1 //===-- interception_linux.cpp ----------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file is a part of AddressSanitizer, an address sanity checker.
10 //
11 // Linux-specific interception methods.
12 //===----------------------------------------------------------------------===//
13 
14 #include "interception.h"
15 
16 #if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \
17     SANITIZER_OPENBSD || SANITIZER_SOLARIS
18 
19 #include <dlfcn.h>   // for dlsym() and dlvsym()
20 
21 namespace __interception {
22 
23 #if SANITIZER_NETBSD
24 static int StrCmp(const char *s1, const char *s2) {
25   while (true) {
26     if (*s1 != *s2)
27       return false;
28     if (*s1 == 0)
29       return true;
30     s1++;
31     s2++;
32   }
33 }
34 #endif
35 
36 static void *GetFuncAddr(const char *name, uptr wrapper_addr) {
37 #if SANITIZER_NETBSD
38   // FIXME: Find a better way to handle renames
39   if (StrCmp(name, "sigaction"))
40     name = "__sigaction14";
41 #endif
42   void *addr = dlsym(RTLD_NEXT, name);
43   if (!addr) {
44     // If the lookup using RTLD_NEXT failed, the sanitizer runtime library is
45     // later in the library search order than the DSO that we are trying to
46     // intercept, which means that we cannot intercept this function. We still
47     // want the address of the real definition, though, so look it up using
48     // RTLD_DEFAULT.
49     addr = dlsym(RTLD_DEFAULT, name);
50 
51     // In case `name' is not loaded, dlsym ends up finding the actual wrapper.
52     // We don't want to intercept the wrapper and have it point to itself.
53     if ((uptr)addr == wrapper_addr)
54       addr = nullptr;
55   }
56   return addr;
57 }
58 
59 bool InterceptFunction(const char *name, uptr *ptr_to_real, uptr func,
60                        uptr wrapper) {
61   void *addr = GetFuncAddr(name, wrapper);
62   *ptr_to_real = (uptr)addr;
63   return addr && (func == wrapper);
64 }
65 
66 // Android and Solaris do not have dlvsym
67 #if !SANITIZER_ANDROID && !SANITIZER_SOLARIS && !SANITIZER_OPENBSD
68 static void *GetFuncAddr(const char *name, const char *ver) {
69   return dlvsym(RTLD_NEXT, name, ver);
70 }
71 
72 bool InterceptFunction(const char *name, const char *ver, uptr *ptr_to_real,
73                        uptr func, uptr wrapper) {
74   void *addr = GetFuncAddr(name, ver);
75   *ptr_to_real = (uptr)addr;
76   return addr && (func == wrapper);
77 }
78 #endif  // !SANITIZER_ANDROID
79 
80 }  // namespace __interception
81 
82 #endif  // SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD ||
83         // SANITIZER_OPENBSD || SANITIZER_SOLARIS
84