[PATCH 4/7] x86/vm86: Move vm86 fields out of thread_struct

[Brian Gerst <brgerst@gmail.com>]

Allocate a separate structure for the vm86 fields.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
 arch/x86/include/asm/processor.h |  9 ++------
 arch/x86/include/asm/vm86.h      |  8 +++++++
 arch/x86/kernel/process.c        |  7 ++++++
 arch/x86/kernel/vm86_32.c        | 47 ++++++++++++++++++++++++----------------
 arch/x86/mm/fault.c              |  4 ++--
 5 files changed, 47 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 35ad554..d636fb8 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -403,13 +403,9 @@ struct thread_struct {
 	unsigned long		cr2;
 	unsigned long		trap_nr;
 	unsigned long		error_code;
-#ifdef CONFIG_X86_32
+#ifdef CONFIG_VM86
 	/* Virtual 86 mode info */
-	struct vm86plus_struct __user *vm86_info;
-	unsigned long		screen_bitmap;
-	unsigned long		v86flags;
-	unsigned long		v86mask;
-	unsigned long		saved_sp0;
+	struct kernel_vm86_info *vm86;
 #endif
 	/* IO permissions: */
 	unsigned long		*io_bitmap_ptr;
@@ -714,7 +710,6 @@ static inline void spin_lock_prefetch(const void *x)
 
 #define INIT_THREAD  {							  \
 	.sp0			= TOP_OF_INIT_STACK,			  \
-	.vm86_info		= NULL,					  \
 	.sysenter_cs		= __KERNEL_CS,				  \
 	.io_bitmap_ptr		= NULL,					  \
 }
diff --git a/arch/x86/include/asm/vm86.h b/arch/x86/include/asm/vm86.h
index 1d8de3f..a02967d 100644
--- a/arch/x86/include/asm/vm86.h
+++ b/arch/x86/include/asm/vm86.h
@@ -58,6 +58,14 @@ struct kernel_vm86_struct {
  */
 };
 
+struct kernel_vm86_info {
+	struct vm86plus_struct __user *vm86_info;
+	unsigned long screen_bitmap;
+	unsigned long v86flags;
+	unsigned long v86mask;
+	unsigned long saved_sp0;
+};
+
 #ifdef CONFIG_VM86
 
 void handle_vm86_fault(struct kernel_vm86_regs *, long);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9cad694..5dcd037 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -110,6 +110,13 @@ void exit_thread(void)
 		kfree(bp);
 	}
 
+#ifdef CONFIG_VM86
+	if (t->vm86) {
+		kfree(t->vm86);
+		t->vm86 = NULL;
+	}
+#endif
+
 	fpu__drop(fpu);
 }
 
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index e6c2b47..dce0a1c 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -44,6 +44,7 @@
 #include <linux/ptrace.h>
 #include <linux/audit.h>
 #include <linux/stddef.h>
+#include <linux/slab.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -81,8 +82,8 @@
 /*
  * virtual flags (16 and 32-bit versions)
  */
-#define VFLAGS	(*(unsigned short *)&(current->thread.v86flags))
-#define VEFLAGS	(current->thread.v86flags)
+#define VFLAGS	(*(unsigned short *)&(current->thread.vm86->v86flags))
+#define VEFLAGS	(current->thread.vm86->v86flags)
 
 #define set_flags(X, new, mask) \
 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
@@ -96,6 +97,7 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
 	struct pt_regs *ret;
 	struct task_struct *tsk = current;
 	struct vm86plus_struct __user *user;
+	struct kernel_vm86_info *vm86 = current->thread.vm86;
 	long err = 0;
 
 	/*
@@ -105,12 +107,12 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
 	 */
 	local_irq_enable();
 
-	if (!tsk->thread.vm86_info) {
+	if (!vm86 || !vm86->vm86_info) {
 		pr_alert("no vm86_info: BAD\n");
 		do_exit(SIGSEGV);
 	}
-	set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | tsk->thread.v86mask);
-	user = tsk->thread.vm86_info;
+	set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->v86mask);
+	user = vm86->vm86_info;
 
 	if (!access_ok(VERIFY_WRITE, user, VMPI.is_vm86pus ?
 		       sizeof(struct vm86plus_struct) :
@@ -137,7 +139,7 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
 		put_user_ex(regs->fs, &user->regs.fs);
 		put_user_ex(regs->gs, &user->regs.gs);
 
