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1da177e4 LT |
1 | /* |
2 | * arch/alpha/lib/strncpy_from_user.S | |
3 | * Contributed by Richard Henderson (rth@tamu.edu) | |
4 | * | |
5 | * Just like strncpy except in the return value: | |
6 | * | |
7 | * -EFAULT if an exception occurs before the terminator is copied. | |
8 | * N if the buffer filled. | |
9 | * | |
10 | * Otherwise the length of the string is returned. | |
11 | */ | |
12 | ||
13 | ||
14 | #include <asm/errno.h> | |
15 | #include <asm/regdef.h> | |
16 | ||
17 | ||
18 | /* Allow an exception for an insn; exit if we get one. */ | |
19 | #define EX(x,y...) \ | |
20 | 99: x,##y; \ | |
21 | .section __ex_table,"a"; \ | |
22 | .long 99b - .; \ | |
23 | lda $31, $exception-99b($0); \ | |
24 | .previous | |
25 | ||
26 | ||
27 | .set noat | |
28 | .set noreorder | |
29 | .text | |
30 | ||
31 | .globl __strncpy_from_user | |
32 | .ent __strncpy_from_user | |
33 | .frame $30, 0, $26 | |
34 | .prologue 0 | |
35 | ||
36 | .align 3 | |
37 | $aligned: | |
38 | /* On entry to this basic block: | |
39 | t0 == the first destination word for masking back in | |
40 | t1 == the first source word. */ | |
41 | ||
42 | /* Create the 1st output word and detect 0's in the 1st input word. */ | |
43 | lda t2, -1 # e1 : build a mask against false zero | |
44 | mskqh t2, a1, t2 # e0 : detection in the src word | |
45 | mskqh t1, a1, t3 # e0 : | |
46 | ornot t1, t2, t2 # .. e1 : | |
47 | mskql t0, a1, t0 # e0 : assemble the first output word | |
48 | cmpbge zero, t2, t8 # .. e1 : bits set iff null found | |
49 | or t0, t3, t0 # e0 : | |
50 | beq a2, $a_eoc # .. e1 : | |
51 | bne t8, $a_eos # .. e1 : | |
52 | ||
53 | /* On entry to this basic block: | |
54 | t0 == a source word not containing a null. */ | |
55 | ||
56 | $a_loop: | |
57 | stq_u t0, 0(a0) # e0 : | |
58 | addq a0, 8, a0 # .. e1 : | |
59 | EX( ldq_u t0, 0(a1) ) # e0 : | |
60 | addq a1, 8, a1 # .. e1 : | |
61 | subq a2, 1, a2 # e0 : | |
62 | cmpbge zero, t0, t8 # .. e1 (stall) | |
63 | beq a2, $a_eoc # e1 : | |
64 | beq t8, $a_loop # e1 : | |
65 | ||
66 | /* Take care of the final (partial) word store. At this point | |
67 | the end-of-count bit is set in t8 iff it applies. | |
68 | ||
69 | On entry to this basic block we have: | |
70 | t0 == the source word containing the null | |
71 | t8 == the cmpbge mask that found it. */ | |
72 | ||
73 | $a_eos: | |
74 | negq t8, t12 # e0 : find low bit set | |
75 | and t8, t12, t12 # e1 (stall) | |
76 | ||
77 | /* For the sake of the cache, don't read a destination word | |
78 | if we're not going to need it. */ | |
79 | and t12, 0x80, t6 # e0 : | |
80 | bne t6, 1f # .. e1 (zdb) | |
81 | ||
82 | /* We're doing a partial word store and so need to combine | |
83 | our source and original destination words. */ | |
84 | ldq_u t1, 0(a0) # e0 : | |
85 | subq t12, 1, t6 # .. e1 : | |
86 | or t12, t6, t8 # e0 : | |
87 | unop # | |
88 | zapnot t0, t8, t0 # e0 : clear src bytes > null | |
89 | zap t1, t8, t1 # .. e1 : clear dst bytes <= null | |
90 | or t0, t1, t0 # e1 : | |
91 | ||
92 | 1: stq_u t0, 0(a0) | |
93 | br $finish_up | |
94 | ||
