Fixes for __cxa_finalize
* Ability to register atexit handler from atexit handler
* Correct way to handle both forms of atexit handler
Bug: https://code.google.com/p/android/issues/detail?id=66595
Bug: 4998315
Change-Id: I39529afaef97b6e1469c21389d54c0d7d175da28
diff --git a/libc/arch-common/bionic/atexit.h b/libc/arch-common/bionic/atexit.h
index 16ae7aa..90aa030 100644
--- a/libc/arch-common/bionic/atexit.h
+++ b/libc/arch-common/bionic/atexit.h
@@ -26,11 +26,20 @@
* SUCH DAMAGE.
*/
+#include <stddef.h>
+
extern void* __dso_handle;
extern int __cxa_atexit(void (*)(void*), void*, void*);
__attribute__ ((visibility ("hidden")))
+void __atexit_handler_wrapper(void* func) {
+ if (func != NULL) {
+ (*(void (*)(void))func)();
+ }
+}
+
+__attribute__ ((visibility ("hidden")))
int atexit(void (*func)(void)) {
- return (__cxa_atexit((void (*)(void*)) func, (void*) 0, &__dso_handle));
+ return (__cxa_atexit(&__atexit_handler_wrapper, func, &__dso_handle));
}
diff --git a/libc/stdlib/atexit.c b/libc/stdlib/atexit.c
index 4e14434..b051e22 100644
--- a/libc/stdlib/atexit.c
+++ b/libc/stdlib/atexit.c
@@ -41,11 +41,52 @@
struct atexit *__atexit;
/*
+ * TODO: Read this before upstreaming:
+ *
+ * As of Apr 2014 there is a bug regaring function type detection logic in
+ * Free/Open/NetBSD implementations of __cxa_finalize().
+ *
+ * What it is about:
+ * First of all there are two kind of atexit handlers:
+ * 1) void handler(void) - this is the regular type
+ * available for to user via atexit(.) function call.
+ *
+ * 2) void internal_handler(void*) - this is the type
+ * __cxa_atexit() function expects. This handler is used
+ * by C++ compiler to register static destructor calls.
+ * Note that calling this function as the handler of type (1)
+ * results in incorrect this pointer in static d-tors.
+ *
+ * What is wrong with BSD implementations:
+ *
+ * They use dso argument to identify the handler type. The problem
+ * with it is dso is also used to identify the handlers associated
+ * with particular dynamic library and allow __cxa_finalize to call correct
+ * set of functions on dlclose(). And it cannot identify both.
+ *
+ * What is correct way to identify function type?
+ *
+ * Consider this:
+ * 1. __cxa_finalize and __cxa_atexit are part of libc and do not have access to hidden
+ * &__dso_handle.
+ * 2. __cxa_atexit has only 3 arguments: function pointer, function argument, dso.
+ * none of them can be reliably used to pass information about handler type.
+ * 3. following http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor (3.3.5.3 - B)
+ * translation of user atexit -> __cxa_atexit(f, NULL, NULL) results in crashes
+ * on exit() after dlclose() of a library with an atexit() call.
+ *
+ * One way to resolve this is to always call second form of handler, which will
+ * result in storing unused argument in register/stack depending on architecture
+ * and should not present any problems.
+ *
+ * Another way is to make them dso-local in one way or the other.
+ */
+
+/*
* Function pointers are stored in a linked list of pages. The list
* is initially empty, and pages are allocated on demand. The first
* function pointer in the first allocated page (the last one in
* the linked list) was reserved for the cleanup function.
- * TODO: switch to the regular FreeBSD/NetBSD atexit implementation.
*
* Outside the following functions, all pages are mprotect()'ed
* to prevent unintentional/malicious corruption.
