1 .\" $OpenBSD: elf.5,v 1.12 2003/10/27 20:23:58 jmc Exp $
2 .\"Copyright (c) 1999 Jeroen Ruigrok van der Werven
3 .\"All rights reserved.
5 .\" %%%LICENSE_START(PERMISSIVE_MISC)
6 .\"Redistribution and use in source and binary forms, with or without
7 .\"modification, are permitted provided that the following conditions
9 .\"1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\"2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
15 .\"THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 .\"ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 .\"IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 .\"ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 .\"FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 .\"DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 .\"OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 .\"HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 .\"LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 .\"OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" $FreeBSD: src/share/man/man5/elf.5,v 1.21 2001/10/01 16:09:23 ru Exp $
30 .\" Slightly adapted - aeb, 2004-01-01
31 .\" 2005-07-15, Mike Frysinger <vapier@gentoo.org>, various fixes
32 .\" 2007-10-11, Mike Frysinger <vapier@gentoo.org>, various fixes
33 .\" 2007-12-08, mtk, Converted from mdoc to man macros
35 .TH ELF 5 2020-04-11 "Linux" "Linux Programmer's Manual"
37 elf \- format of Executable and Linking Format (ELF) files
40 .\" .B #include <elf_abi.h>
46 defines the format of ELF executable binary files.
47 Amongst these files are
48 normal executable files, relocatable object files, core files, and shared
51 An executable file using the ELF file format consists of an ELF header,
52 followed by a program header table or a section header table, or both.
53 The ELF header is always at offset zero of the file.
55 table and the section header table's offset in the file are defined in the
57 The two tables describe the rest of the particularities of
60 .\" Applications which wish to process ELF binary files for their native
61 .\" architecture only should include
63 .\" in their source code.
64 .\" These applications should need to refer to
65 .\" all the types and structures by their generic names
67 .\" and to the macros by
69 .\" Applications written this way can be compiled on any architecture,
70 .\" regardless of whether the host is 32-bit or 64-bit.
72 .\" Should an application need to process ELF files of an unknown
73 .\" architecture, then the application needs to explicitly use either
77 .\" type and structure names.
78 .\" Likewise, the macros need to be identified by
83 This header file describes the above mentioned headers as C structures
84 and also includes structures for dynamic sections, relocation sections and
88 The following types are used for N-bit architectures (N=32,64,
102 ElfN_Addr Unsigned program address, uintN_t
103 ElfN_Off Unsigned file offset, uintN_t
104 ElfN_Section Unsigned section index, uint16_t
105 ElfN_Versym Unsigned version symbol information, uint16_t
106 Elf_Byte unsigned char
112 .\" Elf32_Size Unsigned object size
116 (Note: the *BSD terminology is a bit different.
126 In order to avoid confusion these types are replaced by explicit ones
129 All data structures that the file format defines follow the
131 size and alignment guidelines for the relevant class.
133 data structures contain explicit padding to ensure 4-byte alignment
134 for 4-byte objects, to force structure sizes to a multiple of 4, and so on.
136 .SS ELF header (Ehdr)
137 The ELF header is described by the type
147 unsigned char e_ident[EI_NIDENT];
156 uint16_t e_phentsize;
158 uint16_t e_shentsize;
165 The fields have the following meanings:
171 This array of bytes specifies how to interpret the file,
172 independent of the processor or the file's remaining contents.
173 Within this array everything is named by macros, which start with
176 and may contain values which start with the prefix
178 The following macros are defined:
182 The first byte of the magic number.
183 It must be filled with
188 The second byte of the magic number.
189 It must be filled with
194 The third byte of the magic number.
195 It must be filled with
200 The fourth byte of the magic number.
201 It must be filled with
206 The fifth byte identifies the architecture for this binary:
211 This class is invalid.
214 This defines the 32-bit architecture.
215 It supports machines with files
216 and virtual address spaces up to 4 Gigabytes.
219 This defines the 64-bit architecture.
224 The sixth byte specifies the data encoding of the processor-specific
226 Currently, these encodings are supported:
234 Two's complement, little-endian.
237 Two's complement, big-endian.
242 The seventh byte is the version number of the ELF specification:
257 The eighth byte identifies the operating system
258 and ABI to which the object is targeted.
