patch-2.1.7 linux/arch/alpha/lib/strncpy_from_user.S

• Lines: 369
• Date: Thu Oct 31 13:59:59 1996
• Orig file: v2.1.6/linux/arch/alpha/lib/strncpy_from_user.S
• Orig date: Sat Oct 19 10:07:28 1996

diff -u --recursive --new-file v2.1.6/linux/arch/alpha/lib/strncpy_from_user.S linux/arch/alpha/lib/strncpy_from_user.S
@@ -6,59 +6,334 @@
  *
  * -EFAULT       if an exception occurs before the terminator is copied.
  * N             if the buffer filled.
- * 
- * Otherwise the length of the string is returned.
  *
- * Additionally, the fourth argument should be `&current->tss.ex'.
+ * Otherwise the length of the string is returned.
  */
 
+
 #include <asm/errno.h>
+#include <alpha/regdef.h>
+
+
+/* Allow an exception for an insn; exit if we get one.  */
+#define EX(x,y...)			\
+	99: x,##y;			\
+	.section __ex_table,"a";	\
+	.gprel32 99b;			\
+	lda $31, $exception-99b($0); 	\
+	.text
+
 
 	.set noat
 	.set noreorder
-
 	.text
 
-	.align 3
 	.globl __strncpy_from_user
 	.ent __strncpy_from_user
+	.frame $30, 0, $26
+
+	.align 3
+$aligned:
+	/* On entry to this basic block:
+	   t0 == the first destination word for masking back in
+	   t1 == the first source word.  */
+
+	/* Create the 1st output word and detect 0's in the 1st input word.  */
+	lda	t2, -1		# e1    : build a mask against false zero
+	mskqh	t2, a1, t2	# e0    :   detection in the src word
+	mskqh	t1, a1, t3	# e0    :
+	ornot	t1, t2, t2	# .. e1 :
+	mskql	t0, a1, t0	# e0    : assemble the first output word
+	cmpbge	zero, t2, t7	# .. e1 : bits set iff null found
+	or	t0, t3, t0	# e0    :
+	beq	a2, $a_eoc	# .. e1 :
+	bne	t7, $a_eos	# .. e1 :
+
+	/* On entry to this basic block:
+	   t0 == a source word not containing a null.  */
+
+$a_loop:
+	stq_u	t0, 0(a0)	# e0    :
+	addq	a0, 8, a0	# .. e1 :
+	EX( ldq_u t0, 0(a1) )	# e0    :
+	addq	a1, 8, a1	# .. e1 :
+	subq	a2, 1, a2	# e0    :
+	cmpbge	zero, t0, t7	# .. e1 (stall)
+	beq	a2, $a_eoc      # e1    :
+	beq	t7, $a_loop	# e1    :
+
+	/* Take care of the final (partial) word store.  At this point
+	   the end-of-count bit is set in t7 iff it applies.
+
+	   On entry to this basic block we have:
+	   t0 == the source word containing the null
+	   t7 == the cmpbge mask that found it.  */
+
+$a_eos:
+	negq	t7, t8		# e0    : find low bit set
+	and	t7, t8, t8	# e1 (stall)
+
+	/* For the sake of the cache, don't read a destination word
+	   if we're not going to need it.  */
+	and	t8, 0x80, t6	# e0    :
+	bne	t6, 1f		# .. e1 (zdb)
+
+	/* We're doing a partial word store and so need to combine
+	   our source and original destination words.  */
+	ldq_u	t1, 0(a0)	# e0    :
+	subq	t8, 1, t6	# .. e1 :
+	or	t8, t6, t7	# e0    :
+	unop			#
+	zapnot	t0, t7, t0	# e0    : clear src bytes > null
+	zap	t1, t7, t1	# .. e1 : clear dst bytes <= null
+	or	t0, t1, t0	# e1    :
+
+1:	stq_u	t0, 0(a0)
+	br	$finish_up
+
+	/* Add the end-of-count bit to the eos detection bitmask.  */
+$a_eoc:
+	or	t10, t7, t7
+	br	$a_eos
 
