[PATCH 6.18 499/752] arm64: Disable branch profiling for all arm64 code

Sasha Levin
2026-02-28T17:55:13Z

From: Breno Leitao <leitao@debian.org>

[ Upstream commit f22c81bebf8bda6e54dc132df0ed54f6bf8756f9 ]

The arm64 kernel doesn't boot with annotated branches
(PROFILE_ANNOTATED_BRANCHES) enabled and CONFIG_DEBUG_VIRTUAL together.

Bisecting it, I found that disabling branch profiling in arch/arm64/mm
solved the problem. Narrowing down a bit further, I found that
physaddr.c is the file that needs to have branch profiling disabled to
get the machine to boot.

I suspect that it might invoke some ftrace helper very early in the boot
process and ftrace is still not enabled(!?).

Rather than playing whack-a-mole with individual files, disable branch
profiling for the entire arch/arm64 tree, similar to what x86 already
does in arch/x86/Kbuild.

Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/Kbuild | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
index 5bfbf7d79c99b..d876bc0e54211 100644
--- a/arch/arm64/Kbuild
+++ b/arch/arm64/Kbuild
@@ -1,4 +1,8 @@
# SPDX-License-Identifier: GPL-2.0-only
+
+# Branch profiling isn't noinstr-safe
+subdir-ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING
+
obj-y += kernel/ mm/ net/
obj-$(CONFIG_KVM) += kvm/
obj-$(CONFIG_XEN) += xen/
--
2.51.0