x86/fpu: Remove 'ubuf' parameter from the copy_kernel_to_xstate() API

No change in functionality.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20170923130016.21448-13-mingo@kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/fpu/xstate.h

@@ -50,6 +50,6 @@ const void *get_xsave_field_ptr(int xstate_field);
 int using_compacted_format(void);
 int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
 int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
-int copy_kernel_to_xstate(const void *kbuf, const void __user *ubuf, struct xregs_state *xsave);
+int copy_kernel_to_xstate(const void *kbuf, struct xregs_state *xsave);
 int copy_user_to_xstate(const void *kbuf, const void __user *ubuf, struct xregs_state *xsave);
 #endif

arch/x86/kernel/fpu/regset.c

@@ -136,7 +136,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
 
 	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
 		if (kbuf)
-			ret = copy_kernel_to_xstate(kbuf, ubuf, xsave);
+			ret = copy_kernel_to_xstate(kbuf, xsave);
 		else
 			ret = copy_user_to_xstate(kbuf, ubuf, xsave);
 	} else {

arch/x86/kernel/fpu/xstate.c

@@ -1089,8 +1089,7 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i
  * there we check the CPU has XSAVES and a whole standard-sized buffer
  * exists.
  */
-int copy_kernel_to_xstate(const void *kbuf, const void __user *ubuf,
-		     struct xregs_state *xsave)
+int copy_kernel_to_xstate(const void *kbuf, struct xregs_state *xsave)
 {
 	unsigned int offset, size;
 	int i;
@@ -1100,12 +1099,7 @@ int copy_kernel_to_xstate(const void *kbuf, const void __user *ubuf,
 	offset = offsetof(struct xregs_state, header);
 	size = sizeof(xfeatures);
 
-	if (kbuf) {
 	memcpy(&xfeatures, kbuf + offset, size);
-	} else {
-		if (__copy_from_user(&xfeatures, ubuf + offset, size))
-			return -EFAULT;
-	}
 
 	/*
 	 * Reject if the user sets any disabled or supervisor features:
@@ -1124,12 +1118,7 @@ int copy_kernel_to_xstate(const void *kbuf, const void __user *ubuf,
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
 
-			if (kbuf) {
 			memcpy(dst, kbuf + offset, size);
-			} else {
-				if (__copy_from_user(dst, ubuf + offset, size))
-					return -EFAULT;
-			}
 		}
 	}