1 files changed, 102 insertions, 0 deletions
diff --git a/arch/alpha/lib/clear_user.S b/arch/alpha/lib/clear_user.S
new file mode 100644
index 000000000..db6c6ca45
--- /dev/null
+++ b/arch/alpha/lib/clear_user.S
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * arch/alpha/lib/clear_user.S
+ * Contributed by Richard Henderson <rth@tamu.edu>
+ *
+ * Zero user space, handling exceptions as we go.
+ *
+ * We have to make sure that $0 is always up-to-date and contains the
+ * right "bytes left to zero" value (and that it is updated only _after_
+ * a successful copy).  There is also some rather minor exception setup
+ * stuff.
+ */
+#include <asm/export.h>
+
+/* Allow an exception for an insn; exit if we get one.  */
+#define EX(x,y...)			\
+	99: x,##y;			\
+	.section __ex_table,"a";	\
+	.long 99b - .;			\
+	lda $31, $exception-99b($31); 	\
+	.previous
+
+	.set noat
+	.set noreorder
+	.align 4
+
+	.globl __clear_user
+	.ent __clear_user
+	.frame	$30, 0, $26
+	.prologue 0
+
+$loop:
+	and	$1, 3, $4	# e0    :
+	beq	$4, 1f		# .. e1 :
+
+0:	EX( stq_u $31, 0($16) )	# e0    : zero one word
+	subq	$0, 8, $0	# .. e1 :
+	subq	$4, 1, $4	# e0    :
+	addq	$16, 8, $16	# .. e1 :
+	bne	$4, 0b		# e1    :
+	unop			#       :
+
+1:	bic	$1, 3, $1	# e0    :
+	beq	$1, $tail	# .. e1 :
+
+2:	EX( stq_u $31, 0($16) )	# e0    : zero four words
+	subq	$0, 8, $0	# .. e1 :
+	EX( stq_u $31, 8($16) )	# e0    :
+	subq	$0, 8, $0	# .. e1 :
+	EX( stq_u $31, 16($16) )	# e0    :
+	subq	$0, 8, $0	# .. e1 :
+	EX( stq_u $31, 24($16) )	# e0    :
+	subq	$0, 8, $0	# .. e1 :
+	subq	$1, 4, $1	# e0    :
+	addq	$16, 32, $16	# .. e1 :
+	bne	$1, 2b		# e1    :
+
+$tail:
+	bne	$2, 1f		# e1    : is there a tail to do?
+	ret	$31, ($26), 1	# .. e1 :
+
+1:	EX( ldq_u $5, 0($16) )	# e0    :
+	clr	$0		# .. e1 :
+	nop			# e1    :
+	mskqh	$5, $0, $5	# e0    :
+	EX( stq_u $5, 0($16) )	# e0    :
+	ret	$31, ($26), 1	# .. e1 :
+
+__clear_user:
+	and	$17, $17, $0
+	and	$16, 7, $4	# e0    : find dest misalignment
+	beq	$0, $zerolength # .. e1 :
+	addq	$0, $4, $1	# e0    : bias counter
+	and	$1, 7, $2	# e1    : number of bytes in tail
+	srl	$1, 3, $1	# e0    :
+	beq	$4, $loop	# .. e1 :
+
+	EX( ldq_u $5, 0($16) )	# e0    : load dst word to mask back in
+	beq	$1, $oneword	# .. e1 : sub-word store?
+
+	mskql	$5, $16, $5	# e0    : take care of misaligned head
+	addq	$16, 8, $16	# .. e1 :
+	EX( stq_u $5, -8($16) )	# e0    :
+	addq	$0, $4, $0	# .. e1 : bytes left -= 8 - misalignment
+	subq	$1, 1, $1	# e0    :
+	subq	$0, 8, $0	# .. e1 :
+	br	$loop		# e1    :
+	unop			#       :
+
+$oneword:
+	mskql	$5, $16, $4	# e0    :
+	mskqh	$5, $2, $5	# e0    :
+	or	$5, $4, $5	# e1    :
+	EX( stq_u $5, 0($16) )	# e0    :
+	clr	$0		# .. e1 :
+
+$zerolength:
+$exception:
+	ret	$31, ($26), 1	# .. e1 :
+
+	.end __clear_user
+	EXPORT_SYMBOL(__clear_user)