1 //=-- lsan_common_linux.cc ------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file is a part of LeakSanitizer.
11 // Implementation of common leak checking functionality. Linux-specific code.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "sanitizer_common/sanitizer_platform.h"
16 #include "lsan_common.h"
17
18 #if CAN_SANITIZE_LEAKS && SANITIZER_LINUX
19 #include <link.h>
20
21 #include "sanitizer_common/sanitizer_common.h"
22 #include "sanitizer_common/sanitizer_flags.h"
23 #include "sanitizer_common/sanitizer_linux.h"
24 #include "sanitizer_common/sanitizer_stackdepot.h"
25
26 namespace __lsan {
27
28 static const char kLinkerName[] = "ld";
29 // We request 2 modules matching "ld", so we can print a warning if there's more
30 // than one match. But only the first one is actually used.
31 static char linker_placeholder[2 * sizeof(LoadedModule)] ALIGNED(64);
32 static LoadedModule *linker = 0;
33
IsLinker(const char * full_name)34 static bool IsLinker(const char* full_name) {
35 return LibraryNameIs(full_name, kLinkerName);
36 }
37
InitializePlatformSpecificModules()38 void InitializePlatformSpecificModules() {
39 internal_memset(linker_placeholder, 0, sizeof(linker_placeholder));
40 uptr num_matches = GetListOfModules(
41 reinterpret_cast<LoadedModule *>(linker_placeholder), 2, IsLinker);
42 if (num_matches == 1) {
43 linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
44 return;
45 }
46 if (num_matches == 0)
47 VReport(1, "LeakSanitizer: Dynamic linker not found. "
48 "TLS will not be handled correctly.\n");
49 else if (num_matches > 1)
50 VReport(1, "LeakSanitizer: Multiple modules match \"%s\". "
51 "TLS will not be handled correctly.\n", kLinkerName);
52 linker = 0;
53 }
54
ProcessGlobalRegionsCallback(struct dl_phdr_info * info,size_t size,void * data)55 static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size,
56 void *data) {
57 Frontier *frontier = reinterpret_cast<Frontier *>(data);
58 for (uptr j = 0; j < info->dlpi_phnum; j++) {
59 const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]);
60 // We're looking for .data and .bss sections, which reside in writeable,
61 // loadable segments.
62 if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) ||
63 (phdr->p_memsz == 0))
64 continue;
65 uptr begin = info->dlpi_addr + phdr->p_vaddr;
66 uptr end = begin + phdr->p_memsz;
67 uptr allocator_begin = 0, allocator_end = 0;
68 GetAllocatorGlobalRange(&allocator_begin, &allocator_end);
69 if (begin <= allocator_begin && allocator_begin < end) {
70 CHECK_LE(allocator_begin, allocator_end);
71 CHECK_LT(allocator_end, end);
72 if (begin < allocator_begin)
73 ScanRangeForPointers(begin, allocator_begin, frontier, "GLOBAL",
74 kReachable);
75 if (allocator_end < end)
76 ScanRangeForPointers(allocator_end, end, frontier, "GLOBAL",
77 kReachable);
78 } else {
79 ScanRangeForPointers(begin, end, frontier, "GLOBAL", kReachable);
80 }
81 }
82 return 0;
83 }
84
85 // Scans global variables for heap pointers.
ProcessGlobalRegions(Frontier * frontier)86 void ProcessGlobalRegions(Frontier *frontier) {
87 if (!flags()->use_globals) return;
88 // FIXME: dl_iterate_phdr acquires a linker lock, so we run a risk of
89 // deadlocking by running this under StopTheWorld. However, the lock is
90 // reentrant, so we should be able to fix this by acquiring the lock before
91 // suspending threads.
92 dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier);
93 }
94
GetCallerPC(u32 stack_id,StackDepotReverseMap * map)95 static uptr GetCallerPC(u32 stack_id, StackDepotReverseMap *map) {
96 CHECK(stack_id);
97 uptr size = 0;
98 const uptr *trace = map->Get(stack_id, &size);
99 // The top frame is our malloc/calloc/etc. The next frame is the caller.
100 if (size >= 2)
101 return trace[1];
102 return 0;
103 }
104
105 struct ProcessPlatformAllocParam {
106 Frontier *frontier;
107 StackDepotReverseMap *stack_depot_reverse_map;
108 };
109
110 // ForEachChunk callback. Identifies unreachable chunks which must be treated as
111 // reachable. Marks them as reachable and adds them to the frontier.
ProcessPlatformSpecificAllocationsCb(uptr chunk,void * arg)112 static void ProcessPlatformSpecificAllocationsCb(uptr chunk, void *arg) {
113 CHECK(arg);
114 ProcessPlatformAllocParam *param =
115 reinterpret_cast<ProcessPlatformAllocParam *>(arg);
116 chunk = GetUserBegin(chunk);
117 LsanMetadata m(chunk);
118 if (m.allocated() && m.tag() != kReachable) {
119 u32 stack_id = m.stack_trace_id();
120 uptr caller_pc = 0;
121 if (stack_id > 0)
122 caller_pc = GetCallerPC(stack_id, param->stack_depot_reverse_map);
123 // If caller_pc is unknown, this chunk may be allocated in a coroutine. Mark
124 // it as reachable, as we can't properly report its allocation stack anyway.
125 if (caller_pc == 0 || linker->containsAddress(caller_pc)) {
126 m.set_tag(kReachable);
127 param->frontier->push_back(chunk);
128 }
129 }
130 }
131
132 // Handles dynamically allocated TLS blocks by treating all chunks allocated
133 // from ld-linux.so as reachable.
134 // Dynamic TLS blocks contain the TLS variables of dynamically loaded modules.
135 // They are allocated with a __libc_memalign() call in allocate_and_init()
136 // (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those
137 // blocks, but we can make sure they come from our own allocator by intercepting
138 // __libc_memalign(). On top of that, there is no easy way to reach them. Their
139 // addresses are stored in a dynamically allocated array (the DTV) which is
140 // referenced from the static TLS. Unfortunately, we can't just rely on the DTV
141 // being reachable from the static TLS, and the dynamic TLS being reachable from
142 // the DTV. This is because the initial DTV is allocated before our interception
143 // mechanism kicks in, and thus we don't recognize it as allocated memory. We
144 // can't special-case it either, since we don't know its size.
145 // Our solution is to include in the root set all allocations made from
146 // ld-linux.so (which is where allocate_and_init() is implemented). This is
147 // guaranteed to include all dynamic TLS blocks (and possibly other allocations
148 // which we don't care about).
ProcessPlatformSpecificAllocations(Frontier * frontier)149 void ProcessPlatformSpecificAllocations(Frontier *frontier) {
150 if (!flags()->use_tls) return;
151 if (!linker) return;
152 StackDepotReverseMap stack_depot_reverse_map;
153 ProcessPlatformAllocParam arg = {frontier, &stack_depot_reverse_map};
154 ForEachChunk(ProcessPlatformSpecificAllocationsCb, &arg);
155 }
156
157 } // namespace __lsan
158 #endif // CAN_SANITIZE_LEAKS && SANITIZER_LINUX
159