[PATCH] x86: unify sys_iopl

[Jeremy Fitzhardinge]

The 32 and 64-bit versions of sys_iopl were needlessly different:
 - The 32-bit version ignored its function argument and directly
   fetched the parameter from struct regs, presumably code dating
   from the neolithic era.
 - The 64-bit version never called set_iopl_mask().  Usually this
   is a no-op for 64-bit, but it is also a pvop, which meant that
   that iopl never worked for 64-bit guests under Xen.
 - Both versions use the archaic style of getting pt_regs passed
   to them.  We can get the current pt_regs with task_pt_regs, which
   avoids worrying about the fine details of stack layout.

We can use the body of the 32-bit function with a few small
adjustments to the function definition.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/syscalls.h b/arch/x86/include/asm/syscalls.h
index 372b76e..5336ce2 100644
--- a/arch/x86/include/asm/syscalls.h
+++ b/arch/x86/include/asm/syscalls.h
@@ -33,11 +33,11 @@ long sys_rt_sigreturn(struct pt_regs *);
 asmlinkage int sys_set_thread_area(struct user_desc __user *);
 asmlinkage int sys_get_thread_area(struct user_desc __user *);
 
-/* X86_32 only */
-#ifdef CONFIG_X86_32
 /* kernel/ioport.c */
-long sys_iopl(struct pt_regs *);
+asmlinkage long sys_iopl(unsigned int);
 
+/* X86_32 only */
+#ifdef CONFIG_X86_32
 /* kernel/process_32.c */
 int sys_clone(struct pt_regs *);
 int sys_execve(struct pt_regs *);
@@ -70,8 +70,6 @@ int sys_vm86(struct pt_regs *);
 #else /* CONFIG_X86_32 */
 
 /* X86_64 only */
-/* kernel/ioport.c */
-asmlinkage long sys_iopl(unsigned int, struct pt_regs *);
 
 /* kernel/process_64.c */
 asmlinkage long sys_clone(unsigned long, unsigned long,
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 99c4d30..bad4f22 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -119,11 +119,10 @@ static int do_iopl(unsigned int level, struct pt_regs *regs)
 	return 0;
 }
 
-#ifdef CONFIG_X86_32
-long sys_iopl(struct pt_regs *regs)
+asmlinkage long sys_iopl(unsigned int level)
 {
-	unsigned int level = regs->bx;
 	struct thread_struct *t = &current->thread;
+	struct pt_regs *regs = task_pt_regs(current);
 	int rc;
 
 	rc = do_iopl(level, regs);
@@ -135,9 +134,3 @@ long sys_iopl(struct pt_regs *regs)
 out:
 	return rc;
 }
-#else
-asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs)
-{
-	return do_iopl(level, regs);
-}
-#endif


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