Re: [PATCH v13 11/40] arm64/gcs: Provide basic EL2 setup to allow GCS usage at EL0 and EL1

[Nathan Chancellor]

Hi Mark,

On Tue, Oct 01, 2024 at 11:58:50PM +0100, Mark Brown wrote:
> There is a control HCRX_EL2.GCSEn which must be set to allow GCS
> features to take effect at lower ELs and also fine grained traps for GCS
> usage at EL0 and EL1.  Configure all these to allow GCS usage by EL0 and
> EL1.
> 
> We also initialise GCSCR_EL1 and GCSCRE0_EL1 to ensure that we can
> execute function call instructions without faulting regardless of the
> state when the kernel is started.
> 
> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@xxxxxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>

I just bisected a build failure from a failed linker script assertion
that I see with allmodconfig to this change in -next as commit
ff5181d8a2a8 ("arm64/gcs: Provide basic EL2 setup to allow GCS usage at
EL0 and EL1"):

  $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- mrproper allmodconfig vmlinux
  aarch64-linux-ld: HYP init code too big
  make[4]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
  ...

I see this with both GCC 14 and clang 19, in case toolchain version
matters. Bisect log included as well.

Cheers,
Nathan

# bad: [b6270c3bca987530eafc6a15f9d54ecd0033e0e3] Add linux-next specific files for 20241009
# good: [75b607fab38d149f232f01eae5e6392b394dd659] Merge tag 'sched_ext-for-6.12-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
git bisect start 'b6270c3bca987530eafc6a15f9d54ecd0033e0e3' '75b607fab38d149f232f01eae5e6392b394dd659'
# bad: [76d36603db22f0f0774c19147b25f5a0bcac64e6] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git
git bisect bad 76d36603db22f0f0774c19147b25f5a0bcac64e6
# bad: [e90a3e76b4b8080f633a167179f3a76b93077270] Merge branch 'renesas-clk' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git
git bisect bad e90a3e76b4b8080f633a167179f3a76b93077270
# good: [dd60a5d8b8ac2e7dc6810182a6dbc251a746f09e] Merge branch 'perf-tools-next' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git
git bisect good dd60a5d8b8ac2e7dc6810182a6dbc251a746f09e
# bad: [fa74fd4773673726bfa8f89d15805d8a1b26f855] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-omap.git
git bisect bad fa74fd4773673726bfa8f89d15805d8a1b26f855
# bad: [a7833d5793f83512f1fb6f36fa7588ea03da6b1b] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/amlogic/linux.git
git bisect bad a7833d5793f83512f1fb6f36fa7588ea03da6b1b
# bad: [c9c0de66c9b5f295f09a116f15401465bdd13263] Merge branch 'for-next/core' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
git bisect bad c9c0de66c9b5f295f09a116f15401465bdd13263
# bad: [506496bcbb4204c9ff5cfe82b1b90e1f14366992] arm64/gcs: Ensure that new threads have a GCS
git bisect bad 506496bcbb4204c9ff5cfe82b1b90e1f14366992
# good: [d0aa2b4351862cc2ce8d97e00c96bffc02ea16af] arm64/gcs: Provide put_user_gcs()
git bisect good d0aa2b4351862cc2ce8d97e00c96bffc02ea16af
# bad: [6497b66ba6945f142902c7e8fce86e47016ead1c] arm64/mm: Map pages for guarded control stack
git bisect bad 6497b66ba6945f142902c7e8fce86e47016ead1c
# bad: [6487c963083c24ede289d4267ffa60a9db668cd4] arm64/cpufeature: Runtime detection of Guarded Control Stack (GCS)
git bisect bad 6487c963083c24ede289d4267ffa60a9db668cd4
# bad: [ff5181d8a2a82c982276a7e035896185c390e856] arm64/gcs: Provide basic EL2 setup to allow GCS usage at EL0 and EL1
git bisect bad ff5181d8a2a82c982276a7e035896185c390e856
# first bad commit: [ff5181d8a2a82c982276a7e035896185c390e856] arm64/gcs: Provide basic EL2 setup to allow GCS usage at EL0 and EL1