No description
cab341d29c
In GNU LD, the location counter (the 'dot' variable) always refers to
the byte offset from the start of current object as mentioned in
documentation[1]:
```
'.' actually refers to the byte offset from the start of the current
containing object. Normally this is the SECTIONS statement, whose start
address is 0, hence '.' can be used as an absolute address. If '.' is
used inside a section description however, it refers to the byte offset
from the start of that section, not an absolute address.
```
For example, if the section 'rom_start':
rom_start : {
. = 0x400;
_vector_start = ABSOLUTE(.);
} > FLASH
has a starting address of 0x8000000, then _vector_start will be
0x8000400
However, behavior of LLVM LLD is quite different, the value of the
location counter is always absolute (see discussion [2]), so in the
example above, the linker will return error, because it will interpret
'. = 0x400' as an attempt to move the location counter backwards.
It could be fixed by changing line to '. += 0x400' (#54796) which will
move the location counter by 0x400 for both linkers, but it would work
only when we are at the beginning of section. Consider the following
example:
rom_start : {
. = 0x400;
KEEP(*(.boot_hdr.conf))
. = 0x1000;
KEEP(*(.boot_hdr.ivt))
KEEP(*(.boot_hdr.data))
KEEP(*(.boot_hdr.dcd_data))
. = 0x2000;
_vector_start = .;
} > FLASH
In this case, _vector_start will be 0x2000, but if we change
'. = 0x2000' to '. += 0x2000', then the value of _vector_start depends
on size of data in input sections (but it's 0x3000 at least).
Actually, this example comes from final linker script when compiling
firmware for mimxrt1170_evk_cm7 board. This board failed to boot
(#55296) after #54796 was merged.
This patch introduces method compatible with both linkers. We calculate
relative offset from the beginning of the section and use that value to
calculate number of bytes by which we should move the location counter
to get CONFIG_ROM_START_OFFSET.
[1] https://sourceware.org/binutils/docs/ld/Location-Counter.html
[2] https://discourse.llvm.org/t/lld-location-counter-inside-objects
Signed-off-by: Patryk Duda <pdk@semihalf.com>
|
||
|---|---|---|
| .github | ||
| arch | ||
| boards | ||
| cmake | ||
| doc | ||
| drivers | ||
| dts | ||
| include/zephyr | ||
| kernel | ||
| lib | ||
| misc | ||
| modules | ||
| samples | ||
| scripts | ||
| share | ||
| snippets | ||
| soc | ||
| submanifests | ||
| subsys | ||
| tests | ||
| .checkpatch.conf | ||
| .clang-format | ||
| .codecov.yml | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| .gitlint | ||
| .mailmap | ||
| .yamllint | ||
| CMakeLists.txt | ||
| CODE_OF_CONDUCT.md | ||
| CODEOWNERS | ||
| CONTRIBUTING.rst | ||
| Kconfig | ||
| Kconfig.zephyr | ||
| LICENSE | ||
| MAINTAINERS.yml | ||
| README.rst | ||
| VERSION | ||
| version.h.in | ||
| west.yml | ||
| zephyr-env.cmd | ||
| zephyr-env.sh | ||
.. raw:: html
<a href="https://www.zephyrproject.org">
<p align="center">
<picture>
<source media="(prefers-color-scheme: dark)" srcset="doc/_static/images/logo-readme-dark.svg">
<source media="(prefers-color-scheme: light)" srcset="doc/_static/images/logo-readme-light.svg">
<img src="doc/_static/images/logo-readme-light.svg">
</picture>
</p>
</a>
<a href="https://bestpractices.coreinfrastructure.org/projects/74"><img
src="https://bestpractices.coreinfrastructure.org/projects/74/badge"></a>
<a
href="https://github.com/zephyrproject-rtos/zephyr/actions/workflows/twister.yaml?query=branch%3Amain">
<img
src="https://github.com/zephyrproject-rtos/zephyr/actions/workflows/twister.yaml/badge.svg?event=push"></a>
The Zephyr Project is a scalable real-time operating system (RTOS) supporting
multiple hardware architectures, optimized for resource constrained devices,
and built with security in mind.
The Zephyr OS is based on a small-footprint kernel designed for use on
resource-constrained systems: from simple embedded environmental sensors and
LED wearables to sophisticated smart watches and IoT wireless gateways.
The Zephyr kernel supports multiple architectures, including ARM (Cortex-A,
Cortex-R, Cortex-M), Intel x86, ARC, Nios II, Tensilica Xtensa, and RISC-V,
SPARC, MIPS, and a large number of `supported boards`_.
.. below included in doc/introduction/introduction.rst
Getting Started
***************
Welcome to Zephyr! See the `Introduction to Zephyr`_ for a high-level overview,
and the documentation's `Getting Started Guide`_ to start developing.
.. start_include_here
Community Support
*****************
Community support is provided via mailing lists and Discord; see the Resources
below for details.
.. _project-resources:
Resources
*********
Here's a quick summary of resources to help you find your way around:
* **Help**: `Asking for Help Tips`_
* **Documentation**: http://docs.zephyrproject.org (`Getting Started Guide`_)
* **Source Code**: https://github.com/zephyrproject-rtos/zephyr is the main
repository; https://elixir.bootlin.com/zephyr/latest/source contains a
searchable index
* **Releases**: https://github.com/zephyrproject-rtos/zephyr/releases
* **Samples and example code**: see `Sample and Demo Code Examples`_
* **Mailing Lists**: users@lists.zephyrproject.org and
devel@lists.zephyrproject.org are the main user and developer mailing lists,
respectively. You can join the developer's list and search its archives at
`Zephyr Development mailing list`_. The other `Zephyr mailing list
subgroups`_ have their own archives and sign-up pages.
* **Nightly CI Build Status**: https://lists.zephyrproject.org/g/builds
The builds@lists.zephyrproject.org mailing list archives the CI nightly build results.
* **Chat**: Real-time chat happens in Zephyr's Discord Server. Use
this `Discord Invite`_ to register.
* **Contributing**: see the `Contribution Guide`_
* **Wiki**: `Zephyr GitHub wiki`_
* **Issues**: https://github.com/zephyrproject-rtos/zephyr/issues
* **Security Issues**: Email vulnerabilities@zephyrproject.org to report
security issues; also see our `Security`_ documentation. Security issues are
tracked separately at https://zephyrprojectsec.atlassian.net.
* **Zephyr Project Website**: https://zephyrproject.org
.. _Discord Invite: https://chat.zephyrproject.org
.. _supported boards: http://docs.zephyrproject.org/latest/boards/index.html
.. _Zephyr Documentation: http://docs.zephyrproject.org
.. _Introduction to Zephyr: http://docs.zephyrproject.org/latest/introduction/index.html
.. _Getting Started Guide: http://docs.zephyrproject.org/latest/develop/getting_started/index.html
.. _Contribution Guide: http://docs.zephyrproject.org/latest/contribute/index.html
.. _Zephyr GitHub wiki: https://github.com/zephyrproject-rtos/zephyr/wiki
.. _Zephyr Development mailing list: https://lists.zephyrproject.org/g/devel
.. _Zephyr mailing list subgroups: https://lists.zephyrproject.org/g/main/subgroups
.. _Sample and Demo Code Examples: http://docs.zephyrproject.org/latest/samples/index.html
.. _Security: http://docs.zephyrproject.org/latest/security/index.html
.. _Asking for Help Tips: https://docs.zephyrproject.org/latest/develop/getting_started/index.html#asking-for-help