module Loadable Module

This example builds a small loadable module test case. This includes a character driver under examples/module/drivers. This driver is built using the relocatable ELF format and installed in a ROMFS file system. At run time, the driver module is loaded and exercised. Requires CONFIG_MODULE. Other configuration options:

  • CONFIG_EXAMPLES_ELF_DEVMINOR – The minor device number of the ROMFS block driver. For example, the N in /dev/ramN. Used for registering the RAM block driver that will hold the ROMFS file system containing the ELF executables to be tested. Default: 0.

  • CONFIG_EXAMPLES_ELF_DEVPATH – The path to the ROMFS block driver device. This must match EXAMPLES_ELF_DEVMINOR. Used for registering the RAM block driver that will hold the ROMFS file system containing the ELF executables to be tested. Default: /dev/ram0.

Notes:

  1. The arch Toolchain.defs sets CMODULEFLAGS and LDMODULEFLAGS. For example, on ARM they contain -mlong-calls, -r and the linker script libs/libc/elf/gnu-elf.ld. A board scripts/Make.defs can add an option with +=, for example LDMODULEFLAGS += -melf32lriscv. Do not set these variables again with =: the board then loses the options that the arch adds for the configuration, for example the FDPIC options.

  2. This example also requires genromfs. genromfs can be build as part of the nuttx toolchain. Or can built from the genromfs sources that can be found in the NuttX tools repository (genromfs-0.5.2.tar.gz). In any event, the PATH variable must include the path to the genromfs executable.

  3. ELF size: The ELF files in this example are, be default, quite large because they include a lot of build garbage. You can greatly reduce the size of the ELF binaries are using the objcopy --strip-unneeded command to remove un-necessary information from the ELF files.

  4. Simulator. You cannot use this example with the NuttX simulator on Cygwin. That is because the Cygwin GCC does not generate ELF file but rather some Windows-native binary format.

    If you really want to do this, you can create a NuttX x86 buildroot toolchain and use that be build the ELF executables for the ROMFS file system.