source: rtems/cpukit/include/rtems/rtl/rtl.h @ b36c5209

/*
 *  COPYRIGHT (c) 2012, 2018 Chris Johns <chrisj@rtems.org>
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

/**
 * @file
 *
 * @ingroup rtems_rtl
 *
 * @brief RTEMS Run-Time Linker
 *
 * This is the POSIX interface to run-time loading of code into RTEMS.
 */

#if !defined (_RTEMS_RTL_H_)
#define _RTEMS_RTL_H_

#include <link.h>
#include <rtems/chain.h>
#include <rtems/thread.h>

#include <rtems/rtl/rtl-allocator.h>
#include <rtems/rtl/rtl-archive.h>
#include <rtems/rtl/rtl-fwd.h>
#include <rtems/rtl/rtl-obj.h>
#include <rtems/rtl/rtl-obj-cache.h>
#include <rtems/rtl/rtl-obj-comp.h>
#include <rtems/rtl/rtl-sym.h>
#include <rtems/rtl/rtl-unresolved.h>

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/**
 * @defgroup rtems_rtl RTEMS Runtime Link Editor
 *
 * @ingroup RTEMSAPI
 *
 * The module implements a runtime link editor with the standard dlopen, and
 * dlclose family of functions.
 *
 * The runtime link editor is different to that found on Unix type systems. The
 * object modules are compiled for PIC or position independent code and
 * therefore require relocating when loaded.
 *
 * The object file format is currently ELF and object files can be separate
 * files or in an archive. Object files in an archive are referenced by
 * specifying 'archive:object' format. For example 'libfoo.a:bar.o'.
 */

/**
 * Macros to glue two tokens.
 */
#ifdef __STDC__
#define RTL_XGLUE(a,b) a##b
#else
#define RTL_XGLUE(a,b) a/**/b
#endif

#define RTL_GLUE(a,b) RTL_XGLUE(a,b)

/**
 * The number of buckets in the global symbol table.
 */
#define RTEMS_RTL_SYMS_GLOBAL_BUCKETS (32)

/**
 * The number of relocation record per block in the unresolved table.
 */
#define RTEMS_RTL_UNRESOLVED_BLOCK_SIZE (256)

/**
 * The number of dependency record per block in the dependency table.
 */
#define RTEMS_RTL_DEPENDENCY_BLOCK_SIZE (16)

/**
 * The global debugger interface variable.
 */
extern struct r_debug _rtld_debug;

/**
 * Debugger break function. Call when debugging to have it read the _rtld_debug
 * variable.
 */
extern void _rtld_debug_state (void);

/**
 * The type of constructor/destructor function.
 */
typedef void (*rtems_rtl_cdtor)(void);

/**
 * The global RTL data. This structure is allocated on the heap when the first
 * call to the RTL is made and never released.
 *
 * The global symbol table is a hash table held in this structure and the
 * actual symbols are part of the object's structure. If this is a problem we
 * could look at a hash table per object file.
 */
struct rtems_rtl_data
{
  rtems_recursive_mutex lock;           /**< The RTL lock */
  rtems_rtl_alloc_data  allocator;      /**< The allocator data. */
  rtems_chain_control   objects;        /**< List if loaded object files. */
  rtems_chain_control   pending;        /**< Listof object files needing work. */
  const char*           paths;          /**< Search paths for archives. */
  rtems_rtl_symbols     globals;        /**< Global symbol table. */
  rtems_rtl_archives    archives;       /**< Archive search and loader. */
  rtems_rtl_unresolved  unresolved;     /**< Unresolved symbols. */
  rtems_rtl_obj*        base;           /**< Base object file. */
  rtems_rtl_obj_cache   symbols;        /**< Symbols object file cache. */
  rtems_rtl_obj_cache   strings;        /**< Strings object file cache. */
  rtems_rtl_obj_cache   relocs;         /**< Relocations object file cache. */
  rtems_rtl_obj_comp    decomp;         /**< The decompression compressor. */
  int                   last_errno;     /**< Last error number. */
  char                  last_error[64]; /**< Last error string. */
};

/**
 * Get the RTL data with out locking. This call assumes the RTL is locked.
 *
 * @return rtems_rtl_data* The RTL data after being locked.
 * @retval NULL The RTL data is not initialised.
 */
rtems_rtl_data* rtems_rtl_data_unprotected (void);

