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[Bug 1302245] Re: mmap_min_addr blocks armhf binary support on arm64


** Tags added: kernel-da-key trusty

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  mmap_min_addr blocks armhf binary support on arm64

Status in “linux” package in Ubuntu:

Bug description:
  As of linux 3.13.0_22.44, unprivileged armhf binaries will not run on a default arm64 Ubuntu install on hardware that supports ARMv7 instructions:
  $ LD_LIBRARY_PATH=/home/dannf/armhf/lib:/home/dannf/armhf/lib/arm-linux-gnueabihf /home/dannf/armhf/lib/ld-linux-armhf.so.3 /home/dannf/armhf/bin/true
  /home/dannf/armhf/bin/true: error while loading shared libraries: /home/dannf/armhf/bin/true: failed to map segment from shared object: Operation not permitted

  This appears to be because we set CONFIG_DEFAULT_MMAP_MIN_ADDR to
  65536. If we lower this to 32768, these binaries work:

  $ echo 32768 | sudo tee /proc/sys/vm/mmap_min_addr
  $ LD_LIBRARY_PATH=/home/dannf/armhf/lib:/home/dannf/armhf/lib/arm-linux-gnueabihf /home/dannf/armhf/lib/ld-linux-armhf.so.3 /home/dannf/armhf/bin/true
  $ echo $?

  Of course, lowering this default has some security implications - and
  it isn't clear how generally useful it is to have armhf compatibility
  support on arm64 systems.

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