[10/10] Documentation, boards/rp23xx: Describe FDPIC and add a test configuration - #20132
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[10/10] Documentation, boards/rp23xx: Describe FDPIC and add a test configuration#20132casaroli wants to merge 1 commit into
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…tion. Documentation/components/fdpic.rst covers what an FDPIC module is and what it adds over the position independent ELF support already in the tree, how the loader places one, where shared libraries come from and how they are found, which entry points resolve a function descriptor and the rules for adding another, and how to build a module and a library. A comparison table places it against NXFLAT and PIC ELF, and the reference section records the object layout and the relocations. The tools page added earlier in this series now points at it. pimoroni-pico-2-plus:xipfs-fdpic is the configuration the series was tested on: xipfs on the board's QSPI flash, the ELF loader with CONFIG_FDPIC, and apps/examples/fdpicxip with apps/testing/fs/xipfs. CONFIG_DEFAULT_TASK_STACKSIZE is 4096 there rather than the rp23xx default of 2048. Both sides of the loader need it: a module that calls into the firmware's printf family overflows 2048, and with no MPU that is a lockup rather than a diagnostic. CONFIG_ELF_STACKSIZE follows it, and apps/testing/fs/xipfs sizes its own task from it. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
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depends-on: [/pull/20089 /pull/20130 /pull/20131]
Summary
The last part of the FDPIC series: what it is, and a configuration that runs it.
Documentation/components/fdpic.rstcovers what an FDPIC module is and what it adds over the position independent ELF support already in the tree, how the loader places one, where shared libraries come from and how they are found, which entry points resolve a function descriptor and the rules for adding another, and how to build a module and a library. A comparison table places it against NXFLAT and PIC ELF, and the reference section records the object layout and the relocations.pimoroni-pico-2-plus:xipfs-fdpicis the configuration the series was tested on: xipfs on the board's QSPI flash, the ELF loader withCONFIG_FDPIC,apps/examples/fdpicxipandapps/testing/fs/xipfs.CONFIG_DEFAULT_TASK_STACKSIZEis 4096 there rather than the rp23xx default of 2048. Both sides of the loader need it: a module that calls into the firmware'sprintffamily overflows 2048, and with no MPU that is a lockup rather than a diagnostic.CONFIG_ELF_STACKSIZEfollows it, andapps/testing/fs/xipfssizes its own task from it.Impact
Documentation, one board configuration, and a line in two index pages. No code.
Testing
pimoroni-pico-2-plus:xipfs-fdpicbuilds standing alone on master.tools/refresh.shleaves the new defconfig unchanged, so the CI normalize step stays clean.tools/checkpatch.sh -c -u -m -gpasses.Draft
Draft because it is the tail of the series, and because
[9/10], which loadsDT_NEEDEDlibraries, is not yet opened. Thexipfssuite this configuration runs covers cases that need it, so this should not merge before it.