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Documentation/applications/examples/elf/index.rst: Update for PR #3062 in nuttx-apps

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Update the documentation to align with https://github.com/apache/nuttx-apps/pull/3062

Signed-off-by: Laczen JMS <laczenjms@gmail.com>
This commit is contained in:
Laczen JMS
2025-04-18 10:34:12 +02:00
committed by Alan C. Assis
parent 047a40917c
commit dd29b8a4cf
1 changed files with 16 additions and 11 deletions
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Documentation/applications/examples/elf/index.rst
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@@ -4,9 +4,16 @@
This example builds a small ELF loader test case. This includes several test
programs under ``examples/elf`` tests. These tests are build using the relocatable
ELF format and installed in a ROMFS file system. At run time, each program in
the ROMFS file system is executed. Requires ``CONFIG_ELF``. Other configuration
options:
ELF format and installed in a configurable file system. At run time, the file system
is mounted and each program is executed. Requires ``CONFIG_ELF``.
Two distinct types of file systems are supported: internal (included in the NuttX binary)
and external (not included in the binary). The external file systems need to be uploaded
manually. For the internal file systems the sample supports the ``romfs`` and ``cromfs``
filesystems. For the external file systems any of the provided file systems can be used
(``vfat``, ...), but also the ``romfs`` filesystem for which the image (``romfs.img``) is
automatically generated.
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
@@ -35,24 +42,19 @@ options:
If you use GCC to link, you make also need to include ``-nostdlib``.
3. 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.
4. ELF size: The ELF files in this example are, be default, quite large because
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.
5. Simulator. You cannot use this example with the NuttX simulator on Cygwin.
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.
6. Linker scripts. You might also want to use a linker scripts to combine
5. Linker scripts. You might also want to use a linker scripts to combine
sections better. An example linker script is at
``nuttx/binfmt/elf/gnu-elf.ld``. That example might have to be tuned for
your particular linker output to position additional sections correctly. The
@@ -60,3 +62,6 @@ options:
LDELFFLAGS = -r -e main -T$(TOPDIR)/binfmt/elf/gnu-elf.ld
6. When generating the ``romfs.img`` for external filesystem the image (``romfs.img``)
needs to be manually copied to the start of the configured ``CONFIG_EXAMPLES_ELF_DEVPATH``
using ``openocd`` or your preferred programmer.