The aarch64 cross-compiler built with Yocto's kirkstone release configures -mbranch-protection=standard as default. The resulting PACIASP/AUTIASP instructions are interpreted as NOPs by existing CPUs, but they increase image size and misalign the barebox header in ENTRY_FUNCTION(). Also on ARMv8.3+, where they serve a purpose, we wouldn't benefit from them as we don't setup any pointer authentication keys. Thus disable it. The misaligned barebox header caused is_barebox_arm_head to fail, breaking all code that verified barebox' header, like i.MX8MM imx-usb-loader barebox-side support and barebox_update for some ARM64 SoCs without a SoC-specific header. Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> --- This is a workaround. ENTRY_FUNCTION() should be rewritten for ARM64, so we don't expect function prologue to be exactly two bytes long. Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> v1 -> v2: - revised commit message after understanding ramification better. --- Makefile | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/Makefile b/Makefile index 98da09f18523..3737265316e9 100644 --- a/Makefile +++ b/Makefile @@ -659,6 +659,11 @@ KBUILD_CFLAGS += $(call cc-option,-fno-stack-check) # Platforms that have their setjmp appropriately implemented may override this KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none) +# We don't have the necessary infrastructure to benefit from ARMv8.3+ pointer +# authentication. On older CPUs, they are interpreted as NOPs and blot the +# code and break less portable code that expects a very specific code layout +KBUILD_CFLAGS += $(call cc-option,-mbranch-protection=none) + KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) # Align the bit size of userspace programs with the kernel -- 2.30.2
