.fs, &v86->regs.fs);
+ get_user_ex(vm86regs.gs, &v86->regs.gs);
get_user_ex(vm86->flags, &v86->flags);
get_user_ex(vm86->screen_bitmap, &v86->screen_bitmap);
@@ -302,8 +287,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
} else
memset(&vm86->vm86plus, 0,
sizeof(struct vm86plus_info_struct));
-
- info->regs32 = current_pt_regs();
+ vm86->regs32 = regs32;
vm86->vm86_info = v86;
/*
@@ -311,12 +295,12 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
* has set it up safely, so this makes sure interrupt etc flags are
* inherited from protected mode.
*/
- VEFLAGS = info->regs.pt.flags;
- info->regs.pt.flags &= SAFE_MASK;
- info->regs.pt.flags |= info->regs32->flags & ~SAFE_MASK;
- info->regs.pt.flags |= X86_VM_MASK;
+ VEFLAGS = vm86regs.pt.flags;
+ vm86regs.pt.flags &= SAFE_MASK;
+ vm86regs.pt.flags |= regs32->flags & ~SAFE_MASK;
+ vm86regs.pt.flags |= X86_VM_MASK;
- info->regs.pt.orig_ax = info->regs32->orig_ax;
+ vm86regs.pt.orig_ax = regs32->orig_ax;
switch (vm86->cpu_type) {
case CPU_286:
@@ -336,12 +320,13 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
/*
* Save old state, set default return value (%ax) to 0 (VM86_SIGNAL)
*/
- info->regs32->ax = VM86_SIGNAL;
+ regs32->ax = VM86_SIGNAL;
vm86->saved_sp0 = tsk->thread.sp0;
- lazy_save_gs(info->regs32->gs);
+ lazy_save_gs(regs32->gs);
tss = &per_cpu(cpu_tss, get_cpu());
- tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
+ /* Set new sp0 right below 32-bit regs */
+ tsk->thread.sp0 = (unsigned long) regs32;
if (cpu_has_sep)
tsk->thread.sysenter_cs = 0;
load_sp0(tss, &tsk->thread);
@@ -364,7 +349,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
#endif
"jmp resume_userspace"
: /* no outputs */
- :"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
+ :"r" (&vm86regs), "r" (task_thread_info(tsk)), "r" (0));
unreachable(); /* we never return here */
}
@@ -539,7 +524,7 @@ static void do_int(struct kernel_vm86_regs *regs, int i,
{
unsigned long __user *intr_ptr;
unsigned long segoffs;
- struct kernel_vm86_info *vm86 = current->thread.vm86;
+ struct vm86 *vm86 = current->thread.vm86;
if (regs->pt.cs == BIOSSEG)
goto cannot_handle;
@@ -569,12 +554,14 @@ cannot_handle:
int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
{
- if (current->thread.vm86->vm86plus.is_vm86pus) {
+ struct vm86 *vm86 = current->thread.vm86;
+
+ if (vm86->vm86plus.is_vm86pus) {
if ((trapno == 3) || (trapno == 1)) {
- KVM86->regs32->ax = VM86_TRAP + (trapno << 8);
+ vm86->regs32->ax = VM86_TRAP + (trapno << 8);
/* setting this flag forces the code in entry_32.S to
the path where we call save_v86_state() and change
- the stack pointer to KVM86->regs32 */
+ the stack pointer to regs32 */
set_thread_flag(TIF_NOTIFY_RESUME);
return 0;
}
--
2.4.3
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