[Bug 1501545] Re: Valgrind fails on rdrand when the cpu supports it (haswell)

[Adrien Béraud]

I get the exact same error and bytes.
unhandled instruction bytes: 0xF 0xC7 0xF0 0x89 0x6 0xF 0x42 0xC1

It happens when using std::random_device with GCC 5.2 on willy.

It's weird GCC stopped using /dev/urandom, a very good randomness source
that makes use of RDRAND

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Title:
  Valgrind fails on rdrand when the cpu supports it (haswell)

Status in valgrind package in Ubuntu:
  Confirmed

Bug description:
  vex amd64->IR: unhandled instruction bytes: 0xF 0xC7 0xF0 0x89 0x6 0xF 0x42 0xC1
  vex amd64->IR: REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0
  vex amd64->IR: VEX=0 VEX.L=0 VEX.nVVVV=0x0 ESC=0F
  vex amd64->IR: PFX.66=0 PFX.F2=0 PFX.F3=0

  opcode "rdrand %eax"

  Need valgrind 1:3.11.0-1ubuntu1

  How to reproduce (need haswell or a cpu that supports rdrand)
  http://pastebin.ubuntu.com/12628142/
  g++ -std=c++14 test.cpp -o test
  valgrind ./test

  Bug also needs to be filed upstream

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