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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef InterposerHelper_h
#define InterposerHelper_h
#include <type_traits>
#ifdef MOZ_LINKER
# include "Linker.h"
#else
# include <dlfcn.h>
#endif
#include "mozilla/Assertions.h"
template <typename T>
static inline T dlsym_wrapper(void* aHandle, const char* aName) {
#ifdef MOZ_LINKER
return reinterpret_cast<T>(__wrap_dlsym(aHandle, aName));
#else
return reinterpret_cast<T>(dlsym(aHandle, aName));
#endif // MOZ_LINKER
}
static inline void* dlopen_wrapper(const char* aPath, int flags) {
#ifdef MOZ_LINKER
return __wrap_dlopen(aPath, flags);
#else
return dlopen(aPath, flags);
#endif // MOZ_LINKER
}
template <typename T>
static T get_real_symbol(const char* aName, T aReplacementSymbol) {
// T can only be a function pointer
static_assert(std::is_function<typename std::remove_pointer<T>::type>::value);
// Find the corresponding function in the linked libraries
T real_symbol = dlsym_wrapper<T>(RTLD_NEXT, aName);
#if defined(ANDROID)
if (real_symbol == nullptr) {
// On old versions of Android the application runtime links in libc before
// we get a chance to link libmozglue, so its symbols don't appear when
// resolving them with RTLD_NEXT. This behavior differ between the
// different versions of Android so we'll just look for them directly into
// libc.so. Note that this won't work if we're trying to interpose
// functions that are in other libraries, but hopefully we'll never have
// to do that.
void* handle = dlopen_wrapper("libc.so", RTLD_LAZY);
if (handle) {
real_symbol = dlsym_wrapper<T>(handle, aName);
}
}
#endif
if (real_symbol == nullptr) {
MOZ_CRASH_UNSAFE_PRINTF(
"%s() interposition failed but the interposer function is "
"still being called, this won't work!",
aName);
}
if (real_symbol == aReplacementSymbol) {
MOZ_CRASH_UNSAFE_PRINTF(
"We could not obtain the real %s(). Calling the symbol we "
"got would make us enter an infinite loop so stop here instead.",
aName);
}
return real_symbol;
}
#define GET_REAL_SYMBOL(name) get_real_symbol(#name, name)
#endif // InterposerHelper_h
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