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
