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[Simon Chopin <2121033@xxxxxxxxxxxxxxxxxx>]

Note to self on the bearssl thing:

The bearssl autopkgtests create a binary that is linked against
libbearssl *and* lib25519, yet the bearssl autopkgtests didn't warn when
it was run against glibc 2.41-9ubuntu1 (which does not have GCS enable).

It actually makes sense: executables have crt1.o linked in. The old one
didn't have the GCS bit, so that propagated into the final executable.
The linker only complains about shared libs if the executable itself has
GCS.

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https://bugs.launchpad.net/bugs/2121033

Title:
  lib25519 doesn't expose GCS attribute on arm64

Status in glibc package in Ubuntu:
  New
Status in lib25519 package in Ubuntu:
  Triaged

Bug description:
  In GCC 15 all arm64 binaries that have standard branch protection
  (present in our default flags) started using GCS. However, the linker
  will issue warnings if mixing libraries that expose GCS compatibility
  with non-GCS ones.

  This is the case for lib25519, as it contains asm files that needs to
  be manually annotated to export the proper section.

  It's a fairly annoying issue, since glibc *does* expose GCS info since
  2.42-0ubuntu1, thus triggering the warning:

  ❯ readelf -n libc.so.6

  Displaying notes found in: .note.gnu.property
    Owner                Data size 	Description
    GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
        Properties: AArch64 feature: BTI, PAC, GCS

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