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arm64: don't pass user trapframe to kdb_trap()
Needs ReviewPublic

Authored by mhorne on Dec 22 2020, 2:30 PM.

Details

Summary

This effectively undoes the changes made in r321571. While useful, it is
inconsistent with how other architectures handle trapframes. This change
is required to get a working gdb(4) stub on arm64, as otherwise the
backtrace will begin one frame too early.

With D27705, this information can still be obtained via show registers/u.

Diff Detail

Repository
rS FreeBSD src repository - subversion
Lint
Lint OK
Unit
No Unit Test Coverage
Build Status
Buildable 35957
Build 32846: arc lint + arc unit

Event Timeline

This revision is now accepted and ready to land.Dec 30 2020, 9:23 PM
sys/arm64/arm64/trap.c
422–423

You need to remove this so the next instruction is executed

Remove the tf_elr manipulation.

This revision now requires review to proceed.Jan 5 2021, 9:39 PM
jrtc27 added inline comments.
sys/arm64/arm64/trap.c
422–423

Is it not now going to just return and immediately re-trap on the same breakpoint instruction?

sys/arm64/arm64/trap.c
422–423

For ddb, tf_elr is advanced by BKPT_SKIP in db_stop_at_pc. For gdb, the client advances the PC.

Previously this would have been applied to td->td_frame, not frame, hence the need for the manual increment here.

sys/arm64/arm64/trap.c
422–423

Ok thanks