Missing support for building position independent code

[jnohlgard]

Adding support for building position independent code would make it easier to build images for online firmware updates, since the binary can be relocated by the bootloader to a suitable location depending on available memory. Running binaries from RAM should also be possible without any special linker scripts.

I have not investigated the details but the a rough draft of the changes needed are:

• Add -fPIC to CFLAGS, possibly -fpie as well.
• add linker script handling of .got (global offset table) and .got.plt (procedure linkage table)
• fill GOT during boot (I don't know if gcc provides code for this or if we need to write our own)

[jnohlgard]

Maybe relevant #6450 #7167 #6922 #7081

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[miri64]

@kaspar030 @kYc0o isn't this fixed via your work?

[kYc0o]

Unfortunately not. This is about dynamic loading of position independent code during compile time, if I'm not mistaken. Our approach is rather to boot images at a fixed position given by a specific linker script, which the method discussed here would avoid.

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This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.