sh/lib/checksum.S

35  * computes a partial checksum, e.g. for TCP/UDP fragments
46 	   * is aligned on either a 2-byte or 4-byte boundary.  We get at
47 	   * least a twofold speedup on 486 and Pentium if it is 4-byte aligned.
48 	   * Fortunately, it is easy to convert 2-byte alignment to 4-byte
53 	bt/s	2f		! Jump if alignment is ok.
54 	 mov	r4, r7		! Keep a copy to check for alignment
57 	bt	21f		! Jump if alignment is boundary of 2bytes.
61 	add	#-1, r5
62 	bt	9f
65 	addc	r0, r6		! t=0 from previous tst
73 	bt	2f
75 	! buf is 2 byte aligned (len could be 0)
76 	add	#-2, r5		! Alignment uses up two bytes.
78 	bt/s	1f		! Jump if we had at least two bytes.
80 	bra	6f
86 	bf	2f
89 	! buf is 4 byte aligned (len could be 0)
91 	mov	#-5, r0
94 	bt/s	4f		! if it's =0, go to 4f
118 	! here, we know r1==0
122 	and	#0x1c, r0
124 	bt	6f
128 	mov	#0, r2
137 	addc	r1, r6		! r1==0 here, so it means add carry-bit
143 	bt	9f		! if it's =0 go to 9f
146 	bf	7f
150 	bt/s	8f
162 	mov	#0, r0
164 9:
168 	bt	10f
187  * thus we can call a custom exception handler for all access types.
189  * FIXME: could someone double-check whether I haven't mixed up some SRC and
196 	.section __ex_table, "a";	\
197 	.long 9999b, 6001f	;	\
202 	.section __ex_table, "a";	\
203 	.long 9999b, 6002f	;	\
217 	mov.l	r5,@-r15
218 	mov.l	r6,@-r15
225 	bf	3f		! Different alignments, use slow version
227 	bf	3f		! If not, do it the slow way
231 	bt	2f		! Jump if alignment is ok.
232 	add	#-2,r6		! Alignment uses up two bytes.
234 	bt/s	1f
237 	bra	4f
245 	bt	4f
269 	mov	#0,r0
274 	bt	7f
275 	bra	5f
278 	! src and dest equally aligned, but to a two byte boundary.
279 	! Handle first two bytes as a special case
287 	mov	#0,r0
291 	mov	#-5,r0
294 	bt/s	2f
330 	mov	#0,r0
334 	mov	#0x1c,r0
337 	bf/s	4f
349 	mov	#0,r0
355 	bf	7f
358 	bf	5f
364 	bt/s	6f
376 	mov	#0,r0
386 	mov	#-EFAULT,r1
389 	! zero the complete destination - computing the rest
393 	mov	#0,r7
398 	mov.l	8000f,r0
406 	mov	#-EFAULT,r1
408 	mov.l	8001f,r0