/**
 * Get the RTL global symbol table with out locking. This call assumes
 * the RTL is locked.
 *
 * @return rtems_rtl_symbols* The RTL global symbols after being locked.
 * @retval NULL The RTL data is not initialised.
 */
rtems_rtl_symbols* rtems_rtl_global_symbols (void);

/**
 * Get the RTL last error string with out locking. This call assumes the RTL is
 * locked.
 *
 * @return const char* The RTL's laste error.
 * @retval NULL The RTL data is not initialised.
 */
const char* rtems_rtl_last_error_unprotected (void);

/**
 * Get the RTL objects table with out locking. This call assumes the RTL
 * is locked.
 *
 * @return rtems_chain_control* The RTL objects chain.
 * @retval NULL The RTL data is not initialised.
 */
rtems_chain_control* rtems_rtl_objects_unprotected (void);

/**
 * Get the RTL pending with out locking. This call assumes the RTL is locked.
 *
 * @return rtems_chain_control* The RTL pending list control.
 * @retval NULL The RTL data is not initialised.
 */
rtems_chain_control* rtems_rtl_pending_unprotected (void);

/**
 * Get the RTL unresolved table with out locking. This call assumes the RTL
 * is locked.
 *
 * @return rtems_rtl_unresolv* The RTL unresolved symbols and reloc records.
 * @retval NULL The RTL data is not initialised.
 */
rtems_rtl_unresolved* rtems_rtl_unresolved_unprotected (void);

/**
 * Get the RTL archives with out locking. This call assumes the RTL is locked.
 *
 * @return rtems_rtl_archives* The RTL acrhives.
 * @retval NULL The RTL data is not initialised.
 */
rtems_rtl_archives* rtems_rtl_archives_unprotected (void);

/**
 * Get the RTL symbols, strings, or relocations object file caches. This call
 * assmes the RTL is locked.
 *
 * @param symbols Pointer to the location to set the cache into. Returns NULL
 *                is rtl is not initialised. If NULL is passed in no value set.
 * @param strings Pointer to the location to set the cache into. Returns NULL
 *                is rtl is not initialised. If NULL is passed in no value set.
 * @param relocs Pointer to the location to set the cache into. Returns NULL
 *               is rtl is not initialised. If NULL is passed in no value set.
 */
void rtems_rtl_obj_caches (rtems_rtl_obj_cache** symbols,
                           rtems_rtl_obj_cache** strings,
                           rtems_rtl_obj_cache** relocs);

/**
 * Flush all the object file caches.
 */
void rtems_rtl_obj_caches_flush (void);

/**
 * Get the RTL decompressor setting for the cache and the offset in the file
 * the compressed stream starts. This call assumes the RTL is locked.
 *
 * @param decomp Pointer to the location to set the compressor into. Returns
 *               NULL is rtl is not initialised.
 * @param cache The cache to read the file with. Saves needing an extrs buffer.
 * @param offset The offset in the file the compressed stream starts.
 */
void rtems_rtl_obj_decompress (rtems_rtl_obj_comp** decomp,
                               rtems_rtl_obj_cache* cache,
                               int                  fd,
                               int                  compression,
                               off_t                offset);

/**
 * Update the mask in the object files. You can clear flags and then set
 * flags. A zero (0) does not clear or set the flags. This is global to all
 * object files that are laoded.
 *
 * @param clear The flag's clear mask, a 0 does not clear any flags.
 * @param set The flag's set mask, a 0 does not set any flags.
 */
void rtems_rtl_obj_update_flags (uint32_t clear, uint32_t set);

/**
 * Lock the Run-time Linker.
 *
 * @return rtems_rtl_data* The RTL data after being locked.
 * @retval NULL The RTL data could not be initialised or locked. Typically this
 *              means the lock could not be created.
 */
rtems_rtl_data* rtems_rtl_lock (void);

/**
 * Unlock the Run-time Linker.
 */
void rtems_rtl_unlock (void);

/**
 * Check a pointer is a valid object file descriptor returning the pointer as
 * that type.
 *
 * Assumes the RTL has been locked.
 *
 * @param handle Pointer to the object file to be validated.
 * @return rtl_obj* The object file descriptor. NULL is returned if invalid.
 */
rtems_rtl_obj* rtems_rtl_check_handle (void* handle);

/**
 * Find the object given a file name.
 *
 * @param name The name of the object file.
 * @retval NULL No object file with that name found.
 * @return rtems_rtl_obj* The object file descriptor.
 */
rtems_rtl_obj* rtems_rtl_find_obj (const char* name);

