source: rtems/cpukit/include/rtems/rtl/rtl-unresolved.h @ d8c70ba6

Last change on this file since d8c70ba6 was 89c59be, checked in by Chris Johns <chrisj@…>, on Dec 17, 2018 at 5:36:48 AM

libdl: Add symbol searching and loading from archives.

  • Load archive symbol tables to support searching of archives for symbols.
  • Search archive symbols and load the object file that contains the symbol.
  • Search the global and archives until all remaining unresolved symbols are not found. Group the loaded object files in the pending queue.
  • Run the object file and loaded dependents as a group before adding to the main object list.
  • Remove orphaned object files after references are removed.

Updates #3686

  • Property mode set to 100644
File size: 7.8 KB
Line 
1/*
2 *  COPYRIGHT (c) 2012, 2018 Chris Johns <chrisj@rtems.org>
3 *
4 *  The license and distribution terms for this file may be
5 *  found in the file LICENSE in this distribution or at
6 *  http://www.rtems.org/license/LICENSE.
7 */
8/**
9 * @file
10 *
11 * @ingroup rtems_rtl
12 *
13 * @brief RTEMS Run-Time Linker Object File Unresolved Relocations Table.
14 *
15 * The unresolved relocation table holds relocations in a loaded object file
16 * which reference unresolved external symbols. The support is needed to allow
17 * dependent object files to load. In the case of dependent object files one
18 * will have unresolved externals until the dependent object file is also
19 * loaded. There is no load order that resolves this.
20 *
21 * The unresolved relocation table is a single table used by all object files
22 * with unresolved symbols. It made of blocks linked together where blocks are
23 * allocated as requiered. The table is always maintained compacted. That is as
24 * relocations are resolved and removed the table is compacted. The only
25 * pointer in the table is the object file poniter. This is used to identify
26 * which object the relocation belongs to. There are no linking or back
27 * pointers in the unresolved relocations table. The table is scanned for each
28 * object file's relocations. This is not fast but the table should be small
29 * and if it happens to grow large you have other more pressing issues to
30 * resolve in your application.
31 *
32 * The table holds two (2) types of records:
33 *
34 *  # Symbol name strings.
35 *  # Relocations.
36 *
37 * The symbol name a relocation references is held in a specific symbol name
38 * string record in the table the relocation record references. The record
39 * counts the number of references and the string is removed from the table
40 * when the reference count reaches 0. There can be many relocations
41 * referencing the symbol. The strings are referenced by a single 16bit
42 * unsigned integer which is the count of the string in the table.
43 *
44 * The section the relocation is for in the object is the section number. The
45 * relocation data is series of machine word sized fields:
46 *
47 * # Offset in the section.
48 * # Relocation info (format specific)
49 * # Additional format specific data.
50 */
51
52#if !defined (_RTEMS_RTL_UNRESOLVED_H_)
53#define _RTEMS_RTL_UNRESOLVED_H_
54
55#include <rtems.h>
56#include "rtl-obj-fwd.h"
57
58#ifdef __cplusplus
59extern "C" {
60#endif /* __cplusplus */
61
62/**
63 * Hack to work around machine size. This needs to be cleaned up
64 * to better support 64bit targets.
65 */
66typedef uint32_t rtems_rtl_word;
67
68/**
69 * The types of records in the blocks.
70 */
71typedef enum rtems_rtl_unresolved_rtype
72{
73  rtems_rtl_unresolved_empty = 0,  /**< The records is empty. Must always be 0 */
74  rtems_rtl_unresolved_symbol = 1, /**< The record is a symbol. */
75  rtems_rtl_unresolved_reloc = 2   /**< The record is a relocation record. */
76} rtems_rtl_unresolved_rtype;
77
78/**
79 * Unresolved external symbol flags.
80 */
81#define RTEMS_RTL_UNRESOLV_SYM_SEARCH_ARCHIVE (1 << 0) /**< Search the archive. */
82
83/**
84 * Unresolved externals symbols. The symbols are reference counted and separate
85 * from the relocation records because a number of records could reference the
86 * same symbol.
87 *
88 * The name is extended in the allocator of the record in the unresolved data
89 * block. The 10 is a minimum that is added to by joining more than one record.
90 */
91typedef struct rtems_rtl_unresolv_symbol
92{
93  uint16_t   refs;     /**< The number of references to this name. */
94  uint16_t   flags;    /**< Flags to manage the symbol. */
95  uint16_t   length;   /**< The length of this name. */
96  const char name[10]; /**< The symbol name. */
97} rtems_rtl_unresolv_symbol;
98
99/**
100 * Unresolved externals symbols require the relocation records to be held
