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> |
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.. 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