ldso: support RTLD_NOLOAD

So application query if specified module is loaded or not with
dlopen.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

ldso/include/dl-elf.h

@@ -26,16 +26,18 @@ static __inline__ void _dl_map_cache(void) { }
 static __inline__ void _dl_unmap_cache(void) { }
 #endif
 
+#define DL_RESOLVE_SECURE		0x0001
+#define DL_RESOLVE_NOLOAD		0x0002
 
 /* Function prototypes for non-static stuff in readelflib1.c */
 extern void _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
 	unsigned long rel_addr, unsigned long rel_size);
 extern int _dl_parse_relocation_information(struct dyn_elf *rpnt,
 	struct r_scope_elem *scope, unsigned long rel_addr, unsigned long rel_size);
-extern struct elf_resolve * _dl_load_shared_library(int secure,
+extern struct elf_resolve * _dl_load_shared_library(unsigned rflags,
 	struct dyn_elf **rpnt, struct elf_resolve *tpnt, char *full_libname,
 	int trace_loaded_objects);
-extern struct elf_resolve * _dl_load_elf_shared_library(int secure,
+extern struct elf_resolve * _dl_load_elf_shared_library(unsigned rflags,
 	struct dyn_elf **rpnt, const char *libname);
 extern struct elf_resolve *_dl_check_if_named_library_is_loaded(const char *full_libname,
 	int trace_loaded_objects);

ldso/ldso/dl-elf.c

@@ -132,7 +132,7 @@ _dl_protect_relro (struct elf_resolve *l)
 /* This function's behavior must exactly match that
  * in uClibc/ldso/util/ldd.c */
 static struct elf_resolve *
-search_for_named_library(const char *name, int secure, const char *path_list,
+search_for_named_library(const char *name, unsigned rflags, const char *path_list,
 	struct dyn_elf **rpnt)
 {
 	char *path, *path_n, *mylibname;
@@ -174,7 +174,7 @@ search_for_named_library(const char *name, int secure, const char *path_list,
 				_dl_strcpy(mylibname, "."); /* Assume current dir if empty path */
 			_dl_strcat(mylibname, "/");
 			_dl_strcat(mylibname, name);
-			if ((tpnt = _dl_load_elf_shared_library(secure, rpnt, mylibname)) != NULL)
+			if ((tpnt = _dl_load_elf_shared_library(rflags, rpnt, mylibname)) != NULL)
 				return tpnt;
 			path_n = path+1;
 		}
@@ -187,7 +187,7 @@ search_for_named_library(const char *name, int secure, const char *path_list,
 unsigned long _dl_error_number;
 unsigned long _dl_internal_error_number;
 
-struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
+struct elf_resolve *_dl_load_shared_library(unsigned rflags, struct dyn_elf **rpnt,
 	struct elf_resolve *tpnt, char *full_libname, int attribute_unused trace_loaded_objects)
 {
 	char *pnt;
@@ -216,7 +216,7 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 
 	if (libname != full_libname) {
 		_dl_if_debug_dprint("\ttrying file='%s'\n", full_libname);
-		tpnt1 = _dl_load_elf_shared_library(secure, rpnt, full_libname);
+		tpnt1 = _dl_load_elf_shared_library(rflags, rpnt, full_libname);
 		if (tpnt1) {
 			return tpnt1;
 		}
@@ -231,7 +231,7 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 	if (pnt) {
 		pnt += (unsigned long) tpnt->dynamic_info[DT_STRTAB];
 		_dl_if_debug_dprint("\tsearching RPATH='%s'\n", pnt);
-		if ((tpnt1 = search_for_named_library(libname, secure, pnt, rpnt)) != NULL)
+		if ((tpnt1 = search_for_named_library(libname, rflags, pnt, rpnt)) != NULL)
 			return tpnt1;
 	}
 #endif
@@ -240,7 +240,7 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 	/* Check in LD_{ELF_}LIBRARY_PATH, if specified and allowed */
 	if (_dl_library_path) {
 		_dl_if_debug_dprint("\tsearching LD_LIBRARY_PATH='%s'\n", _dl_library_path);
-		if ((tpnt1 = search_for_named_library(libname, secure, _dl_library_path, rpnt)) != NULL)
+		if ((tpnt1 = search_for_named_library(libname, rflags, _dl_library_path, rpnt)) != NULL)
 		{
 			return tpnt1;
 		}
@@ -254,7 +254,7 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 	if (pnt) {
 		pnt += (unsigned long) tpnt->dynamic_info[DT_STRTAB];
 		_dl_if_debug_dprint("\tsearching RUNPATH='%s'\n", pnt);
-		if ((tpnt1 = search_for_named_library(libname, secure, pnt, rpnt)) != NULL)
+		if ((tpnt1 = search_for_named_library(libname, rflags, pnt, rpnt)) != NULL)
 			return tpnt1;
 	}
 #endif
@@ -277,7 +277,7 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 			     || libent[i].flags == LIB_ELF_LIBC0
 			     ||	libent[i].flags == LIB_ELF_LIBC5)
 			 && _dl_strcmp(libname, strs + libent[i].sooffset) == 0
-			 && (tpnt1 = _dl_load_elf_shared_library(secure, rpnt, strs + libent[i].liboffset))
+			 && (tpnt1 = _dl_load_elf_shared_library(rflags, rpnt, strs + libent[i].liboffset))
 			) {
 				return tpnt1;
 			}
@@ -288,14 +288,14 @@ struct elf_resolve *_dl_load_shared_library(int secure, struct dyn_elf **rpnt,
 	/* Look for libraries wherever the shared library loader
 	 * was installed */
 	_dl_if_debug_dprint("\tsearching ldso dir='%s'\n", _dl_ldsopath);
-	tpnt1 = search_for_named_library(libname, secure, _dl_ldsopath, rpnt);
+	tpnt1 = search_for_named_library(libname, rflags, _dl_ldsopath, rpnt);
 	if (tpnt1 != NULL)
 		return tpnt1;
 #endif
 	/* Lastly, search the standard list of paths for the library.
 	   This list must exactly match the list in uClibc/ldso/util/ldd.c */
 	_dl_if_debug_dprint("\tsearching full lib path list\n");
-	tpnt1 = search_for_named_library(libname, secure,
+	tpnt1 = search_for_named_library(libname, rflags,
 					UCLIBC_RUNTIME_PREFIX "lib:"
 					UCLIBC_RUNTIME_PREFIX "usr/lib"
 #ifndef __LDSO_CACHE_SUPPORT__
@@ -437,7 +437,7 @@ map_writeable (int infile, ElfW(Phdr) *ppnt, int piclib, int flags,
  * are required.
  */
 
-struct elf_resolve *_dl_load_elf_shared_library(int secure,
+struct elf_resolve *_dl_load_elf_shared_library(unsigned rflags,
 	struct dyn_elf **rpnt, const char *libname)
 {
 	ElfW(Ehdr) *epnt;
@@ -474,9 +474,9 @@ struct elf_resolve *_dl_load_elf_shared_library(int secure,
 		_dl_close(infile);
 		return NULL;
 	}
-	/* If we are in secure mode (i.e. a setu/gid binary using LD_PRELOAD),
+	/* If we are in secure mode (i.e. a setuid/gid binary using LD_PRELOAD),
 	   we don't load the library if it isn't setuid. */
-	if (secure) {
+	if (rflags & DL_RESOLVE_SECURE) {
 		if (!(st.st_mode & S_ISUID)) {
 			_dl_close(infile);
 			return NULL;
@@ -492,6 +492,10 @@ struct elf_resolve *_dl_load_elf_shared_library(int secure,
 			return tpnt;
 		}
 	}
+	if (rflags & DL_RESOLVE_NOLOAD) {
+		_dl_close(infile);
+		return NULL;
+	}
 	header = _dl_mmap((void *) 0, _dl_pagesize, PROT_READ | PROT_WRITE,
 			MAP_PRIVATE | MAP_ANONYMOUS | MAP_UNINITIALIZE, -1, 0);
 	if (_dl_mmap_check_error(header)) {

ldso/ldso/ldso.c

@@ -858,7 +858,9 @@ of this helper program; chances are you did not intend to run this program.\n\
 			if (!_dl_secure || _dl_strchr(str, '/') == NULL) {
 				_dl_if_debug_dprint("\tfile='%s';  needed by '%s'\n", str, _dl_progname);
 
