From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001
From: root <root@artemis.panaceas.org>
Date: Fri, 25 Dec 2015 04:40:36 +0000
Subject: initial_commit

---
 arch/alpha/lib/strlen_user.S | 91 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 arch/alpha/lib/strlen_user.S

(limited to 'arch/alpha/lib/strlen_user.S')

diff --git a/arch/alpha/lib/strlen_user.S b/arch/alpha/lib/strlen_user.S
new file mode 100644
index 00000000..508a18e9
--- /dev/null
+++ b/arch/alpha/lib/strlen_user.S
@@ -0,0 +1,91 @@
+/*
+ * arch/alpha/lib/strlen_user.S
+ *
+ * Return the length of the string including the NUL terminator
+ * (strlen+1) or zero if an error occurred.
+ *
+ * In places where it is critical to limit the processing time,
+ * and the data is not trusted, strnlen_user() should be used.
+ * It will return a value greater than its second argument if
+ * that limit would be exceeded. This implementation is allowed
+ * to access memory beyond the limit, but will not cross a page
+ * boundary when doing so.
+ */
+
+#include <asm/regdef.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 v0, $exception-99b(zero);	\
+	.previous
+
+
+	.set noreorder
+	.set noat
+	.text
+
+	.globl __strlen_user
+	.ent __strlen_user
+	.frame sp, 0, ra
+
+	.align 3
+__strlen_user:
+	ldah	a1, 32767(zero)	# do not use plain strlen_user() for strings
+				# that might be almost 2 GB long; you should
+				# be using strnlen_user() instead
+
+	.globl __strnlen_user
+
+	.align 3
+__strnlen_user:
+	.prologue 0
+
+	EX( ldq_u t0, 0(a0) )	# load first quadword (a0 may be misaligned)
+	lda     t1, -1(zero)
+	insqh   t1, a0, t1
+	andnot  a0, 7, v0
+	or      t1, t0, t0
+	subq	a0, 1, a0	# get our +1 for the return 
+	cmpbge  zero, t0, t1	# t1 <- bitmask: bit i == 1 <==> i-th byte == 0
+	subq	a1, 7, t2
+	subq	a0, v0, t0
+	bne     t1, $found
+
+	addq	t2, t0, t2
+	addq	a1, 1, a1
+
+	.align 3
+$loop:	ble	t2, $limit
+	EX( ldq t0, 8(v0) )
+	subq	t2, 8, t2
+	addq    v0, 8, v0	# addr += 8
+	cmpbge  zero, t0, t1
+	beq     t1, $loop
+
+$found:	negq    t1, t2		# clear all but least set bit
+	and     t1, t2, t1
+
+	and     t1, 0xf0, t2	# binary search for that set bit
+	and	t1, 0xcc, t3
+	and	t1, 0xaa, t4
+	cmovne	t2, 4, t2
+	cmovne	t3, 2, t3
+	cmovne	t4, 1, t4
+	addq	t2, t3, t2
+	addq	v0, t4, v0
+	addq	v0, t2, v0
+	nop			# dual issue next two on ev4 and ev5
+	subq    v0, a0, v0
+$exception:
+	ret
+
+	.align 3		# currently redundant
+$limit:
+	subq	a1, t2, v0
+	ret
+
+	.end __strlen_user
-- 
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