locore.S: stash boot arguments in saved registers
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Authored by mhorne on Nov 5 2024, 8:42 PM.

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br
jrtc27
jhb

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riscv

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rGc7fa232e9b70: locore.S: stash boot arguments in saved registers

Summary

Switch the boot argument registers to the unused s3 and s4. This ensures
the values will not be clobbered by SBI or function calls; they are
consumed late in the assembly routine.

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rG FreeBSD src repository

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Event Timeline

mhorne created this revision.Nov 5 2024, 8:42 PM

Herald added a subscriber: imp. · View Herald TranscriptNov 5 2024, 8:42 PM

Harbormaster completed remote builds in B60409: Diff 146073.Nov 5 2024, 8:42 PM

mhorne requested review of this revision.Nov 5 2024, 8:42 PM

mhorne added a parent revision: D47456: sbi: export machine register accessors.

mhorne added a child revision: D47458: riscv: T-HEAD early locore workaround.

As with D47458, C code should not be run prior to enabling translation so we're running at the right address, so IMO this patch is a sign of going down the wrong road. Yes, Linux does horrendously fragile things like this, but that doesn't mean we should do the same.

Reduce the change, just switch to using s3/s4 registers, still needed to
preserve the values across SBI calls.

Harbormaster completed remote builds in B60424: Diff 146101.Nov 6 2024, 3:51 PM

mhorne retitled this revision from locore.S: prepare for C function calls earlier to locore.S: stash boot arguments in saved registers.Nov 6 2024, 3:52 PM

mhorne edited the summary of this revision. (Show Details)

This revision was not accepted when it landed; it landed in state Needs Review.Nov 25 2024, 9:09 PM

Closed by commit rGc7fa232e9b70: locore.S: stash boot arguments in saved registers (authored by mhorne). · Explain Why

This revision was automatically updated to reflect the committed changes.

mhorne added a commit: rGc7fa232e9b70: locore.S: stash boot arguments in saved registers.