meson: link with -Wl,-z,gcs-report-dynamic=none (#38901)

There is a botched arm64 linker transition going on, where a new feature
is enabled (GCS) and the linker fails the build unless all object files
being linked are built with the new specific feature. This was enabled
in the toolchain (GCC 15) _before_ all libraries were rebuilt, including
glibc, so everything fails. The toolchain maintainers declined to fix it
and instead say that this is a useless warning to have, and to just
disable it and ignore it.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110461
> systemd fails to build from source on arm64 if built with GCC-15, currently in
> experimental.
>
> GCC-15 includes support for an arm64 security feature called Guarded Control
> Stack (GCS). To help with GCS adoption, the linker warns about shared libraries
> built without GCS. For example:
>
> /usr/lib/gcc/aarch64-linux-gnu/15/../../../aarch64-linux-gnu/libncursesw.so.6:
> warning: GCS is required by -z gcs, but this shared library lacks the necessary property note.
> The dynamic loader might not enable GCS or refuse to load the program unless
> all the shared library dependencies have the GCS marking.
>
> The warning is harmless, and can be ignored. However, systemd is built with
> --fatal-warnings, and for this reason will fail to build on arm64 once GCC-15
> becomes the default compiler in Debian.

[585/3230] Linking target src/core/libsystemd-core-258.so
FAILED: src/core/libsystemd-core-258.so
gcc  -o src/core/libsystemd-core-258.so  -Wl,--as-needed -Wl,--no-undefined -shared -fPIC -Wl,-soname,libsystemd-core-258.so -Wl,--whole-archive -Wl,--start-group src/core/libsystemd-core-258.a -Wl,--no-whole-archive -fstack-protector -Wl,-z,relro -specs=/usr/share/debhelper/dh_package_notes/debian-package-notes.specs -g -O2 -Werror=implicit-function-declaration -ffile-prefix-map=/work/src=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -mbranch-protection=standard -O0 -g -Og -Wdate-time '-Wl,-rpath,$ORIGIN/../shared' src/shared/libsystemd-shared-258.so -shared -Wl,--version-script=/work/src/src/shared/libshared.sym /usr/lib/aarch64-linux-gnu/libacl.so /usr/lib/aarch64-linux-gnu/libaudit.so /usr/lib/aarch64-linux-gnu/libblkid.so -ldl -lm /usr/lib/aarch64-linux-gnu/libmount.so -lrt /usr/lib/aarch64-linux-gnu/libseccomp.so /usr/lib/aarch64-linux-gnu/libselinux.so -Wl,--end-group -pthread -Wl,--fatal-warnings -Wl,-z,now -Wl,-z,relro -Wl,--gc-sections -Wl,--warn-common
src/shared/libsystemd-shared-258.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libacl.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libaudit.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libblkid.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/lib/aarch64-linux-gnu/libm.so.6: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/lib/aarch64-linux-gnu/libmvec.so.1: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libmount.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libseccomp.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/usr/lib/aarch64-linux-gnu/libselinux.so: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/lib/aarch64-linux-gnu/libc.so.6: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
/lib/ld-linux-aarch64.so.1: warning: GCS is required by -z gcs, but this shared library lacks the necessary property note. The dynamic loader might not enable GCS or refuse to load the program unless all the shared library dependencies have the GCS marking.
collect2: error: ld returned 1 exit status

(cherry picked from commit 310ab611396e5a7820a820e35fa9763b5528e137)

diff --git a/meson.build b/meson.build
index a764b4f5cba1a575ad63a5458950280d1dca4ff7..103febfd70be2a548d6a4381999e8808dea73d2e 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -455,6 +455,7 @@ possible_link_flags = [
         '-Wl,--fatal-warnings',
         '-Wl,-z,now',
         '-Wl,-z,relro',
+        '-Wl,-z,gcs-report-dynamic=none',
 ]
 
 if get_option('b_sanitize') == 'none'