[Bug 1912107] Re: Option to constrain linux-user exec() to emulated CPU only

[Mingye Wang]

** Changed in: qemu
       Status: Incomplete => Confirmed

** Changed in: qemu
       Status: Confirmed => New

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https://bugs.launchpad.net/bugs/1912107

Title:
  Option to constrain linux-user exec() to emulated CPU only

Status in QEMU:
  New

Bug description:
  When trying to reproduce a bug someone reported on an actual AMD K10[1], ​I 
tried to directly throw `qemu_x86-64 -cpu 
  ​phenom path/to/wrongly-labelled-instruction-set/gcc 1.c` at the problem, but 
failed to get an "illegal instruction" as expected. A quick investigation 
reveals that the error is actually caused by one of gcc's child processess, and 
that the said process is being ran directly on the host. A similar problem 
happens with trying to call stuff with /usr/bin/env.

   ​[1]: https://github.com/Homebrew/brew/issues/1034

  Since both the host and the guest are x86_64, I deemed binfmt
  inapplicable to my case. I believe that QEMU should offer a way to
  modify exec() and other spawning syscalls so that execution remains on
  an emulated CPU in such a case. Call it an extra layer of binfmt, if
  you must.

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