259 Some fields in other ELF structures have flags
260 and values that have platform-specific meanings;
261 the interpretation of those fields is determined by the value of this byte.
267 Same as ELFOSABI_SYSV
273 .\" synonym: ELFOSABI_NONE
287 .\" .BR ELFOSABI_HURD
291 .\" .BR ELFOSABI_86OPEN
292 .\" 86Open Common IA32 ABI
299 .\" .BR ELFOSABI_MONTEREY
300 .\" Monterey project ABI
325 .BR ELFOSABI_STANDALONE
326 Stand-alone (embedded) ABI
332 The ninth byte identifies the version of the ABI
333 to which the object is targeted.
334 This field is used to distinguish among incompatible versions of an ABI.
335 The interpretation of this version number
336 is dependent on the ABI identified by the
339 Applications conforming to this specification use the value 0.
343 These bytes are reserved and set to zero.
345 which read them should ignore them.
349 the future if currently unused bytes are given meanings.
350 .\" As reported by Yuri Kozlov and confirmed by Mike Frysinger, EI_BRAND is
351 .\" not in GABI (http://www.sco.com/developers/gabi/latest/ch4.eheader.html)
352 .\" It looks to be a BSDism
355 .\" Start of architecture identification.
364 This member of the structure identifies the object file type:
386 This member specifies the required architecture for an individual file.
400 Sun Microsystems SPARC
424 MIPS RS3000 (big-endian only)
429 .\" .BR EM_MIPS_RS4_BE
430 .\" MIPS RS4000 (big-endian only). Deprecated
432 .\" EM_MIPS_RS3_LE (MIPS R3000 little-endian)
440 SPARC with enhanced instruction set
456 Advanced RISC Machines
482 .\" Compaq [DEC] Alpha
485 .\" Compaq [DEC] Alpha with enhanced instruction set
490 This member identifies the file version:
503 This member gives the virtual address to which the system first transfers
504 control, thus starting the process.
505 If the file has no associated entry
506 point, this member holds zero.
509 This member holds the program header table's file offset in bytes.
511 the file has no program header table, this member holds zero.
514 This member holds the section header table's file offset in bytes.
516 file has no section header table, this member holds zero.
519 This member holds processor-specific flags associated with the file.
520 Flag names take the form EF_`machine_flag'.
521 Currently, no flags have been defined.
524 This member holds the ELF header's size in bytes.
527 This member holds the size in bytes of one entry in the file's
528 program header table; all entries are the same size.
531 This member holds the number of entries in the program header
537 gives the table's size
539 If a file has no program header,
541 holds the value zero.
543 If the number of entries in the program header table is
544 larger than or equal to
545 .\" This is a Linux extension, added in Linux 2.6.34.
547 (0xffff), this member holds
549 (0xffff) and the real number of entries in the program header table is held
552 member of the initial entry in section header table.
555 member of the initial entry contains the value zero.
559 This is defined as 0xffff, the largest number
561 can have, specifying where the actual number of program headers is assigned.
567 This member holds a sections header's size in bytes.
568 A section header is one
569 entry in the section header table; all entries are the same size.
572 This member holds the number of entries in the section header table.
578 gives the section header table's size in bytes.
579 If a file has no section
582 holds the value of zero.
584 If the number of entries in the section header table is
585 larger than or equal to
589 holds the value zero and the real number of entries in the section header
592 member of the initial entry in section header table.
595 member of the initial entry in the section header table holds
599 This member holds the section header table index of the entry associated
600 with the section name string table.
601 If the file has no section name string
602 table, this member holds the value
605 If the index of section name string table section is
606 larger than or equal to
608 (0xff00), this member holds
610 (0xffff) and the real index of the section name string table section
613 member of the initial entry in section header table.
616 member of the initial entry in section header table contains the value zero.
618 .SS Program header (Phdr)
619 An executable or shared object file's program header table is an array of
620 structures, each describing a segment or other information the system needs
621 to prepare the program for execution.
626 Program headers are meaningful only for executable and shared object files.
627 A file specifies its own program header size with the ELF header's
632 The ELF program header is described by the type
636 depending on the architecture:
668 The main difference between the 32-bit and the 64-bit program header lies
669 in the location of the
671 member in the total struct.
674 This member of the structure indicates what kind of segment this array
675 element describes or how to interpret the array element's information.
