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 extern __typeof (_dl_find_object) __dl_find_object;
   8 hidden_proto (__dl_find_object)
   9
  10 /* Internally used flag.  */
  11 #define __RTLD_DLOPEN   0x80000000
  12 #define __RTLD_SPROF    0x40000000
  13 #define __RTLD_OPENEXEC 0x20000000
  14 #define __RTLD_CALLMAP  0x10000000
  15 #define __RTLD_AUDIT    0x08000000
  16 #define __RTLD_SECURE   0x04000000 /* Apply additional security checks.  */
  17 #define __RTLD_NOIFUNC  0x02000000 /* Suppress calling ifunc functions.  */
  18 #define __RTLD_VDSO     0x01000000 /* Tell _dl_new_object the object is
  19                                       system-loaded.  */
  20
  21 #define __LM_ID_CALLER  -2
  22
  23 /* These variables are defined and initialized in the startup code.  */
  24 extern int __libc_argc attribute_hidden;
  25 extern char **__libc_argv attribute_hidden;
  26
  27 /* Now define the internal interfaces.  */
  28
  29 /* Use RTLD_NOW here because:
  30    1. In pthread_cancel_init we want to use RTLD_NOW to reduce the stack usage
  31       of future cancellation operations, particularly when the target thread
  32       is running with a small stack.  Likewise for consistency we do the same
  33       thing in __libgcc_s_init.  RTLD_NOW will rarely make a difference for
  34       __libgcc_s_init because unwinding is already in progress, so libgcc_s.so
  35       has already been loaded if its unwinder is used (Bug 22636).
  36    2. It allows us to provide robust fallback code at dlopen time for
  37       incorrectly configured systems that mix old libnss_* modules
  38       with newly installed libraries e.g. old libnss_dns.so.2 with new
  39       libresolv.so.2.  Using RTLD_LAZY here causes a failure at the
  40       time the symbol is called and at that point it is much harder to
  41       safely return an error (Bug 22766).
  42
  43    The use of RTLD_NOW also impacts gconv module loading, backtracing
  44    (where the unwinder form libgcc_s.so is used), and IDNA functions
  45    (which load libidn2), all of which load their respective DSOs on
  46    demand, and so should not impact program startup.  That is to say
  47    that the DSOs are loaded as part of an API call and therefore we
  48    will be calling that family of API functions shortly so RTLD_NOW or
  49    RTLD_LAZY is not a big difference in performance, but RTLD_NOW has
  50    better error handling semantics for the library.  */
  51 #define __libc_dlopen(name) \
  52   __libc_dlopen_mode (name, RTLD_NOW | __RTLD_DLOPEN)
  53 extern void *__libc_dlopen_mode  (const char *__name, int __mode)
  54   attribute_hidden;
  55 extern void *__libc_dlsym   (void *__map, const char *__name)
  56   attribute_hidden;
  57 extern void *__libc_dlvsym (void *map, const char *name, const char *version)
  58   attribute_hidden;
  59 extern int   __libc_dlclose (void *__map)
  60   attribute_hidden;
  61
  62 /* Locate shared object containing the given address.  */
  63 #ifdef ElfW
  64 extern int _dl_addr (const void *address, Dl_info *info,
  65                      struct link_map **mapp, const ElfW(Sym) **symbolp)
  66   attribute_hidden;
  67 #endif
  68
  69 struct link_map;
  70
  71 /* Close an object previously opened by _dl_open.  */
  72 extern void _dl_close (void *map) attribute_hidden;
  73 /* Same as above, but without locking and safety checks for user
  74    provided map arguments.  */
  75 extern void _dl_close_worker (struct link_map *map, bool force)
  76     attribute_hidden;
  77
  78 /* Look up NAME in shared object HANDLE (which may be RTLD_DEFAULT or
  79    RTLD_NEXT).  WHO is the calling function, for RTLD_NEXT.  Returns
  80    the symbol value, which may be NULL.  */
  81 extern void *_dl_sym (void *handle, const char *name, void *who)
  82   attribute_hidden;
  83
  84 /* Look up version VERSION of symbol NAME in shared object HANDLE
  85    (which may be RTLD_DEFAULT or RTLD_NEXT).  WHO is the calling
  86    function, for RTLD_NEXT.  Returns the symbol value, which may be
  87    NULL.  */
  88 extern void *_dl_vsym (void *handle, const char *name, const char *version,
  89                        void *who) attribute_hidden;
  90
  91 /* Helper function for <dlfcn.h> functions.  Runs the OPERATE function via
  92    _dl_catch_error.  Returns zero for success, nonzero for failure; and
  93    arranges for `dlerror' to return the error details.
  94    ARGS is passed as argument to OPERATE.  */
  95 extern int _dlerror_run (void (*operate) (void *), void *args) attribute_hidden;
  96
  97 /* This structure is used to make the outer (statically linked)
  98    implementation of dlopen and related functions to the inner libc
  99    after static dlopen, via the GLRO (dl_dlfcn_hook) pointer.  */
 100 struct dlfcn_hook
 101 {
 102   /* Public interfaces.  */
 103   void *(*dlopen) (const char *file, int mode, void *dl_caller);
 104   int (*dlclose) (void *handle);
 105   void *(*dlsym) (void *handle, const char *name, void *dl_caller);
 106   void *(*dlvsym) (void *handle, const char *name, const char *version,
 107                    void *dl_caller);
 108   char *(*dlerror) (void);
 109   int (*dladdr) (const void *address, Dl_info *info);
 110   int (*dladdr1) (const void *address, Dl_info *info,
 111                   void **extra_info, int flags);
 112   int (*dlinfo) (void *handle, int request, void *arg);
 113   void *(*dlmopen) (Lmid_t nsid, const char *file, int mode, void *dl_caller);
 114
 115   /* Internal interfaces.  */
 116   void* (*libc_dlopen_mode)  (const char *__name, int __mode);
 117   void* (*libc_dlsym)  (void *map, const char *name);
 118   void* (*libc_dlvsym)  (void *map, const char *name, const char *version);
 119   int   (*libc_dlclose) (void *map);
 120 };
 121
 122 /* Note: These prototypes are for initializing _dlfcn_hook in static
 123    builds; see __rtld_static_init.  Internal calls in glibc should use
 124    the __libc_dl* functions defined in elf/dl-libc.c instead.  */
 125
 126 extern void *__dlopen (const char *file, int mode, void *caller);
 127 extern void *__dlmopen (Lmid_t nsid, const char *file, int mode,
 128                         void *dl_caller);
 129 extern int __dlclose (void *handle);
 130 extern void *__dlsym (void *handle, const char *name, void *dl_caller);
 131 extern void *__dlvsym (void *handle, const char *name, const char *version,
 132                        void *dl_caller);
 133 extern int __dladdr (const void *address, Dl_info *info);
 134 extern int __dladdr1 (const void *address, Dl_info *info,
 135                       void **extra_info, int flags);
 136 extern int __dlinfo (void *handle, int request, void *arg);
 137 extern char *__dlerror (void);
 138
 139 #ifndef SHARED
 140 # undef DL_CALL_FCT
 141 # define DL_CALL_FCT(fctp, args) ((fctp) args)
 142 #endif
 143
 144 #endif
 145 #endif