xtensa/lib/usercopy.S

8  *  of the Xtensa link-time HAL, and those files may differ per
11  *  could lose the special functionality for accessing user-space
24  * size_t __xtensa_copy_user (void *dst, const void *src, size_t len);
37  *   This code tries to use fall-through braches for the common
64 	# a2/ dst, a3/ src, a4/ len
66 	mov	a11, a4		# preserve original len for error case
75 	__ssa8	a3		# set shift amount from byte offset
77 	movi	a2, 0		# return success for len==0
84 .Ldst1mod2:	# dst is only byte aligned
85 	bltui	a4, 7, .Lbytecopy	# do short copies byte by byte
87 	# copy 1 byte
92 	addi	a4, a4, -1
95 .Ldst2mod4:	# dst 16-bit aligned
97 	bltui	a4, 6, .Lbytecopy	# do short copies byte by byte
104 	addi	a4, a4, -2
108  * Byte by byte copy
111 	.byte	0		# 1 mod 4 alignment for LOOPNEZ
129 	movi	a2, 0		# return success for len bytes copied
133  * Destination and source are word-aligned.
135 	# copy 16 bytes per iteration for word-aligned dst and word-aligned src
137 	.byte	0		# (0 mod 4 alignment for LBEG)
185 	# copy 1 byte
189 	movi	a2, 0		# return success for len bytes copied
197 	.byte	0		# 1 mod 4 alignement for LOOPNEZ
200 	# copy 16 bytes per iteration for word-aligned dst and unaligned src
262 	# copy 1 byte
266 	movi	a2, 0		# return success for len bytes copied
274 /* a2 = original dst; a5 = current dst; a11= original len
275  * bytes_copied = a5 - a2
276  * retval = bytes_not_copied = original len - bytes_copied
277  * retval = a11 - (a5 - a2)
282 	sub	a2, a5, a2	/* a2 <-- bytes copied */
283 	sub	a2, a11, a2	/* a2 <-- bytes not copied */