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* [rng] Allow entropy source to be selected at runtimeMichael Brown2023-02-171-52/+0Star
| | | | | | | | | | | | | | | | | | | | | | | | As noted in commit 3c83843 ("[rng] Check for several functioning RTC interrupts"), experimentation shows that Hyper-V cannot be trusted to reliably generate RTC interrupts. (As noted in commit f3ba0fb ("[hyperv] Provide timer based on the 10MHz time reference count MSR"), Hyper-V appears to suffer from a general problem in reliably generating any legacy interrupts.) An alternative entropy source is therefore required for an image that may be used in a Hyper-V Gen1 virtual machine. The x86 RDRAND instruction provides a suitable alternative entropy source, but may not be supported by all CPUs. We must therefore allow for multiple entropy sources to be compiled in, with the single active entropy source selected only at runtime. Restructure the internal entropy API to allow a working entropy source to be detected and chosen at runtime. Enable the RDRAND entropy source for all x86 builds, since it is likely to be substantially faster than any other source. Signed-off-by: Michael Brown <mcb30@ipxe.org>
* [rng] Use fixed-point calculations for min-entropy quantitiesMichael Brown2018-03-201-2/+2
| | | | | | | | | | | | | | We currently perform various min-entropy calculations using build-time floating-point arithmetic. No floating-point code ends up in the final binary, since the results are eventually converted to integers and asserted to be compile-time constants. Though this mechanism is undoubtedly cute, it inhibits us from using "-mno-sse" to prevent the use of SSE registers by the compiler. Fix by using fixed-point arithmetic instead. Signed-off-by: Michael Brown <mcb30@ipxe.org>
* [legal] Relicense files under GPL2_OR_LATER_OR_UBDLMichael Brown2015-03-021-1/+1
| | | | | | | Relicense files for which I am the sole author (as identified by util/relicense.pl). Signed-off-by: Michael Brown <mcb30@ipxe.org>
* [rng] Allow entropy_enable() to return an errorMichael Brown2012-03-181-1/+2
| | | | Signed-off-by: Michael Brown <mcb30@ipxe.org>
* [rng] Add ANS X9.82 Approved Source of Entropy InputMichael Brown2012-02-211-0/+51
ANS X9.82 specifies several Approved Sources of Entropy Input (SEI). One such SEI uses an entropy source as the Source of Entropy Input, condensing each entropy source output after each GetEntropy call. This can be implemented relatively cheaply in iPXE and avoids the need to allocate potentially very large buffers. (Note that the terms "entropy source" and "Source of Entropy Input" are not synonyms within the context of ANS X9.82.) Use the iPXE API mechanism to allow entropy sources to be selected at compilation time. Signed-off-by: Michael Brown <mcb30@ipxe.org>