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Revamp the mechanism for enumerating and calling shared objects'

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init and fini functions.  Now the code is very careful to hold no
locks when calling these functions.  Thus the dynamic linker cannot
be re-entered with a lock already held.

Remove the tolerance for recursive locking that I added in revision
1.2 of dllockinit.c.  Recursive locking shouldn't happen any more.

Mozilla and JDK users: I'd appreciate confirmation that things still
work right (or at least the same) with these changes.
This commit is contained in:
John Polstra 2000-01-09 21:13:48 +00:00
parent 234c72c615
commit 9bfb1dfc29
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=55687
6 changed files with 183 additions and 135 deletions
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21
libexec/rtld-elf/alpha/lockdflt.c
View File

@ -1,5 +1,5 @@
/*-
* Copyright 1999 John D. Polstra.
* Copyright 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -51,11 +51,8 @@ void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigset_t old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
if (l->depth == 0)
l->old_mask = old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
@ -84,15 +81,7 @@ void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
assert(l->depth >= 0);
if (l->depth == 0)
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}

21
libexec/rtld-elf/amd64/lockdflt.c
View File

@ -1,5 +1,5 @@
/*-
* Copyright 1999 John D. Polstra.
* Copyright 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -51,11 +51,8 @@ void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigset_t old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
if (l->depth == 0)
l->old_mask = old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
@ -84,15 +81,7 @@ void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
assert(l->depth >= 0);
if (l->depth == 0)
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}

21
libexec/rtld-elf/i386/lockdflt.c
View File

@ -1,5 +1,5 @@
/*-
* Copyright 1999 John D. Polstra.
* Copyright 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -51,11 +51,8 @@ void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigset_t old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
if (l->depth == 0)
l->old_mask = old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
@ -84,15 +81,7 @@ void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
assert(l->depth >= 0);
if (l->depth == 0)
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}

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

@ -1,5 +1,5 @@
/*-
* Copyright 1999 John D. Polstra.
* Copyright 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -51,11 +51,8 @@ void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigset_t old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &old_mask);
if (l->depth == 0)
l->old_mask = old_mask;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
@ -84,15 +81,7 @@ void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
assert(l->depth >= 0);
if (l->depth == 0)
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}

