[PATCH] i386: Update sys_vm86 to cope with changed pt_regs and %gs usage

sys_vm86 uses a struct kernel_vm86_regs, which is identical to pt_regs, but
adds an extra space for all the segment registers.  Previously this structure
was completely independent, so changes in pt_regs had to be reflected in
kernel_vm86_regs.  This changes just embeds pt_regs in kernel_vm86_regs, and
makes the appropriate changes to vm86.c to deal with the new naming.

Also, since %gs is dealt with differently in the kernel, this change adjusts
vm86.c to reflect this.

While making these changes, I also cleaned up some frankly bizarre code which
was added when auditing was added to sys_vm86.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>

1 files changed, 74 insertions, 47 deletions

diff --git a/arch/i386/kernel/vm86.c b/arch/i386/kernel/vm86.c
index cbcd61d6120b..be2f96e67f78 100644
--- a/arch/i386/kernel/vm86.c
+++ b/arch/i386/kernel/vm86.c
@@ -43,6 +43,7 @@
 #include <linux/highmem.h>
 #include <linux/ptrace.h>
 #include <linux/audit.h>
+#include <linux/stddef.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -72,10 +73,10 @@
 /*
  * 8- and 16-bit register defines..
  */
-#define AL(regs)        (((unsigned char *)&((regs)->eax))[0])
-#define AH(regs)        (((unsigned char *)&((regs)->eax))[1])
-#define IP(regs)        (*(unsigned short *)&((regs)->eip))
-#define SP(regs)        (*(unsigned short *)&((regs)->esp))
+#define AL(regs)        (((unsigned char *)&((regs)->pt.eax))[0])
+#define AH(regs)        (((unsigned char *)&((regs)->pt.eax))[1])
+#define IP(regs)        (*(unsigned short *)&((regs)->pt.eip))
+#define SP(regs)        (*(unsigned short *)&((regs)->pt.esp))
 
 /*
  * virtual flags (16 and 32-bit versions)
@@ -89,10 +90,37 @@
 #define SAFE_MASK       (0xDD5)
 #define RETURN_MASK     (0xDFF)
 
-#define VM86_REGS_PART2 orig_eax
-#define VM86_REGS_SIZE1 \
-        ( (unsigned)( & (((struct kernel_vm86_regs *)0)->VM86_REGS_PART2) ) )
-#define VM86_REGS_SIZE2 (sizeof(struct kernel_vm86_regs) - VM86_REGS_SIZE1)
+/* convert kernel_vm86_regs to vm86_regs */
+static int copy_vm86_regs_to_user(struct vm86_regs __user *user,
+                                  const struct kernel_vm86_regs *regs)
+{
+        int ret = 0;
+
+        /* kernel_vm86_regs is missing xfs, so copy everything up to
+           (but not including) xgs, and then rest after xgs. */
+        ret += copy_to_user(user, regs, offsetof(struct kernel_vm86_regs, pt.xgs));
+        ret += copy_to_user(&user->__null_gs, &regs->pt.xgs,
+                            sizeof(struct kernel_vm86_regs) -
+                            offsetof(struct kernel_vm86_regs, pt.xgs));
+
+        return ret;
+}
+
+/* convert vm86_regs to kernel_vm86_regs */
+static int copy_vm86_regs_from_user(struct kernel_vm86_regs *regs,
+                                    const struct vm86_regs __user *user,
+                                    unsigned extra)
+{
+        int ret = 0;
+
+        ret += copy_from_user(regs, user, offsetof(struct kernel_vm86_regs, pt.xgs));
+        ret += copy_from_user(&regs->pt.xgs, &user->__null_gs,
+                              sizeof(struct kernel_vm86_regs) -
+                              offsetof(struct kernel_vm86_regs, pt.xgs) +
+                              extra);
+
+        return ret;
+}
 
 struct pt_regs * FASTCALL(save_v86_state(struct kernel_vm86_regs * regs));
 struct pt_regs * fastcall save_v86_state(struct kernel_vm86_regs * regs)
@@ -112,10 +140,8 @@ struct pt_regs * fastcall save_v86_state(struct kernel_vm86_regs * regs)
                 printk("no vm86_info: BAD\n");
                 do_exit(SIGSEGV);
         }
-        set_flags(regs->eflags, VEFLAGS, VIF_MASK | current->thread.v86mask);
-        tmp = copy_to_user(&current->thread.vm86_info->regs,regs, VM86_REGS_SIZE1);
-        tmp += copy_to_user(&current->thread.vm86_info->regs.VM86_REGS_PART2,
-                &regs->VM86_REGS_PART2, VM86_REGS_SIZE2);
+        set_flags(regs->pt.eflags, VEFLAGS, VIF_MASK | 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);
         if (tmp) {
                 printk("vm86: could not access userspace vm86_info\n");
@@ -129,9 +155,11 @@ struct pt_regs * fastcall save_v86_state(struct kernel_vm86_regs * regs)
         current->thread.saved_esp0 = 0;
         put_cpu();
 
