A minimal embedded Linux system may only has a very few of functions and only uses a minimal subset of the posix syscalls, the unused syscalls will never be used and eventually in a dead status, that also means disk storage and memory footprint waste. Based on dead code elimination support, it is able to further eliminate the above dead or unused syscalls. Firstly, both a new common CONFIG_TRIM_UNUSED_SYSCALLS option and a new architecture specific HAVE_TRIM_UNUSED_SYSCALLS are added to enable or disable such feature. Secondly, a new CONFIG_USED_SYSCALLS option is added to allow configure the syscalls used in a target system. CONFIG_USED_SYSCALLS can be a list of the used syscalls or a file to store such a list. Based on the above options, it is able to only reserve the used syscalls and let CONFIG_LD_DEAD_CODE_DATA_ELIMINATION trim the unused ones for us automatically. Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx> --- init/Kconfig | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index 4350d8ba7db4..aa648ce8bca1 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1457,6 +1457,11 @@ config BPF bool select CRYPTO_LIB_SHA1 +config HAVE_TRIM_UNUSED_SYSCALLS + bool + depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION + default n + menuconfig EXPERT bool "Configure standard kernel features (expert users)" # Unhide debug options, to make the on-by-default options visible @@ -1683,6 +1688,43 @@ config MEMBARRIER If unsure, say Y. +config TRIM_UNUSED_SYSCALLS + bool "Trim unused syscalls (EXPERIMENTAL)" if EXPERT + default n + depends on HAVE_TRIM_UNUSED_SYSCALLS + depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION + select LD_DEAD_CODE_DATA_ELIMINATION + help + Say Y here to trim all of the unused syscalls for a target system. + + Note, this is only for minimal embedded systems, please don't use it + for generic Linux distributions. + + If unsure, say N. + +config USED_SYSCALLS + string "Configure used syscalls (EXPERIMENTAL)" if EXPERT + depends on TRIM_UNUSED_SYSCALLS + default "" + help + This option allows to configure the syscalls used in a target system, + the unused ones will be disabled and trimmed by TRIM_UNUSED_SYSCALLS. + + The used syscalls should be listed one by one like this: + + write exit reboot + + Or put them into a file specified by this option, one syscall per + line is recommended for such a config file: + + write + exit + reboot + + Note, If keep this empty, all of the syscalls will be trimmed. + + If unsure, please disable TRIM_UNUSED_SYSCALLS. + config KALLSYMS bool "Load all symbols for debugging/ksymoops" if EXPERT default y -- 2.25.1
