porting from https://github.com/kokke/tiny-bignum-c commit ac136565378c624365e0f5f556d386b3966bff32 and adapting to the nuttx
Signed-off-by: makejian <makejian@xiaomi.com>
Make.dep file should be updated by .config changed after first make.
There are 2 cases affected for this problem:
1) Add source files by config symbol
2) Include header files in #ifdef directive
These 2 cases may not be included in Make.dep and this may prevent the
differential build from working correctly.
This reverts commit 79af7fbf4ef0185fa501e23a900a2ad933f845a7.
Because:
* btashton reported some issues in local builds:
https://github.com/apache/incubator-nuttx/pull/603#issuecomment-602264860
* this might be related to the current CI breakage:
> /bin/sh: 1: /__w/incubator-nuttx/incubator-nuttx/nuttx/tools/mkdeps: not found
Entropy pool gathers environmental noise from device drivers, user-space, etc., and returns good random numbers, suitable for cryptographic use. Based on entropy pool design from *BSDs and uses BLAKE2Xs algorithm for CSPRNG output.
Patch also adds /dev/urandom support for using entropy pool RNG and new 'getrandom' system call for getting randomness without file-descriptor usage (thus avoiding file-descriptor exhaustion attacks). The 'getrandom' interface is similar as 'getentropy' and 'getrandom' available on OpenBSD and Linux respectively.
