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authorOleg Nesterov <oleg@redhat.com>2015-07-21 15:40:13 +0200
committerIngo Molnar <mingo@kernel.org>2015-07-31 10:38:04 +0200
commita83cfeb92132c279b20bbc8ed3cef833b0fe417e (patch)
tree993d56e06db2cf0b927ba39b578cb9310720fdff /kernel/events/uprobes.c
parent6c58d0e4cc26ea8882928e64c0de9afed4fc37cb (diff)
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@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Anton Arapov <arapov@gmail.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150721134013.GA4755@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events/uprobes.c')
-rw-r--r--kernel/events/uprobes.c27
1 files changed, 16 insertions, 11 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4c941feae3a2..98e4d97b8c31 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;