On some distros and configurations, it might be useful to allow for specifying a directory where Clang stores its ThinLTO cache. More specifically, when building the VirtualBox extramodules on Arch with its proper 'makepkg' build system and DKMS, against an already installed ThinLTO kernel, the build fails because it tries to create the ThinLTO cache in a directory that is not user-writable. A similar problem has been reported with openSUSE's OBS build system. Add a Kconfig option that allows users to choose a directory in which Clang's ThinLTO can store its cache. Link: https://github.com/ClangBuiltLinux/linux/issues/1104 Signed-off-by: Tor Vic <torvic9@xxxxxxxxxxx> --- Makefile | 5 +++-- arch/Kconfig | 10 ++++++++++ scripts/Makefile.lib | 4 ++++ scripts/Makefile.modfinal | 4 ++++ 4 files changed, 21 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index c3f9bd191b89..472bc8bfff03 100644 --- a/Makefile +++ b/Makefile @@ -932,7 +932,8 @@ endif ifdef CONFIG_LTO_CLANG ifdef CONFIG_LTO_CLANG_THIN CC_FLAGS_LTO := -flto=thin -fsplit-lto-unit -KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod_prefix).thinlto-cache +export thinlto-dir = $(if $(CONFIG_LTO_CLANG_THIN_CACHEDIR),$(CONFIG_LTO_CLANG_THIN_CACHEDIR)/) +KBUILD_LDFLAGS += --thinlto-cache-dir=$(thinlto-dir)$(extmod_prefix).thinlto-cache else CC_FLAGS_LTO := -flto endif @@ -1728,7 +1729,7 @@ PHONY += compile_commands.json clean-dirs := $(KBUILD_EXTMOD) clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \ - $(KBUILD_EXTMOD)/compile_commands.json $(KBUILD_EXTMOD)/.thinlto-cache + $(KBUILD_EXTMOD)/compile_commands.json $(thinlto-dir)$(KBUILD_EXTMOD)/.thinlto-cache PHONY += help help: diff --git a/arch/Kconfig b/arch/Kconfig index 129df498a8e1..19e4d140e12a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -696,6 +696,16 @@ config LTO_CLANG_THIN https://clang.llvm.org/docs/ThinLTO.html If unsure, say Y. + +config LTO_CLANG_THIN_CACHEDIR + string "Clang ThinLTO cache directory" + depends on LTO_CLANG_THIN + default "" + help + This option allows users to choose a directory that stores + Clang's ThinLTO cache. + Leave empty for default. + endchoice config ARCH_SUPPORTS_CFI_CLANG diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 10950559b223..bca87a6aa35b 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -197,6 +197,10 @@ endif part-of-module = $(if $(filter $(basename $@).o, $(real-obj-m)),y) quiet_modtag = $(if $(part-of-module),[M], ) +ifdef CONFIG_LTO_CLANG_THIN +KBUILD_LDFLAGS += --thinlto-cache-dir=$(thinlto-dir)$(extmod-prefix).thinlto-cache +endif + modkern_cflags = \ $(if $(part-of-module), \ $(KBUILD_CFLAGS_MODULE) $(CFLAGS_MODULE), \ diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal index 5e9b8057fb24..ab0d72e21318 100644 --- a/scripts/Makefile.modfinal +++ b/scripts/Makefile.modfinal @@ -35,6 +35,10 @@ ifdef CONFIG_LTO_CLANG # avoid a second slow LTO link prelink-ext := .lto +ifdef CONFIG_LTO_CLANG_THIN +KBUILD_LDFLAGS += --thinlto-cache-dir=$(thinlto-dir)$(extmod-prefix).thinlto-cache +endif # CONFIG_LTO_CLANG_THIN + # ELF processing was skipped earlier because we didn't have native code, # so let's now process the prelinked binary before we link the module. -- 2.32.0
