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Differential D40873

kinst: skip trampoline searching for riscv and arm64
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Authored by christos on Jul 4 2023, 9:35 AM.
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markj
Summary

RISCV and ARM64 use PAGE_SIZE-long trampolines as a workaround to a QEMU
bug occuring when there are multiple trampolines live in the same page.
However, BITSET(9) doesn't seem to be working properly when the bitset
size is 1, so in this case we skip the bit searching completely.

This is most likely a temporary fix.

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rG FreeBSD src repository
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Build Status
Buildable 52423
Build 49314: arc lint + arc unit

Event Timeline

christos created this revision.Jul 4 2023, 9:35 AM
Herald added a subscriber: imp. · View Herald TranscriptJul 4 2023, 9:35 AM
christos requested review of this revision.Jul 4 2023, 9:35 AM
Harbormaster completed remote builds in B52423: Diff 124155.Jul 4 2023, 9:35 AM
christos added a child revision: D39884: kinst: port to riscv.Jul 4 2023, 9:40 AM
christos added a parent revision: D40872: dtrace: cache current probe in kdtrace_thread_t.
christos retitled this revision from kinst: skip trampoline searching for riscv to kinst: skip trampoline searching for riscv and arm64.Jul 4 2023, 10:47 AM
christos updated this revision to Diff 124162.Jul 4 2023, 10:48 AM

Add arm64 here as well

Harbormaster completed remote builds in B52428: Diff 124162.Jul 4 2023, 10:48 AM
christos edited the summary of this revision. (Show Details)Jul 4 2023, 10:48 AM
markj added inline comments.Jul 4 2023, 1:15 PM
sys/cddl/dev/kinst/trampoline.c
140

We are not completely sure that it's a QEMU bug, so I would write "apparent QEMU bug". Also, did you try to reproduce the problem on amd64 in QEMU? The problem might be there too.

(I also don't understand why bitset(9) doesn't work properly in this case and would prefer to have an explanation for that.)

christos abandoned this revision.Jul 4 2023, 1:54 PM

Revision Contents
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PathSize
sys/
cddl/
dev/
kinst/
11 lines

Diff 124155

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sys/cddl/dev/kinst/trampoline.c

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