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OPENSSL_instrument_bus2.3
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.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32 .\" .\" Standard preamble: .\" ======================================================================== .de Sh \" Subsection heading .br .if t .Sp .ne 5 .PP \fB\\$1\fR .PP .. .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. | will give a .\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to .\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C' .\" expand to `' in nroff, nothing in troff, for use with C<>. .tr \(*W-|\(bv\*(Tr .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' 'br\} .\" .\" If the F register is turned on, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . nr % 0 . rr F .\} .\" .\" For nroff, turn off justification. 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The subroutines in question instrument these references for purposes of gathering entropy for random number generator. In order to make it bus-bound a 'flush cache line' instruction is used between probes. In addition probes are added to \fBvector\fR elements in atomic or interlocked manner, which should contribute additional noise on multi-processor systems. This also means that \fBvector[num]\fR should be zeroed upon invocation (if you want to retrieve actual probe values). .PP OPENSSL_instrument_bus performs \fBnum\fR probes and records the number of oscillator cycles every probe took. .PP OPENSSL_instrument_bus2 on the other hand \fBaccumulates\fR consecutive probes with the same value, i.e. in a way it records duration of periods when probe values appeared deterministic. The subroutine performs at most \fBmax\fR probes in attempt to fill the \fBvector[num]\fR, with \fBmax\fR value of 0 meaning \*(L"as many as it takes.\*(R" .SH "RETURN VALUE" .IX Header "RETURN VALUE" Return value of 0 indicates that \s-1CPU\s0 is not capable of performing the benchmark, either because oscillator counter or 'flush cache line' is not available on current platform. For reference, on x86 'flush cache line' was introduced with the \s-1SSE2\s0 extensions. .PP Otherwise number of recorded values is returned.