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
26namespace __lsan {
27
28static 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.
31static char linker_placeholder[2 * sizeof(LoadedModule)] ALIGNED(64);
32static LoadedModule *linker = 0;
33
34static bool IsLinker(const char* full_name) {
35  return LibraryNameIs(full_name, kLinkerName);
36}
37
38void 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
55static 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.
86void 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
95static 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
105struct 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.
112static 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).
149void 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