-        loadsegment(fs, current->thread.saved_fs);
-        loadsegment(gs, current->thread.saved_gs);
         ret = KVM86->regs32;
+
+        loadsegment(fs, current->thread.saved_fs);
+        ret->xgs = current->thread.saved_gs;
+
         return ret;
 }
 
@@ -183,9 +211,9 @@ asmlinkage int sys_vm86old(struct pt_regs regs)
         tsk = current;
         if (tsk->thread.saved_esp0)
                 goto out;
-        tmp  = copy_from_user(&info, v86, VM86_REGS_SIZE1);
-        tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2,
-                (long)&info.vm86plus - (long)&info.regs.VM86_REGS_PART2);
+        tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+                                       offsetof(struct kernel_vm86_struct, vm86plus) -
+                                       sizeof(info.regs));
         ret = -EFAULT;
         if (tmp)
                 goto out;
@@ -233,9 +261,9 @@ asmlinkage int sys_vm86(struct pt_regs regs)
         if (tsk->thread.saved_esp0)
                 goto out;
         v86 = (struct vm86plus_struct __user *)regs.ecx;
-        tmp  = copy_from_user(&info, v86, VM86_REGS_SIZE1);
-        tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2,
-                (long)&info.regs32 - (long)&info.regs.VM86_REGS_PART2);
+        tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+                                       offsetof(struct kernel_vm86_struct, regs32) -
+                                       sizeof(info.regs));
         ret = -EFAULT;
         if (tmp)
                 goto out;
@@ -252,15 +280,15 @@ out:
 static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
 {
         struct tss_struct *tss;
-        long eax;
 /*
  * make sure the vm86() system call doesn't try to do anything silly
  */
-        info->regs.__null_ds = 0;
-        info->regs.__null_es = 0;
+        info->regs.pt.xds = 0;
+        info->regs.pt.xes = 0;
+        info->regs.pt.xgs = 0;
 
-/* we are clearing fs,gs later just before "jmp resume_userspace",
- * because starting with Linux 2.1.x they aren't no longer saved/restored
+/* we are clearing fs later just before "jmp resume_userspace",
+ * because it is not saved/restored.
  */
 
 /*
@@ -268,10 +296,10 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
  * has set it up safely, so this makes sure interrupt etc flags are
  * inherited from protected mode.
  */
-        VEFLAGS = info->regs.eflags;
-        info->regs.eflags &= SAFE_MASK;
-        info->regs.eflags |= info->regs32->eflags & ~SAFE_MASK;
-        info->regs.eflags |= VM_MASK;
+        VEFLAGS = info->regs.pt.eflags;
+        info->regs.pt.eflags &= SAFE_MASK;
+        info->regs.pt.eflags |= info->regs32->eflags & ~SAFE_MASK;
+        info->regs.pt.eflags |= VM_MASK;
 
         switch (info->cpu_type) {
                 case CPU_286:
@@ -294,7 +322,7 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
         info->regs32->eax = 0;
         tsk->thread.saved_esp0 = tsk->thread.esp0;
         savesegment(fs, tsk->thread.saved_fs);
-        savesegment(gs, tsk->thread.saved_gs);
+        tsk->thread.saved_gs = info->regs32->xgs;
 
         tss = &per_cpu(init_tss, get_cpu());
         tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
@@ -306,19 +334,18 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
         tsk->thread.screen_bitmap = info->screen_bitmap;
         if (info->flags & VM86_SCREEN_BITMAP)
                 mark_screen_rdonly(tsk->mm);
-        __asm__ __volatile__("xorl %eax,%eax; movl %eax,%fs; movl %eax,%gs\n\t");
-        __asm__ __volatile__("movl %%eax, %0\n" :"=r"(eax));
 
         /*call audit_syscall_exit since we do not exit via the normal paths */
         if (unlikely(current->audit_context))
-                audit_syscall_exit(AUDITSC_RESULT(eax), eax);
+                audit_syscall_exit(AUDITSC_RESULT(0), 0);
 
