linux-kernel - [PATCH v2 tip/perf/core 0/5] uprobes,mm: speculative lockless VMA-to-uprobe lookup

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Message-ID: <20241001225207.2215639-1-andrii@kernel.org>
Date: Tue,  1 Oct 2024 15:52:02 -0700
From: Andrii Nakryiko <andrii@...nel.org>
To: linux-trace-kernel@...r.kernel.org,
	peterz@...radead.org,
	oleg@...hat.com
Cc: rostedt@...dmis.org,
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	surenb@...gle.com,
	akpm@...ux-foundation.org,
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	Andrii Nakryiko <andrii@...nel.org>
Subject: [PATCH v2 tip/perf/core 0/5] uprobes,mm: speculative lockless VMA-to-uprobe lookup

Implement speculative (lockless) resolution of VMA to inode to uprobe,
bypassing the need to take mmap_lock for reads, if possible. Patch #1 by Suren
adds mm_struct helpers that help detect whether mm_struct were changed, which
is used by uprobe logic to validate that speculative results can be trusted
after all the lookup logic results in a valid uprobe instance. Patch #2
follows to make mm_lock_seq into 64-bit counter (on 64-bit architectures).

Patch #3 adds back RCU-delayed freeing for FMODE_BACKING files, which is
necessary to make speculation safe to access struct file's memory in any
possible situation.

Patch #4 is a simplification to uprobe VMA flag checking, suggested by Oleg.

And, finally, patch #5 is the speculative VMA-to-uprobe resolution logic. See
corresponding patch for details and benchmarking results.

v1->v2:
- adjusted vma_end_write_all() comment to point out it should never be called
  manually now, but I wasn't sure how ACQUIRE/RELEASE comments should be
  reworded (previously requested by Jann), so I'd appreciate some help there
  (Jann);
- int -> long change for mm_lock_seq, as agreed at LPC2024 (Jann, Suren, Liam);
- kfree_rcu_mightsleep() for FMODE_BACKING (Suren, Christian);
- vm_flags simplification in find_active_uprobe_rcu() and
  find_active_uprobe_speculative() (Oleg);
- guard(rcu)() simplified find_active_uprobe_speculative() implementation.

Andrii Nakryiko (4):
  mm: switch to 64-bit mm_lock_seq/vm_lock_seq on 64-bit architectures
  fs: add back RCU-delayed freeing of FMODE_BACKING file
  uprobes: simplify find_active_uprobe_rcu() VMA checks
  uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution

Suren Baghdasaryan (1):
  mm: introduce mmap_lock_speculation_{start|end}

 fs/file_table.c           |  2 +-
 include/linux/mm.h        |  6 ++--
 include/linux/mm_types.h  |  7 ++--
 include/linux/mmap_lock.h | 72 ++++++++++++++++++++++++++++++++-------
 kernel/events/uprobes.c   | 46 ++++++++++++++++++++++++-
 kernel/fork.c             |  3 --
 6 files changed, 114 insertions(+), 22 deletions(-)

-- 
2.43.5