Kernel dso support for 'dl_iterate_phdr' function
Kernel provides virtual DSO for stack unwinding/exception handlind info for
signal usage case. Stack unwinding routines use 'dl_iterate_phdr' function
for additional DWARF info gathering from DSOs. Patch enables virtual DSO
enumeration via dl_iterate_phdr function.
Signed-off-by: Sergey Melnikov <sergey.melnikov@intel.com>
Change-Id: Ic2882b28f40b456a088bc1e63c50cbfda7e4a102
diff --git a/libc/bionic/dl_iterate_phdr_static.c b/libc/bionic/dl_iterate_phdr_static.c
index 90ed1b7..fc79ce5 100644
--- a/libc/bionic/dl_iterate_phdr_static.c
+++ b/libc/bionic/dl_iterate_phdr_static.c
@@ -27,39 +27,56 @@
*/
#include <elf.h>
+#include <sys/auxv.h>
#include <sys/types.h>
#include <link.h>
-/* Dynamic binaries get this from the dynamic linker (system/linker), which
- * we don't pull in for static bins. We also don't have a list of so's to
- * iterate over, since there's really only a single monolithic blob of
- * code/data.
- *
- * All we need to do is to find where the executable is in memory, and grab the
- * phdr and phnum from there.
- */
-
/* ld provides this to us in the default link script */
-extern void *__executable_start;
+extern void* __executable_start;
-int
-dl_iterate_phdr(int (*cb)(struct dl_phdr_info *info, size_t size, void *data),
- void *data)
-{
- struct dl_phdr_info dl_info;
- Elf32_Ehdr *ehdr = (Elf32_Ehdr *) &__executable_start;
- Elf32_Phdr *phdr = (Elf32_Phdr *)((unsigned long)ehdr + ehdr->e_phoff);
+int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data), void* data) {
+ Elf32_Ehdr* ehdr = (Elf32_Ehdr*) &__executable_start;
- /* TODO: again, copied from linker.c. Find a better home for this
- * later. */
+ // TODO: again, copied from linker.c. Find a better home for this later.
if (ehdr->e_ident[EI_MAG0] != ELFMAG0) return -1;
if (ehdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
if (ehdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
if (ehdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
- dl_info.dlpi_addr = 0;
- dl_info.dlpi_name = NULL;
- dl_info.dlpi_phdr = phdr;
- dl_info.dlpi_phnum = ehdr->e_phnum;
- return cb(&dl_info, sizeof (struct dl_phdr_info), data);
+ // Dynamic binaries get their dl_iterate_phdr from the dynamic linker, but
+ // static binaries get this. We don't have a list of shared objects to
+ // iterate over, since there's really only a single monolithic blob of
+ // code/data, plus optionally a VDSO.
+
+ struct dl_phdr_info exe_info;
+ exe_info.dlpi_addr = 0;
+ exe_info.dlpi_name = NULL;
+ exe_info.dlpi_phdr = (Elf32_Phdr*) ((unsigned long) ehdr + ehdr->e_phoff);
+ exe_info.dlpi_phnum = ehdr->e_phnum;
+
+#ifdef AT_SYSINFO_EHDR
+ // Try the executable first.
+ int rc = cb(&exe_info, sizeof(exe_info), data);
+ if (rc != 0) {
+ return rc;
+ }
+
+ // Try the VDSO if that didn't work.
+ Elf32_Ehdr* ehdr_vdso = (Elf32_Ehdr*) getauxval(AT_SYSINFO_EHDR);
+ struct dl_phdr_info vdso_info;
+ vdso_info.dlpi_addr = 0;
+ vdso_info.dlpi_name = NULL;
+ vdso_info.dlpi_phdr = (Elf32_Phdr*) ((char*) ehdr_vdso + ehdr_vdso->e_phoff);
+ vdso_info.dlpi_phnum = ehdr_vdso->e_phnum;
+ for (size_t i = 0; i < vdso_info.dlpi_phnum; ++i) {
+ if (vdso_info.dlpi_phdr[i].p_type == PT_LOAD) {
+ vdso_info.dlpi_addr = (Elf32_Addr) ehdr_vdso - vdso_info.dlpi_phdr[i].p_vaddr;
+ break;
+ }
+ }
+ return cb(&vdso_info, sizeof(vdso_info), data);
+#else
+ // There's only the executable to try.
+ return cb(&exe_info, sizeof(exe_info), data);
+#endif
}
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 9c35cfc..386f6dc 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -1586,6 +1586,28 @@
}
/*
+ * This function add vdso to internal dso list.
+ * It helps to stack unwinding through signal handlers.
+ * Also, it makes bionic more like glibc.
+ */
+static void add_vdso(KernelArgumentBlock& args UNUSED) {
+#ifdef AT_SYSINFO_EHDR
+ Elf32_Ehdr* ehdr_vdso = reinterpret_cast<Elf32_Ehdr*>(args.getauxval(AT_SYSINFO_EHDR));
+
+ soinfo* si = soinfo_alloc("[vdso]");
+ si->phdr = reinterpret_cast<Elf32_Phdr*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
+ si->phnum = ehdr_vdso->e_phnum;
+ si->link_map.l_name = si->name;
+ for (size_t i = 0; i < si->phnum; ++i) {
+ if (si->phdr[i].p_type == PT_LOAD) {
+ si->link_map.l_addr = reinterpret_cast<Elf32_Addr>(ehdr_vdso) - si->phdr[i].p_vaddr;
+ break;
+ }
+ }
+#endif
+}
+
+/*
* This code is called after the linker has linked itself and
* fixed it's own GOT. It is safe to make references to externs
* and other non-local data at this point.
