[$] A vDSO implementation of getrandom()

Most developers probably do not see the generation of random numbers asbeing a performance bottleneck for their programs, but there are seeminglyexceptions. Over the last few years, Jason Donenfeld has brought a newlevel of energy to the development of the kernel's random-number generator;he is now directing his efforts toward improving performance for user spacewith this patchseries that provides an implementation of the getrandom()system call in the kernel's "virtual dynamicshared object" (vDSO) area. The result is, indeed, better performance,but not all developers see this benefit as being worth the additionalcomplexity required to achieve it.