1 /*
2 * Copyright (C) 2024 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "berberis/base/maps_snapshot.h"
18
19 #include <cstdint>
20 #include <cstdio>
21 #include <mutex>
22 #include <optional>
23
24 #include "berberis/base/arena_string.h"
25 #include "berberis/base/forever_alloc.h"
26 #include "berberis/base/tracing.h"
27
28 namespace berberis {
29
GetInstance()30 MapsSnapshot* MapsSnapshot::GetInstance() {
31 static auto* g_maps_snapshot = PrivateNewForever<MapsSnapshot>::Alloc();
32 return g_maps_snapshot;
33 }
34
Update()35 void MapsSnapshot::Update() {
36 std::scoped_lock lock(mutex_);
37
38 FILE* maps_file = fopen("/proc/self/maps", "r");
39 if (!maps_file) {
40 TRACE("Error opening /proc/self/maps");
41 return;
42 }
43
44 maps_.clear();
45
46 char line[512], pathname[256];
47 uintptr_t start, end;
48 while (fgets(line, sizeof(line), maps_file)) {
49 // Maximum string size 255 so that we have space for the terminating '\0'.
50 int match_count = sscanf(
51 line, "%" SCNxPTR "-%" SCNxPTR " %*s %*lx %*x:%*x %*lu%*[ ]%255s", &start, &end, pathname);
52 if (match_count == 2 || match_count == 3) {
53 // If there is no pathname we still memorize the record, so that we can differentiate this
54 // case from missing mapping, e.g. when the snapshot is not up to date.
55 const char* recorded_pathname = (match_count == 3) ? pathname : "";
56 // Addresses go in the increasing order in /proc/self/maps, so we hint to add new records
57 // to the end of the map.
58 maps_.emplace_hint(
59 maps_.end(), start, Record{start, end, ArenaString{recorded_pathname, &arena_}});
60 }
61 }
62
63 fclose(maps_file);
64 }
65
FindMappedObjectName(uintptr_t addr)66 std::optional<const ArenaString> MapsSnapshot::FindMappedObjectName(uintptr_t addr) {
67 std::scoped_lock lock(mutex_);
68 auto next_it = maps_.upper_bound(addr);
69 if (next_it == maps_.begin()) {
70 return std::nullopt;
71 }
72 auto& rec = std::prev(next_it)->second;
73 if (addr >= rec.start && addr < rec.end) {
74 // Make sure we return a copy since the storage may be
75 // invalidated as soon as we release the lock.
76 return rec.pathname;
77 }
78 return std::nullopt;
79 }
80
81 } // namespace berberis
82