[PATCH 2/5] x86/vm86: Move vm86 fields out of thread_struct

From: Brian Gerst
Date: Sat Jul 11 2015 - 02:11:24 EST

Allocate a separate structure for the vm86 fields.

Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
---
arch/x86/include/asm/processor.h | 11 ++------
arch/x86/include/asm/vm86.h | 10 ++++++++
arch/x86/kernel/process.c | 7 +++++
arch/x86/kernel/vm86_32.c | 55 +++++++++++++++++++++++-----------------
arch/x86/mm/fault.c | 4 +--
5 files changed, 53 insertions(+), 34 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 43e6519..8085463 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -403,15 +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 vm86_struct __user *vm86_info;
- unsigned long screen_bitmap;
- unsigned long v86flags;
- unsigned long v86mask;
- unsigned long saved_sp0;
- unsigned int saved_fs;
- unsigned int saved_gs;
+ struct kernel_vm86_info *vm86;
#endif
/* IO permissions: */
unsigned long *io_bitmap_ptr;
@@ -716,7 +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..88f14e3 100644
--- a/arch/x86/include/asm/vm86.h
+++ b/arch/x86/include/asm/vm86.h
@@ -58,6 +58,16 @@ struct kernel_vm86_struct {
*/
};

+struct kernel_vm86_info {
+ struct vm86_struct __user *vm86_info;
+ unsigned long screen_bitmap;
+ unsigned long v86flags;
+ unsigned long v86mask;
+ unsigned long saved_sp0;
+ unsigned int saved_fs;
+ unsigned int saved_gs;
+};
+
#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 71a8b0a..8b29c9b 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)))
@@ -130,6 +131,7 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
struct tss_struct *tss;
struct pt_regs *ret;
unsigned long tmp;
+ struct kernel_vm86_info *vm86 = current->thread.vm86;

/*
* This gets called from entry.S with interrupts disabled, but
@@ -138,29 +140,29 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
*/
local_irq_enable();

- if (!current->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 | current->thread.v86mask);
- tmp = copy_vm86_regs_to_user(&current->thread.vm86_info->regs, regs);
- tmp += put_user(current->thread.screen_bitmap, &current->thread.vm86_info->screen_bitmap);
+ set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->v86mask);
+ tmp = copy_vm86_regs_to_user(&vm86->vm86_info->regs, regs);
+ tmp += put_user(vm86->screen_bitmap, &vm86->vm86_info->screen_bitmap);
if (tmp) {
pr_alert("could not access userspace vm86_info\n");
do_exit(SIGSEGV);
}

tss = &per_cpu(cpu_tss, get_cpu());
- current->thread.sp0 = current->thread.saved_sp0;
+ current->thread.sp0 = vm86->saved_sp0;
current->thread.sysenter_cs = __KERNEL_CS;
load_sp0(tss, &current->thread);
- current->thread.saved_sp0 = 0;
+ vm86->saved_sp0 = 0;
put_cpu();

ret = KVM86->regs32;

- ret->fs = current->thread.saved_fs;
- set_user_gs(ret, current->thread.saved_gs);
+ ret->fs = vm86->saved_fs;
+ set_user_gs(ret, vm86->saved_gs);

return ret;
}
@@ -249,8 +251,15 @@ 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;

- 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 (plus) {
if (copy_vm86_regs_from_user(&info->regs, &v86->regs,
@@ -266,7 +275,7 @@ static long do_sys_vm86(struct vm86plus_struct __user *v86, bool plus,
memset(&info->vm86plus, 0, sizeof(struct vm86plus_info_struct));
}
info->regs32 = current_pt_regs();
- tsk->thread.vm86_info = (struct vm86_struct __user *) v86;
+ vm86->vm86_info = (struct vm86_struct __user *) v86;

/*
* make sure the vm86() system call doesn't try to do anything silly
@@ -290,16 +299,16 @@ 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;
}

@@ -307,9 +316,9 @@ 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;
- tsk->thread.saved_fs = info->regs32->fs;
- tsk->thread.saved_gs = get_user_gs(info->regs32);
+ vm86->saved_sp0 = tsk->thread.sp0;
+ vm86->saved_fs = info->regs32->fs;
+ vm86->saved_gs = get_user_gs(info->regs32);

tss = &per_cpu(cpu_tss, get_cpu());
tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
@@ -318,7 +327,7 @@ 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);

@@ -388,7 +397,7 @@ 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);
@@ -398,7 +407,7 @@ 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);
@@ -413,7 +422,7 @@ 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

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