95 | /* Add the end-of-count bit to the eos detection bitmask. */ | |
96 | $a_eoc: | |
97 | or t10, t8, t8 | |
98 | br $a_eos | |
99 | ||
100 | /*** The Function Entry Point ***/ | |
101 | .align 3 | |
102 | __strncpy_from_user: | |
103 | mov a0, v0 # save the string start | |
104 | beq a2, $zerolength | |
105 | ||
106 | /* Are source and destination co-aligned? */ | |
107 | xor a0, a1, t1 # e0 : | |
108 | and a0, 7, t0 # .. e1 : find dest misalignment | |
109 | and t1, 7, t1 # e0 : | |
110 | addq a2, t0, a2 # .. e1 : bias count by dest misalignment | |
111 | subq a2, 1, a2 # e0 : | |
112 | and a2, 7, t2 # e1 : | |
113 | srl a2, 3, a2 # e0 : a2 = loop counter = (count - 1)/8 | |
114 | addq zero, 1, t10 # .. e1 : | |
115 | sll t10, t2, t10 # e0 : t10 = bitmask of last count byte | |
116 | bne t1, $unaligned # .. e1 : | |
117 | ||
118 | /* We are co-aligned; take care of a partial first word. */ | |
119 | ||
120 | EX( ldq_u t1, 0(a1) ) # e0 : load first src word | |
121 | addq a1, 8, a1 # .. e1 : | |
122 | ||
123 | beq t0, $aligned # avoid loading dest word if not needed | |
124 | ldq_u t0, 0(a0) # e0 : | |
125 | br $aligned # .. e1 : | |
126 | ||
127 | ||
128 | /* The source and destination are not co-aligned. Align the destination | |
129 | and cope. We have to be very careful about not reading too much and | |
130 | causing a SEGV. */ | |
131 | ||
132 | .align 3 | |
133 | $u_head: | |
134 | /* We know just enough now to be able to assemble the first | |
135 | full source word. We can still find a zero at the end of it | |
136 | that prevents us from outputting the whole thing. | |
137 | ||
138 | On entry to this basic block: | |
139 | t0 == the first dest word, unmasked | |
140 | t1 == the shifted low bits of the first source word | |
141 | t6 == bytemask that is -1 in dest word bytes */ | |
142 | ||
143 | EX( ldq_u t2, 8(a1) ) # e0 : load second src word | |
144 | addq a1, 8, a1 # .. e1 : | |
145 | mskql t0, a0, t0 # e0 : mask trailing garbage in dst | |
146 | extqh t2, a1, t4 # e0 : | |
147 | or t1, t4, t1 # e1 : first aligned src word complete | |
148 | mskqh t1, a0, t1 # e0 : mask leading garbage in src | |
149 | or t0, t1, t0 # e0 : first output word complete | |
150 | or t0, t6, t6 # e1 : mask original data for zero test | |
151 | cmpbge zero, t6, t8 # e0 : | |
152 | beq a2, $u_eocfin # .. e1 : | |
153 | bne t8, $u_final # e1 : | |
154 | ||
155 | lda t6, -1 # e1 : mask out the bits we have | |
156 | mskql t6, a1, t6 # e0 : already seen | |
157 | stq_u t0, 0(a0) # e0 : store first output word | |
158 | or t6, t2, t2 # .. e1 : | |
159 | cmpbge zero, t2, t8 # e0 : find nulls in second partial | |
160 | addq a0, 8, a0 # .. e1 : | |
161 | subq a2, 1, a2 # e0 : | |
162 | bne t8, $u_late_head_exit # .. e1 : | |
163 | ||
164 | /* Finally, we've got all the stupid leading edge cases taken care | |
165 | of and we can set up to enter the main loop. */ | |
166 | ||
167 | extql t2, a1, t1 # e0 : position hi-bits of lo word | |
168 | EX( ldq_u t2, 8(a1) ) # .. e1 : read next high-order source word | |
169 | addq a1, 8, a1 # e0 : | |
170 | cmpbge zero, t2, t8 # e1 (stall) | |
171 | beq a2, $u_eoc # e1 : | |
172 | bne t8, $u_eos # e1 : | |