+	/*** The Function Entry Point ***/
+	.align 3
 __strncpy_from_user:
-	.frame $30, 0, $26
-	.prologue 0
 
-	ldq	$20, 0($19)
-	beq	$18, 9f
-	br	$28, 1f		# set up exception return address
+	mov	a0, v0		# save the string start
+	beq	a2, $zerolength
 
-	lda	$0, -EFAULT
-	ret
+	/* Are source and destination co-aligned?  */
+	xor	a0, a1, t1	# e0    :
+	and	a0, 7, t0	# .. e1 : find dest misalignment
+	and	t1, 7, t1	# e0    :
+	addq	a2, t0, a2	# .. e1 : bias count by dest misalignment
+	subq	a2, 1, a2	# e0    :
+	and	a2, 7, t2	# e1    :
+	srl	a2, 3, a2	# e0    : a2 = loop counter = (count - 1)/8
+	addq	zero, 1, t10	# .. e1 :
+	sll	t10, t2, t10	# e0    : t10 = bitmask of last count byte
+	bne	t1, $unaligned	# .. e1 :
+
+	/* We are co-aligned; take care of a partial first word.  */
+
+	EX( ldq_u t1, 0(a1) )	# e0    : load first src word
+	addq	a1, 8, a1	# .. e1 :
+
+	beq	t0, $aligned	# avoid loading dest word if not needed
+	ldq_u	t0, 0(a0)	# e0    :
+	br	$aligned	# .. e1 :
+
+
+/* The source and destination are not co-aligned.  Align the destination
+   and cope.  We have to be very careful about not reading too much and
+   causing a SEGV.  */
+
+	.align 3
+$u_head:
+	/* We know just enough now to be able to assemble the first
+	   full source word.  We can still find a zero at the end of it
+	   that prevents us from outputting the whole thing.
+
+	   On entry to this basic block:
+	   t0 == the first dest word, unmasked
+	   t1 == the shifted low bits of the first source word
+	   t6 == bytemask that is -1 in dest word bytes */
+
+	EX( ldq_u t2, 8(a1) )	# e0    : load second src word
+	addq	a1, 8, a1	# .. e1 :
+	mskql	t0, a0, t0	# e0    : mask trailing garbage in dst
+	extqh	t2, a1, t4	# e0    :
+	or	t1, t4, t1	# e1    : first aligned src word complete
+	mskqh	t1, a0, t1	# e0    : mask leading garbage in src
+	or	t0, t1, t0	# e0    : first output word complete
+	or	t0, t6, t6	# e1    : mask original data for zero test
+	cmpbge	zero, t6, t7	# e0    :
+	beq	a2, $u_eocfin	# .. e1 :
+	bne	t7, $u_final	# e1    :
+
+	lda	t6, -1			# e1    : mask out the bits we have
+	mskql	t6, a1, t6		# e0    :   already seen
+	stq_u	t0, 0(a0)		# e0    : store first output word
+	or      t6, t2, t2		# .. e1 :
+	cmpbge	zero, t2, t7		# e0    : find nulls in second partial
+	addq	a0, 8, a0		# .. e1 :
+	subq	a2, 1, a2		# e0    :
+	bne	t7, $u_late_head_exit	# .. e1 :
+
+	/* Finally, we've got all the stupid leading edge cases taken care
+	   of and we can set up to enter the main loop.  */
+
+	extql	t2, a1, t1	# e0    : position hi-bits of lo word
+	EX( ldq_u t2, 8(a1) )	# .. e1 : read next high-order source word
+	addq	a1, 8, a1	# e0    :
+	cmpbge	zero, t2, t7	# e1 (stall)
+	beq	a2, $u_eoc	# e1    :
+	bne	t7, $u_eos	# e1    :
+
+	/* Unaligned copy main loop.  In order to avoid reading too much,
+	   the loop is structured to detect zeros in aligned source words.
