Hi Zhangjin, > 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. I think changing this sentence to "Say Y here to trim all of the unused syscalls, excluding those defined in USED_SYSCALLS." would be clearer. By the way, consider adding the three files syscall_table_used.c, compat_syscall_table_used.c, and traps_used.c to the .gitignore file. > + > + 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 > --
