powerpc: Define and use get_user_instr() et. al.

Define specialised get_user_instr(), __get_user_instr() and
__get_user_instr_inatomic() macros for reading instructions from user
and/or kernel space.
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Reviewed-by: Alistair Popple <alistair@popple.id.au>
[mpe: Squash in addition of get_user_instr() & __user annotations]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200506034050.24806-17-jniethe5@gmail.com

arch/powerpc/include/asm/uaccess.h

@@ -105,6 +105,15 @@ static inline int __access_ok(unsigned long addr, unsigned long size,
 #define __put_user_inatomic(x, ptr) \
 	__put_user_nosleep((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
 
+#define get_user_instr(x, ptr) \
+	get_user((x).val, (u32 __user *)(ptr))
+
+#define __get_user_instr(x, ptr) \
+	__get_user_nocheck((x).val, (u32 __user *)(ptr), sizeof(u32), true)
+
+#define __get_user_instr_inatomic(x, ptr) \
+	__get_user_nosleep((x).val, (u32 __user *)(ptr), sizeof(u32))
+
 extern long __put_user_bad(void);
 
 /*

arch/powerpc/kernel/align.c

@@ -305,7 +305,7 @@ int fix_alignment(struct pt_regs *regs)
 	 */
 	CHECK_FULL_REGS(regs);
 
-	if (unlikely(__get_user(instr.val, (unsigned int __user *)regs->nip)))
+	if (unlikely(__get_user_instr(instr, (void __user *)regs->nip)))
 		return -EFAULT;
 	if ((regs->msr & MSR_LE) != (MSR_KERNEL & MSR_LE)) {
 		/* We don't handle PPC little-endian any more... */

arch/powerpc/kernel/hw_breakpoint.c

@@ -249,7 +249,7 @@ static bool stepping_handler(struct pt_regs *regs, struct perf_event *bp,
 	struct instruction_op op;
 	unsigned long addr = info->address;
 
-	if (__get_user_inatomic(instr.val, (unsigned int *)regs->nip))
+	if (__get_user_instr_inatomic(instr, (void __user *)regs->nip))
 		goto fail;
 
 	ret = analyse_instr(&op, regs, instr);

arch/powerpc/kernel/vecemu.c

@@ -266,7 +266,7 @@ int emulate_altivec(struct pt_regs *regs)
 	unsigned int va, vb, vc, vd;
 	vector128 *vrs;
 
-	if (get_user(instr.val, (unsigned int __user *)regs->nip))
+	if (get_user_instr(instr, (void __user *)regs->nip))
 		return -EFAULT;
 
 	word = ppc_inst_val(instr);