[PATCH master] Kbuild: disable ARM64 pointer authentication
a.fatoum at pengutronix.de
Wed Oct 19 05:43:33 PDT 2022
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.
This fixes a breakage to the extended firmware mechanism when
building my i.MX8M barebox with the Kirkstone toolchain.
Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
This is a workaround. ENTRY_FUNCTION() should be rewritten for ARM64,
so we don't expect function prologue to be exactly two bytes long.
Makefile | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Makefile b/Makefile
index 98da09f18523..3737265316e9 100644
@@ -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
More information about the barebox