6.12-stable review patch. If anyone has any objections, please let me know.
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From: Nathan Chancellor nathan@kernel.org
commit aef25be35d23ec768eed08bfcf7ca3cf9685bc28 upstream.
The Hexagon-specific constant extender optimization in LLVM may crash on Linux kernel code [1], such as fs/bcache/btree_io.c after commit 32ed4a620c54 ("bcachefs: Btree path tracepoints") in 6.12:
clang: llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp:745: bool (anonymous namespace)::HexagonConstExtenders::ExtRoot::operator<(const HCE::ExtRoot &) const: Assertion `ThisB->getParent() == OtherB->getParent()' failed. Stack dump: 0. Program arguments: clang --target=hexagon-linux-musl ... fs/bcachefs/btree_io.c 1. <eof> parser at end of file 2. Code generation 3. Running pass 'Function Pass Manager' on module 'fs/bcachefs/btree_io.c'. 4. Running pass 'Hexagon constant-extender optimization' on function '@__btree_node_lock_nopath'
Without assertions enabled, there is just a hang during compilation.
This has been resolved in LLVM main (20.0.0) [2] and backported to LLVM 19.1.0 but the kernel supports LLVM 13.0.1 and newer, so disable the constant expander optimization using the '-mllvm' option when using a toolchain that is not fixed.
Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/issues/99714 [1] Link: https://github.com/llvm/llvm-project/commit/68df06a0b2998765cb0a41353fcf0919... [2] Link: https://github.com/llvm/llvm-project/commit/2ab8d93061581edad3501561722ebd56... [3] Reviewed-by: Brian Cain bcain@quicinc.com Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/hexagon/Makefile | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/arch/hexagon/Makefile +++ b/arch/hexagon/Makefile @@ -32,3 +32,9 @@ KBUILD_LDFLAGS += $(ldflags-y) TIR_NAME := r19 KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -DTHREADINFO_REG=$(TIR_NAME) -D__linux__ KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME) + +# Disable HexagonConstExtenders pass for LLVM versions prior to 19.1.0 +# https://github.com/llvm/llvm-project/issues/99714 +ifneq ($(call clang-min-version, 190100),y) +KBUILD_CFLAGS += -mllvm -hexagon-cext=false +endif