Hi Greg, On Mon, Feb 19, 2024 at 06:02:39PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > This is a note to let you know that I've just added the patch titled > > um: Fix adding '-no-pie' for clang > > to the 5.15-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > um-fix-adding-no-pie-for-clang.patch > and it can be found in the queue-5.15 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. > > > From 846cfbeed09b45d985079a9173cf390cc053715b Mon Sep 17 00:00:00 2001 > From: Nathan Chancellor <nathan@xxxxxxxxxx> > Date: Tue, 23 Jan 2024 15:59:54 -0700 > Subject: um: Fix adding '-no-pie' for clang > > From: Nathan Chancellor <nathan@xxxxxxxxxx> > > commit 846cfbeed09b45d985079a9173cf390cc053715b upstream. > > The kernel builds with -fno-PIE, so commit 883354afbc10 ("um: link > vmlinux with -no-pie") added the compiler linker flag '-no-pie' via > cc-option because '-no-pie' was only supported in GCC 6.1.0 and newer. > > While this works for GCC, this does not work for clang because cc-option > uses '-c', which stops the pipeline right before linking, so '-no-pie' > is unconsumed and clang warns, causing cc-option to fail just as it > would if the option was entirely unsupported: > > $ clang -Werror -no-pie -c -o /dev/null -x c /dev/null > clang-16: error: argument unused during compilation: '-no-pie' [-Werror,-Wunused-command-line-argument] > > A recent version of clang exposes this because it generates a relocation > under '-mcmodel=large' that is not supported in PIE mode: > > /usr/sbin/ld: init/main.o: relocation R_X86_64_32 against symbol `saved_command_line' can not be used when making a PIE object; recompile with -fPIE > /usr/sbin/ld: failed to set dynamic section sizes: bad value > clang: error: linker command failed with exit code 1 (use -v to see invocation) > > Remove the cc-option check altogether. It is wasteful to invoke the > compiler to check for '-no-pie' because only one supported compiler > version does not support it, GCC 5.x (as it is supported with the > minimum version of clang and GCC 6.1.0+). Use a combination of the > gcc-min-version macro and CONFIG_CC_IS_CLANG to unconditionally add > '-no-pie' with CONFIG_LD_SCRIPT_DYN=y, so that it is enabled with all > compilers that support this. Furthermore, using gcc-min-version can help > turn this back into > > LINK-$(CONFIG_LD_SCRIPT_DYN) += -no-pie > > when the minimum version of GCC is bumped past 6.1.0. > > Cc: stable@xxxxxxxxxxxxxxx > Closes: https://github.com/ClangBuiltLinux/linux/issues/1982 > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- > arch/um/Makefile | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > --- a/arch/um/Makefile > +++ b/arch/um/Makefile > @@ -118,7 +118,9 @@ archprepare: > $(Q)$(MAKE) $(build)=$(HOST_DIR)/um include/generated/user_constants.h > > LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static > -LINK-$(CONFIG_LD_SCRIPT_DYN) += $(call cc-option, -no-pie) > +ifdef CONFIG_LD_SCRIPT_DYN > +LINK-$(call gcc-min-version, 60100)$(CONFIG_CC_IS_CLANG) += -no-pie 5.15 does not have support for gcc-min-version, so I think this just breaks ARCH=um for GCC. I do not think this patch matters much in 5.15 and earlier, we only test ARCH=um with Linux 6.1 and newer, so it can be dropped. Cheers, Nathan
