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Differential D59280

dtrace/arm: Fix and de-pessimize dtrace_copy
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Authored by freebsd_dev.thsi.be on Aug 30 2026, 10:51 PM.
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andrew
fuz
gnn
markj
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rGc874d312e78f: dtrace/arm: Fix and de-pessimize dtrace_copy
Summary

Use an unprivileged load to access user memory from dtrace_copy, which
is running in SVC mode.

Abort the loop if the load is trapped, as it is useless, hence
wasteful, to keep faulting on successive addresses. I believe that
this de-pessimization should also be done on aarch64 and riscv.

PR: 298064
MFC after: 1 month

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rG FreeBSD src repository
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Event Timeline

freebsd_dev.thsi.be created this revision.Aug 30 2026, 10:51 PM
Herald added a subscriber: imp. · View Herald TranscriptAug 30 2026, 10:51 PM
freebsd_dev.thsi.be requested review of this revision.Aug 30 2026, 10:51 PM
Harbormaster completed remote builds in B76339: Diff 185460.Aug 30 2026, 10:51 PM
freebsd_dev.thsi.be added a parent revision: D59279: sys/arm: Fix DTrace trap hook.Aug 30 2026, 10:51 PM
freebsd_dev.thsi.be added a child revision: D59281: dtrace/arm: Really trap translation faults.
freebsd_dev.thsi.be updated this revision to Diff 185502.Aug 31 2026, 5:46 PM
Harbormaster completed remote builds in B76354: Diff 185502.Aug 31 2026, 5:46 PM
markj accepted this revision.Sep 2 2026, 1:15 PM
This revision is now accepted and ready to land.Sep 2 2026, 1:15 PM
Closed by commit rGc874d312e78f: dtrace/arm: Fix and de-pessimize dtrace_copy (authored by freebsd_dev.thsi.be, committed by markj). · Explain WhySep 3 2026, 3:05 PM
This revision was automatically updated to reflect the committed changes.
markj added a commit: rGc874d312e78f: dtrace/arm: Fix and de-pessimize dtrace_copy.
freebsd_dev.thsi.be mentioned this in D59341: dtrace/arm64: de-pessimize dtrace_copy.Sep 3 2026, 3:13 PM

Revision Contents
Changeset List

PathSize
sys/
cddl/
dev/
dtrace/
arm/
11 lines

Diff 185706

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sys/cddl/dev/dtrace/arm/dtrace_asm.S

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