.\" @(#) dlopen.3 1.6 90/01/31 SMI
.\" $FreeBSD: head/lib/libc/gen/dlopen.3 211397 2010-08-16 15:18:30Z joel $
.\"
-.Dd April 28, 2011
+.Dd April 6, 2012
.Dt DLOPEN 3
.Os
.Sh NAME
-.Nm dlopen
+.Nm dlopen ,
+.Nm fdlopen
.Nd returns handle to dynamically loaded shared object
.Sh LIBRARY
This function is not in a library.
.In dlfcn.h
.Ft void *
.Fn dlopen "const char *name" "int mode"
+.Ft void *
+.Fn fdlopen "int fd" "int mode"
.Sh DESCRIPTION
The
.Fn dlopen
function
provides access to the shared object in
-.Fa path ,
+.Fa name ,
returning a descriptor that can be used for later
references to the object in calls to other dl functions.
If
option of the static linker
.Xr ld 1 .
.It Dv RTLD_NOLOAD
-Ony return valid handle for the object if it is already loaded in
+Only return valid handle for the object if it is already loaded in
the process address space, otherwise
.Dv NULL
is returned.
Other mode flags may be specified, which will be applied for promotion
for the found object.
.El
-.Sh RETURN VALUE
-The
+.Pp
+If
.Fn dlopen
-function
-returns a null pointer in the event of an error.
+fails, it returns a null pointer, and sets an error condition which may
+be interrogated with
+.Fn dlerror .
+.Pp
The
+.Fn fdlopen
+function is similar to
+.Fn dlopen ,
+but it takes the file descriptor argument
+.Fa fd ,
+which is used for the file operations needed to load an object
+into the address space.
+The file descriptor
+.Fa fd
+is not closed by the function regardless a result of execution,
+but a duplicate of the file descriptor is.
+This may be important if a
+.Xr lockf 3
+lock is held on the passed descriptor.
+The
+.Fa fd
+argument -1 is interpreted as a reference to the main
+executable of the process, similar to
+.Va NULL
+value for the
+.Fa name
+argument to
+.Fn dlopen .
+The
+.Fn fdlopen
+function can be used by the code that needs to perform
+additional checks on the loaded objects, to prevent races with
+symlinking or renames.
+.El
+.Sh RETURN VALUE
+The functions return a null pointer in the event of an error.
Whenever an error has been detected, a message detailing it can be
retrieved via a call to
.Fn dlerror .
static void digest_dynamic(Obj_Entry *, int);
static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
static Obj_Entry *dlcheck(void *);
-static Obj_Entry *dlopen_object(const char *name, Obj_Entry *refobj,
+static Obj_Entry *dlopen_object(const char *name, int fd, Obj_Entry *refobj,
int lo_flags, int mode);
static Obj_Entry *do_load_object(int, const char *, char *, struct stat *, int);
static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
static void unload_filtees(Obj_Entry *);
static int load_needed_objects(Obj_Entry *, int);
static int load_preload_objects(void);
-static Obj_Entry *load_object(const char *, const Obj_Entry *, int);
+static Obj_Entry *load_object(const char *, int fd, const Obj_Entry *, int);
static void map_stacks_exec(RtldLockState *);
static Obj_Entry *obj_from_addr(const void *);
static void objlist_call_fini(Objlist *, Obj_Entry *, RtldLockState *);
int flags, RtldLockState *lockstate);
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 char *search_library_path(const char *, const char *);
static const void **get_program_var_addr(const char *, RtldLockState *);
(func_ptr_type) &dlclose,
(func_ptr_type) &dlerror,
(func_ptr_type) &dlopen,
+ (func_ptr_type) &fdlopen,
(func_ptr_type) &dlfunc,
(func_ptr_type) &dlsym,
(func_ptr_type) &dlvsym,
{
for (; needed != NULL; needed = needed->next) {
- needed->obj = dlopen_object(obj->strtab + needed->name, obj,
+ needed->obj = dlopen_object(obj->strtab + needed->name, -1, obj,
flags, ((ld_loadfltr || obj->z_loadfltr) ? RTLD_NOW : RTLD_LAZY) |
RTLD_LOCAL);
}
Obj_Entry *obj1;
for (; needed != NULL; needed = needed->next) {
- obj1 = needed->obj = load_object(obj->strtab + needed->name, obj,
+ obj1 = needed->obj = load_object(obj->strtab + needed->name, -1, obj,
flags & ~RTLD_LO_NOLOAD);
if (obj1 == NULL && !ld_tracing && (flags & RTLD_LO_FILTEES) == 0)
return (-1);
savech = p[len];
p[len] = '\0';
- obj = load_object(p, NULL, 0);
+ obj = load_object(p, -1, NULL, 0);
if (obj == NULL)
return -1; /* XXX - cleanup */
p[len] = savech;
return 0;
}
+static const char *
+printable_path(const char *path)
+{
+
+ return (path == NULL ? "<unknown>" : path);
+}
+
/*
- * Load a shared object into memory, if it is not already loaded.
