libc: fix executable destruction support.
This change allows an executable to call its destructor functions
(declared with __attribute__((destructor))) to be properly called
when it normally exits.
Note that this is different from calling the destructors of a shared
library when it is unloaded with dlclose() or through program exit,
which are already supported.
Bug: 3106500
Change-Id: I1412ef5407f13b613fc6cb6103e0a691dbee4b1a
diff --git a/libc/bionic/libc_init_common.c b/libc/bionic/libc_init_common.c
index d78d673..f7579bd 100644
--- a/libc/bionic/libc_init_common.c
+++ b/libc/bionic/libc_init_common.c
@@ -84,3 +84,39 @@
/* setup system properties - requires environment */
__system_properties_init();
}
+
+/* This function will be called during normal program termination
+ * to run the destructors that are listed in the .fini_array section
+ * of the executable, if any.
+ *
+ * 'fini_array' points to a list of function addresses. The first
+ * entry in the list has value -1, the last one has value 0.
+ */
+void __libc_fini(void* array)
+{
+ int count;
+ void** fini_array = array;
+ const size_t minus1 = ~(size_t)0; /* ensure proper sign extension */
+
+ /* Sanity check - first entry must be -1 */
+ if (array == NULL || (size_t)fini_array[0] != minus1) {
+ return;
+ }
+
+ /* skip over it */
+ fini_array += 1;
+
+ /* Count the number of destructors. */
+ for (count = 0; fini_array[count] != NULL; count++);
+
+ /* Now call each destructor in reverse order. */
+ while (count > 0) {
+ void (*func)() = (void (*)) fini_array[--count];
+
+ /* Sanity check, any -1 in the list is ignored */
+ if ((size_t)func == minus1)
+ continue;
+
+ func();
+ }
+}
diff --git a/libc/bionic/libc_init_common.h b/libc/bionic/libc_init_common.h
index 8663c61..6016d4d 100644
--- a/libc/bionic/libc_init_common.h
+++ b/libc/bionic/libc_init_common.h
@@ -39,5 +39,6 @@
} structors_array_t;
extern void __libc_init_common(uintptr_t *elfdata);
+extern void __libc_fini(void* finit_array);
#endif
diff --git a/libc/bionic/libc_init_dynamic.c b/libc/bionic/libc_init_dynamic.c
index 682ebcf..f64b6f2 100644
--- a/libc/bionic/libc_init_dynamic.c
+++ b/libc/bionic/libc_init_dynamic.c
@@ -57,9 +57,9 @@
* This ensures that the function is called by the dynamic linker
* as soon as the shared library is loaded.
*/
-void __attribute__((constructor)) __libc_prenit(void);
+void __attribute__((constructor)) __libc_preinit(void);
-void __libc_prenit(void)
+void __libc_preinit(void)
{
/* Read the ELF data pointer form a special slot of the
* TLS area, then call __libc_init_common with it.
@@ -83,14 +83,19 @@
malloc_debug_init();
}
+/* This function is called from the executable's _start entry point
+ * (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
+ * called by the dynamic linker after it has loaded all shared
+ * libraries the executable depends on.
+ *
+ * Note that the dynamic linker has also run all constructors in the
+ * executable at this point.
+ */
__noreturn void __libc_init(uintptr_t *elfdata,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors)
{
- /* When we reach this point, all initializers have been already
- * run by the dynamic linker, so ignore 'structors'.
- */
int argc = (int)*elfdata;
char** argv = (char**)(elfdata + 1);
char** envp = argv + argc + 1;
@@ -99,5 +104,12 @@
* do never use it. Therefore, we ignore it.
*/
+ /* The executable may have its own destructors listed in its .fini_array
+ * so we need to ensure that these are called when the program exits
+ * normally.
+ */
+ if (structors->fini_array)
+ __cxa_atexit(__libc_fini,structors->fini_array,NULL);
+
exit(slingshot(argc, argv, envp));
}
diff --git a/libc/bionic/libc_init_static.c b/libc/bionic/libc_init_static.c
index d097b6b..3634c7b 100644
--- a/libc/bionic/libc_init_static.c
+++ b/libc/bionic/libc_init_static.c
@@ -85,5 +85,12 @@
argv = (char**)(elfdata + 1);
envp = argv + argc + 1;
+ /* The executable may have its own destructors listed in its .fini_array
+ * so we need to ensure that these are called when the program exits
+ * normally.
+ */
+ if (structors->fini_array)
+ __cxa_atexit(__libc_fini,structors->fini_array,NULL);
+
exit(slingshot(argc, argv, envp));
}