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bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
1 #!/usr/bin/perl
2 # -----------------------------------------------------------------------
3 #
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
4 # Copyright 2007-2008 rPath, Inc. - All Rights Reserved
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
5 #
6 # This file is part of the Linux kernel, and is made available under
7 # the terms of the GNU General Public License version 2 or (at your
8 # option) any later version; incorporated herein by reference.
9 #
10 # -----------------------------------------------------------------------
11 #
12
13 #
14 # Usage: timeconst.pl HZ > timeconst.h
15 #
16
17 # Precomputed values for systems without Math::BigInt
18 # Generated by:
19 # timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
20 %canned_values = (
21 24 => [
22 '0xa6aaaaab','0x2aaaaaa',26,
23 125,3,
24 '0xc49ba5e4','0x1fbe76c8b4',37,
25 3,125,
26 '0xa2c2aaab','0xaaaa',16,
27 125000,3,
28 '0xc9539b89','0x7fffbce4217d',47,
29 3,125000,
30 ], 32 => [
31 '0xfa000000','0x6000000',27,
32 125,4,
33 '0x83126e98','0xfdf3b645a',36,
34 4,125,
35 '0xf4240000','0x0',17,
36 31250,1,
37 '0x8637bd06','0x3fff79c842fa',46,
38 1,31250,
39 ], 48 => [
40 '0xa6aaaaab','0x6aaaaaa',27,
41 125,6,
42 '0xc49ba5e4','0xfdf3b645a',36,
43 6,125,
44 '0xa2c2aaab','0x15555',17,
45 62500,3,
46 '0xc9539b89','0x3fffbce4217d',46,
47 3,62500,
48 ], 64 => [
49 '0xfa000000','0xe000000',28,
50 125,8,
51 '0x83126e98','0x7ef9db22d',35,
52 8,125,
53 '0xf4240000','0x0',18,
54 15625,1,
55 '0x8637bd06','0x1fff79c842fa',45,
56 1,15625,
57 ], 100 => [
58 '0xa0000000','0x0',28,
59 10,1,
60 '0xcccccccd','0x733333333',35,
61 1,10,
62 '0x9c400000','0x0',18,
63 10000,1,
64 '0xd1b71759','0x1fff2e48e8a7',45,
65 1,10000,
66 ], 122 => [
67 '0x8325c53f','0xfbcda3a',28,
68 500,61,
69 '0xf9db22d1','0x7fbe76c8b',35,
70 61,500,
71 '0x8012e2a0','0x3ef36',18,
72 500000,61,
73 '0xffda4053','0x1ffffbce4217',45,
74 61,500000,
75 ], 128 => [
76 '0xfa000000','0x1e000000',29,
77 125,16,
78 '0x83126e98','0x3f7ced916',34,
79 16,125,
80 '0xf4240000','0x40000',19,
81 15625,2,
82 '0x8637bd06','0xfffbce4217d',44,
83 2,15625,
84 ], 200 => [
85 '0xa0000000','0x0',29,
86 5,1,
87 '0xcccccccd','0x333333333',34,
88 1,5,
89 '0x9c400000','0x0',19,
90 5000,1,
91 '0xd1b71759','0xfff2e48e8a7',44,
92 1,5000,
93 ], 250 => [
94 '0x80000000','0x0',29,
95 4,1,
96 '0x80000000','0x180000000',33,
97 1,4,
98 '0xfa000000','0x0',20,
99 4000,1,
100 '0x83126e98','0x7ff7ced9168',43,
101 1,4000,
102 ], 256 => [
103 '0xfa000000','0x3e000000',30,
104 125,32,
105 '0x83126e98','0x1fbe76c8b',33,
106 32,125,
107 '0xf4240000','0xc0000',20,
108 15625,4,
109 '0x8637bd06','0x7ffde7210be',43,
110 4,15625,
111 ], 300 => [
112 '0xd5555556','0x2aaaaaaa',30,
113 10,3,
114 '0x9999999a','0x1cccccccc',33,
115 3,10,
116 '0xd0555556','0xaaaaa',20,
117 10000,3,
118 '0x9d495183','0x7ffcb923a29',43,
119 3,10000,
