include/dlfcn.h

   1 #ifndef _DLFCN_H
   2 #include <dlfcn/dlfcn.h>
   3 #ifndef _ISOMAC
   4 #include <link.h>               /* For ElfW.  */
   5 #include <stdbool.h>
   6
   7 rtld_hidden_proto (_dl_find_object)
   8
   9 /* Internally used flag.  */
  10 #define __RTLD_DLOPEN   0x80000000
  11 #define __RTLD_SPROF    0x40000000
  12 #define __RTLD_OPENEXEC 0x20000000
  13 #define __RTLD_CALLMAP  0x10000000
  14 #define __RTLD_AUDIT    0x08000000
  15 #define __RTLD_SECURE   0x04000000 /* Apply additional security checks.  */
  16 #define __RTLD_NOIFUNC  0x02000000 /* Suppress calling ifunc functions.  */
  17 #define __RTLD_VDSO     0x01000000 /* Tell _dl_new_object the object is
  18                                       system-loaded.  */
  19
  20 #define __LM_ID_CALLER  -2
  21
  22 /* These variables are defined and initialized in the startup code.  */
  23 extern int __libc_argc attribute_hidden;
  24 extern char **__libc_argv attribute_hidden;
  25
  26 /* Now define the internal interfaces.  */
  27
  28 /* Use RTLD_NOW here because:
  29    1. In pthread_cancel_init we want to use RTLD_NOW to reduce the stack usage
  30       of future cancellation operations, particularly when the target thread
  31       is running with a small stack.  Likewise for consistency we do the same
  32       thing in __libgcc_s_init.  RTLD_NOW will rarely make a difference for
  33       __libgcc_s_init because unwinding is already in progress, so libgcc_s.so
  34       has already been loaded if its unwinder is used (Bug 22636).
  35    2. It allows us to provide robust fallback code at dlopen time for
  36       incorrectly configured systems that mix old libnss_* modules
  37       with newly installed libraries e.g. old libnss_dns.so.2 with new
  38       libresolv.so.2.  Using RTLD_LAZY here causes a failure at the
  39       time the symbol is called and at that point it is much harder to
  40       safely return an error (Bug 22766).
  41
  42    The use of RTLD_NOW also impacts gconv module loading, backtracing
  43    (where the unwinder form libgcc_s.so is used), and IDNA functions
  44    (which load libidn2), all of which load their respective DSOs on
  45    demand, and so should not impact program startup.  That is to say
  46    that the DSOs are loaded as part of an API call and therefore we
  47    will be calling that family of API functions shortly so RTLD_NOW or
  48    RTLD_LAZY is not a big difference in performance, but RTLD_NOW has
  49    better error handling semantics for the library.  */
  50 #define __libc_dlopen(name) \
  51   __libc_dlopen_mode (name, RTLD_NOW | __RTLD_DLOPEN)
  52 extern void *__libc_dlopen_mode  (const char *__name, int __mode)
  53   attribute_hidden;
  54 extern void *__libc_dlsym   (void *__map, const char *__name)
  55   attribute_hidden;
  56 extern void *__libc_dlvsym (void *map, const char *name, const char *version)
  57   attribute_hidden;
  58 extern int   __libc_dlclose (void *__map)
  59   attribute_hidden;
  60
  61 /* Locate shared object containing the given address.  */
  62 #ifdef ElfW
  63 extern int _dl_addr (const void *address, Dl_info *info,
  64                      struct link_map **mapp, const ElfW(Sym) **symbolp)
  65   attribute_hidden;
  66 #endif
  67
  68 struct link_map;
  69
  70 /* Close an object previously opened by _dl_open.  */
  71 extern void _dl_close (void *map) attribute_hidden;
  72 /* Same as above, but without locking and safety checks for user
  73    provided map arguments.  */
  74 extern void _dl_close_worker (struct link_map *map, bool force)
  75     attribute_hidden;
  76
  77 /* Look up NAME in shared object HANDLE (which may be RTLD_DEFAULT or
  78    RTLD_NEXT).  WHO is the calling function, for RTLD_NEXT.  Returns
  79    the symbol value, which may be NULL.  */
  80 extern void *_dl_sym (void *handle, const char *name, void *who)
  81   attribute_hidden;
  82
  83 /* Look up version VERSION of symbol NAME in shared object HANDLE
  84    (which may be RTLD_DEFAULT or RTLD_NEXT).  WHO is the calling
  85    function, for RTLD_NEXT.  Returns the symbol value, which may be
  86    NULL.  */
  87 extern void *_dl_vsym (void *handle, const char *name, const char *version,
  88                        void *who) attribute_hidden;
  89
  90 /* Helper function for <dlfcn.h> functions.  Runs the OPERATE function via
  91    _dl_catch_error.  Returns zero for success, nonzero for failure; and
  92    arranges for `dlerror' to return the error details.
  93    ARGS is passed as argument to OPERATE.  */
  94 extern int _dlerror_run (void (*operate) (void *), void *args) attribute_hidden;
  95
  96 /* This structure is used to make the outer (statically linked)
  97    implementation of dlopen and related functions to the inner libc
  98    after static dlopen, via the GLRO (dl_dlfcn_hook) pointer.  */
  99 struct dlfcn_hook
 100 {
 101   /* Public interfaces.  */
 102   void *(*dlopen) (const char *file, int mode, void *dl_caller);
 103   int (*dlclose) (void *handle);
 104   void *(*dlsym) (void *handle, const char *name, void *dl_caller);
 105   void *(*dlvsym) (void *handle, const char *name, const char *version,
 106                    void *dl_caller);
 107   char *(*dlerror) (void);
 108   int (*dladdr) (const void *address, Dl_info *info);
 109   int (*dladdr1) (const void *address, Dl_info *info,
 110                   void **extra_info, int flags);
 111   int (*dlinfo) (void *handle, int request, void *arg);
 112   void *(*dlmopen) (Lmid_t nsid, const char *file, int mode, void *dl_caller);
 113
 114   /* Internal interfaces.  */
 115   void* (*libc_dlopen_mode)  (const char *__name, int __mode);
 116   void* (*libc_dlsym)  (void *map, const char *name);
 117   void* (*libc_dlvsym)  (void *map, const char *name, const char *version);
 118   int   (*libc_dlclose) (void *map);
 119 };
 120
 121 /* Note: These prototypes are for initializing _dlfcn_hook in static
 122    builds; see __rtld_static_init.  Internal calls in glibc should use
 123    the __libc_dl* functions defined in elf/dl-libc.c instead.  */
 124
 125 extern void *__dlopen (const char *file, int mode, void *caller);
 126 extern void *__dlmopen (Lmid_t nsid, const char *file, int mode,
 127                         void *dl_caller);
 128 extern int __dlclose (void *handle);
 129 extern void *__dlsym (void *handle, const char *name, void *dl_caller);
 130 extern void *__dlvsym (void *handle, const char *name, const char *version,
 131                        void *dl_caller);
 132 extern int __dladdr (const void *address, Dl_info *info);
 133 extern int __dladdr1 (const void *address, Dl_info *info,
 134                       void **extra_info, int flags);
 135 extern int __dlinfo (void *handle, int request, void *arg);
 136 extern char *__dlerror (void);
 137
 138 #endif
 139 #endif