From fc463f66ee81dd4be431a044b05fbfcb8ceecf7d Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Wed, 9 May 2018 23:00:00 +1000 Subject: [PATCH] kbuild: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selectable if enabled Architectures that are capable can select HAVE_LD_DEAD_CODE_DATA_ELIMINATION to enable selection of that option (as an EXPERT kernel option). Signed-off-by: Nicholas Piggin Signed-off-by: Masahiro Yamada --- arch/Kconfig | 15 --------------- init/Kconfig | 27 +++++++++++++++++++++++++++ 2 files changed, 27 insertions(+), 15 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 42f008e7fa16..ef09f2d5c1d1 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -603,21 +603,6 @@ config THIN_ARCHIVES Select this if the architecture wants to use thin archives instead of ld -r to create the built-in.o files. -config LD_DEAD_CODE_DATA_ELIMINATION - bool - help - Select this if the architecture wants to do dead code and - data elimination with the linker by compiling with - -ffunction-sections -fdata-sections and linking with - --gc-sections. - - This requires that the arch annotates or otherwise protects - its external entry points from being discarded. Linker scripts - must also merge .text.*, .data.*, and .bss.* correctly into - output sections. Care must be taken not to pull in unrelated - sections (e.g., '.text.init'). Typically '.' in section names - is used to distinguish them from label names / C identifiers. - config LTO def_bool n diff --git a/init/Kconfig b/init/Kconfig index 3117647cea21..fb0233ce7f10 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1276,6 +1276,33 @@ config CC_OPTIMIZE_FOR_SIZE endchoice +config HAVE_LD_DEAD_CODE_DATA_ELIMINATION + bool + help + This requires that the arch annotates or otherwise protects + its external entry points from being discarded. Linker scripts + must also merge .text.*, .data.*, and .bss.* correctly into + output sections. Care must be taken not to pull in unrelated + sections (e.g., '.text.init'). Typically '.' in section names + is used to distinguish them from label names / C identifiers. + +config LD_DEAD_CODE_DATA_ELIMINATION + bool "Dead code and data elimination (EXPERIMENTAL)" + depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION + depends on EXPERT + help + Select this if the architecture wants to do dead code and + data elimination with the linker by compiling with + -ffunction-sections -fdata-sections, and linking with + --gc-sections. + + This can reduce on disk and in-memory size of the kernel + code and static data, particularly for small configs and + on small systems. This has the possibility of introducing + silently broken kernel if the required annotations are not + present. This option is not well tested yet, so use at your + own risk. + config SYSCTL bool