120 ], 512 => [
121 '0xfa000000','0x7e000000',31,
122 125,64,
123 '0x83126e98','0xfdf3b645',32,
124 64,125,
125 '0xf4240000','0x1c0000',21,
126 15625,8,
127 '0x8637bd06','0x3ffef39085f',42,
128 8,15625,
129 ], 1000 => [
130 '0x80000000','0x0',31,
131 1,1,
132 '0x80000000','0x0',31,
133 1,1,
134 '0xfa000000','0x0',22,
135 1000,1,
136 '0x83126e98','0x1ff7ced9168',41,
137 1,1000,
138 ], 1024 => [
139 '0xfa000000','0xfe000000',32,
140 125,128,
141 '0x83126e98','0x7ef9db22',31,
142 128,125,
143 '0xf4240000','0x3c0000',22,
144 15625,16,
145 '0x8637bd06','0x1fff79c842f',41,
146 16,15625,
147 ], 1200 => [
148 '0xd5555556','0xd5555555',32,
149 5,6,
150 '0x9999999a','0x66666666',31,
151 6,5,
152 '0xd0555556','0x2aaaaa',22,
153 2500,3,
154 '0x9d495183','0x1ffcb923a29',41,
155 3,2500,
156 ]
157 );
158
159 $has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';
160
161 sub bint($)
162 {
163 my($x) = @_;
164 return Math::BigInt->new($x);
165 }
166
167 #
168 # Constants for division by reciprocal multiplication.
169 # (bits, numerator, denominator)
170 #
171 sub fmul($$$)
172 {
173 my ($b,$n,$d) = @_;
174
175 $n = bint($n);
176 $d = bint($d);
177
178 return scalar (($n << $b)+$d-bint(1))/$d;
179 }
180
181 sub fadj($$$)
182 {
183 my($b,$n,$d) = @_;
184
185 $n = bint($n);
186 $d = bint($d);
187
188 $d = $d/bgcd($n, $d);
189 return scalar (($d-bint(1)) << $b)/$d;
190 }
191
192 sub fmuls($$$) {
193 my($b,$n,$d) = @_;
194 my($s,$m);
195 my($thres) = bint(1) << ($b-1);
196
197 $n = bint($n);
198 $d = bint($d);
199
200 for ($s = 0; 1; $s++) {
201 $m = fmul($s,$n,$d);
202 return $s if ($m >= $thres);
203 }
204 return 0;
205 }
206
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
207 # Generate a hex value if the result fits in 64 bits;
208 # otherwise skip.
209 sub bignum_hex($) {
210 my($x) = @_;
211 my $s = $x->as_hex();
212
213 return (length($s) > 18) ? undef : $s;
214 }
215
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
216 # Provides mul, adj, and shr factors for a specific
217 # (bit, time, hz) combination
218 sub muladj($$$) {
219 my($b, $t, $hz) = @_;
220 my $s = fmuls($b, $t, $hz);
221 my $m = fmul($s, $t, $hz);
222 my $a = fadj($s, $t, $hz);
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
223 return (bignum_hex($m), bignum_hex($a), $s);
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
224 }
225
226 # Provides numerator, denominator values
227 sub numden($$) {
228 my($n, $d) = @_;
229 my $g = bgcd($n, $d);
230 return ($n/$g, $d/$g);
231 }
232
233 # All values for a specific (time, hz) combo
234 sub conversions($$) {
235 my ($t, $hz) = @_;
236 my @val = ();
237
238 # HZ_TO_xx
239 push(@val, muladj(32, $t, $hz));
240 push(@val, numden($t, $hz));
241
242 # xx_TO_HZ
243 push(@val, muladj(32, $hz, $t));
244 push(@val, numden($hz, $t));
245
246 return @val;
247 }
248
249 sub compute_values($) {
250 my($hz) = @_;
251 my @val = ();
252 my $s, $m, $a, $g;
253
254 if (!$has_bigint) {
255 die "$0: HZ == $hz not canned and ".