216
libexec/rtld-elf/rtld.c
View File

@ -1,5 +1,5 @@
/*-
* Copyright 1996, 1997, 1998, 1999 John D. Polstra.
* Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -73,13 +73,16 @@ typedef struct Struct_LockInfo {
* Function declarations.
*/
static const char *basename(const char *);
static void call_fini_functions(Obj_Entry *);
static void call_init_functions(Obj_Entry *);
static void die(void);
static void digest_dynamic(Obj_Entry *);
static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
static Obj_Entry *dlcheck(void *);
static char *find_library(const char *, const Obj_Entry *);
static void funclist_call(Funclist *);
static void funclist_clear(Funclist *);
static void funclist_init(Funclist *);
static void funclist_push_head(Funclist *, InitFunc);
static void funclist_push_tail(Funclist *, InitFunc);
static const char *gethints(void);
static void init_dag(Obj_Entry *);
static void init_dag1(Obj_Entry *root, Obj_Entry *obj);
@ -102,7 +105,7 @@ static void set_program_var(const char *, const void *);
static const Elf_Sym *symlook_list(const char *, unsigned long,
Objlist *, const Obj_Entry **, bool in_plt);
static void trace_loaded_objects(Obj_Entry *obj);
static void unload_object(Obj_Entry *, bool do_fini_funcs);
static void unload_object(Obj_Entry *);
static void unref_dag(Obj_Entry *);
void r_debug_state(void);
@ -158,7 +161,7 @@ static func_ptr_type exports[] = {
/*
* Global declarations normally provided by crt1. The dynamic linker is
* not build with crt1, so we have to provide them ourselves.
* not built with crt1, so we have to provide them ourselves.
*/
char *__progname;
char **environ;
@ -209,6 +212,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
Elf_Auxinfo *auxp;
const char *argv0;
Obj_Entry *obj;
Funclist initlist;
/*
* On entry, the dynamic linker itself has not been relocated yet.
@ -325,15 +329,22 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
if (load_needed_objects(obj_main) == -1)
die();
for (obj = obj_list; obj != NULL; obj = obj->next)
/*
* Make a list of all objects loaded at startup. Also construct
* the list of init functions to call, in reverse order.
*/
funclist_init(&initlist);
for (obj = obj_list; obj != NULL; obj = obj->next) {
objlist_add(&list_main, obj);
if (obj->init != NULL && !obj->mainprog)
funclist_push_head(&initlist, obj->init);
}
if (ld_tracing) { /* We're done */
trace_loaded_objects(obj_main);
exit(0);
}
dbg("relocating objects");
if (relocate_objects(obj_main,
ld_bind_now != NULL && *ld_bind_now != '\0') == -1)
die();
@ -351,8 +362,10 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
r_debug_state(); /* say hello to gdb! */
dbg("calling _init functions");
call_init_functions(obj_main->next);
funclist_call(&initlist);
wlock_acquire();
funclist_clear(&initlist);
lock_release();
dbg("transferring control to program entry point = %p", obj_main->entry);
@ -417,26 +430,6 @@ basename(const char *name)
return p != NULL ? p + 1 : name;
}
static void
call_fini_functions(Obj_Entry *first)
{
Obj_Entry *obj;
for (obj = first; obj != NULL; obj = obj->next)
if (obj->fini != NULL)
(*obj->fini)();
}
static void
call_init_functions(Obj_Entry *first)
{
if (first != NULL) {
call_init_functions(first->next);
if (first->init != NULL)
(*first->init)();
}
}
static void
die(void)
{
@ -565,11 +558,11 @@ digest_dynamic(Obj_Entry *obj)
break;
case DT_INIT:
obj->init = (void (*)(void)) (obj->relocbase + dynp->d_un.d_ptr);
obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
break;
case DT_FINI:
obj->fini = (void (*)(void)) (obj->relocbase + dynp->d_un.d_ptr);
obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
break;
case DT_DEBUG:
@ -834,6 +827,55 @@ find_symdef(unsigned long symnum, Obj_Entry *refobj,
return def;
}
static void
funclist_call(Funclist *list)
{
Funclist_Entry *elm;
STAILQ_FOREACH(elm, list, link) {
dbg("calling init/fini function at %p", elm->func);
(*elm->func)();
}
}
static void
funclist_clear(Funclist *list)
{
Funclist_Entry *elm;
while (!STAILQ_EMPTY(list)) {
elm = STAILQ_FIRST(list);
STAILQ_REMOVE_HEAD(list, link);
free(elm);
}
}
static void
funclist_init(Funclist *list)
{
STAILQ_INIT(list);
}
static void
funclist_push_head(Funclist *list, InitFunc func)
{
Funclist_Entry *elm;
elm = NEW(Funclist_Entry);
elm->func = func;
STAILQ_INSERT_HEAD(list, elm, link);
}
static void
funclist_push_tail(Funclist *list, InitFunc func)
{
Funclist_Entry *elm;
elm = NEW(Funclist_Entry);
elm->func = func;
STAILQ_INSERT_TAIL(list, elm, link);
}
/*
* Return the search path from the ldconfig hints file, reading it if
* necessary. Returns NULL if there are problems with the hints file,
@ -1214,8 +1256,12 @@ relocate_objects(Obj_Entry *first, bool bind_now)
static void
rtld_exit(void)
{
Obj_Entry *obj;
dbg("rtld_exit()");
call_fini_functions(obj_list->next);
for (obj = obj_list->next; obj != NULL; obj = obj->next)
if (obj->fini != NULL)
(*obj->fini)();
}
static char *
@ -1258,6 +1304,8 @@ int
dlclose(void *handle)
{
Obj_Entry *root;
Obj_Entry *obj;
Funclist finilist;
wlock_acquire();
root = dlcheck(handle);
@ -1266,11 +1314,31 @@ dlclose(void *handle)
return -1;
}
GDB_STATE(RT_DELETE);
unload_object(root, true);
/* Unreference the object and its dependencies. */
root->dl_refcount--;
GDB_STATE(RT_CONSISTENT);
unref_dag(root);
if (root->refcount == 0) {
/*
* The object is no longer referenced, so we must unload it.
* First, make a list of the fini functions and then call them
* with no locks held.
*/
funclist_init(&finilist);
for (obj = obj_list->next; obj != NULL; obj = obj->next)
if (obj->refcount == 0 && obj->fini != NULL)
funclist_push_tail(&finilist, obj->fini);
lock_release();
funclist_call(&finilist);
wlock_acquire();
funclist_clear(&finilist);
/* Finish cleaning up the newly-unreferenced objects. */
GDB_STATE(RT_DELETE);
unload_object(root);
GDB_STATE(RT_CONSISTENT);
}
lock_release();
return 0;
}
@ -1338,6 +1406,10 @@ dlopen(const char *name, int mode)
{
Obj_Entry **old_obj_tail;
Obj_Entry *obj;
Obj_Entry *initobj;
Funclist initlist;
funclist_init(&initlist);
wlock_acquire();
GDB_STATE(RT_ADD);
@ -1363,15 +1435,27 @@ dlopen(const char *name, int mode)
if (load_needed_objects(obj) == -1 ||
(init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) {
unload_object(obj, false);
obj->dl_refcount--;
unref_dag(obj);
if (obj->refcount == 0)
unload_object(obj);
obj = NULL;
} else
call_init_functions(obj);
} else {
/* Make list of init functions to call, in reverse order */
for (initobj = obj; initobj != NULL; initobj = initobj->next)
if (initobj->init != NULL)
funclist_push_head(&initlist, initobj->init);
}
}
}
GDB_STATE(RT_CONSISTENT);
/* Call the init functions with no locks held. */
lock_release();
funclist_call(&initlist);
wlock_acquire();
funclist_clear(&initlist);
lock_release();
return obj;
}
@ -1734,44 +1818,40 @@ trace_loaded_objects(Obj_Entry *obj)
}
/*
* Note, this is called only for objects loaded by dlopen().
* Unload a dlopened object and its dependencies from memory and from
* our data structures. It is assumed that the DAG rooted in the
* object has already been unreferenced, and that the object has a
* reference count of 0.
*/
static void
unload_object(Obj_Entry *root, bool do_fini_funcs)
unload_object(Obj_Entry *root)
{
unref_dag(root);
if (root->refcount == 0) { /* We are finished with some objects. */
Obj_Entry *obj;
Obj_Entry **linkp;
Objlist_Entry *elm;
Obj_Entry *obj;
Obj_Entry **linkp;
Objlist_Entry *elm;
/* Finalize objects that are about to be unmapped. */
if (do_fini_funcs)
for (obj = obj_list->next; obj != NULL; obj = obj->next)
if (obj->refcount == 0 && obj->fini != NULL)
(*obj->fini)();
assert(root->refcount == 0);
/* Remove the DAG from all objects' DAG lists. */
STAILQ_FOREACH(elm, &root->dagmembers , link)
objlist_remove(&elm->obj->dldags, root);
/* Remove the DAG from all objects' DAG lists. */
STAILQ_FOREACH(elm, &root->dagmembers , link)
objlist_remove(&elm->obj->dldags, root);
/* Remove the DAG from the RTLD_GLOBAL list. */
objlist_remove(&list_global, root);
/* Remove the DAG from the RTLD_GLOBAL list. */
objlist_remove(&list_global, root);
/* Unmap all objects that are no longer referenced. */
linkp = &obj_list->next;
while ((obj = *linkp) != NULL) {
if (obj->refcount == 0) {
dbg("unloading \"%s\"", obj->path);
munmap(obj->mapbase, obj->mapsize);
linkmap_delete(obj);
*linkp = obj->next;
obj_free(obj);
} else
linkp = &obj->next;
}
obj_tail = linkp;
/* Unmap all objects that are no longer referenced. */
linkp = &obj_list->next;
while ((obj = *linkp) != NULL) {
if (obj->refcount == 0) {
dbg("unloading \"%s\"", obj->path);
munmap(obj->mapbase, obj->mapsize);
linkmap_delete(obj);
*linkp = obj->next;
obj_free(obj);
} else
linkp = &obj->next;
}
obj_tail = linkp;
}
static void

