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Fix order of destructors between main binary and libraries.

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Since inits for the main binary are run from rtld (for some time), the
rtld_exit atexit(3) handler, which is passed from rtld to the program
entry and installed by csu, is installed after any atexit(3) handlers
installed by main binary constructors.  This means that rtld_exit() is
fired before main binary handlers.

Typical C++ static constructors are executed from init (either binary
or libs) but use atexit(3) to ensure that destructors are called in
the right order, independent of the linking order.  Also, C++
libraries finalizers call __cxa_finalize(3) to flush library'
atexit(3) entries.  Since atexit(3) entry is cleared after being run,
this would be mostly innocent, except that, atexit(rtld_exit) done
after main binary constructors, makes destructors from libraries
executed before destructors for main.

Fix by reordering atexit(rtld_exit) before inits for main binary, same
as it happened when inits were called by csu.  Do it using new private
libc symbol with pre-defined ABI.

Reported. tested, and reviewed by:	kan
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2019-04-15 13:03:09 +00:00
parent dad02d7d08
commit 760e34772c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=346225
3 changed files with 22 additions and 1 deletions
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1
lib/libc/stdlib/Symbol.map
View File

@ -129,4 +129,5 @@ FBSDprivate_1.0 {
_system;
__libc_system;
__cxa_thread_call_dtors;
__libc_atexit;
};

1
lib/libc/stdlib/atexit.c
View File

@ -142,6 +142,7 @@ atexit(void (*func)(void))
error = atexit_register(&fn);
return (error);
}
__weak_reference(atexit, __libc_atexit);
/**
* Register a block to be performed at exit.

21
libexec/rtld-elf/rtld.c
View File

@ -151,6 +151,7 @@ static int rtld_dirname(const char *, char *);
static int rtld_dirname_abs(const char *, char *);
static void *rtld_dlopen(const char *name, int fd, int mode);
static void rtld_exit(void);
static void rtld_nop_exit(void);
static char *search_library_path(const char *, const char *, const char *,
int *);
static char *search_library_pathfds(const char *, const char *, int *);
@ -295,6 +296,8 @@ const char *ld_path_rtld = _PATH_RTLD;
const char *ld_standard_library_path = STANDARD_LIBRARY_PATH;
const char *ld_env_prefix = LD_;
static void (*rtld_exit_ptr)(void);
/*
* Fill in a DoneList with an allocation large enough to hold all of
* the currently-loaded objects. Keep this as a macro since it calls
@ -756,6 +759,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
*ld_bind_now != '\0', SYMLOOK_EARLY, &lockstate) == -1)
rtld_die();
rtld_exit_ptr = rtld_exit;
if (obj_main->crt_no_init)
preinit_main();
objlist_call_init(&initlist, &lockstate);
@ -778,7 +782,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
dbg("transferring control to program entry point = %p", obj_main->entry);
/* Return the exit procedure and the program entry point. */
*exit_proc = rtld_exit;
*exit_proc = rtld_exit_ptr;
*objp = obj_main;
return (func_ptr_type) obj_main->entry;
}
@ -2662,6 +2666,7 @@ objlist_call_init(Objlist *list, RtldLockState *lockstate)
Obj_Entry *obj;
char *saved_msg;
Elf_Addr *init_addr;
void (*reg)(void (*)(void));
int index;
/*
@ -2690,7 +2695,16 @@ objlist_call_init(Objlist *list, RtldLockState *lockstate)
*/
elm->obj->init_done = true;
hold_object(elm->obj);
reg = NULL;
if (elm->obj == obj_main && obj_main->crt_no_init) {
reg = (void (*)(void (*)(void)))get_program_var_addr(
"__libc_atexit", lockstate);
}
lock_release(rtld_bind_lock, lockstate);
if (reg != NULL) {
reg(rtld_exit);
rtld_exit_ptr = rtld_nop_exit;
}
/*
* It is legal to have both DT_INIT and DT_INIT_ARRAY defined.
@ -3004,6 +3018,11 @@ rtld_exit(void)
lock_release(rtld_bind_lock, &lockstate);
}
static void
rtld_nop_exit(void)
{
}
/*
* Iterate over a search path, translate each element, and invoke the
* callback on the result.