As __start must be placed at a precise location, a separate, explicit
input section is needed to guarantee this.
Why is this an issue ? NuttX uses --entry=__start which puts __start in
its correct location, but out-of-tree builds won't work, so it more robust
to use an explicit section for the startup code and enforce its placement
in the linker script.
Usually the startup script is placed under /etc. The contents of the etc directory
are compiled and linked with Nuttx binary in the form of romfs. After startup,
it will be mounted by Nsh.
etc is generated by the different boards, that use genromfs and xxd tools to generate
and compile it into the Nuttx, for example: boards/arm/at32/at32f437-mini/tool/mkromfs.sh
The more common method is etc image generated from the content in the corresponding
board/arch/board/board/src/etc directory, and added by Makefile for example:
boards/sim/sim/sim/src/etc.
But in kernel/protected mode, Nuttx kernel and apps are run in different privileged/
non-privileged mode or the isolated binarys, so as that nsh should use syscall to
access Nuttx kernel by exported API. In this scenario, nsh can not mount the etc image
content, because that is generated in board and as a part of Nuttx kernel.
changes:
- move etc romfs mount from nsh to Nuttx, but keep the script to parse and execute.
- move and rename the related CONFIG, move customized nsh_romfsimg.h to etc_romfs.c
in boards, and no need declaration for romfs_img/romfs_img_len.
This commit changes and updates all configurations in Nuttx arch/board as much as possible,
but if any missing, please refer to the following simple guide:
- rename CONFIG_NSH_ROMFSETC to CONFIG_ETC_ROMFS, and delete CONFIG_NSH_ARCHROMFS in defconfig
- rename the etc romfs mount configs, for example CONFIG_NSH_FATDEVNO to CONFIG_ETC_FATDEVNO
- move customized nsh_romfsimg.h to etc_romfs.c in board/arch/board/board/src and no need
declaration for romfs_img/romfs_img_len.
- delete default nsh_romfsimg.h, if ROMFSETC is enabled, should generate and compile etc_romfs.c
in board/arch/board/board/src.
Signed-off-by: fangxinyong <fangxinyong@xiaomi.com>
Ville Juven