+	   This has, unfortunately, effectively pulled half of a loop
+	   iteration out into the head and half into the tail, but it does
+	   prevent nastiness from accumulating in the very thing we want
+	   to run as fast as possible.
+
+	   On entry to this basic block:
+	   t1 == the shifted high-order bits from the previous source word
+	   t2 == the unshifted current source word
+
+	   We further know that t2 does not contain a null terminator.  */
+
+	.align 3
+$u_loop:
+	extqh	t2, a1, t0	# e0    : extract high bits for current word
+	addq	a1, 8, a1	# .. e1 :
+	extql	t2, a1, t3	# e0    : extract low bits for next time
+	addq	a0, 8, a0	# .. e1 :
+	or	t0, t1, t0	# e0    : current dst word now complete
+	EX( ldq_u t2, 0(a1) )	# .. e1 : load high word for next time
+	stq_u	t0, -8(a0)	# e0    : save the current word
+	mov	t3, t1		# .. e1 :
+	subq	a2, 1, a2	# e0    :
+	cmpbge	zero, t2, t7	# .. e1 : test new word for eos
+	beq	a2, $u_eoc	# e1    :
+	beq	t7, $u_loop	# e1    :
+
+	/* We've found a zero somewhere in the source word we just read.
+	   If it resides in the lower half, we have one (probably partial)
+	   word to write out, and if it resides in the upper half, we
+	   have one full and one partial word left to write out.
+
+	   On entry to this basic block:
+	   t1 == the shifted high-order bits from the previous source word
+	   t2 == the unshifted current source word.  */
+$u_eos:
+	extqh	t2, a1, t0	# e0    :
+	or	t0, t1, t0	# e1    : first (partial) source word complete
+
+	cmpbge	zero, t0, t7	# e0    : is the null in this first bit?
+	bne	t7, $u_final	# .. e1 (zdb)
+
+	stq_u	t0, 0(a0)	# e0    : the null was in the high-order bits
+	addq	a0, 8, a0	# .. e1 :
+	subq	a2, 1, a2	# e1    :
+
+$u_late_head_exit:
+	extql	t2, a1, t0	# .. e0 :
+	cmpbge	zero, t0, t7	# e0    :
+	or	t7, t10, t6	# e1    :
+	cmoveq	a2, t6, t7	# e0    :
+	nop			# .. e1 :
+
+	/* Take care of a final (probably partial) result word.
+	   On entry to this basic block:
+	   t0 == assembled source word
+	   t7 == cmpbge mask that found the null.  */
+$u_final:
+	negq	t7, t6		# e0    : isolate low bit set
+	and	t6, t7, t8	# e1    :
+
+	and	t8, 0x80, t6	# e0    : avoid dest word load if we can
+	bne	t6, 1f		# .. e1 (zdb)
+
+	ldq_u	t1, 0(a0)	# e0    :
+	subq	t8, 1, t6	# .. e1 :
+	or	t6, t8, t7	# e0    :
+	zapnot	t0, t7, t0	# .. e1 : kill source bytes > null
+	zap	t1, t7, t1	# e0    : kill dest bytes <= null
+	or	t0, t1, t0	# e1    :
+
+1:	stq_u	t0, 0(a0)	# e0    :
+	br	$finish_up
+
+$u_eoc:				# end-of-count
+	extqh	t2, a1, t0
+	or	t0, t1, t0
+	cmpbge	zero, t0, t7
+
+$u_eocfin:			# end-of-count, final word
+	or	t10, t7, t7
+	br	$u_final
+
+	/* Unaligned copy entry point.  */
+	.align 3
+$unaligned:
+
+	EX( ldq_u t1, 0(a1) )	# e0    : load first source word
+
+	and	a0, 7, t4	# .. e1 : find dest misalignment
+	and	a1, 7, t5	# e0    : find src misalignment
 
