uprobes/core: Optimize probe hits with the help of a counter
Maintain a per-mm counter: number of uprobes that are inserted
on this process address space.
This counter can be used at probe hit time to determine if we
need a lookup in the uprobes rbtree. Everytime a probe gets
inserted successfully, the probe count is incremented and
everytime a probe gets removed, the probe count is decremented.
The new uprobe_munmap hook ensures the count is correct on a
unmap or remap of a region. We expect that once a
uprobe_munmap() is called, the vma goes away. So
uprobe_unregister() finding a probe to unregister would either
mean unmap event hasnt occurred yet or a mmap event on the same
executable file occured after a unmap event.
Additionally, uprobe_mmap hook now also gets called:
a. on every executable vma that is COWed at fork.
b. a vma of interest is newly mapped; breakpoint insertion also
happens at the required address.
On process creation, make sure the probes count in the child is
set correctly.
Special cases that are taken care include:
a. mremap
b. VM_DONTCOPY vmas on fork()
c. insertion/removal races in the parent during fork().
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120330182646.10018.85805.sendpatchset@srdronam.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index 5a863d3..7c112fb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -218,6 +218,7 @@
mutex_lock(&mapping->i_mmap_mutex);
__remove_shared_vm_struct(vma, file, mapping);
mutex_unlock(&mapping->i_mmap_mutex);
+ uprobe_munmap(vma);
}
}
@@ -546,8 +547,14 @@
if (file) {
mapping = file->f_mapping;
- if (!(vma->vm_flags & VM_NONLINEAR))
+ if (!(vma->vm_flags & VM_NONLINEAR)) {
root = &mapping->i_mmap;
+ uprobe_munmap(vma);
+
+ if (adjust_next)
+ uprobe_munmap(next);
+ }
+
mutex_lock(&mapping->i_mmap_mutex);
if (insert) {
/*
@@ -626,6 +633,7 @@
if (remove_next) {
if (file) {
+ uprobe_munmap(next);
fput(file);
if (next->vm_flags & VM_EXECUTABLE)
removed_exe_file_vma(mm);
