From: Kris Van Hees <kris.van.hees@oracle.com>
Date: Mon, 26 Jan 2015 21:19:54 +0000 (-0500)
Subject: dtrace: do not vmalloc/vfree from probe context
X-Git-Tag: v4.1.12-92~313^2~18
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=78ae543a2a16bc91eff67f7b096996d593fdb893;p=users%2Fjedix%2Flinux-maple.git

dtrace: do not vmalloc/vfree from probe context

The dtrace_stacktrace() code was using vmalloc/vfree in cases where no
array for PCs was provided (as was the case for getting the stackdepth).
When this code gets called from probe context, we might be processing an
interrupt or trap, and it is not safe to use vmalloc/vfree in that context.
We now pass in a (pre-allocated) scratch buffer instead.

Orabug: 20456889

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Acked-by: Nick Alcock <nick.alcock@oracle.com>
---

diff --git a/kernel/dtrace/dtrace_os.c b/kernel/dtrace/dtrace_os.c
index 3e66613e7ee4..9be9b7379137 100644
--- a/kernel/dtrace/dtrace_os.c
+++ b/kernel/dtrace/dtrace_os.c
@@ -391,9 +391,10 @@ void dtrace_stacktrace(stacktrace_state_t *st)
 	trace.entries = (typeof(trace.entries))st->pcs;
 	trace.skip = st->depth;
 
-	if (st->pcs == NULL)
-		trace.entries = vmalloc(trace.max_entries *
-					sizeof(trace.entries[0]));
+	if (st->pcs == NULL) {
+		st->depth = 0;
+		return;
+	}
 
 	save_stack_trace(&trace);
 
@@ -410,9 +411,6 @@ void dtrace_stacktrace(stacktrace_state_t *st)
 	st->depth = trace.nr_entries;
 #endif
 
-	if (st->pcs == NULL)
-		vfree(trace.entries);
-
 	if (st->fps != NULL) {
 		for (i = 0; i < st->limit; i++)
 			st->fps[i] = 0;