From 850ded46c64299f04d15e39caaba21963fb966f8 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Mon, 16 Aug 2021 11:05:19 -0700 Subject: kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG With CONFIG_LTO_CLANG, we currently link modules into native code just before modpost, which means with TRIM_UNUSED_KSYMS enabled, we still look at the LLVM bitcode in the .o files when generating the list of used symbols. As the bitcode doesn't yet have calls to compiler intrinsics and llvm-nm doesn't see function references that only exist in function-level inline assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to work with LTO. This change moves module LTO linking to happen earlier, and thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS entirely, allowing us to also drop the whitelist from gen_autoksyms.sh. Link: https://github.com/ClangBuiltLinux/linux/issues/1369 Signed-off-by: Sami Tolvanen Reviewed-by: Alexander Lobakin Tested-by: Alexander Lobakin Signed-off-by: Masahiro Yamada --- scripts/Makefile.lib | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'scripts/Makefile.lib') diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 10950559b223..af1c920a585c 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -225,6 +225,13 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \ $(addprefix -I,$(DTC_INCLUDE)) \ -undef -D__DTS__ +ifeq ($(CONFIG_LTO_CLANG),y) +# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we +# need to run LTO to compile them into native code (.lto.o) before further +# processing. +mod-prelink-ext := .lto +endif + # Objtool arguments are also needed for modfinal with LTO, so we define # then here to avoid duplication. objtool_args = \ -- cgit v1.2.3 From 44815c90210cd858c4a116c3eb35270160cecf81 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sat, 28 Aug 2021 18:51:01 +0900 Subject: kbuild: clean up objtool_args slightly The code: $(if $(or $(CONFIG_GCOV_KERNEL),$(CONFIG_LTO_CLANG)), ...) ... can be simpled to: $(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), ...) Also, remove meaningless commas at the end of $(if ...). Signed-off-by: Masahiro Yamada --- scripts/Makefile.lib | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'scripts/Makefile.lib') diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index af1c920a585c..cd011f3f6f78 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -236,13 +236,12 @@ endif # then here to avoid duplication. objtool_args = \ $(if $(CONFIG_UNWINDER_ORC),orc generate,check) \ - $(if $(part-of-module), --module,) \ + $(if $(part-of-module), --module) \ $(if $(CONFIG_FRAME_POINTER),, --no-fp) \ - $(if $(or $(CONFIG_GCOV_KERNEL),$(CONFIG_LTO_CLANG)), \ - --no-unreachable,) \ - $(if $(CONFIG_RETPOLINE), --retpoline,) \ - $(if $(CONFIG_X86_SMAP), --uaccess,) \ - $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount,) + $(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\ + $(if $(CONFIG_RETPOLINE), --retpoline) \ + $(if $(CONFIG_X86_SMAP), --uaccess) \ + $(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) # Useful for describing the dependency of composite objects # Usage: -- cgit v1.2.3