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[v3,4/4] kernel-yocto: Set CLANG_FLAGS for kernel config checks when using clang

Message ID 20260708151816.2115030-5-Harish.Sadineni@windriver.com
State Under Review
Headers show
Series Add Clang toolchain support for kernel builds | expand

Commit Message

Harish Sadineni July 8, 2026, 3:18 p.m. UTC 
From: Harish Sadineni <Harish.Sadineni@windriver.com>

When building with `TOOLCHAIN = "clang"`, the kernel's configuration
check (do_kernel_configcheck) fails with:

  kconfiglib.KconfigError: scripts/Kconfig.include:51: Sorry, this
  assembler is not supported.

Fix by setting `CLANG_FLAGS = "-fintegrated-as"` in the environment
when `TOOLCHAIN` contains "clang". This variable is used by the kernel
build system (via scripts/Kconfig.include) to pass additional flags to
clang during config checks, ensuring the assembler test passes.

Acked-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Harish Sadineni <Harish.Sadineni@windriver.com>
---
 meta/classes-recipe/kernel-arch.bbclass  | 2 ++
 meta/classes-recipe/kernel-yocto.bbclass | 3 +++
 2 files changed, 5 insertions(+)
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Patch

diff --git a/meta/classes-recipe/kernel-arch.bbclass b/meta/classes-recipe/kernel-arch.bbclass
index 6ebc0f13ea..c0ff60c0de 100644
--- a/meta/classes-recipe/kernel-arch.bbclass
+++ b/meta/classes-recipe/kernel-arch.bbclass
@@ -93,3 +93,5 @@  KERNEL_AR:toolchain-clang = "llvm-ar ${HOST_AR_KERNEL_ARCH}"
 KERNEL_OBJCOPY:toolchain-clang = "llvm-objcopy ${HOST_OBJCOPY_KERNEL_ARCH}"
 KERNEL_STRIP:toolchain-clang = "llvm-strip"
 TOOLCHAIN = "gcc"
+TOOLCHAIN:riscv64 = "${@bb.utils.contains('KERNEL_FEATURES', 'rust', 'clang', 'gcc', d)}"
+
diff --git a/meta/classes-recipe/kernel-yocto.bbclass b/meta/classes-recipe/kernel-yocto.bbclass
index e7fdeb5d4b..78a4a7ade7 100644
--- a/meta/classes-recipe/kernel-yocto.bbclass
+++ b/meta/classes-recipe/kernel-yocto.bbclass
@@ -603,6 +603,9 @@  python do_kernel_configcheck() {
     env['STRIP'] = d.getVar('KERNEL_STRIP')
     env['ARCH'] = d.getVar('ARCH')
     env['srctree'] = s
+    toolchain = d.getVar('TOOLCHAIN') or ''
+    if 'clang' in toolchain:
+        env['CLANG_FLAGS'] = " -fintegrated-as"
 
     try:
         configs = subprocess.check_output(['scc', '--configs', '-o', s + '/.kernel-meta'], env=env).decode('utf-8')