Re: [PATCH 2/2][MIPS][RFC] Emit .note.GNU-stack for hard-float linux targets.

[Dragan Mladjenovic <dmladjenovic@wavecomp.com>]

On 10.08.2019. 00:15, Joseph Myers wrote:
> On Fri, 9 Aug 2019, Jeff Law wrote:
>
>>> 2019-08-05  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>
>>>
>>> 	* config.in: Regenerated.
>>> 	* config/mips/linux.h (NEED_INDICATE_EXEC_STACK): Define to 1
>>> 	for TARGET_LIBC_GNUSTACK.
>>> 	* configure: Regenerated.
>>> 	* configure.ac: Define TARGET_LIBC_GNUSTACK if glibc version is
>>> 	found 2.31 or greater.
>> My only concern here is the configure bits.  So for example, will it do
>> the right thing if you're cross-compiling to a MIPS linux target?  If
>> so, how?  If not, do we need to make it a first class configure option
>> so that it can be specified when building cross MIPS linux toolchains?
>
> The key point of using GCC_GLIBC_VERSION_GTE_IFELSE is that (a) it checks
> the target glibc headers if available when GCC is built and (b) if not
> available, you can still use --with-glibc-version when configuring GCC, to
> get the right configuration in a bootstrap compiler built before glibc is
> built (the latter is necessary on some architectures to get the right
> stack-protector configuration for bootstrapping glibc, but may be useful
> in other cases as well).
>
> My main concern about this patch is the one I gave in
> <https://sourceware.org/ml/libc-alpha/2019-08/msg00086.html> about what
> the configuration mechanism should be, on a whole-toolchain level, to say
> whether you are OK with a requirement for a 4.8 or later kernel.
>

Sorry for the late reply.

I was waiting to backport [1] to most of the glibc release branches in 
use, but I got sidetracked along the way.

After this patch lands the preferred way to configure gcc would be using 
--with-glibc-version=2.31 and to use said glibc.
If the user/distribution can live with minimal kernel requirement of 4.8
the glibc used should be configured with --enable-kernel=4.8.
I also plan to backport the [1] to limit the opportunity for building 
the possibly broken glibc with the gcc w/ enabled .note.GNU-stack.

This is all tedious and user has to be aware of all of it to make it 
work, but hopefully over time the distributions will default to 
--with-glibc-version=2.31 and --enable-kernel=4.8. I guess providing the 
detailed NEWS entry for this change would help a bit.

Is there any objections to getting this on the trunk before the end of
stage1?

[1] https://sourceware.org/ml/libc-alpha/2019-08/msg00639.html

Best regards,
Dragan