173 | ||
174 | /* Unaligned copy main loop. In order to avoid reading too much, | |
175 | the loop is structured to detect zeros in aligned source words. | |
176 | This has, unfortunately, effectively pulled half of a loop | |
177 | iteration out into the head and half into the tail, but it does | |
178 | prevent nastiness from accumulating in the very thing we want | |
179 | to run as fast as possible. | |
180 | ||
181 | On entry to this basic block: | |
182 | t1 == the shifted high-order bits from the previous source word | |
183 | t2 == the unshifted current source word | |
184 | ||
185 | We further know that t2 does not contain a null terminator. */ | |
186 | ||
187 | .align 3 | |
188 | $u_loop: | |
189 | extqh t2, a1, t0 # e0 : extract high bits for current word | |
190 | addq a1, 8, a1 # .. e1 : | |
191 | extql t2, a1, t3 # e0 : extract low bits for next time | |
192 | addq a0, 8, a0 # .. e1 : | |
193 | or t0, t1, t0 # e0 : current dst word now complete | |
194 | EX( ldq_u t2, 0(a1) ) # .. e1 : load high word for next time | |
195 | stq_u t0, -8(a0) # e0 : save the current word | |
196 | mov t3, t1 # .. e1 : | |
197 | subq a2, 1, a2 # e0 : | |
198 | cmpbge zero, t2, t8 # .. e1 : test new word for eos | |
199 | beq a2, $u_eoc # e1 : | |
200 | beq t8, $u_loop # e1 : | |
201 | ||
202 | /* We've found a zero somewhere in the source word we just read. | |
203 | If it resides in the lower half, we have one (probably partial) | |
204 | word to write out, and if it resides in the upper half, we | |
205 | have one full and one partial word left to write out. | |
206 | ||
207 | On entry to this basic block: | |
208 | t1 == the shifted high-order bits from the previous source word | |
209 | t2 == the unshifted current source word. */ | |
210 | $u_eos: | |
211 | extqh t2, a1, t0 # e0 : | |
212 | or t0, t1, t0 # e1 : first (partial) source word complete | |
213 | ||
214 | cmpbge zero, t0, t8 # e0 : is the null in this first bit? | |
215 | bne t8, $u_final # .. e1 (zdb) | |
216 | ||
217 | stq_u t0, 0(a0) # e0 : the null was in the high-order bits | |
218 | addq a0, 8, a0 # .. e1 : | |
219 | subq a2, 1, a2 # e1 : | |
220 | ||
221 | $u_late_head_exit: | |
222 | extql t2, a1, t0 # .. e0 : | |
223 | cmpbge zero, t0, t8 # e0 : | |
224 | or t8, t10, t6 # e1 : | |
225 | cmoveq a2, t6, t8 # e0 : | |
226 | nop # .. e1 : | |
227 | ||
228 | /* Take care of a final (probably partial) result word. | |
229 | On entry to this basic block: | |
230 | t0 == assembled source word | |
231 | t8 == cmpbge mask that found the null. */ | |
232 | $u_final: | |
233 | negq t8, t6 # e0 : isolate low bit set | |
234 | and t6, t8, t12 # e1 : | |
235 | ||
236 | and t12, 0x80, t6 # e0 : avoid dest word load if we can | |
237 | bne t6, 1f # .. e1 (zdb) | |
238 | ||
239 | ldq_u t1, 0(a0) # e0 : | |
240 | subq t12, 1, t6 # .. e1 : | |
241 | or t6, t12, t8 # e0 : | |
242 | zapnot t0, t8, t0 # .. e1 : kill source bytes > null | |
243 | zap t1, t8, t1 # e0 : kill dest bytes <= null | |
244 | or t0, t1, t0 # e1 : | |
245 | ||
246 | 1: stq_u t0, 0(a0) # e0 : | |
247 | br $finish_up | |
248 | ||
249 | $u_eoc: # end-of-count | |
