[Qemu-devel] Re: [Bug 739785] Re: qemu-i386 on ARM bash: fork: Invalid argument

[Peter Maydell]

On 28 March 2011 21:13, moonman <address@hidden> wrote:
> Hello,
>
> address@hidden ~]# strace -ff -o ls-strace.log chroot /i386 
> /usr/bin/qemu-i386 /bin/ls
> b?   d?    e?            l?  mu-e386i  ome  oot  roc  s?  u?
> bin  diae  hlrc.tin.gar  m?  o?        oot  q    s?   t?  v?
>
> address@hidden ~]# strace -ff -o bash-strace.log chroot /i386 
> /usr/bin/qemu-i386 /bin/bash -c /bin/ls
> /bin/bash: /bin/: %snnca eotcuxe btearinfiy

Something odd is going on here... Excerpts from the strace:

readlink("roc/self/f", 0x81abf80, 4095) = -1 ENOENT (No such file or
directory)

open("/0):/usr/libalo/eNG=Sn_UF.UT!\304\27\10P\254\32\10\267\304\27\10\20/LC_IDENTIFICATION",
O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/0):/usr/libalo/eNG=Sn_UF.ut/LC_IDENTIFICATION",
O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/0):/usr/libalo/eNG=Sn_UF/LC_IDENTIFICATION",
O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/0):/usr/libalo/eNG=Sn.UT!\304\27\10P\254\32\10\267\304\27\10\20/LC_IDENTIFICATION",
O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/0):/usr/libalo/eNG=Sn.ut/LC_IDENTIFICATION",
O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
open("/0):/usr/libalo/eNG=Sn/LC_IDENTIFICATION", O_RDONLY|O_LARGEFILE)
= -1 ENOENT (No such file or directory)
write(2, "/bin/bash: /bin/: %snnca eotcuxe"..., 47) = 47

That's clearly an attempt to open something in /proc/self, something
in /usr/lib/locale/, and to print a "cannot execute" message, but
everything's got rather twisted.

Swap every two pairs of bytes (or equivalently, rotate sets of four
characters by two) in this:
: %snnca eotcuxe
...and as if by magic, something comprehensible appears:
%s: cannot execu

Now, running x86 binaries on an ARM host does work for me, but I've
only tested on a Cortex-A8 (ARMv7) host. I think that what's happening
here is that qemu is doing unaligned accesses. On ARMv7 unaligned
accesses "work", ie you get the word you asked for. On ARMv5 the
effect is that the unaligned address is rounded down to a multiple of
four, we load 32 bits and then rotate them -- so you get the effects
you see above.

Short answer: looks like QEMU doesn't currently work on ARMv5 hosts
(although ARMv7 are fine). I'll look into this if I can manage to
scare up some suitable hardware.

-- 
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https://bugs.launchpad.net/bugs/739785

Title:
  qemu-i386 user mode on ARMv5 host fails (bash: fork: Invalid argument)

Status in QEMU:
  New

Bug description:
  Good time of day everybody,

  I have been trying to make usermode qemu on ARM with plugapps
  (archlinux) with archlinux i386 chroot to work.

  1. I installed arch linux in a virtuabox and created a chroot for it with 
mkarchroot. Transferred it to my pogo plug into /i386/
  2. I comiled qemu-i386 static and put it into /i386/usr/bin/
  ./configure --static --disable-blobs --disable-system 
--target-list=i386-linux-user
  make

  3. I also compiled linux kernel 2.6.38 with CONFIG_BINFMT_MISC=y and 
installed it.
  uname -a
  Linux Plugbox 2.6.38 #4 PREEMPT Fri Mar 18 22:19:10 CDT 2011 armv5tel 
Feroceon 88FR131 rev 1 (v5l) Marvell SheevaPlug Reference Board GNU/Linux

  4. Added the following options into /etc/rc.local
  /sbin/modprobe binfmt_misc
  /bin/mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc
  echo 
':qemu-i386:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03\x00:\xff\xff\xff\xff\xff\xfe\xfe\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfb\xff\xff\xff:/usr/bin/qemu-i386:'
 >/proc/sys/fs/binfmt_misc/register

  5. Also copied ld-linux.so.3 (actually ld-2.13.so because ld-
  linux.so.3 is a link to that file) from /lib/ to /i386/lib/

  6.Now i chroot into /i386 and I get this:
  address@hidden i386]# chroot .
  [II aI hnve ao address@hidden /]# pacman -Suy
  bash: fork: Invalid argument

  7.I also downloaded linux-user-test-0.3 from qemu website and ran the test:
  address@hidden linux-user-test-0.3]# make
  ./qemu-linux-user.sh
  [qemu-i386]
  ../qemu-0.14.0/i386-linux-user/qemu-i386 -L ./gnemul/qemu-i386 i386/ls -l 
dummyfile
  BUG IN DYNAMIC LINKER ld.so: dl-version.c: 210: _dl_check_map_versions: 
Assertion `needed != ((void *)0)' failed!
  make: *** [test] Error 127