On Wed, Apr 08, 2020 at 12:53:52AM +0900, Masahiro Yamada wrote: > Staring v4.18, Kconfig evaluates compiler capabilities, and hides CONFIG > options your compiler does not support. This works well if you configure > and build the kernel on the same host machine. > > It is inconvenient if you prepare the .config that is carried to a > different build environment (typically this happens when you package > the kernel for distros) because using a different compiler potentially > produces different CONFIG options than the real build environment. > So, you probably want to make as many options visible as possible. > In other words, you need to create a super-set of CONFIG options that > cover any build environment. If some of the CONFIG options turned out > to be unsupported on the build machine, they are automatically disabled > by the nature of Kconfig. > > However, it is not feasible to get a full-featured compiler for every > arch. > > This issue was discussed here: > > https://lkml.org/lkml/2019/12/9/620 > > Other than distros, savedefconfig is also a problem. Some arch sub-systems > periodically resync defconfig files. If you use a less-capable compiler > for savedefconfig, options that do not meet 'depends on $(cc-option,...)' > will be forcibly disabled. So, 'make defconfig && make savedefconfig' > may silently change the behavior. > > This commit adds a set of dummy toolchains that pretend to support any > feature. > > Most of compiler features are tested by cc-option, which simply checks > the exit code of $(CC). The dummy tools are shell scripts that always > exit with 0. So, $(cc-option, ...) is evaluated as 'y'. > > There are more complicated checks such as: > > scripts/gcc-x86_{32,64}-has-stack-protector.sh > scripts/gcc-plugin.sh > scripts/tools-support-relr.sh > > scripts/dummy-tools/gcc passes all checks. > > From the top directory of the source tree, you can do: > > $ make CROSS_COMPILE=scripts/dummy-tools/ oldconfig > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Reviewed-by: Philipp Rudo <prudo@xxxxxxxxxxxxx> > --- > > Changes in v2: > - support --version and -v for ld, objdump, nm Great, "make ARCH=powerpc CROSS_COMPILE=scripts/dummy-tools/ help" no longer spits out "/bin/sh: line 0: [: -ge: unary operator expected" and everything looks to work as expected. Tested-by: Jeremy Cline <jcline@xxxxxxxxxx> > > scripts/dummy-tools/gcc | 91 +++++++++++++++++++++++++++++++++++++ > scripts/dummy-tools/ld | 30 ++++++++++++ > scripts/dummy-tools/nm | 1 + > scripts/dummy-tools/objcopy | 1 + > 4 files changed, 123 insertions(+) > create mode 100755 scripts/dummy-tools/gcc > create mode 100755 scripts/dummy-tools/ld > create mode 120000 scripts/dummy-tools/nm > create mode 120000 scripts/dummy-tools/objcopy > > diff --git a/scripts/dummy-tools/gcc b/scripts/dummy-tools/gcc > new file mode 100755 > index 000000000000..33487e99d83e > --- /dev/null > +++ b/scripts/dummy-tools/gcc > @@ -0,0 +1,91 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0-only > +# > +# Staring v4.18, Kconfig evaluates compiler capabilities, and hides CONFIG > +# options your compiler does not support. This works well if you configure and > +# build the kernel on the same host machine. > +# > +# It is inconvenient if you prepare the .config that is carried to a different > +# build environment (typically this happens when you package the kernel for > +# distros) because using a different compiler potentially produces different > +# CONFIG options than the real build environment. So, you probably want to make > +# as many options visible as possible. In other words, you need to create a > +# super-set of CONFIG options that cover any build environment. If some of the > +# CONFIG options turned out to be unsupported on the build machine, they are > +# automatically disabled by the nature of Kconfig. > +# > +# However, it is not feasible to get a full-featured compiler for every arch. > +# Hence these dummy toolchains to make all compiler tests pass. > +# > +# Usage: > +# > +# From the top directory of the source tree, run > +# > +# $ make CROSS_COMPILE=scripts/dummy-tools/ oldconfig > +# > +# Most of compiler features are tested by cc-option, which simply checks the > +# exit code of $(CC). This script does nothing and just exits with 0 in most > +# cases. So, $(cc-option, ...) is evaluated as 'y'. > +# > +# This scripts caters to more checks; handle --version and pre-process __GNUC__ > +# etc. to pretend to be GCC, and also do right things to satisfy some scripts. > + > +# Check if the first parameter appears in the rest. Succeeds if found. > +# This helper is useful if a particular option was passed to this script. > +# Typically used like this: > +# arg_contain <word-you-are-searching-for> "$@" > +arg_contain () > +{ > + search="$1" > + shift > + > + while [ $# -gt 0 ] > + do > + if [ "$search" = "$1" ]; then > + return 0 > + fi > + shift > + done > + > + return 1 > +} > + > +# To set CONFIG_CC_IS_GCC=y > +if arg_contain --version "$@"; then > + echo "gcc (scripts/dummy-tools/gcc)" > + exit 0 > +fi > + > +if arg_contain -E "$@"; then > + # For scripts/gcc-version.sh; This emulates GCC 20.0.0 > + if arg_contain - "$@"; then > + sed 's/^__GNUC__$/20/; s/^__GNUC_MINOR__$/0/; s/^__GNUC_PATCHLEVEL__$/0/' > + exit 0 > + else > + echo "no input files" >&2 > + exit 1 > + fi > +fi > + > +if arg_contain -S "$@"; then > + # For scripts/gcc-x86-*-has-stack-protector.sh > + if arg_contain -fstack-protector "$@"; then > + echo "%gs" > + exit 0 > + fi > +fi > + > +# For scripts/gcc-plugin.sh > +if arg_contain -print-file-name=plugin "$@"; then > + plugin_dir=$(mktemp -d) > + > + sed -n 's/.*#include "\(.*\)"/\1/p' $(dirname $0)/../gcc-plugins/gcc-common.h | > + while read header > + do > + mkdir -p $plugin_dir/include/$(dirname $header) > + touch $plugin_dir/include/$header > + done > + > + echo $plugin_dir > + exit 0 > +fi > diff --git a/scripts/dummy-tools/ld b/scripts/dummy-tools/ld > new file mode 100755 > index 000000000000..f68233050405 > --- /dev/null > +++ b/scripts/dummy-tools/ld > @@ -0,0 +1,30 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0-only > + > +# Dummy script that always succeeds. > + > +# Check if the first parameter appears in the rest. Succeeds if found. > +# This helper is useful if a particular option was passed to this script. > +# Typically used like this: > +# arg_contain <word-you-are-searching-for> "$@" > +arg_contain () > +{ > + search="$1" > + shift > + > + while [ $# -gt 0 ] > + do > + if [ "$search" = "$1" ]; then > + return 0 > + fi > + shift > + done > + > + return 1 > +} > + > +if arg_contain --version "$@" || arg_contain -v "$@"; then > + progname=$(basename $0) > + echo "GNU $progname (scripts/dummy-tools/$progname) 2.50" > + exit 0 > +fi > diff --git a/scripts/dummy-tools/nm b/scripts/dummy-tools/nm > new file mode 120000 > index 000000000000..c0648b38dd42 > --- /dev/null > +++ b/scripts/dummy-tools/nm > @@ -0,0 +1 @@ > +ld > \ No newline at end of file > diff --git a/scripts/dummy-tools/objcopy b/scripts/dummy-tools/objcopy > new file mode 120000 > index 000000000000..c0648b38dd42 > --- /dev/null > +++ b/scripts/dummy-tools/objcopy > @@ -0,0 +1 @@ > +ld > \ No newline at end of file > -- > 2.17.1 >
