x86/fpu: Remove 'ubuf' parameter from the copy_xstate_to_kernel() APIs

The 'ubuf' parameter is unused in the _kernel() side of the API, remove it.

This simplifies the code and makes it easier to think about.

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/20170923130016.21448-4-mingo@kernel.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -48,7 +48,7 @@ void fpu__xstate_clear_all_cpu_caps(void);
 void *get_xsave_addr(struct xregs_state *xsave, int xstate);
 const void *get_xsave_field_ptr(int xstate_field);
 int using_compacted_format(void);
-int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf, void __user *ubuf, struct xregs_state *xsave);
+int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf, struct xregs_state *xsave);
 int copy_xstate_to_user(unsigned int pos, unsigned int count, void *kbuf, void __user *ubuf, struct xregs_state *xsave);
 int copy_user_to_xstate(const void *kbuf, const void __user *ubuf,
 		     struct xregs_state *xsave);

arch/x86/kernel/fpu/regset.c

@@ -93,7 +93,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
 
 	if (using_compacted_format()) {
 		if (kbuf)
-			ret = copy_xstate_to_kernel(pos, count, kbuf, ubuf, xsave);
+			ret = copy_xstate_to_kernel(pos, count, kbuf, xsave);
 		else
 			ret = copy_xstate_to_user(pos, count, kbuf, ubuf, xsave);
 	} else {

arch/x86/kernel/fpu/xstate.c

@@ -926,7 +926,7 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
  */
 static inline int
 __copy_xstate_to_kernel(unsigned int pos, unsigned int count,
-			void *kbuf, void __user *ubuf,
+			void *kbuf,
 			const void *data, const int start_pos,
 			const int end_pos)
 {
@@ -936,12 +936,7 @@ __copy_xstate_to_kernel(unsigned int pos, unsigned int count,
 	if (end_pos < 0 || pos < end_pos) {
 		unsigned int copy = (end_pos < 0 ? count : min(count, end_pos - pos));
 
-		if (kbuf) {
 		memcpy(kbuf + pos, data, copy);
-		} else {
-			if (__copy_to_user(ubuf + pos, data, copy))
-				return -EFAULT;
-		}
 	}
 	return 0;
 }
@@ -953,8 +948,7 @@ __copy_xstate_to_kernel(unsigned int pos, unsigned int count,
  * It supports partial copy but pos always starts from zero. This is called
  * from xstateregs_get() and there we check the CPU has XSAVES.
  */
-int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf,
-			void __user *ubuf, struct xregs_state *xsave)
+int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf, struct xregs_state *xsave)
 {
 	unsigned int offset, size;
 	int ret, i;
@@ -979,8 +973,7 @@ int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf,
 	offset = offsetof(struct xregs_state, header);
 	size = sizeof(header);
 
-	ret = __copy_xstate_to_kernel(offset, size, kbuf, ubuf, &header, 0, count);
-
+	ret = __copy_xstate_to_kernel(offset, size, kbuf, &header, 0, count);
 	if (ret)
 		return ret;
 
@@ -994,8 +987,7 @@ int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf,
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
 
-			ret = __copy_xstate_to_kernel(offset, size, kbuf, ubuf, src, 0, count);
-
+			ret = __copy_xstate_to_kernel(offset, size, kbuf, src, 0, count);
 			if (ret)
 				return ret;
 
@@ -1011,8 +1003,7 @@ int copy_xstate_to_kernel(unsigned int pos, unsigned int count, void *kbuf,
 	offset = offsetof(struct fxregs_state, sw_reserved);
 	size = sizeof(xstate_fx_sw_bytes);
 
-	ret = __copy_xstate_to_kernel(offset, size, kbuf, ubuf, xstate_fx_sw_bytes, 0, count);
-
+	ret = __copy_xstate_to_kernel(offset, size, kbuf, xstate_fx_sw_bytes, 0, count);
 	if (ret)
 		return ret;