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

/*
 *  COPYRIGHT (c) 2012, 2019 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 Object File Unresolved Relocations Table.
 *
 * The unresolved relocation table holds relocations in a loaded object file
 * which reference unresolved external symbols. The support is needed to allow
 * dependent object files to load. In the case of dependent object files one
 * will have unresolved externals until the dependent object file is also
 * loaded. There is no load order that resolves this.
 *
 * The unresolved relocation table is a single table used by all object files
 * with unresolved symbols. It made of blocks linked together where blocks are
 * allocated as requiered. The table is always maintained compacted. That is as
 * relocations are resolved and removed the table is compacted. The only
 * pointer in the table is the object file poniter. This is used to identify
 * which object the relocation belongs to. There are no linking or back
 * pointers in the unresolved relocations table. The table is scanned for each
 * object file's relocations. This is not fast but the table should be small
 * and if it happens to grow large you have other more pressing issues to
 * resolve in your application.
 *
 * The table holds two (2) types of records:
 *
 *  # Symbol name strings.
 *  # Relocations.
 *
 * The symbol name a relocation references is held in a specific symbol name
 * string record in the table the relocation record references. The record
 * counts the number of references and the string is removed from the table
 * when the reference count reaches 0. There can be many relocations
 * referencing the symbol. The strings are referenced by a single 16bit
 * unsigned integer which is the count of the string in the table.
 *
 * The section the relocation is for in the object is the section number. The
 * relocation data is series of machine word sized fields:
 *
 * # Offset in the section.
 * # Relocation info (format specific)
 * # Additional format specific data.
 */

#if !defined (_RTEMS_RTL_UNRESOLVED_H_)
#define _RTEMS_RTL_UNRESOLVED_H_

#include <rtems.h>
#include <rtems/chain.h>
#include "rtl-obj-fwd.h"

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

/**
 * Hack to work around machine size. This needs to be cleaned up
 * to better support 64bit targets.
 */
typedef uint32_t rtems_rtl_word;

/**
 * The types of records in the blocks.
 */
typedef enum rtems_rtl_unresolved_rtype
{
  rtems_rtl_unresolved_empty = 0,  /**< The records is empty. Must always be 0 */
  rtems_rtl_unresolved_symbol = 1, /**< The record is a symbol. */
  rtems_rtl_unresolved_reloc = 2,  /**< The record is a relocation record. */
  rtems_rtl_trampoline_reloc = 3   /**< The record is a trampoline relocation record. */
} rtems_rtl_unresolved_rtype;

/**
 * Unresolved external symbol flags.
 */
#define RTEMS_RTL_UNRESOLV_SYM_SEARCH_ARCHIVE (1 << 0) /**< Search the archive. */
#define RTEMS_RTL_UNRESOLV_SYM_HAS_ERROR      (1 << 1) /**< The symbol load
                                                        *   has an error. */

/**
 * Unresolved externals symbols. The symbols are reference counted and separate
 * from the relocation records because a number of records could reference the
 * same symbol.
 *
 * The name is extended in the allocator of the record in the unresolved data
 * block. The 10 is a minimum that is added to by joining more than one record.
 */
typedef struct rtems_rtl_unresolv_symbol
{
  uint16_t   refs;     /**< The number of references to this name. */
  uint16_t   flags;    /**< Flags to manage the symbol. */
  uint16_t   length;   /**< The length of this name. */
  const char name[];   /**< The symbol name. */
} rtems_rtl_unresolv_symbol;

/**
 * Unresolved externals symbols require the relocation records to be held
 * and referenced.
 */
typedef struct rtems_rtl_unresolv_reloc
{
  rtems_rtl_obj* obj;     /**< The relocation's object file. */
  uint16_t       flags;   /**< Format specific flags. */
  uint16_t       name;    /**< The symbol's name. */
  uint16_t       sect;    /**< The target section. */
  rtems_rtl_word rel[3];  /**< Relocation record. */
} rtems_rtl_unresolv_reloc;

