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Subject[PATCH 06/14] perf callchain: Reference count maps
Date
From: Krister Johansen <kjlx@templeofstupid.com>

If dso__load_kcore frees all of the existing maps, but one has already
been attached to a callchain cursor node, then we can get a SIGSEGV in
any function that happens to try to use this invalid cursor. Use the
existing map refcount mechanism to forestall cleanup of a map until the
cursor iterates past the node.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: stable@kernel.org
Fixes: 84c2cafa2889 ("perf tools: Reference count struct map")
Link: http://lkml.kernel.org/r/20170106062331.GB2707@templeofstupid.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/callchain.c | 11 +++++++++--
tools/perf/util/callchain.h | 6 ++++++
tools/perf/util/hist.c | 7 +++++++
3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
index e16db30dfe40..aba953421a03 100644
--- a/tools/perf/util/callchain.c
+++ b/tools/perf/util/callchain.c
@@ -449,7 +449,7 @@ fill_node(struct callchain_node *node, struct callchain_cursor *cursor)
}
call->ip = cursor_node->ip;
call->ms.sym = cursor_node->sym;
- call->ms.map = cursor_node->map;
+ call->ms.map = map__get(cursor_node->map);

if (cursor_node->branch) {
call->branch_count = 1;
@@ -489,6 +489,7 @@ add_child(struct callchain_node *parent,

list_for_each_entry_safe(call, tmp, &new->val, list) {
list_del(&call->list);
+ map__zput(call->ms.map);
free(call);
}
free(new);
@@ -773,6 +774,7 @@ merge_chain_branch(struct callchain_cursor *cursor,
list->ms.map, list->ms.sym,
false, NULL, 0, 0);
list_del(&list->list);
+ map__zput(list->ms.map);
free(list);
}

@@ -823,7 +825,8 @@ int callchain_cursor_append(struct callchain_cursor *cursor,
}

node->ip = ip;
- node->map = map;
+ map__zput(node->map);
+ node->map = map__get(map);
node->sym = sym;
node->branch = branch;
node->nr_loop_iter = nr_loop_iter;
@@ -1154,11 +1157,13 @@ static void free_callchain_node(struct callchain_node *node)

list_for_each_entry_safe(list, tmp, &node->parent_val, list) {
list_del(&list->list);
+ map__zput(list->ms.map);
free(list);
}

list_for_each_entry_safe(list, tmp, &node->val, list) {
list_del(&list->list);
+ map__zput(list->ms.map);
free(list);
}

@@ -1222,6 +1227,7 @@ int callchain_node__make_parent_list(struct callchain_node *node)
goto out;
*new = *chain;
new->has_children = false;
+ map__get(new->ms.map);
list_add_tail(&new->list, &head);
}
parent = parent->parent;
@@ -1242,6 +1248,7 @@ int callchain_node__make_parent_list(struct callchain_node *node)
out:
list_for_each_entry_safe(chain, new, &head, list) {
list_del(&chain->list);
+ map__zput(chain->ms.map);
free(chain);
}
return -ENOMEM;
diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
index 35c8e379530f..4f4b60f1558a 100644
--- a/tools/perf/util/callchain.h
+++ b/tools/perf/util/callchain.h
@@ -5,6 +5,7 @@
#include <linux/list.h>
#include <linux/rbtree.h>
#include "event.h"
+#include "map.h"
#include "symbol.h"

#define HELP_PAD "\t\t\t\t"
@@ -184,8 +185,13 @@ int callchain_merge(struct callchain_cursor *cursor,
*/
static inline void callchain_cursor_reset(struct callchain_cursor *cursor)
{
+ struct callchain_cursor_node *node;
+
cursor->nr = 0;
cursor->last = &cursor->first;
+
+ for (node = cursor->first; node != NULL; node = node->next)
+ map__zput(node->map);
}

int callchain_cursor_append(struct callchain_cursor *cursor, u64 ip,
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index cff2e9041b15..32c6a939e4cc 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1,6 +1,7 @@
#include "util.h"
#include "build-id.h"
#include "hist.h"
+#include "map.h"
#include "session.h"
#include "sort.h"
#include "evlist.h"
@@ -1019,6 +1020,10 @@ int hist_entry_iter__add(struct hist_entry_iter *iter, struct addr_location *al,
int max_stack_depth, void *arg)
{
int err, err2;
+ struct map *alm = NULL;
+
+ if (al && al->map)
+ alm = map__get(al->map);

err = sample__resolve_callchain(iter->sample, &callchain_cursor, &iter->parent,
iter->evsel, al, max_stack_depth);
@@ -1058,6 +1063,8 @@ int hist_entry_iter__add(struct hist_entry_iter *iter, struct addr_location *al,
if (!err)
err = err2;

+ map__put(alm);
+
return err;
}

--
2.9.3
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