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    Subject[tip: x86/build] x86/build: Check whether the compiler is sane
    The following commit has been merged into the x86/build branch of tip:

    Commit-ID: 73da86741e7f75c9f1b5c8a2660c90aa41840972
    Gitweb: https://git.kernel.org/tip/73da86741e7f75c9f1b5c8a2660c90aa41840972
    Author: Borislav Petkov <bp@suse.de>
    AuthorDate: Thu, 23 Apr 2020 19:28:28 +02:00
    Committer: Borislav Petkov <bp@suse.de>
    CommitterDate: Mon, 27 Apr 2020 13:31:57 +02:00

    x86/build: Check whether the compiler is sane

    Add a check script to verify whether the compiler is sane. This is
    x86-only for now and checks one thing only but should be useful for more
    checks in the future.

    Suggested-by: Martin Liška <mliska@suse.cz>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
    Tested-by: Nick Desaulniers <ndesaulniers@google.com>
    Link: https://lkml.kernel.org/r/20200423173058.GE26021@zn.tnic
    ---
    arch/x86/Makefile | 4 ++++
    scripts/x86-check-compiler.sh | 9 +++++++++
    2 files changed, 13 insertions(+)
    create mode 100755 scripts/x86-check-compiler.sh

    diff --git a/arch/x86/Makefile b/arch/x86/Makefile
    index 00e378d..38d3eec 100644
    --- a/arch/x86/Makefile
    +++ b/arch/x86/Makefile
    @@ -1,6 +1,10 @@
    # SPDX-License-Identifier: GPL-2.0
    # Unified Makefile for i386 and x86_64

    +# Check the compiler
    +sane_compiler := $(shell $(srctree)/scripts/x86-check-compiler.sh $(CC))
    +$(if $(sane_compiler),$(error $(CC) check failed. Aborting),)
    +
    # select defconfig based on actual architecture
    ifeq ($(ARCH),x86)
    ifeq ($(shell uname -m),x86_64)
    diff --git a/scripts/x86-check-compiler.sh b/scripts/x86-check-compiler.sh
    new file mode 100755
    index 0000000..b2b5b54
    --- /dev/null
    +++ b/scripts/x86-check-compiler.sh
    @@ -0,0 +1,9 @@
    +#!/bin/sh
    +# SPDX-License-Identifier: GPL-2.0
    +
    +# Check whether the compiler tail-call optimizes across an asm() statement.
    +# Fail the build if it does.
    +
    +echo "int foo(int a); int bar(int a) { int r = foo(a); asm(\"\"); return r; }" |\
    + $* -O2 -x c -c -S - -o - 2>/dev/null |\
    + grep -E "^[[:blank:]]+jmp[[:blank:]]+.*"
    \
     
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