Re: [PATCH 1/2] kbuild: Hoist '--orphan-handling' into Kconfig
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-11-17 11:04:24
Also in:
linux-arm-kernel, linux-kbuild, lkml
Nathan Chancellor [off-list ref] writes:
Currently, '--orphan-handling=warn' is spread out across four different architectures in their respective Makefiles, which makes it a little unruly to deal with in case it needs to be disabled for a specific linker version (in this case, ld.lld 10.0.1). To make it easier to control this, hoist this warning into Kconfig and the main Makefile so that disabling it is simpler, as the warning will only be enabled in a couple places (main Makefile and a couple of compressed boot folders that blow away LDFLAGS_vmlinx) and making it conditional is easier due to Kconfig syntax. One small additional benefit of this is saving a call to ld-option on incremental builds because we will have already evaluated it for CONFIG_LD_ORPHAN_WARN. To keep the list of supported architectures the same, introduce CONFIG_ARCH_WANT_LD_ORPHAN_WARN, which an architecture can select to gain this automatically after all of the sections are specified and size asserted. A special thanks to Kees Cook for the help text on this config. Link: https://github.com/ClangBuiltLinux/linux/issues/1187 Signed-off-by: Nathan Chancellor <redacted> --- Makefile | 6 ++++++ arch/Kconfig | 9 +++++++++ arch/arm/Kconfig | 1 + arch/arm/Makefile | 4 ---- arch/arm/boot/compressed/Makefile | 4 +++- arch/arm64/Kconfig | 1 + arch/arm64/Makefile | 4 ---- arch/powerpc/Kconfig | 1 + arch/powerpc/Makefile | 1 -
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
quoted hunk ↗ jump to hunk
arch/x86/Kconfig | 1 + arch/x86/Makefile | 3 --- arch/x86/boot/compressed/Makefile | 4 +++- init/Kconfig | 3 +++ 13 files changed, 28 insertions(+), 14 deletions(-)diff --git a/Makefile b/Makefile index 008aba5f1a20..c443afd61886 100644 --- a/Makefile +++ b/Makefile@@ -984,6 +984,12 @@ ifeq ($(CONFIG_RELR),y) LDFLAGS_vmlinux += --pack-dyn-relocs=relr endif +# We never want expected sections to be placed heuristically by the +# linker. All sections should be explicitly named in the linker script. +ifeq ($(CONFIG_LD_ORPHAN_WARN),y) +LDFLAGS_vmlinux += --orphan-handling=warn +endif
This is a nit, but you can use ifdef with bool CONFIG symbols in Makefiles, which reads a bit nicer, eg: ifdef CONFIG_LD_ORPHAN_WARN LDFLAGS_vmlinux += --orphan-handling=warn endif cheers