linux/kernel/events
Oleg Nesterov d790d34653 uprobes: Teach find_active_uprobe() to provide the "is_swbp" info
A separate patch to simplify the review, and for the
documentation.

The patch adds another "int *is_swbp" argument to
find_active_uprobe(), so far its only caller doesn't use this
info.

With this patch find_active_uprobe() additionally does:

	- if find_vma() + ->vm_start check fails, *is_swbp = -EFAULT

	- otherwise, if valid_vma() + find_uprobe() fails, it holds
	  the result of is_swbp_at_addr(), can be negative too. The
	  latter is only possible if we raced with another thread
	  which did munmap/etc after we hit this bp.

IOW. If find_active_uprobe(&is_swbp) returns NULL, the caller
can look at is_swbp to figure out whether the current insn is bp
or not, or detect the race with another thread if it is
negative.

Note: I think that performance-wise this change is fine. This
adds is_swbp_at_addr(), but only if we raced with
uprobe_unregister() or if we hit the "normal" int3 but this mm
has uprobes as well. And even in this case the slow
read_opcode() path is very unlikely, this insn recently
triggered do_int3(), __copy_from_user_inatomic() shouldn't fail
in the likely case.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192914.GD8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-06-06 17:15:24 +02:00
..
callchain.c perf: Don't call release_callchain_buffers() if allocation fails 2012-01-21 09:33:41 +01:00
core.c perf: Remove duplicate invocation on perf_event_for_each 2012-05-31 14:01:00 -03:00
hw_breakpoint.c Merge branch 'x86/cleanups' into perf/uprobes 2012-03-13 16:33:03 +01:00
internal.h Merge branch 'perf/urgent' into perf/core 2011-12-06 06:43:49 +01:00
Makefile uprobes: Move to kernel/events/ 2012-02-22 11:08:00 +01:00
ring_buffer.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-01-08 13:21:22 -08:00
uprobes.c uprobes: Teach find_active_uprobe() to provide the "is_swbp" info 2012-06-06 17:15:24 +02:00