[Qemu-devel] [Bug 1818483] Re: qemu user mode does not support binfmt_misc config with flags include "P"

[YunQiang Su]

This patch is for linux kernel.

It will set the 3rd bit of AT_FLAGS, if P is set for binfmt_misc.

The major concern is that AT_FLAGS is never used, then, should we use it
here?

** Patch added: "binfmt_preserve_argv0.patch"
   
https://bugs.launchpad.net/qemu/+bug/1818483/+attachment/5252516/+files/binfmt_preserve_argv0.patch

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1818483

Title:
  qemu user mode does not support binfmt_misc config with flags include
  "P"

Status in QEMU:
  New

Bug description:
  Hi Sir:
  During our test in chroot environment with qemu-user-static, we got some test 
cases failed because of program output warning with unexpected full path name.
  For example in test module "Devscripts"
  the test item for broken tarball expected the warning info:
  <tar: This does not look like a tar archive
  tar: ******* >
  but the output was:
  </bin/tar: This does not look like a tar archive
  /bin/tar: ******>
  the cause is the config file of binfmt_misc was set not to send argv0, for 
example:
  type command "tar" after chroot:
  ==========================
  address@hidden:~/projects_lpeng/qemu/mips_2/sid$ sudo chroot .
  [sudo] password for lpeng: 
  address@hidden:/# tar
  /bin/tar: You must specify one of the '-Acdtrux', '--delete' or 
'--test-label' options
  Try '/bin/tar --help' or '/bin/tar --usage' for more information.
  address@hidden:/# 
  ===========================

  by adding output log in main()@qemu/Linux-user/main.c
  we found the original input command was changed, and qemu do not know that, 
we got the input args:
  argv_0----/usr/bin/qemu-mips64el-static---
  argv_1----/bin/tar---
  argv_2----NULL---

  Next step we modified the flags=P in the corresponding config under folder 
/proc/sys/fs/binfmt_misc, then binfmt_misc sent argv[0] to qemu.
  But chroot could not start bash because in current qemu dose not consider 
about this unexpected one more"argv[0]"

  
  After modified qemu code temporary to handle the new argv list we got the 
input args, and from argv[2] is the original input command
  argv_0----/usr/bin/qemu-mips64el-static---
  argv_1----/bin/tar---
  argv_2----tar---

  We need the original input from command line, so is it possible that let 
binfmt_misc to pass one more additional args or env to qemu as a token of the 
binfmt_misc flag, then qemu can judge how to parse the input args by it?
  looking forward your suggestions.

  Thanks
  luyou

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1818483/+subscriptions