256 "Math::BigInt not available\n";
257 }
258
259 # MSEC conversions
260 push(@val, conversions(1000, $hz));
261
262 # USEC conversions
263 push(@val, conversions(1000000, $hz));
264
265 return @val;
266 }
267
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
268 sub outputval($$)
269 {
270 my($name, $val) = @_;
271 my $csuf;
272
273 if (defined($val)) {
274 if ($name !~ /SHR/) {
275 $val = "U64_C($val)";
276 }
277 printf "#define %-23s %s\n", $name.$csuf, $val.$csuf;
278 }
279 }
280
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
281 sub output($@)
282 {
283 my($hz, @val) = @_;
284 my $pfx, $bit, $suf, $s, $m, $a;
285
286 print "/* Automatically generated by kernel/timeconst.pl */\n";
287 print "/* Conversion constants for HZ == $hz */\n";
288 print "\n";
289 print "#ifndef KERNEL_TIMECONST_H\n";
290 print "#define KERNEL_TIMECONST_H\n";
291 print "\n";
292
293 print "#include <linux/param.h>\n";
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
294 print "#include <linux/types.h>\n";
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
295
296 print "\n";
297 print "#if HZ != $hz\n";
298 print "#error \"kernel/timeconst.h has the wrong HZ value!\"\n";
299 print "#endif\n";
300 print "\n";
301
302 foreach $pfx ('HZ_TO_MSEC','MSEC_TO_HZ',
c98aa86 timeconst.pl: correct reversal of USEC_TO_HZ and HZ_TO_USEC
H. Peter Anvin authored
303 'HZ_TO_USEC','USEC_TO_HZ') {
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
304 foreach $bit (32) {
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
305 foreach $suf ('MUL', 'ADJ', 'SHR') {
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
306 outputval("${pfx}_$suf$bit", shift(@val));
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
307 }
308 }
309 foreach $suf ('NUM', 'DEN') {
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
310 outputval("${pfx}_$suf", shift(@val));
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
311 }
312 }
313
314 print "\n";
315 print "#endif /* KERNEL_TIMECONST_H */\n";
316 }
317
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
318 # Pretty-print Perl values
319 sub perlvals(@) {
320 my $v;
321 my @l = ();
322
323 foreach $v (@_) {
324 if (!defined($v)) {
325 push(@l, 'undef');
326 } elsif ($v =~ /^0x/) {
327 push(@l, "\'".$v."\'");
328 } else {
329 push(@l, $v.'');
330 }
331 }
332 return join(',', @l);
333 }
334
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
335 ($hz) = @ARGV;
336
337 # Use this to generate the %canned_values structure
338 if ($hz eq '--can') {
339 shift(@ARGV);
340 @hzlist = sort {$a <=> $b} (@ARGV);
341
342 print "# Precomputed values for systems without Math::BigInt\n";
343 print "# Generated by:\n";
344 print "# timeconst.pl --can ", join(' ', @hzlist), "\n";
345 print "\%canned_values = (\n";
346 my $pf = "\t";
347 foreach $hz (@hzlist) {
348 my @values = compute_values($hz);
349 print "$pf$hz => [\n";
350 while (scalar(@values)) {
351 my $bit;
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
352 foreach $bit (32) {
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
353 my $m = shift(@values);
354 my $a = shift(@values);
355 my $s = shift(@values);
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
356 print "\t\t", perlvals($m,$a,$s), ",\n";
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
357 }
358 my $n = shift(@values);
359 my $d = shift(@values);
b9095fd Make constants in kernel/timeconst.h fixed 64 bits
H. Peter Anvin authored
360 print "\t\t", perlvals($n,$d), ",\n";
bdc8078 avoid overflows in kernel/time.c
H. Peter Anvin authored
361 }
362 print "\t]";
363 $pf = ', ';
364 }
365 print "\n);\n";
366 } else {
367 $hz += 0; # Force to number
368 if ($hz < 1) {
369 die "Usage: $0 HZ\n";
370 }
371
372 @val = @{$canned_values{$hz}};
373 if (!defined(@val)) {
374 @val = compute_values($hz);
375 }
376 output($hz, @val);
377 }
378 exit 0;
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