@@ -94,7 +135,7 @@
__atexit_invalid = 0;
}
fnp = &p->fns[p->ind++];
- fnp->fn_ptr.cxa_func = func;
+ fnp->cxa_func = func;
fnp->fn_arg = arg;
fnp->fn_dso = dso;
if (mprotect(p, pgsize, PROT_READ))
@@ -113,57 +154,59 @@
void
__cxa_finalize(void *dso)
{
- struct atexit *p, *q;
+ struct atexit *p, *q, *original_atexit;
struct atexit_fn fn;
- int n, pgsize = getpagesize();
+ int n, pgsize = getpagesize(), original_ind;
static int call_depth;
if (__atexit_invalid)
return;
-
_ATEXIT_LOCK();
call_depth++;
- for (p = __atexit; p != NULL; p = p->next) {
- for (n = p->ind; --n >= 0;) {
- if (p->fns[n].fn_ptr.cxa_func == NULL)
- continue; /* already called */
- if (dso != NULL && dso != p->fns[n].fn_dso)
- continue; /* wrong DSO */
-
+ p = original_atexit = __atexit;
+ n = original_ind = p != NULL ? p->ind : 0;
+ while (p != NULL) {
+ if (p->fns[n].cxa_func != NULL /* not called */
+ && (dso == NULL || dso == p->fns[n].fn_dso)) { /* correct DSO */
/*
* Mark handler as having been already called to avoid
* dupes and loops, then call the appropriate function.
*/
fn = p->fns[n];
if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
- p->fns[n].fn_ptr.cxa_func = NULL;
+ p->fns[n].cxa_func = NULL;
mprotect(p, pgsize, PROT_READ);
}
+
_ATEXIT_UNLOCK();
-#if ANDROID
- /* it looks like we should always call the function
- * with an argument, even if dso is not NULL. Otherwise
- * static destructors will not be called properly on
- * the ARM.
- */
- (*fn.fn_ptr.cxa_func)(fn.fn_arg);
-#else /* !ANDROID */
- if (dso != NULL)
- (*fn.fn_ptr.cxa_func)(fn.fn_arg);
- else
- (*fn.fn_ptr.std_func)();
-#endif /* !ANDROID */
+ (*fn.cxa_func)(fn.fn_arg);
_ATEXIT_LOCK();
+ // check for new atexit handlers
+ if ((__atexit->ind != original_ind) || (__atexit != original_atexit)) {
+ // need to restart now to preserve correct
+ // call order - LIFO
+ p = original_atexit = __atexit;
+ n = original_ind = p->ind;
+ continue;
+ }
+ }
+ if (n == 0) {
+ p = p->next;
+ n = p != NULL ? p->ind : 0;
+ } else {
+ --n;
}
}
+ --call_depth;
+
/*
* If called via exit(), unmap the pages since we have now run
* all the handlers. We defer this until calldepth == 0 so that
* we don't unmap things prematurely if called recursively.
*/
- if (dso == NULL && --call_depth == 0) {
+ if (dso == NULL && call_depth == 0) {
for (p = __atexit; p != NULL; ) {
q = p;
p = p->next;
diff --git a/libc/stdlib/atexit.h b/libc/stdlib/atexit.h
index 4b3e5ab..2e88ad6 100644
--- a/libc/stdlib/atexit.h
+++ b/libc/stdlib/atexit.h
@@ -37,10 +37,7 @@
int ind; /* next index in this table */
int max; /* max entries >= ATEXIT_SIZE */
struct atexit_fn {
- union {
- void (*std_func)(void);
- void (*cxa_func)(void *);
- } fn_ptr;
+ void (*cxa_func)(void *);
void *fn_arg; /* argument for CXA callback */
void *fn_dso; /* shared module handle */
} fns[1]; /* the table itself */
diff --git a/tests/Android.mk b/tests/Android.mk
index fccf3f1..4e82591 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -210,6 +210,18 @@
include $(LOCAL_PATH)/Android.build.mk
# -----------------------------------------------------------------------------
+# This library used by atexit tests
+# -----------------------------------------------------------------------------
+
+libtest_atexit_src_files := \
+ atexit_testlib.cpp
+
+module := libtest_atexit
+build_type := target
+build_target := SHARED_LIBRARY