+ * Load a shared object into memory, if it is not already loaded. The
+ * object may be specified by name or by user-supplied file descriptor
+ * fd_u. In the later case, the fd_u descriptor is not closed, but its
+ * duplicate is.
*
* Returns a pointer to the Obj_Entry for the object. Returns NULL
* on failure.
*/
static Obj_Entry *
-load_object(const char *name, const Obj_Entry *refobj, int flags)
+load_object(const char *name, int fd_u, const Obj_Entry *refobj, int flags)
{
Obj_Entry *obj;
- int fd = -1;
+ int fd;
struct stat sb;
char *path;
- for (obj = obj_list->next; obj != NULL; obj = obj->next)
- if (object_match_name(obj, name))
- return obj;
+ if (name != NULL) {
+ for (obj = obj_list->next; obj != NULL; obj = obj->next) {
+ if (object_match_name(obj, name))
+ return (obj);
+ }
- path = find_library(name, refobj);
- if (path == NULL)
- return NULL;
+ path = find_library(name, refobj);
+ if (path == NULL)
+ return (NULL);
+ } else
+ path = NULL;
/*
- * If we didn't find a match by pathname, open the file and check
- * again by device and inode. This avoids false mismatches caused
- * by multiple links or ".." in pathnames.
+ * If we didn't find a match by pathname, or the name is not
+ * supplied, open the file and check again by device and inode.
+ * This avoids false mismatches caused by multiple links or ".."
+ * in pathnames.
*
* To avoid a race, we open the file and use fstat() rather than
* using stat().
*/
- if ((fd = open(path, O_RDONLY)) == -1) {
- _rtld_error("Cannot open \"%s\"", path);
- free(path);
- return NULL;
+ fd = -1;
+ if (fd_u == -1) {
+ if ((fd = open(path, O_RDONLY)) == -1) {
+ _rtld_error("Cannot open \"%s\"", path);
+ free(path);
+ return (NULL);
+ }
+ } else {
+ fd = dup(fd_u);
+ if (fd == -1) {
+ _rtld_error("Cannot dup fd");
+ free(path);
+ return (NULL);
+ }
}
if (fstat(fd, &sb) == -1) {
- _rtld_error("Cannot fstat \"%s\"", path);
+ _rtld_error("Cannot fstat \"%s\"", printable_path(path));
close(fd);
free(path);
return NULL;
for (obj = obj_list->next; obj != NULL; obj = obj->next)
if (obj->ino == sb.st_ino && obj->dev == sb.st_dev)
break;
- if (obj != NULL) {
+ if (obj != NULL && name != NULL) {
object_add_name(obj, name);
free(path);
close(fd);
*/
if (dangerous_ld_env) {
if (fstatfs(fd, &fs) != 0) {
- _rtld_error("Cannot fstatfs \"%s\"", path);
+ _rtld_error("Cannot fstatfs \"%s\"", printable_path(path));
return NULL;
}
if (fs.f_flags & MNT_NOEXEC) {
return NULL;
}
}
- dbg("loading \"%s\"", path);
- obj = map_object(fd, path, sbp);
+ dbg("loading \"%s\"", printable_path(path));
+ obj = map_object(fd, printable_path(path), sbp);
if (obj == NULL)
return NULL;
- object_add_name(obj, name);
+ /*
+ * If DT_SONAME is present in the object, digest_dynamic2 already
+ * added it to the object names.
+ */
+ if (name != NULL)
+ object_add_name(obj, name);
obj->path = path;
digest_dynamic(obj, 0);
if (obj->z_noopen && (flags & (RTLD_LO_DLOPEN | RTLD_LO_TRACE)) ==
void *
dlopen(const char *name, int mode)
{
+
+ return (rtld_dlopen(name, -1, mode));
+}
+
+void *
+fdlopen(int fd, int mode)
+{
+
+ return (rtld_dlopen(NULL, fd, mode));
+}
+
+static void *
+rtld_dlopen(const char *name, int fd, int mode)
+{
RtldLockState lockstate;
int lo_flags;
if (ld_tracing != NULL)
lo_flags |= RTLD_LO_TRACE;
- return (dlopen_object(name, obj_main, lo_flags,
+ return (dlopen_object(name, fd, obj_main, lo_flags,
mode & (RTLD_MODEMASK | RTLD_GLOBAL)));
}
}
static Obj_Entry *
-dlopen_object(const char *name, Obj_Entry *refobj, int lo_flags, int mode)
+dlopen_object(const char *name, int fd, Obj_Entry *refobj, int lo_flags,
+ int mode)
{
Obj_Entry **old_obj_tail;
Obj_Entry *obj;
old_obj_tail = obj_tail;
obj = NULL;
- if (name == NULL) {
+ if (name == NULL && fd == -1) {
obj = obj_main;
obj->refcount++;
} else {
- obj = load_object(name, refobj, lo_flags);
+ obj = load_object(name, fd, refobj, lo_flags);
}
if (obj) {
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