18
libexec/rtld-elf/rtld.h
View File

@ -1,5 +1,5 @@
/*-
* Copyright 1996-1998 John D. Polstra.
* Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -52,6 +52,7 @@ typedef unsigned char bool;
struct stat;
struct Struct_Obj_Entry;
/* Lists of shared objects */
typedef struct Struct_Objlist_Entry {
STAILQ_ENTRY(Struct_Objlist_Entry) link;
struct Struct_Obj_Entry *obj;
@ -59,6 +60,17 @@ typedef struct Struct_Objlist_Entry {
typedef STAILQ_HEAD(Struct_Objlist, Struct_Objlist_Entry) Objlist;
/* Lists of init or fini functions */
typedef void (*InitFunc)(void);
typedef struct Struct_Funclist_Entry {
STAILQ_ENTRY(Struct_Funclist_Entry) link;
InitFunc func;
} Funclist_Entry;
typedef STAILQ_HEAD(Struct_Funclist, Struct_Funclist_Entry) Funclist;
/* Lists of shared object dependencies */
typedef struct Struct_Needed_Entry {
struct Struct_Needed_Entry *next;
struct Struct_Obj_Entry *obj;
@ -122,8 +134,8 @@ typedef struct Struct_Obj_Entry {
const char *rpath; /* Search path specified in object */
Needed_Entry *needed; /* Shared objects needed by this one (%) */
void (*init)(void); /* Initialization function to call */
void (*fini)(void); /* Termination function to call */
InitFunc init; /* Initialization function to call */
InitFunc fini; /* Termination function to call */
bool mainprog; /* True if this is the main program */
bool rtld; /* True if this is the dynamic linker */