Commit 4c451dba authored Oct 25, 2016 by Greg Hackmann Committed by Alistair Strachan Dec 05, 2018

ANDROID: Kbuild, LLVMLinux: allow overriding clang target triple



Android has an unusual setup where the kernel needs to target
[arch]-linux-gnu to avoid Android userspace-specific flags and
optimizations, but AOSP doesn't ship a matching binutils.

Add a new variable CLANG_TRIPLE which can override the "-target" triple
used to compile the kernel, while using a different CROSS_COMPILE to
pick the binutils/gcc installation.  For Android you'd do something
like:

  export CLANG_TRIPLE=aarch64-linux-gnu-
  export CROSS_COMPILE=aarch64-linux-android-

If you don't need something like this, leave CLANG_TRIPLE unset and it
will default to CROSS_COMPILE.

Change-Id: I85d63599c6ab8ed458071cdf9197d85b1f7f150b
Signed-off-by: Greg Hackmann <ghackmann@google.com>
[astrachan: Added a script to check for incorrectly falling back to the
            default when CLANG_TRIPLE is unset]
Bug: 118439987
Bug: 120440614
Test: make CLANG_TRIPLE=x86_64-linux-gnu CC=clang
Signed-off-by: Alistair Strachan <astrachan@google.com>

parent 13e7e057

Makefile

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -482,7 +482,11 @@ endif

	ifeq ($(cc-name),clang)		ifeq ($(cc-name),clang)
	ifneq ($(CROSS_COMPILE),)		ifneq ($(CROSS_COMPILE),)
	CLANG_TARGET := --target=$(notdir $(CROSS_COMPILE:%-=%))		CLANG_TRIPLE ?= $(CROSS_COMPILE)
			CLANG_TARGET := --target=$(notdir $(CLANG_TRIPLE:%-=%))
			ifeq ($(shell $(srctree)/scripts/clang-android.sh $(CC) $(CLANG_TARGET)), y)
			$(error "Clang with Android --target detected. Did you specify CLANG_TRIPLE?")
			endif
	GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD)))		GCC_TOOLCHAIN_DIR := $(dir $(shell which $(LD)))
	CLANG_PREFIX := --prefix=$(GCC_TOOLCHAIN_DIR)		CLANG_PREFIX := --prefix=$(GCC_TOOLCHAIN_DIR)
	GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)		GCC_TOOLCHAIN := $(realpath $(GCC_TOOLCHAIN_DIR)/..)

scripts/clang-android.sh

0 → 100755

+4 −0

Original line number	Original line	Diff line number	Diff line
			#!/bin/sh
			# SPDX-License-Identifier: GPL-2.0

			$* -dM -E - </dev/null 2>&1 \| grep -q __ANDROID__ && echo "y"