x86/vm86: Eliminate 'struct kernel_vm86_struct'

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@gmail.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1438148483-11932-4-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/vm86.h b/arch/x86/include/asm/vm86.h
index 47c7648338ee4dac1b4350539b5d6ad44021adae..226d6c157ebc34fd6c89ab3ae12ee81467a0b87c 100644 (file)
--- 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 f71b4b9452f104bdcbb60d39170375caa53d0604..696ef767f2be13c26814a1ae2d6235d2a1a5dd6c 100644 (file)
--- 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;
                }