On Thu, Sep 9, 2021 at 12:42 AM ashimida <ashimida@xxxxxxxxxxxxxxxxx> wrote: > > Kernel compiled with tool chain CROSS_COMPILE=aarch64-linux-android- > will panic during the startup phase. > > Clang's --target option comes from $(CROSS_COMPILE). At the time > -fstack-protector-strong is enabled, and compiled with command: > make CC=clang HOSTCC=clang ARCH=arm64 CROSS_COMPILE=aarch64-linux-android- > > clang will insert code like: > mrs x8, TPIDR_EL0 //default value is zero > str x8, [sp] > ldr x8, [x8, #40] //access addr 0x40 > > instead of the code that accesses __stack_chk_guard to get the > canary, which will cause the kernel to crash due to 0x40 > address access. > > This patch (from android) is used to remind the user that current > tool chain cannot be used as the "--target" of clang, the user > should specify an additional "--target" through CLANG_TRIPLE. Hi Ashimida, Thanks for sending this patch; I recognize it from Android, which we had to carry for years due to: 1. reliance on GNU `as` ie. "GAS" 2. not distributing binary prefixes of GNU binutils with a target triple that clang recognized. (ie. Android's binutils were prefixed aarch64-linux-android- while Clang expected something more like aarch64-linux-gnu for --target=) We solved this by working out the issues in clang's assembler. With LLVM=1 LLVM_IAS=1, we no longer rely on GNU binutils, and no longer need such patch. You'll find it's been dropped from Android Common Kernels now. With mainline, LLVM_IAS=1 is now the default when building with LLVM=1, and CROSS_COMPILE is now inferred from ARCH for LLVM=1 as well. So all you should need is: $ ARCH=arm64 make LLVM=1 -j$(nproc) Is there a reason why the above doesn't work for you? I do not wish to see this patch upstream (or downstream; it should be unnecessary). > > Signed-off-by: ashimida <ashimida@xxxxxxxxxxxxxxxxx> > --- > Makefile | 6 +++++- > scripts/clang-android.sh | 4 ++++ > 2 files changed, 9 insertions(+), 1 deletion(-) > create mode 100755 scripts/clang-android.sh > > diff --git a/Makefile b/Makefile > index 61741e9..09bb314 100644 > --- a/Makefile > +++ b/Makefile > @@ -586,7 +586,11 @@ CC_VERSION_TEXT = $(subst $(pound),,$(shell $(CC) --version 2>/dev/null | head - > > ifneq ($(findstring clang,$(CC_VERSION_TEXT)),) > ifneq ($(CROSS_COMPILE),) > -CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > +CLANG_TRIPLE ?= $(CROSS_COMPILE) > +CLANG_FLAGS += --target=$(notdir $(CLANG_TRIPLE:%-=%)) > +ifeq ($(shell $(srctree)/scripts/clang-android.sh $(CC) $(CLANG_FLAGS)), y) > +$(error "Clang with Android --target detected. Did you specify CLANG_TRIPLE?") > +endif > endif > ifeq ($(LLVM_IAS),1) > CLANG_FLAGS += -integrated-as > diff --git a/scripts/clang-android.sh b/scripts/clang-android.sh > new file mode 100755 > index 0000000..9186c4f > --- /dev/null > +++ b/scripts/clang-android.sh > @@ -0,0 +1,4 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0 > + > +$* -dM -E - </dev/null 2>&1 | grep -q __ANDROID__ && echo "y" > -- > 2.7.4 > -- Thanks, ~Nick Desaulniers
