Commit-ID: a83cfeb92132c279b20bbc8ed3cef833b0fe417e
Gitweb: http://git.kernel.org/tip/a83cfeb92132c279b20bbc8ed3cef833b0fe417e
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Tue, 21 Jul 2015 15:40:13 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 31 Jul 2015 10:38:04 +0200
uprobes: Change handle_trampoline() to find the next chain beforehand
No functional changes, preparation.
Add the new helper, find_next_ret_chain(), which finds the first
!chained entry and returns its ->next. Yes, it is suboptimal. We
probably want to turn ->chained into ->start_of_this_chain
pointer and avoid another loop. But this needs the boring
changes in dup_utask(), so lets do this later.
Change the main loop in handle_trampoline() to unwind the stack
until ri is equal to the pointer returned by this new helper.
Tested-by: Pratyush Anand <panand@xxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Acked-by: Anton Arapov <arapov@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150721134013.GA4755@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/uprobes.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4c941fe..98e4d97 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1766,11 +1766,22 @@ handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
up_read(&uprobe->register_rwsem);
}
+static struct return_instance *find_next_ret_chain(struct return_instance *ri)
+{
+ bool chained;
+
+ do {
+ chained = ri->chained;
+ ri = ri->next; /* can't be NULL if chained */
+ } while (chained);
+
+ return ri;
+}
+
static void handle_trampoline(struct pt_regs *regs)
{
struct uprobe_task *utask;
- struct return_instance *ri;
- bool chained;
+ struct return_instance *ri, *next;
utask = current->utask;
if (!utask)
@@ -1780,24 +1791,18 @@ static void handle_trampoline(struct pt_regs *regs)
if (!ri)
goto sigill;
+ next = find_next_ret_chain(ri);
/*
* TODO: we should throw out return_instance's invalidated by
* longjmp(), currently we assume that the probed function always
* returns.
*/
instruction_pointer_set(regs, ri->orig_ret_vaddr);
-
- for (;;) {
+ do {
handle_uretprobe_chain(ri, regs);
-
- chained = ri->chained;
ri = free_ret_instance(ri);
utask->depth--;
-
- if (!chained)
- break;
- BUG_ON(!ri);
- }
+ } while (ri != next);
utask->return_instances = ri;
return;
--
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