@@ -1710,6 +1732,8 @@
exit(EXIT_FAILURE);
}
+ add_vdso(args);
+
si->CallPreInitConstructors();
for (size_t i = 0; gLdPreloads[i] != NULL; ++i) {
diff --git a/tests/Android.mk b/tests/Android.mk
index fe794c4..d94c77c 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -74,6 +74,7 @@
regex_test.cpp \
signal_test.cpp \
stack_protector_test.cpp \
+ stack_unwinding_test.cpp \
stdio_test.cpp \
stdlib_test.cpp \
string_test.cpp \
@@ -87,6 +88,18 @@
test_dynamic_src_files = \
dlfcn_test.cpp \
+include $(CLEAR_VARS)
+LOCAL_MODULE := bionic-unit-tests-unwind-test-impl
+LOCAL_CFLAGS += $(test_c_flags) -fexceptions -fnon-call-exceptions
+LOCAL_SRC_FILES := stack_unwinding_test_impl.c
+include $(BUILD_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := bionic-unit-tests-unwind-test-impl-host
+LOCAL_CFLAGS += $(test_c_flags) -fexceptions -fnon-call-exceptions
+LOCAL_SRC_FILES := stack_unwinding_test_impl.c
+include $(BUILD_HOST_STATIC_LIBRARY)
+
# Build tests for the device (with bionic's .so). Run with:
# adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
include $(CLEAR_VARS)
@@ -97,6 +110,7 @@
LOCAL_SHARED_LIBRARIES += libdl
LOCAL_SRC_FILES := $(test_src_files) $(test_dynamic_src_files)
LOCAL_WHOLE_STATIC_LIBRARIES := bionic-unit-tests-clang
+LOCAL_STATIC_LIBRARIES += bionic-unit-tests-unwind-test-impl
include $(BUILD_NATIVE_TEST)
# Build tests for the device (with bionic's .a). Run with:
@@ -107,7 +121,7 @@
LOCAL_CFLAGS += $(test_c_flags)
LOCAL_FORCE_STATIC_EXECUTABLE := true
LOCAL_SRC_FILES := $(test_src_files)
-LOCAL_STATIC_LIBRARIES += libstlport_static libstdc++ libm libc
+LOCAL_STATIC_LIBRARIES += libstlport_static libstdc++ libm libc bionic-unit-tests-unwind-test-impl
LOCAL_WHOLE_STATIC_LIBRARIES := bionic-unit-tests-clang
include $(BUILD_NATIVE_TEST)
@@ -142,6 +156,7 @@
LOCAL_LDFLAGS += -lpthread -ldl
LOCAL_LDFLAGS += $(test_dynamic_ldflags)
LOCAL_SRC_FILES := $(test_src_files) $(test_dynamic_src_files)
+LOCAL_STATIC_LIBRARIES += bionic-unit-tests-unwind-test-impl-host
include $(BUILD_HOST_NATIVE_TEST)
endif
diff --git a/tests/stack_unwinding_test.cpp b/tests/stack_unwinding_test.cpp
new file mode 100644
index 0000000..3b18daa
--- /dev/null
+++ b/tests/stack_unwinding_test.cpp
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2013 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.
+ */
+
+/*
+ * Contributed by: Intel Corporation
+ */
+
+#include <gtest/gtest.h>
+
+#if defined(i386) // Only our x86 unwinding is good enough. Switch to libunwind?
+
+extern "C" {
+ void do_test();
+}
+
+// We have to say "DeathTest" here so gtest knows to run this test (which exits)
+// in its own process.
+TEST(stack_unwinding_DeathTest, unwinding_through_signal_frame) {
+ ::testing::FLAGS_gtest_death_test_style = "threadsafe";
+ ASSERT_EXIT(do_test(), ::testing::ExitedWithCode(42), "");
+}
+
+#endif
diff --git a/tests/stack_unwinding_test_impl.c b/tests/stack_unwinding_test_impl.c
new file mode 100644
index 0000000..b0099f0
--- /dev/null
+++ b/tests/stack_unwinding_test_impl.c
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 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.
+ */
+
+/*
+ * Contributed by: Intel Corporation
+ */
+
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unwind.h>
+
+#define noinline __attribute__((__noinline__))
+#define unused __attribute__((__unused__))
+
+static noinline _Unwind_Reason_Code stop_fn(int a unused,
+ _Unwind_Action action,
+ _Unwind_Exception_Class b unused, struct _Unwind_Exception* c unused,
+ struct _Unwind_Context* d unused, void* e unused) {
+ if ((action & _UA_END_OF_STACK) != 0) {
+ // We reached the end of the stack without executing foo_cleanup. Test failed.
+ abort();
+ }
+ return _URC_NO_REASON;
+}
+
+static void noinline foo_cleanup(char* param unused) {
+ exit(42);
+}
+
+static void noinline do_crash() {
+ char* ptr = NULL;
+ *ptr = 0; // Deliberately cause a SIGSEGV.
+}
+
+static void noinline foo() {
+ char c1 __attribute__((cleanup(foo_cleanup)));
+ do_crash();
+}
+
+// It's SEGSEGV handler. We start forced stack unwinding here.
+// If libgcc don't find dso for signal frame stack unwinding will be finished.
+// libgcc pass to stop_fn _UA_END_OF_STACK flag.
+// Test pass condition: stack unwinding through signal frame and foo1_handler execution.
+static void noinline sigsegv_handler(int param unused) {
+ struct _Unwind_Exception* exception = (struct _Unwind_Exception*) malloc(sizeof(*exception));
+ memset(&exception->exception_class, 0, sizeof(exception->exception_class));
+ exception->exception_cleanup = 0;
+ _Unwind_ForcedUnwind(exception, stop_fn, 0);
+}
+
+void do_test() {
+ signal(SIGSEGV, &sigsegv_handler);
+ foo();
+}
