[Qemu-devel] [Bug 1591611] Re: chroot using qemu-x86_64-static fails on ppc64el

[Peter Maydell]

If you've got working code for the signal handlers you can submit those
as patches now if you like.
(http://wiki.qemu.org/Contribute/SubmitAPatch has info on the formatting
hoops.) We have a feature freeze for QEMU 2.7 coming up on the 28th
June, so before then would be ideal.

Judging by the assertion, something is going wrong with libc's attempt
to set the child tidptr via the ctid argument to clone and the
CLONE_CHILD_SETTID flag.

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https://bugs.launchpad.net/bugs/1591611

Title:
  chroot using qemu-x86_64-static fails on ppc64el

Status in QEMU:
  New

Bug description:
  When attempting to use qemu-x86_64-static from qemu 2.5.0 on a ppc64el
  host to chroot into an amd64 environment, all commands fail with an
  assertion error.  /usr/bin/qemu-x86_64-static from the host was copied
  into the chroot /usr/bin, and the host has multiformat support in the
  kernel.

  Sample output illustrating the problem, as well as bash builtins
  working:

  # chroot /virtualbox/scratchdisks_local_001/amd64_chroot qemu-x86_64-static 
/bin/bash
  # ls
  bash: ../sysdeps/nptl/fork.c:136: __libc_fork: Assertion `({ __typeof 
(self->tid) __value; if (sizeof (__value) == 1) asm volatile ("movb 
%%fs:%P2,%b0" : "=q" (__value) : "0" (0), "i" (__builtin_offsetof (struct 
pthread, tid))); else if (sizeof (__value) == 4) asm volatile ("movl 
%%fs:%P1,%0" : "=r" (__value) : "i" (__builtin_offsetof (struct pthread, 
tid))); else { if (sizeof (__value) != 8) abort (); asm volatile ("movq 
%%fs:%P1,%q0" : "=r" (__value) : "i" (__builtin_offsetof (struct pthread, 
tid))); } __value; }) != ppid' failed.
  setup_frame: not implemented
  setup_frame: not implemented
  qemu: uncaught target signal 11 (Segmentation fault) - core dumped
  Segmentation fault
  setup_frame: not implemented
  setup_frame: not implemented
  # echo TEST
  TEST
  # cat test
  bash: ../sysdeps/nptl/fork.c:136: __libc_fork: Assertion `({ __typeof 
(self->tid) __value; if (sizeof (__value) == 1) asm volatile ("movb 
%%fs:%P2,%b0" : "=q" (__value) : "0" (0), "i" (__builtin_offsetof (struct 
pthread, tid))); else if (sizeof (__value) == 4) asm volatile ("movl 
%%fs:%P1,%0" : "=r" (__value) : "i" (__builtin_offsetof (struct pthread, 
tid))); else { if (sizeof (__value) != 8) abort (); asm volatile ("movq 
%%fs:%P1,%q0" : "=r" (__value) : "i" (__builtin_offsetof (struct pthread, 
tid))); } __value; }) != ppid' failed.
  qemu: uncaught target signal 11 (Segmentation fault) - core dumped
  Segmentation fault

  It is currently unknown if other host architectures (e.g. aarch64) are
  also affected.

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