** Changed in: linux-azure (Ubuntu Noble)
Status: Confirmed => Fix Committed
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https://bugs.launchpad.net/bugs/2071445
Title:
Ubuntu 24.04 for Azure unable to run 32bit binaries
Status in linux-azure package in Ubuntu:
Triaged
Status in linux-signed-azure package in Ubuntu:
Invalid
Status in linux-signed-azure-6.8 package in Ubuntu:
Invalid
Status in linux-azure source package in Noble:
Fix Committed
Bug description:
[Impact]
## Issue details
The configuration of the kernel in linux-image-6.8.0-1008-azure is
incompatible with the way libc6:i386 is built.
This leads to the error "The futex facility returned an unexpected error
code." and application crash when trying to execute many 32bit applications in
x86-64 machines.
In very short the issue is the following:
This kernel image is compiled with CONFIG_COMPAT_32BIT_TIME=n, unlike the
vanilla Ubuntu 24.04 kernel images.
But, the glibc / libc6:i386 distributed with Ubuntu24.04 is compiled needing
the syscalls enabled with that option.
i.e. **This kernel configuration is just incompatible with the provided
glibc**
In detail:
glibc when built for 32bit, if not told which kernel is built for, will
decide if the time_t value fits or not in a 32bit time_t, and do either the 32
or 64bit syscall:
https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/futex-internal.c;h=0bb1dd51f66802521afd71b9246222ed0ea0d862;hb=refs/heads/release/2.39/master#l90
calls with no deadline fit in the 32bit version, but as the kernel does not
provide this syscall, glibc will just get a ENOSYS, and glibc will error out
aborting the program
```
abort (abort.c:79)
__libc_message_impl.cold (libc_fatal.c:132)
__libc_fatal (libc_fatal.c:141)
futex_fatal_error (futex-internal.h:87)
__futex_abstimed_wait_common (futex-internal.c:119)
```
after printing "The futex facility returned an unexpected error code.\n":
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/nptl/futex-internal.h;h=0e87e92d15ab92f5069463719a494e97d9800431;hb=refs/heads/release/2.39/master#l87
## Expected behavior:
* No crashes for 32bit applications with this kernel
* This kernel image built with CONFIG_COMPAT_32BIT_TIME=y
## Aditional info:
For reference, this is the current vanilla Ubuntu 24.04 kernel for x86_64 and
this config:
```
$ uname -a
Linux <redacted> 6.8.0-35-generic #35-Ubuntu SMP PREEMPT_DYNAMIC Mon May 20
15:51:52 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
$ grep CONFIG_COMPAT_32BIT_TIME /boot/config-$(uname -r)
CONFIG_COMPAT_32BIT_TIME=y
```
On the other hand this is the kernel config for this kernel image:
```
Linux <> 6.8.0-1008-azure #8-Ubuntu SMP Fri May 17 10:44:55 UTC 2024 x86_64
x86_64 x86_64 GNU/Linux
# CONFIG_COMPAT_32BIT_TIME is not set
```
Related github issue (the issue was found in github ubuntu 24.04 runners)
https://github.com/actions/runner-images/issues/9977
[Fix]
Reenable COMPAT_32BIT_TIME
[Test Case]
See above.
[Where Problems Could Occur]
Disabling COMPAT_32BIT_TIME in Noble azure introduced a regression
when running x86 binaries, so the fix is not expected to break
anything (new).
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/2071445/+subscriptions
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