[Toybox] [landley/toybox] Segfault using toybox stat on Android emulator (#36)

[Rob Landley]

On 07/21/2016 02:58 AM, Michael Eder wrote:
> |toybox stat| is crashing on Android emulator running Android 5.1.1
> (Lollipop)
> 
> |root at generic:/data/local # ./toybox-armv6l stat script.sh File:
> `script.sh' Size: 14722 Blocks: 32 IO Blocks: 4096 regular file Device:
> 1f01h/7937d Inode: 14524 Links: 1 Access: (770/-rwxrwx---Segmentation
> fault |

Hmmm... Under qemu-system-arm I get:

$ ./toybox stat toybox
  File: `toybox'
  Size: 297768   Blocks: 588     IO Blocks: 1024        regular file
Device: 810h/2064d       Inode: 23       Links: 1
Access: (555/-r-xr-xr-x)        Uid: (0/    root)       Gid: (0/    root)
Access: 2016-07-22 06:43:49.980000000
Modify: 2016-07-22 06:43:50.010000000
Change: 2016-07-22 06:43:50.020000000

I tried building current git from source, and "wget
http://landley.net/toybox/bin/toybox-armv6l" and both behaved the same
for me.

Possibly qemu isn't complaining about an unaligned access correctly? (I
thought it was...)

> I tried with the latest release version from the toybox website
> <http://landley.net/toybox/bin/> for arm-v6l as well as a version built
> from latest git using your cross-compiler for armv6 from your homepage:
> 
> |root at generic:/data/local # ./toybox stat toybox File: `toybox' Size:
> 467296 Blocks: 920 IO Blocks: 4096 regular file Device: 1f01h/7937d
> Inode: 14531 Links: 1 Access: (555/-r-xr-xr-xSegmentation fault |
> 
> It seems that the emulator is running ARMv7l, but AFAIK it should be
> compatible to ARMv6l binaries:

Yeah, it should.

You're running a binary statically built against uClibc with the old gcc
4.2 toolchain, so it's not a bionic thing nor a toolchain thing. You
built current git so it's not version skew.

What it really sounds like is the vanilla qemu I'm using and the android
emulator you're using are doing something different? Or maybe a kernel
.config issue? (I rebuilt qemu from current git to make sure it wasn't
the oldish version i was using, and I still get the full unsegfaulted
output.

Now it's possible what's happening is that the next thing it tries to do
is fetch the uid, and the android kernel code is behaving differently
because of how they've set up user ID's.

Or maybe it's a problem trying to display a uid that's not in
/etc/passwd, which sadly I can't easily test here at the moment because
I just noticed that "chown 123:123 toybox" is saying:

  chown: user '123'

Which is broken in a couple ways (there should be a ":errno message" on
the end of that if it's an actual error, and numeric user IDs should
work even if they're not in /etc/passwd) so I need to off and fix THAT
before cycling back to this. :)

If I can't reproduce this with a bit more fiddling here, I should
download this android emulator and build environment. I'm guessing that
would be from... Android NDK version 10c?

  https://developer.android.com/about/versions/android-5.0-changes.html
  https://developer.android.com/ndk/downloads/revision_history.html

(Sigh, is the NDK standalone with its own emulator or does it assume you
have the SDK installed already? The NDK page assumes you already know
this. Oh well, I can dig through it, lemme fix the chown thing first...)

Thanks,

Rob