-				tpnt1 = _dl_load_shared_library(_dl_secure, &rpnt, NULL, str, trace_loaded_objects);
+				tpnt1 = _dl_load_shared_library(
+					_dl_secure ? DL_RESOLVE_SECURE : 0,
+					&rpnt, NULL, str, trace_loaded_objects);
 				if (!tpnt1) {
 #ifdef __LDSO_LDD_SUPPORT__
 					if (trace_loaded_objects || _dl_trace_prelink)

ldso/libdl/libdl.c

@@ -52,11 +52,13 @@ extern struct link_map *_dl_update_slotinfo(unsigned long int req_modid);
 
 /* When libdl is loaded as a shared library, we need to load in
  * and use a pile of symbols from ldso... */
-
-extern struct elf_resolve * _dl_load_shared_library(int, struct dyn_elf **,
+#include <dl-elf.h>
+#if 0
+extern struct elf_resolve * _dl_load_shared_library(unsigned, struct dyn_elf **,
 	struct elf_resolve *, char *, int);
 extern int _dl_fixup(struct dyn_elf *rpnt, struct r_scope_elem *scope, int lazy);
 extern void _dl_protect_relro(struct elf_resolve * tpnt);
+#endif
 extern int _dl_errno;
 extern struct dyn_elf *_dl_symbol_tables;
 extern struct dyn_elf *_dl_handles;
@@ -308,7 +310,7 @@ void *dlopen(const char *libname, int flag)
 #endif
 
 	/* A bit of sanity checking... */
-	if (!(flag & (RTLD_LAZY|RTLD_NOW))) {
+	if (!(flag & (RTLD_LAZY|RTLD_NOW|RTLD_NOLOAD))) {
 		_dl_error_number = LD_BAD_HANDLE;
 		return NULL;
 	}
@@ -378,8 +380,9 @@ void *dlopen(const char *libname, int flag)
 	/* Try to load the specified library */
 	_dl_if_debug_print("Trying to dlopen '%s', RTLD_GLOBAL:%d RTLD_NOW:%d\n",
 			(char*)libname, (flag & RTLD_GLOBAL ? 1:0), (now_flag & RTLD_NOW ? 1:0));
-	tpnt = _dl_load_shared_library(0, &rpnt, tfrom, (char*)libname, 0);
 
+	tpnt = _dl_load_shared_library((flag & RTLD_NOLOAD) ? DL_RESOLVE_NOLOAD : 0,
+					&rpnt, tfrom, (char*)libname, 0);
 	if (tpnt == NULL) {
 		_dl_unmap_cache();
 		return NULL;

libc/sysdeps/linux/common/bits/dlfcn.h

@@ -24,9 +24,9 @@
 /* The MODE argument to `dlopen' contains one of the following: */
 #define RTLD_LAZY	0x00001	/* Lazy function call binding.  */
 #define RTLD_NOW	0x00002	/* Immediate function call binding.  */
-#if 0 /* uClibc doesnt support these */
-#define	RTLD_BINDING_MASK   0x3	/* Mask of binding time value.  */
+#define RTLD_BINDING_MASK   0x3	/* Mask of binding time value.  */
 #define RTLD_NOLOAD	0x00004	/* Do not load the object.  */
+#if 0 /* uClibc doesnt support these */
 #define RTLD_DEEPBIND	0x00008	/* Use deep binding.  */
 #endif