+include $(LOCAL_PATH)/Android.build.mk
+
+# -----------------------------------------------------------------------------
# Tests for the device using bionic's .so. Run with:
# adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
# -----------------------------------------------------------------------------
@@ -217,6 +229,7 @@
libBionicTests \
bionic-unit-tests_src_files := \
+ atexit_test.cpp \
dlext_test.cpp \
dlfcn_test.cpp \
@@ -263,11 +276,14 @@
ifeq ($(HOST_OS)-$(HOST_ARCH),linux-x86)
+bionic-unit-tests-glibc_src_files := \
+ atexit_test.cpp \
+
bionic-unit-tests-glibc_whole_static_libraries := \
libBionicStandardTests \
bionic-unit-tests-glibc_ldlibs := \
- -lrt \
+ -lrt -ldl \
module := bionic-unit-tests-glibc
module_tag := optional
diff --git a/tests/atexit_test.cpp b/tests/atexit_test.cpp
new file mode 100644
index 0000000..e52235d
--- /dev/null
+++ b/tests/atexit_test.cpp
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gtest/gtest.h>
+
+#include <dlfcn.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include <string>
+
+TEST(atexit, combined_test) {
+ std::string atexit_call_sequence;
+ bool valid_this_in_static_dtor = false;
+ void* handle = dlopen("libtest_atexit.so", RTLD_NOW);
+ ASSERT_TRUE(handle != NULL);
+
+ void* sym = dlsym(handle, "register_atexit");
+ ASSERT_TRUE(sym != NULL);
+ reinterpret_cast<void (*)(std::string*, bool*)>(sym)(&atexit_call_sequence, &valid_this_in_static_dtor);
+
+ ASSERT_EQ(0, dlclose(handle));
+ // this test verifies atexit call from atexit handler. as well as the order of calls
+ ASSERT_EQ("Humpty Dumpty sat on a wall", atexit_call_sequence);
+ ASSERT_TRUE(valid_this_in_static_dtor);
+}
+
+// TODO: test for static dtor calls from from exit(.) -> __cxa_finalize(NULL)
+
diff --git a/tests/atexit_testlib.cpp b/tests/atexit_testlib.cpp
new file mode 100644
index 0000000..36393e7
--- /dev/null
+++ b/tests/atexit_testlib.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <string>
+
+// use external control number from main test
+static std::string* atexit_sequence = NULL;
+static bool* atexit_valid_this_in_static_dtor = NULL;
+
+class AtExitStaticClass;
+
+static const AtExitStaticClass* valid_this = NULL;
+
+static class AtExitStaticClass {
+public:
+ AtExitStaticClass() { valid_this = this; }
+ ~AtExitStaticClass() {
+ if (atexit_valid_this_in_static_dtor) {
+ *atexit_valid_this_in_static_dtor = (valid_this == this);
+ }
+ }
+} staticObj;
+
+// 4
+static void atexit_handler_from_atexit_from_atexit2() {
+ *atexit_sequence += " on";
+}
+
+// 3
+static void atexit_handler_from_atexit_from_atexit1() {
+ *atexit_sequence += " sat";
+}
+
+// 2
+static void atexit_handler_from_atexit() {
+ *atexit_sequence += " Dumpty";
+ // register 2 others
+ atexit(atexit_handler_from_atexit_from_atexit2);
+ atexit(atexit_handler_from_atexit_from_atexit1);
+}
+
+// 1
+static void atexit_handler_with_atexit() {
+ *atexit_sequence += "Humpty";
+ atexit(atexit_handler_from_atexit);
+}
+
+// last
+static void atexit_handler_regular() {
+ *atexit_sequence += " a wall";
+}
+
+extern "C" void register_atexit(std::string* sequence, bool* valid_this_in_static_dtor) {
+ atexit_sequence = sequence;
+ atexit_valid_this_in_static_dtor = valid_this_in_static_dtor;
+ atexit(atexit_handler_regular);
+ atexit(atexit_handler_with_atexit);
+ atexit(NULL);
+}
+