-1:	addq	$20, 1, $21
-	mov	$16, $0		# save the string start
-	stq	$21, 0($19)	# increment exception count
-	bsr	$23, __stxncpy	# do the work of the copy
-
-	zapnot	$1, $22, $5	# was last byte written null?
-	stq	$20, 0($19)	# decrement exception count
-	cmovne	$5, 1, $5
-
-	and	$22, 0xf0, $4	# binary search for the address of the
-	and	$22, 0xcc, $3	# last byte written
-	and	$22, 0xaa, $2
-	bic	$16, 7, $1
-	cmovne	$4, 4, $4
-	cmovne	$3, 2, $3
-	cmovne	$2, 1, $2
-	addq	$1, $4, $1
-	addq	$2, $3, $2
-	addq	$1, $2, $1
-	addq	$1, $5, $1	# add one if we filled the buffer
+	/* Conditionally load the first destination word and a bytemask
+	   with 0xff indicating that the destination byte is sacrosanct.  */
+
+	mov	zero, t0	# .. e1 :
+	mov	zero, t6	# e0    :
+	beq	t4, 1f		# .. e1 :
+	ldq_u	t0, 0(a0)	# e0    :
+	lda	t6, -1		# .. e1 :
+	mskql	t6, a0, t6	# e0    :
+1:
+	subq	a1, t4, a1	# .. e1 : sub dest misalignment from src addr
+
+	/* If source misalignment is larger than dest misalignment, we need
+	   extra startup checks to avoid SEGV.  */
+
+	cmplt	t4, t5, t8	# e1    :
+	extql	t1, a1, t1	# .. e0 : shift src into place
+	lda	t2, -1		# e0    : for creating masks later
+	beq	t8, $u_head	# e1    :
+
+	mskqh	t2, t5, t2	# e0    : begin src byte validity mask
+	cmpbge	zero, t1, t7	# .. e1 : is there a zero?
+	extql	t2, a1, t2	# e0    :
+	or	t7, t10, t6	# .. e1 : test for end-of-count too
+	cmpbge	zero, t2, t3	# e0    :
+	cmoveq	a2, t6, t7	# .. e1 :
+	andnot	t7, t3, t7	# e0    :
+	beq	t7, $u_head	# .. e1 (zdb)
+
+	/* At this point we've found a zero in the first partial word of
+	   the source.  We need to isolate the valid source data and mask
+	   it into the original destination data.  (Incidentally, we know
+	   that we'll need at least one byte of that original dest word.) */
+
+	ldq_u	t0, 0(a0)	# e0    :
+	negq	t7, t6		# .. e1 : build bitmask of bytes <= zero
+	mskqh	t1, t4, t1	# e0    :
+	and	t6, t7, t8	# .. e1 :
+	subq	t8, 1, t6	# e0    :
+	or	t6, t8, t7	# e1    :
+
+	zapnot	t2, t7, t2	# e0    : prepare source word; mirror changes
+	zapnot	t1, t7, t1	# .. e1 : to source validity mask
+
+	andnot	t0, t2, t0	# e0    : zero place for source to reside
+	or	t0, t1, t0	# e1    : and put it there
+	stq_u	t0, 0(a0)	# e0    :
+
+$finish_up:
+	zapnot	t0, t10, t4	# was last byte written null?
+	cmovne	t4, 1, t4
+
+	and	t10, 0xf0, t3	# binary search for the address of the
+	and	t10, 0xcc, t2	# last byte written
+	and	t10, 0xaa, t1
+	bic	a0, 7, t0
+	cmovne	t3, 4, t3
+	cmovne	t2, 2, t2
+	cmovne	t1, 1, t1
+	addq	t0, t3, t0
+	addq	t1, t2, t1
+	addq	t0, t1, t0
+	addq	t0, t4, t0	# add one if we filled the buffer
 
-	subq	$1, $0, $0	# find string length
+	subq	t0, v0, v0	# find string length
 	ret
 
-9:	clr	$0
+$zerolength:
+	clr	v0
+$exception:
 	ret
 
 	.end __strncpy_from_user