/**
 * Trampolines require the relocation records to be held
 */
typedef struct rtems_rtl_tramp_reloc
{
  rtems_rtl_obj* obj;      /**< The relocation's object file. */
  uint16_t       flags;    /**< Format specific flags. */
  uint16_t       sect;     /**< The target section. */
  rtems_rtl_word symvalue; /**< The symbol's value. */
  rtems_rtl_word rel[3];   /**< Relocation record. */
} rtems_rtl_tramp_reloc;

/**
 * Unresolved externals records.
 */
typedef struct rtems_rtl_unresolv_rec
{
  rtems_rtl_unresolved_rtype type;
  union
  {
    rtems_rtl_unresolv_symbol name;   /**< The symbol, or */
    rtems_rtl_unresolv_reloc  reloc;  /**< The relocation record. */
    rtems_rtl_tramp_reloc     tramp;  /**< The trampoline relocation record. */
  } rec;
} rtems_rtl_unresolv_rec;

/**
 * Unresolved blocks.
 */
typedef struct rtems_rtl_unresolv_block
{
  rtems_chain_node       link;  /**< Blocks are chained. */
  uint32_t               recs;  /**< The number of records in the block. */
  rtems_rtl_unresolv_rec rec[]; /**< The records. More follow. */
} rtems_rtl_unresolv_block;

/**
 * Unresolved table holds the names and relocations.
 */
typedef struct rtems_rtl_unresolved
{
  uint32_t            marker;     /**< Block marker. */
  size_t              block_recs; /**< The records per blocks allocated. */
  rtems_chain_control blocks;     /**< List of blocks. */
} rtems_rtl_unresolved;

/**
 * The iterator function used to iterate over the unresolved table.
 *
 * @param rec The current iterator.
 * @param data The user data.
 * @retval true The iterator has finished.
 * @retval false The iterator has not finished. Keep iterating.
 */
typedef bool rtems_rtl_unresolved_iterator (rtems_rtl_unresolv_rec* rec,
                                            void*                   data);

/**
 * Open an unresolved relocation table.
 *
 * @param unresolv The unresolved table to open.
 * @param block_records The number of records per block allocated.
 * @retval true The table is open.
 * @retval false The unresolved relocation table could not created. The RTL
 *               error has the error.
 */
bool rtems_rtl_unresolved_table_open (rtems_rtl_unresolved* unresolved,
                                      size_t                block_records);

/**
 * Close the table and erase the blocks.
 *
 * @param unreolved Close the unresolved table.
 */
void rtems_rtl_unresolved_table_close (rtems_rtl_unresolved* unresolved);

/**
 * Iterate over the table of unresolved entries.
 */
bool rtems_rtl_unresolved_iterate (rtems_rtl_unresolved_iterator iterator,
                                   void*                         data);

/**
 * Add a relocation to the list of unresolved relocations.
 *
 * @param unresolved The unresolved symbol table.
 * @param obj The object table the symbols are for.
 * @param flags Format specific flags.
 * @param name The symbol name the relocation references.
 * @param sect The target section number the relocation references.
 * @param rel The format specific relocation data.
 * @retval true The relocation has been added.
 * @retval false The relocation could not be added.
 */
bool rtems_rtl_unresolved_add (rtems_rtl_obj*        obj,
                               const uint16_t        flags,
                               const char*           name,
                               const uint16_t        sect,
                               const rtems_rtl_word* rel);

/**
 * Resolve the unresolved symbols.
 */
void rtems_rtl_unresolved_resolve (void);

/**
 * Remove a relocation from the list of unresolved relocations.
 *
 * @param unresolved The unresolved symbol table.
 * @param obj The object table the symbols are for.
 * @param esyms The exported symbol table.
 * @param size The size of the table in bytes.
 */
bool rtems_rtl_unresolved_remove (rtems_rtl_obj*        obj,
                                  const char*           name,
                                  const uint16_t        sect,
                                  const rtems_rtl_word* rel);

/**
 * Set all symbols to be archive searchable. This is done when the available
 * archives have been refreshed and there are new archives to search for.
 */
void rtems_rtl_unresolved_set_archive_search (void);

/**
 * Dump the RTL unresolved data.
 */
void rtems_rtl_unresolved_dump (void);

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif