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kernel: syscalls: no need to include all syscalls in binary

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The syscall generation phase parses all header files to look
for potential syscalls, and emits all the relevant files to
enable syscalls. However, this results in all the syscall
marshalling functions being included in the final binary.
This is due to these functions being referred to inside
the dispatch list, resulting in ineffective garbage
collection during linking. Previous commits allows each
drivers and subsystems to specify which header files
containing syscalls are relevant. So this commit changes
the syscall generation to only include the syscalls needed
for the build in the syscall dispatch list and removing
various bits related to that. This allows the linker to
garbage collect unused syscall related function, and thus
reducing final binary size.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2023-05-25 11:41:48 -07:00 • committed by Anas Nashif
commit 80e78208e6
5 changed files with 151 additions and 35 deletions
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22
CMakeLists.txt
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@ -92,6 +92,11 @@ set(PARSE_SYSCALLS_TARGET parse_syscalls_target)
define_property(GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT BRIEF_DOCS " " FULL_DOCS " ")
set_property( GLOBAL PROPERTY PROPERTY_OUTPUT_FORMAT elf32-little${ARCH}) # BFD format
# Contains the list of files with syscall function prototypes.
add_library(syscalls_interface INTERFACE)
set(syscalls_file_list_output
${CMAKE_CURRENT_BINARY_DIR}/misc/generated/syscalls_file_list.txt)
# "zephyr_interface" is a source-less library that encapsulates all the global
# compiler options needed by all source files. All zephyr libraries,
# including the library named "zephyr" link with this library to
@ -728,13 +733,16 @@ add_custom_command(
COMMAND
${PYTHON_EXECUTABLE}
${ZEPHYR_BASE}/scripts/build/parse_syscalls.py
--include ${ZEPHYR_BASE}/include # Read files from this dir
--include ${ZEPHYR_BASE}/drivers # For net sockets
--include ${ZEPHYR_BASE}/subsys/net # More net sockets
--scan ${ZEPHYR_BASE}/include # Read files from this dir
--scan ${ZEPHYR_BASE}/drivers # For net sockets
--scan ${ZEPHYR_BASE}/subsys/net # More net sockets
${parse_syscalls_include_args} # Read files from these dirs also
--json-file ${syscalls_json} # Write this file
--tag-struct-file ${struct_tags_json} # Write subsystem list to this file
--file-list ${syscalls_file_list_output}
$<$<BOOL:${CONFIG_EMIT_ALL_SYSCALLS}>:--emit-all-syscalls>
DEPENDS ${syscalls_subdirs_trigger} ${PARSE_SYSCALLS_HEADER_DEPENDS}
${syscalls_file_list_output} ${syscalls_interface}
)
# Make sure Picolibc is built before the rest of the system; there's no explicit
@ -850,6 +858,14 @@ zephyr_get_include_directories_for_lang(C ZEPHYR_INCLUDES)
add_subdirectory(kernel)
get_property(
syscalls_file_list
TARGET syscalls_interface
PROPERTY INTERFACE_INCLUDE_DIRECTORIES
)
file(CONFIGURE OUTPUT ${syscalls_file_list_output}
CONTENT "@syscalls_file_list@" @ONLY)
# Read list content
get_property(ZEPHYR_LIBS_PROPERTY GLOBAL PROPERTY ZEPHYR_LIBS)