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