250 | extqh t2, a1, t0 | |
251 | or t0, t1, t0 | |
252 | cmpbge zero, t0, t8 | |
253 | ||
254 | $u_eocfin: # end-of-count, final word | |
255 | or t10, t8, t8 | |
256 | br $u_final | |
257 | ||
258 | /* Unaligned copy entry point. */ | |
259 | .align 3 | |
260 | $unaligned: | |
261 | ||
262 | EX( ldq_u t1, 0(a1) ) # e0 : load first source word | |
263 | ||
264 | and a0, 7, t4 # .. e1 : find dest misalignment | |
265 | and a1, 7, t5 # e0 : find src misalignment | |
266 | ||
267 | /* Conditionally load the first destination word and a bytemask | |
268 | with 0xff indicating that the destination byte is sacrosanct. */ | |
269 | ||
270 | mov zero, t0 # .. e1 : | |
271 | mov zero, t6 # e0 : | |
272 | beq t4, 1f # .. e1 : | |
273 | ldq_u t0, 0(a0) # e0 : | |
274 | lda t6, -1 # .. e1 : | |
275 | mskql t6, a0, t6 # e0 : | |
276 | 1: | |
277 | subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr | |
278 | ||
279 | /* If source misalignment is larger than dest misalignment, we need | |
280 | extra startup checks to avoid SEGV. */ | |
281 | ||
282 | cmplt t4, t5, t12 # e1 : | |
283 | extql t1, a1, t1 # .. e0 : shift src into place | |
284 | lda t2, -1 # e0 : for creating masks later | |
285 | beq t12, $u_head # e1 : | |
286 | ||
287 | mskqh t2, t5, t2 # e0 : begin src byte validity mask | |
288 | cmpbge zero, t1, t8 # .. e1 : is there a zero? | |
289 | extql t2, a1, t2 # e0 : | |
290 | or t8, t10, t5 # .. e1 : test for end-of-count too | |
291 | cmpbge zero, t2, t3 # e0 : | |
292 | cmoveq a2, t5, t8 # .. e1 : | |
293 | andnot t8, t3, t8 # e0 : | |
294 | beq t8, $u_head # .. e1 (zdb) | |
295 | ||
296 | /* At this point we've found a zero in the first partial word of | |
297 | the source. We need to isolate the valid source data and mask | |
298 | it into the original destination data. (Incidentally, we know | |
299 | that we'll need at least one byte of that original dest word.) */ | |
300 | ||
301 | ldq_u t0, 0(a0) # e0 : | |
302 | negq t8, t6 # .. e1 : build bitmask of bytes <= zero | |
303 | mskqh t1, t4, t1 # e0 : | |
304 | and t6, t8, t12 # .. e1 : | |
305 | subq t12, 1, t6 # e0 : | |
306 | or t6, t12, t8 # e1 : | |
307 | ||
308 | zapnot t2, t8, t2 # e0 : prepare source word; mirror changes | |
309 | zapnot t1, t8, t1 # .. e1 : to source validity mask | |
310 | ||
311 | andnot t0, t2, t0 # e0 : zero place for source to reside | |
312 | or t0, t1, t0 # e1 : and put it there | |
313 | stq_u t0, 0(a0) # e0 : | |
314 | ||
315 | $finish_up: | |
316 | zapnot t0, t12, t4 # was last byte written null? | |
317 | cmovne t4, 1, t4 | |
318 | ||
319 | and t12, 0xf0, t3 # binary search for the address of the | |
320 | and t12, 0xcc, t2 # last byte written | |
321 | and t12, 0xaa, t1 | |
322 | bic a0, 7, t0 | |
323 | cmovne t3, 4, t3 | |
324 | cmovne t2, 2, t2 | |
325 | cmovne t1, 1, t1 | |
326 | addq t0, t3, t0 | |
327 | addq t1, t2, t1 | |
328 | addq t0, t1, t0 | |
329 | addq t0, t4, t0 # add one if we filled the buffer | |
330 | ||
331 | subq t0, v0, v0 # find string length | |
332 | ret | |
333 | ||
334 | $zerolength: | |
335 | clr v0 | |
336 | $exception: | |
337 | ret | |
338 | ||
339 | .end __strncpy_from_user |