powerpc/sstep: Convert to scoped user access

Commit 861574d ("powerpc/uaccess: Implement masked user access")
provides optimised user access by avoiding the cost of access_ok().

Convert single step emulation functions to scoped user access to
benefit from masked user access.

Scoped user access also make the code simpler.

Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/8f2d85bddacff18046096dc255fd94f6a0f8b230.1773137010.git.chleroy@kernel.org

Author: Christophe Leroy (CS GROUP)

arch/powerpc/lib/sstep.c

@@ -329,20 +329,17 @@ __read_mem_aligned(unsigned long *dest, unsigned long ea, int nb, struct pt_regs
 static nokprobe_inline int
 read_mem_aligned(unsigned long *dest, unsigned long ea, int nb, struct pt_regs *regs)
 {
-	int err;
+	void __user *uea = (void __user *)ea;
 
 	if (is_kernel_addr(ea))
 		return __read_mem_aligned(dest, ea, nb, regs);
 
-	if (user_read_access_begin((void __user *)ea, nb)) {
-		err = __read_mem_aligned(dest, ea, nb, regs);
-		user_read_access_end();
-	} else {
-		err = -EFAULT;
-		regs->dar = ea;
-	}
+	scoped_user_read_access_size(uea, nb, efault)
+		return __read_mem_aligned(dest, (unsigned long)uea, nb, regs);
 
-	return err;
+efault:
+	regs->dar = ea;
+	return -EFAULT;
 }
 
 /*
@@ -385,20 +382,17 @@ static __always_inline int __copy_mem_in(u8 *dest, unsigned long ea, int nb, str
 
 static nokprobe_inline int copy_mem_in(u8 *dest, unsigned long ea, int nb, struct pt_regs *regs)
 {
-	int err;
+	void __user *uea = (void __user *)ea;
 
 	if (is_kernel_addr(ea))
 		return __copy_mem_in(dest, ea, nb, regs);
 
-	if (user_read_access_begin((void __user *)ea, nb)) {
-		err = __copy_mem_in(dest, ea, nb, regs);
-		user_read_access_end();
-	} else {
-		err = -EFAULT;
-		regs->dar = ea;
-	}
+	scoped_user_read_access_size(uea, nb, efault)
+		return __copy_mem_in(dest, (unsigned long)uea, nb, regs);
 
-	return err;
+efault:
+	regs->dar = ea;
+	return -EFAULT;
 }
 
 static nokprobe_inline int read_mem_unaligned(unsigned long *dest,
@@ -465,20 +459,17 @@ __write_mem_aligned(unsigned long val, unsigned long ea, int nb, struct pt_regs
 static nokprobe_inline int
 write_mem_aligned(unsigned long val, unsigned long ea, int nb, struct pt_regs *regs)
 {
-	int err;
+	void __user *uea = (void __user *)ea;
 
 	if (is_kernel_addr(ea))
 		return __write_mem_aligned(val, ea, nb, regs);
 
-	if (user_write_access_begin((void __user *)ea, nb)) {
-		err = __write_mem_aligned(val, ea, nb, regs);
-		user_write_access_end();
-	} else {
-		err = -EFAULT;
-		regs->dar = ea;
-	}
+	scoped_user_write_access_size(uea, nb, efault)
+		return __write_mem_aligned(val, (unsigned long)uea, nb, regs);
 
-	return err;
+efault:
+	regs->dar = ea;
+	return -EFAULT;
 }
 
 /*
@@ -521,20 +512,17 @@ static __always_inline int __copy_mem_out(u8 *dest, unsigned long ea, int nb, st
 
 static nokprobe_inline int copy_mem_out(u8 *dest, unsigned long ea, int nb, struct pt_regs *regs)
 {
-	int err;
+	void __user *uea = (void __user *)ea;
 
 	if (is_kernel_addr(ea))
 		return __copy_mem_out(dest, ea, nb, regs);
 
-	if (user_write_access_begin((void __user *)ea, nb)) {
-		err = __copy_mem_out(dest, ea, nb, regs);
-		user_write_access_end();
-	} else {
-		err = -EFAULT;
-		regs->dar = ea;
-	}
+	scoped_user_write_access_size(uea, nb, efault)
+		return __copy_mem_out(dest, (unsigned long)uea, nb, regs);
 
-	return err;
+efault:
+	regs->dar = ea;
+	return -EFAULT;
 }
 
 static nokprobe_inline int write_mem_unaligned(unsigned long val,
@@ -1065,6 +1053,7 @@ static __always_inline int __emulate_dcbz(unsigned long ea)
 
 int emulate_dcbz(unsigned long ea, struct pt_regs *regs)
 {
+	void __user *uea = (void __user *)ea;
 	int err;
 	unsigned long size = l1_dcache_bytes();
 
@@ -1073,20 +1062,20 @@ int emulate_dcbz(unsigned long ea, struct pt_regs *regs)
 	if (!address_ok(regs, ea, size))
 		return -EFAULT;
 
-	if (is_kernel_addr(ea)) {
-		err = __emulate_dcbz(ea);
-	} else if (user_write_access_begin((void __user *)ea, size)) {
+	if (is_kernel_addr(ea))
 		err = __emulate_dcbz(ea);
-		user_write_access_end();
-	} else {
-		err = -EFAULT;
-	}
+	else
+		scoped_user_write_access_size(uea, size, efault)
+			err = __emulate_dcbz((unsigned long)uea);
 
 	if (err)
 		regs->dar = ea;
 
-
 	return err;
+
+efault:
+	regs->dar = ea;
+	return -EFAULT;
 }
 NOKPROBE_SYMBOL(emulate_dcbz);