kern: factor out the 'writing' bits of user process coredumping
ClosedPublic
Actions

Authored by kevans on Jul 16 2025, 4:50 AM.

Details

Reviewers

markj
kib

Commits

rG8eb37cd06b34: kern: factor out the 'writing' bits of user process coredumping

Summary

Instead of assuming we have a vnode to dump to, pull out the bits that
describe how to write acoredump into a struct coredump_writer; the ctx in
that is expected to be opaque, but used by write/extend functions. This
should not be a functional change- we change two callers to use the classic
vnode write/extend interface.

This opens us up to other possible targets for coredumps, such as a shmfd.

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Skipped

Unit

Tests Skipped

Build Status

Buildable 65474
Build 62357: arc lint + arc unit

Event Timeline

kevans created this revision.Jul 16 2025, 4:50 AM

Herald added subscribers: olce, imp. · View Herald TranscriptJul 16 2025, 4:50 AM

kevans requested review of this revision.Jul 16 2025, 4:50 AM

Harbormaster completed remote builds in B65474: Diff 158586.Jul 16 2025, 4:50 AM

kevans added a parent revision: D51336: kern: allow kern_shm_open2 of an anonymous preconstructed shmfd.Jul 16 2025, 4:50 AM

kevans added a child revision: D51338: kern: abstract away the vnode coredumper to allow pluggable dumpers.

kib added inline comments.Jul 16 2025, 5:04 AM

sys/kern/kern_exec.c
2002	Move these functions to hypothetical vnode dumper source file.

kevans added a child revision: D51349: kern: move the vnode user coredumper out into its own file.Jul 16 2025, 4:12 PM

kevans marked an inline comment as done.Jul 17 2025, 4:39 AM

kevans added inline comments.

sys/kern/kern_exec.c
2002	I left these alone here and moved them along with everything else in the next commit, since that diff had ended up a bit larger than I expected.

markj accepted this revision.Jul 18 2025, 2:18 PM

This revision is now accepted and ready to land.Jul 18 2025, 2:18 PM

Add an init_fn to the coredump_writer

This gives the caller a chance to do some lazy initialization or record the
coredump parameters. It will be documented in coredumper_register(9) in a later
change in this stack.

The vnode dumper could probably move vnode setup/corefile_open to an init
function and avoid leaving a 0-byte .core file around if sv_imgact is just going
to fail in the early stages anyways (racct/limit checking, compressor_init), but
I decided that that's probably more of a cosmetic issue and punted for now.

This revision now requires review to proceed.Jul 23 2025, 11:30 PM

Harbormaster completed remote builds in B65641: Diff 158965.Jul 23 2025, 11:30 PM