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uprobes: Change handle_trampoline() to find the next chain beforehand

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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>
This commit is contained in:
Oleg Nesterov 2015-07-21 15:40:13 +02:00 committed by Ingo Molnar
parent 6c58d0e4cc
commit a83cfeb921
1 changed files with 16 additions and 11 deletions
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27
kernel/events/uprobes.c
View file

@ -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;