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kbuild: Allow LD_DEAD_CODE_DATA_ELIMINATION to be selectable if enabled

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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 <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Nicholas Piggin 2018-05-09 23:00:00 +10:00 committed by Masahiro Yamada
parent 6ca8d9433d
commit 5d20ee3192
2 changed files with 27 additions and 15 deletions
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15
arch/Kconfig
View File

@ -596,21 +596,6 @@ config CC_STACKPROTECTOR_AUTO
endchoice
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 HAVE_ARCH_WITHIN_STACK_FRAMES
bool
help

27
init/Kconfig
View File

@ -1038,6 +1038,33 @@ 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