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To make the interceptor implementation more flexible, allowing for 2 levels of indirection instead of just 1 in the current scheme (where the intercepted function aliases the interceptor implementation), introduce the notion of an interceptor "trampoline". A trampoline may be a real function (and not just an alias, where aliases of aliases do not work), which will simply forward to the interceptor implementation; the intercepted function will then alias the trampoline: func -[alias]-> trampoline -[call]-> interceptor Make the necessary changes to prepare for introducing real trampolines. This change does not yet introduce any real trampolines, and so trampoline == interceptor, and we currently still just have: func -[alias]-> interceptor NFC. Reviewed By: dvyukov, vitalybuka, MaskRay Differential Revision: https://reviews.llvm.org/D151316
84 lines
2.7 KiB
C++
84 lines
2.7 KiB
C++
//===-- interception_linux.cpp ----------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of AddressSanitizer, an address sanity checker.
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//
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// Linux-specific interception methods.
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//===----------------------------------------------------------------------===//
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#include "interception.h"
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#if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \
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SANITIZER_SOLARIS
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#include <dlfcn.h> // for dlsym() and dlvsym()
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namespace __interception {
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#if SANITIZER_NETBSD
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static int StrCmp(const char *s1, const char *s2) {
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while (true) {
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if (*s1 != *s2)
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return false;
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if (*s1 == 0)
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return true;
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s1++;
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s2++;
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}
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}
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#endif
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static void *GetFuncAddr(const char *name, uptr trampoline) {
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#if SANITIZER_NETBSD
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// FIXME: Find a better way to handle renames
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if (StrCmp(name, "sigaction"))
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name = "__sigaction14";
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#endif
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void *addr = dlsym(RTLD_NEXT, name);
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if (!addr) {
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// If the lookup using RTLD_NEXT failed, the sanitizer runtime library is
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// later in the library search order than the DSO that we are trying to
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// intercept, which means that we cannot intercept this function. We still
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// want the address of the real definition, though, so look it up using
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// RTLD_DEFAULT.
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addr = dlsym(RTLD_DEFAULT, name);
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// In case `name' is not loaded, dlsym ends up finding the actual wrapper.
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// We don't want to intercept the wrapper and have it point to itself.
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if ((uptr)addr == trampoline)
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addr = nullptr;
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}
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return addr;
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}
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bool InterceptFunction(const char *name, uptr *ptr_to_real, uptr func,
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uptr trampoline) {
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void *addr = GetFuncAddr(name, trampoline);
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*ptr_to_real = (uptr)addr;
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return addr && (func == trampoline);
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}
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// dlvsym is a GNU extension supported by some other platforms.
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#if SANITIZER_GLIBC || SANITIZER_FREEBSD || SANITIZER_NETBSD
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static void *GetFuncAddr(const char *name, const char *ver) {
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return dlvsym(RTLD_NEXT, name, ver);
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}
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bool InterceptFunction(const char *name, const char *ver, uptr *ptr_to_real,
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uptr func, uptr trampoline) {
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void *addr = GetFuncAddr(name, ver);
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*ptr_to_real = (uptr)addr;
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return addr && (func == trampoline);
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}
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# endif // SANITIZER_GLIBC || SANITIZER_FREEBSD || SANITIZER_NETBSD
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} // namespace __interception
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#endif // SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD ||
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// SANITIZER_SOLARIS
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