On Fri, Apr 03, 2020 at 06:02:24PM +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 subsytems > 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, defconfig && 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 just a shell script that > exits with 0 in most cases. 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 > > I tried my best to implement the dummy scripts to pass 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> > --- > > scripts/dummy-tools/gcc | 91 +++++++++++++++++++++++++++++++++++++ > scripts/dummy-tools/ld | 4 ++ > scripts/dummy-tools/nm | 4 ++ > scripts/dummy-tools/objcopy | 4 ++ > 4 files changed, 103 insertions(+) > create mode 100755 scripts/dummy-tools/gcc > create mode 100755 scripts/dummy-tools/ld > create mode 100755 scripts/dummy-tools/nm > create mode 100755 scripts/dummy-tools/objcopy > <snip> > diff --git a/scripts/dummy-tools/ld b/scripts/dummy-tools/ld > new file mode 100755 > index 000000000000..3bc56ae4cc15 > --- /dev/null > +++ b/scripts/dummy-tools/ld > @@ -0,0 +1,4 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0-only > + > +# Dummy script that always succeeds It looks like scripts/Kbuild.include expects "$(LD) --version" to return something. If it doesn't "ld-ifversion" stops working. Other than that it seems to work as advertised. Thanks! - Jeremy