-		put_user_ex(tsk->thread.screen_bitmap, &user->screen_bitmap);
+		put_user_ex(vm86->screen_bitmap, &user->screen_bitmap);
 	} put_user_catch(err);
 	if (err) {
 		pr_alert("could not access userspace vm86_info\n");
@@ -145,10 +147,10 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
 	}
 
 	tss = &per_cpu(cpu_tss, get_cpu());
-	tsk->thread.sp0 = tsk->thread.saved_sp0;
+	tsk->thread.sp0 = vm86->saved_sp0;
 	tsk->thread.sysenter_cs = __KERNEL_CS;
 	load_sp0(tss, &tsk->thread);
-	tsk->thread.saved_sp0 = 0;
+	vm86->saved_sp0 = 0;
 	put_cpu();
 
 	ret = KVM86->regs32;
@@ -242,9 +244,16 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
 {
 	struct tss_struct *tss;
 	struct task_struct *tsk = current;
+	struct kernel_vm86_info *vm86 = tsk->thread.vm86;
 	unsigned long err = 0;
 
-	if (tsk->thread.saved_sp0)
+	if (!vm86)
+	{
+		if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
+			return -ENOMEM;
+		tsk->thread.vm86 = vm86;
+	}
+	if (vm86->saved_sp0)
 		return -EPERM;
 
 	if (!access_ok(VERIFY_READ, v86, plus ?
@@ -295,7 +304,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
 	}
 
 	info->regs32 = current_pt_regs();
-	tsk->thread.vm86_info = v86;
+	vm86->vm86_info = v86;
 
 /*
  * The flags register is also special: we cannot trust that the user
@@ -311,16 +320,16 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
 
 	switch (info->cpu_type) {
 	case CPU_286:
-		tsk->thread.v86mask = 0;
+		vm86->v86mask = 0;
 		break;
 	case CPU_386:
-		tsk->thread.v86mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		vm86->v86mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 		break;
 	case CPU_486:
-		tsk->thread.v86mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		vm86->v86mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 		break;
 	default:
-		tsk->thread.v86mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		vm86->v86mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 		break;
 	}
 
@@ -328,7 +337,7 @@ 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;
-	tsk->thread.saved_sp0 = tsk->thread.sp0;
+	vm86->saved_sp0 = tsk->thread.sp0;
 	lazy_save_gs(info->regs32->gs);
 
 	tss = &per_cpu(cpu_tss, get_cpu());
@@ -338,7 +347,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
 	load_sp0(tss, &tsk->thread);
 	put_cpu();
 
-	tsk->thread.screen_bitmap = info->screen_bitmap;
+	vm86->screen_bitmap = info->screen_bitmap;
 	if (info->flags & VM86_SCREEN_BITMAP)
 		mark_screen_rdonly(tsk->mm);
 
@@ -408,7 +417,7 @@ static inline void clear_AC(struct kernel_vm86_regs *regs)
 
 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
 {
-	set_flags(VEFLAGS, flags, current->thread.v86mask);
+	set_flags(VEFLAGS, flags, current->thread.vm86->v86mask);
 	set_flags(regs->pt.flags, flags, SAFE_MASK);
 	if (flags & X86_EFLAGS_IF)
 		set_IF(regs);
@@ -418,7 +427,7 @@ static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs
 
 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
 {
-	set_flags(VFLAGS, flags, current->thread.v86mask);
+	set_flags(VFLAGS, flags, current->thread.vm86->v86mask);
 	set_flags(regs->pt.flags, flags, SAFE_MASK);
 	if (flags & X86_EFLAGS_IF)
 		set_IF(regs);
@@ -433,7 +442,7 @@ static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
 	if (VEFLAGS & X86_EFLAGS_VIF)
 		flags |= X86_EFLAGS_IF;
 	flags |= X86_EFLAGS_IOPL;
-	return flags | (VEFLAGS & current->thread.v86mask);
+	return flags | (VEFLAGS & current->thread.vm86->v86mask);
 }
 
 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 81dcebf..5196ac4 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -315,12 +315,12 @@ check_v8086_mode(struct pt_regs *regs, unsigned long address,
 {
 	unsigned long bit;
 
-	if (!v8086_mode(regs))
+	if (!v8086_mode(regs) || !tsk->thread.vm86)
 		return;
 
 	bit = (address - 0xA0000) >> PAGE_SHIFT;
 	if (bit < 32)
-		tsk->thread.screen_bitmap |= 1 << bit;
+		tsk->thread.vm86->screen_bitmap |= 1 << bit;
 }
 
 static bool low_pfn(unsigned long pfn)
-- 
2.4.3