         __asm__ __volatile__(
                 "movl %0,%%esp\n\t"
                 "movl %1,%%ebp\n\t"
+                "mov  %2, %%fs\n\t"
                 "jmp resume_userspace"
                 : /* no outputs */
-                :"r" (&info->regs), "r" (task_thread_info(tsk)));
+                :"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
         /* we never return here */
 }
 
@@ -348,12 +375,12 @@ static inline void clear_IF(struct kernel_vm86_regs * regs)
 
 static inline void clear_TF(struct kernel_vm86_regs * regs)
 {
-        regs->eflags &= ~TF_MASK;
+        regs->pt.eflags &= ~TF_MASK;
 }
 
 static inline void clear_AC(struct kernel_vm86_regs * regs)
 {
-        regs->eflags &= ~AC_MASK;
+        regs->pt.eflags &= ~AC_MASK;
 }
 
 /* It is correct to call set_IF(regs) from the set_vflags_*
@@ -370,7 +397,7 @@ static inline void clear_AC(struct kernel_vm86_regs * regs)
 static inline void set_vflags_long(unsigned long eflags, struct kernel_vm86_regs * regs)
 {
         set_flags(VEFLAGS, eflags, current->thread.v86mask);
-        set_flags(regs->eflags, eflags, SAFE_MASK);
+        set_flags(regs->pt.eflags, eflags, SAFE_MASK);
         if (eflags & IF_MASK)
                 set_IF(regs);
         else
@@ -380,7 +407,7 @@ static inline void set_vflags_long(unsigned long eflags, 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(regs->eflags, flags, SAFE_MASK);
+        set_flags(regs->pt.eflags, flags, SAFE_MASK);
         if (flags & IF_MASK)
                 set_IF(regs);
         else
@@ -389,7 +416,7 @@ static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_reg
 
 static inline unsigned long get_vflags(struct kernel_vm86_regs * regs)
 {
-        unsigned long flags = regs->eflags & RETURN_MASK;
+        unsigned long flags = regs->pt.eflags & RETURN_MASK;
 
         if (VEFLAGS & VIF_MASK)
                 flags |= IF_MASK;
@@ -493,7 +520,7 @@ static void do_int(struct kernel_vm86_regs *regs, int i,
         unsigned long __user *intr_ptr;
         unsigned long segoffs;
 
-        if (regs->cs == BIOSSEG)
+        if (regs->pt.xcs == BIOSSEG)
                 goto cannot_handle;
         if (is_revectored(i, &KVM86->int_revectored))
                 goto cannot_handle;
@@ -505,9 +532,9 @@ static void do_int(struct kernel_vm86_regs *regs, int i,
         if ((segoffs >> 16) == BIOSSEG)
                 goto cannot_handle;
         pushw(ssp, sp, get_vflags(regs), cannot_handle);
-        pushw(ssp, sp, regs->cs, cannot_handle);
+        pushw(ssp, sp, regs->pt.xcs, cannot_handle);
         pushw(ssp, sp, IP(regs), cannot_handle);
-        regs->cs = segoffs >> 16;
+        regs->pt.xcs = segoffs >> 16;
         SP(regs) -= 6;
         IP(regs) = segoffs & 0xffff;
         clear_TF(regs);
@@ -524,7 +551,7 @@ int handle_vm86_trap(struct kernel_vm86_regs * regs, long error_code, int trapno
         if (VMPI.is_vm86pus) {
                 if ( (trapno==3) || (trapno==1) )
                         return_to_32bit(regs, VM86_TRAP + (trapno << 8));
-                do_int(regs, trapno, (unsigned char __user *) (regs->ss << 4), SP(regs));
+                do_int(regs, trapno, (unsigned char __user *) (regs->pt.xss << 4), SP(regs));
                 return 0;
         }
         if (trapno !=1)
@@ -560,10 +587,10 @@ void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code)
                 handle_vm86_trap(regs, 0, 1); \
         return; } while (0)
 
-        orig_flags = *(unsigned short *)&regs->eflags;
+        orig_flags = *(unsigned short *)&regs->pt.eflags;
 
-        csp = (unsigned char __user *) (regs->cs << 4);
-        ssp = (unsigned char __user *) (regs->ss << 4);
+        csp = (unsigned char __user *) (regs->pt.xcs << 4);
+        ssp = (unsigned char __user *) (regs->pt.xss << 4);
         sp = SP(regs);
         ip = IP(regs);
 
@@ -650,7 +677,7 @@ void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code)
                         SP(regs) += 6;
                 }
                 IP(regs) = newip;
-                regs->cs = newcs;
+                regs->pt.xcs = newcs;
                 CHECK_IF_IN_TRAP;
                 if (data32) {
                         set_vflags_long(newflags, regs);