/**
 * Find the object file a symbol is exported from.
 *
 * @param sym The symbol to search with.
 * @retval NULL No object file found.
 * @return rtems_rtl_obj* Reference to the symbol.
 */
rtems_rtl_obj* rtems_rtl_find_obj_with_symbol (const rtems_rtl_obj_sym* sym);

/**
 * Load an object file into memory relocating it. It will not be resolved
 * against other symbols in other object files or the base image.
 *
 * The name can be a file name for an object file or it can be encoded to
 * reference an archive of object modules (static library). This encoding is
 * specific to RTEMS and allows dependences to specify an archive without the
 * searching overhead normally incurred by linkers locating object files in an
 * archive. The file name format rules are:
 *
 *  1. Absolute file references a specific object file in the architecture
 *     specific location on the file system.
 *
 *  2. Relative file references an object format file in the search path.
 *
 *  3. Absolute archive and file reference to a specific location in the file
 *     system. The archive and file are encoded as 'archive:file [@@offset]'
 *     where 'archive' is a valid file at the absolute path in the file system,
 *     and 'file' is a contained in the archive, and optionally an offset to
 *     the 'file' in the 'archive'. If no offset is provided the archive is
 *     searched.
 *
 *  4. Relative archive and file in the search path. The encoding is the same
 *     as described in item 3 of this list.
 *
 * Assumes the RTL has been locked.
 *
 * @param name The name of the object file.
 * @param mode The mode of the load as defined by the dlopen call.
 * @return rtl_obj* The object file descriptor. NULL is returned if the load fails.
 */
rtems_rtl_obj* rtems_rtl_load_object (const char* name, int mode);

/**
 * Unload an object file. This only happens when the user count is 0.
 *
 * Assumes the RTL has been locked.
 *
 * @param obj The object file descriptor.
 * @retval true The object file has been unloaded.
 * @retval false The object file could not be unloaded.
 */
bool rtems_rtl_unload_object (rtems_rtl_obj* obj);

/**
 * Load an object file.  This is the user accessable interface to unloading an
 * object file. See @rtems_rtl_load_object.
 *
 * @param name The name of the object file.
 * @param mode The mode of the load as defined by the dlopen call.
 * @return rtl_obj* The object file descriptor. NULL is returned if the load fails.
 */
rtems_rtl_obj* rtems_rtl_load (const char* name, int mode);

/**
 * Unload an object file. This is the user accessable interface to unloading an
 * object file. See @rtems_rtl_unload_object.
 *
 * Assumes the RTL has been locked.
 *
 * @param obj The object file descriptor.
 * @retval true The object file has been unloaded.
 * @retval false The object file could not be unloaded.
 */
bool rtems_rtl_unload (rtems_rtl_obj* obj);

/**
 * Get the last error message clearing it. This operation locks the run time
 * linker and therefore keeps the RTL thread safe but this call is not thread
 * safe is multiple threads are loading object files at the same time. This
 * call is provided to map to the dlopen family of calls.
 *
 * @param message Pointer to a buffer to copy the message into.
 * @param max_message The maximum message that can be copied.
 * @return int The last error number.
 */
int rtems_rtl_get_error (char* message, size_t max_message);

/**
 * Append the path to the search path.
 *
 * @param path The path to append.
 * @retval false The path could not be appended.
 * @retval true The path was appended.
 */
bool rtems_rtl_path_append (const char* path);

/**
 * Prepend the path to the search path.
 *
 * @param path The path to prepend.
 * @retval false The path could not be prepended.
 * @retval true The path was prepended.
 */

bool rtems_rtl_path_prepend (const char* path);

/**
 * Add an exported symbol table to the global symbol table. This call is
 * normally used by an object file when loaded that contains a global symbol
 * table.
 *
 * @param esyms The exported symbol table.
 * @param count The size of the exported symbol table.
 */
void rtems_rtl_base_sym_global_add (const unsigned char* esyms,
                                    unsigned int         count);

/**
 * Return the object file descriptor for the base image. The object file
 * descriptor returned is created when the run time linker is initialised.
 *
 * Assumes the RTL has been locked.
 *
 * @return rtl_obj* The object file descriptor for the base image. NULL is
 *                  returned if the load fails.
 */
rtems_rtl_obj* rtems_rtl_baseimage (void);

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif