Re: [Buildroot] [PATCH v2 1/1] toolchain/toolchain-external: introduce BR2_TOOLCHAIN_EXTERNAL_UPDATE_LINUX_HEADERS

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Rustam,

Thanks for your patch!

On Sat, 27 Dec 2025 21:14:15 +0000
Rustam Abdullaev <rustamabd@gmail.com> wrote:

> It is important to have matching kernel headers when building packages
> that make use of kernel features such as seccomp, as they depend on
> system call definitions in linux/unistd.h. A typical example of this is
> openssh - building it with the official ARM GNU toolchain and kernel 6.x
> results in a non-working sshd.

Do you have more details on this? Which version of the ARM GNU
toolchain? Which kernel header version do they use? Which kernel
version are you running?

Indeed, there are two cases:

- The kernel headers in the toolchain are newer than the kernel you're
  running => you are doing it wrong, and updating the headers in the
  toolchain are not going to fix the fact that your C library is built
  with headers that are too recent for your kernel (even though I admit
  glibc has some tolerance on this)

- The kernel headers in the toolchain are older than the kernel you're
  running and you're seeing breakage => this is a kernel bug as it
  shouldn't happen.

In both cases, your proposed patch should therefore not be needed.

Could you clarify which situation you're in, so that we can
understand better whether the use-case/issue you're having warrants
this additional complexity?

> Currently restricted to glibc-based toolchains as glibc is backward- and
> forward-compatible with different kernel versions while uClibc and musl
> are not.

Not sure why this matters here though. Could you clarify?

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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