linux: address executable stack warnings

[rlibby]

Test Plan

env CROSS_TOOLCHAIN=amd64-gcc14 make buildkernel buildworld

make tinderbox

I will also look for a kyua test for linux compat.

[kib]

IMO both vdso must be build with nonexec stack, and it is better to explicitly add the gnu section to sources marking the objects.

[rlibby]

In D56894#1303295, @kib wrote:

IMO both vdso must be build with nonexec stack, and it is better to explicitly add the gnu section to sources marking the objects.

Ack, I'll see if I can figure that out. I think this will add the section to the .so objects, but I'll see if I can get it applied earlier.

[kib]

In D56894#1303296, @rlibby wrote:

In D56894#1303295, @kib wrote:

IMO both vdso must be build with nonexec stack, and it is better to explicitly add the gnu section to sources marking the objects.

Ack, I'll see if I can figure that out. I think this will add the section to the .so objects, but I'll see if I can get it applied earlier.

Not a section, but the non-loadable segment PT_GNUSTACK. Either way it appears in the resulting dso, but when specified using section in the source, it it explicit.
I believe linker reports which files are missing it, no?

	.section .note.GNU-stack,"",%progbits

[rlibby]

In D56894#1303299, @kib wrote:

In D56894#1303296, @rlibby wrote:

In D56894#1303295, @kib wrote:

IMO both vdso must be build with nonexec stack, and it is better to explicitly add the gnu section to sources marking the objects.

Ack, I'll see if I can figure that out. I think this will add the section to the .so objects, but I'll see if I can get it applied earlier.

Not a section, but the non-loadable segment PT_GNUSTACK. Either way it appears in the resulting dso, but when specified using section in the source, it it explicit.
I believe linker reports which files are missing it, no?

	.section .note.GNU-stack,"",%progbits

I follow. From D56893

grep-executable-stack.log9 KBDownload

/usr/local/x86_64-unknown-freebsd15.0/bin/ld: warning: linux32_locore.o: missing .note.GNU-stack section implies executable stack
/usr/local/x86_64-unknown-freebsd15.0/bin/ld: warning: linux32_support.o: missing .note.GNU-stack section implies executable stack
...
/usr/local/x86_64-unknown-freebsd15.0/bin/ld: warning: linux_locore.o: missing .note.GNU-stack section implies executable stack
/usr/local/x86_64-unknown-freebsd15.0/bin/ld: warning: linux_vdso_inc.o: missing .note.GNU-stack section implies executable stack

[rlibby]

Okay I started on adding .section .note.GNU-stack,"",%progbits to the asm files, https://github.com/rlibby/freebsd/commit/8e408b3197545f47bd2db1c4827507c503d1d049

But I still see one of the warnings, so I must be missing something...

./sys/GENERIC/modules/usr/src/freebsd/sys/modules/linux/linux.ko.full.meta:/usr/local/x86_64-unknown-freebsd16.0/bin/ld: warning: linux32_vdso.so: missing .note.GNU-stack section implies executable stack

[rlibby]

In D56894#1303307, @rlibby wrote:

Okay I started on adding .section .note.GNU-stack,"",%progbits to the asm files, https://github.com/rlibby/freebsd/commit/8e408b3197545f47bd2db1c4827507c503d1d049

But I still see one of the warnings, so I must be missing something...

./sys/GENERIC/modules/usr/src/freebsd/sys/modules/linux/linux.ko.full.meta:/usr/local/x86_64-unknown-freebsd16.0/bin/ld: warning: linux32_vdso.so: missing .note.GNU-stack section implies executable stack

I'm suspecting it may have to do with the custom linker scripts, which is not something I know much about. We could proceed with what's in 8e408b3197545f47bd2db1c4827507c503d1d049 and just leave it issuing one warning still? Alternately, I could abandon this, I had thought it was going to be an easy warning quashing, and I'm unsure if this is really worth it now.

[kib]

In D56894#1303308, @rlibby wrote:

In D56894#1303307, @rlibby wrote:

Okay I started on adding .section .note.GNU-stack,"",%progbits to the asm files, https://github.com/rlibby/freebsd/commit/8e408b3197545f47bd2db1c4827507c503d1d049

But I still see one of the warnings, so I must be missing something...

./sys/GENERIC/modules/usr/src/freebsd/sys/modules/linux/linux.ko.full.meta:/usr/local/x86_64-unknown-freebsd16.0/bin/ld: warning: linux32_vdso.so: missing .note.GNU-stack section implies executable stack

I'm suspecting it may have to do with the custom linker scripts, which is not something I know much about. We could proceed with what's in 8e408b3197545f47bd2db1c4827507c503d1d049 and just leave it issuing one warning still? Alternately, I could abandon this, I had thought it was going to be an easy warning quashing, and I'm unsure if this is really worth it now.

IMO you should go ahead and commit what you already have. It is the right way to go and should be not thrown away. I promise to take a look after that.

[rlibby]

kib feedback: try working from the bottom up instead. This has the asm
files declare that they don't need an executable stack. It does still
leave this issue building linux.ko.full:
ld: warning: linux32_vdso.so: missing .note.GNU-stack section implies executable stack