101 * and references.
102 */
103typedef struct rtems_rtl_unresolv_reloc
104{
105  rtems_rtl_obj* obj;     /**< The relocation's object file. */
106  uint16_t       flags;   /**< Format specific flags. */
107  uint16_t       name;    /**< The symbol's name. */
108  uint16_t       sect;    /**< The target section. */
109  rtems_rtl_word rel[3];  /**< Relocation record. */
110} rtems_rtl_unresolv_reloc;
111
112/**
113 * Unresolved externals records.
114 */
115typedef struct rtems_rtl_unresolv_rec
116{
117  rtems_rtl_unresolved_rtype type;
118  union
119  {
120    rtems_rtl_unresolv_symbol name;   /**< The symnbol, or */
121    rtems_rtl_unresolv_reloc  reloc;  /**< the relocation record. */
122  } rec;
123} rtems_rtl_unresolv_rec;
124
125/**
126 * Unresolved blocks.
127 */
128typedef struct rtems_rtl_unresolv_block
129{
130  rtems_chain_node       link; /**< Blocks are chained. */
131  uint32_t               recs; /**< The number of records in the block. */
132  rtems_rtl_unresolv_rec rec;  /**< The records. More follow. */
133} rtems_rtl_unresolv_block;
134
135/**
136 * Unresolved table holds the names and relocations.
137 */
138typedef struct rtems_rtl_unresolved
139{
140  uint32_t            marker;     /**< Block marker. */
141  size_t              block_recs; /**< The records per blocks allocated. */
142  rtems_chain_control blocks;     /**< List of blocks. */
143} rtems_rtl_unresolved;
144
145/**
146 * The iterator function used to iterate over the unresolved table.
147 *
148 * @param rec The current iterator.
149 * @param data The user data.
150 * @retval true The iterator has finished.
151 * @retval false The iterator has not finished. Keep iterating.
152 */
153typedef bool rtems_rtl_unresolved_iterator (rtems_rtl_unresolv_rec* rec,
154                                            void*                   data);
155
156/**
157 * Open an unresolved relocation table.
158 *
159 * @param unresolv The unresolved table to open.
160 * @param block_records The number of records per block allocated.
161 * @retval true The table is open.
162 * @retval false The unresolved relocation table could not created. The RTL
163 *               error has the error.
164 */
165bool rtems_rtl_unresolved_table_open (rtems_rtl_unresolved* unresolved,
166                                      size_t                block_records);
167
168/**
169 * Close the table and erase the blocks.
170 *
171 * @param unreolved Close the unresolved table.
172 */
173void rtems_rtl_unresolved_table_close (rtems_rtl_unresolved* unresolved);
174
175/**
176 * Iterate over the table of unresolved entries.
177 */
178bool rtems_rtl_unresolved_iterate (rtems_rtl_unresolved_iterator iterator,
179                                   void*                         data);
180
181/**
182 * Add a relocation to the list of unresolved relocations.
183 *
184 * @param unresolved The unresolved symbol table.
185 * @param obj The object table the symbols are for.
186 * @param flags Format specific flags.
187 * @param name The symbol name the relocation references.
188 * @param sect The target section number the relocation references.
189 * @param rel The format specific relocation data.
190 * @retval true The relocation has been added.
191 * @retval false The relocation could not be added.
192 */
193bool rtems_rtl_unresolved_add (rtems_rtl_obj*        obj,
194                               const uint16_t        flags,
195                               const char*           name,
196                               const uint16_t        sect,
197                               const rtems_rtl_word* rel);
198
199/**
200 * Resolve the unresolved symbols.
201 */
202void rtems_rtl_unresolved_resolve (void);
203
204/**
205 * Remove a relocation from the list of unresolved relocations.
206 *
207 * @param unresolved The unresolved symbol table.
208 * @param obj The object table the symbols are for.
209 * @param esyms The exported symbol table.
210 * @param size The size of the table in bytes.
211 */
212bool rtems_rtl_unresolved_remove (rtems_rtl_obj*        obj,
213                                  const char*           name,
214                                  const uint16_t        sect,
215                                  const rtems_rtl_word* rel);
216
217/**
218 * Set all symbols to be archive searchable. This is done when the available
219 * archives have been refreshed and there are new archives to search for.
220 */
221void rtems_rtl_unresolved_set_archive_search (void);
222
223/**
224 * Dump the RTL unresolved data.
225 */
226void rtems_rtl_unresolved_dump (void);
227
228#ifdef __cplusplus
229}
230#endif /* __cplusplus */
231
232#endif
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