679 The array element is unused and the other members' values are undefined.
680 This lets the program header have ignored entries.
683 The array element specifies a loadable segment, described by
687 The bytes from the file are mapped to the beginning of the memory
689 If the segment's memory size
691 is larger than the file size
695 bytes are defined to hold the value 0 and to follow the segment's
697 The file size may not be larger than the memory size.
698 Loadable segment entries in the program header table appear in ascending
704 The array element specifies dynamic linking information.
707 The array element specifies the location and size of a null-terminated
708 pathname to invoke as an interpreter.
709 This segment type is meaningful
710 only for executable files (though it may occur for shared objects).
711 However it may not occur more than once in a file.
712 If it is present, it must precede any loadable segment entry.
715 The array element specifies the location of notes (ElfN_Nhdr).
718 This segment type is reserved but has unspecified semantics.
720 contain an array element of this type do not conform to the ABI.
723 The array element, if present,
724 specifies the location and size of the program header table itself,
725 both in the file and in the memory image of the program.
726 This segment type may not occur more than once in a file.
728 occur only if the program header table is part of the memory image of the
730 If it is present, it must precede any loadable segment entry.
732 .BR PT_LOPROC ", " PT_HIPROC
733 Values in the inclusive range
734 .RB [ PT_LOPROC ", " PT_HIPROC ]
735 are reserved for processor-specific semantics.
738 GNU extension which is used by the Linux kernel to control the state of the
739 stack via the flags set in the
745 This member holds the offset from the beginning of the file at which
746 the first byte of the segment resides.
749 This member holds the virtual address at which the first byte of the
750 segment resides in memory.
753 On systems for which physical addressing is relevant, this member is
754 reserved for the segment's physical address.
758 not used and must be zero.
761 This member holds the number of bytes in the file image of the segment.
765 This member holds the number of bytes in the memory image of the segment.
769 This member holds a bit mask of flags relevant to the segment:
774 An executable segment.
784 A text segment commonly has the flags
788 A data segment commonly has
794 This member holds the value to which the segments are aligned in memory
796 Loadable process segments must have congruent values for
800 modulo the page size.
801 Values of zero and one mean no alignment is required.
804 should be a positive, integral power of two, and
811 .SS Section header (Shdr)
812 A file's section header table lets one locate all the file's sections.
814 section header table is an array of
822 member gives the byte offset from the beginning of the file to the section
825 holds the number of entries the section header table contains.
827 holds the size in bytes of each entry.
829 A section header table index is a subscript into this array.
831 header table indices are reserved:
832 the initial entry and the indices between
836 The initial entry is used in ELF extensions for
841 in other cases, each field in the initial entry is set to zero.
842 An object file does not have sections for
843 these special indices:
846 This value marks an undefined, missing, irrelevant,
847 or otherwise meaningless section reference.
850 This value specifies the lower bound of the range of reserved indices.
852 .BR SHN_LOPROC ", " SHN_HIPROC
853 Values greater in the inclusive range
854 .RB [ SHN_LOPROC ", " SHN_HIPROC ]
855 are reserved for processor-specific semantics.
858 This value specifies the absolute value for the corresponding reference.
860 example, a symbol defined relative to section number
862 has an absolute value and is not affected by relocation.
865 Symbols defined relative to this section are common symbols,
866 such as FORTRAN COMMON or unallocated C external variables.
869 This value specifies the upper bound of the range of reserved indices.
871 system reserves indices between
876 The section header table does not contain entries for the
879 The section header has the following structure:
892 uint32_t sh_addralign;
909 uint64_t sh_addralign;
915 No real differences exist between the 32-bit and 64-bit section headers.
918 This member specifies the name of the section.
919 Its value is an index
920 into the section header string table section, giving the location of
921 a null-terminated string.
924 This member categorizes the section's contents and semantics.
928 This value marks the section header as inactive.
930 have an associated section.
931 Other members of the section header
932 have undefined values.
935 This section holds information defined by the program, whose
936 format and meaning are determined solely by the program.
939 This section holds a symbol table.
942 provides symbols for link editing, though it may also be used
944 As a complete symbol table, it may contain
945 many symbols unnecessary for dynamic linking.
952 This section holds a string table.
953 An object file may have multiple
954 string table sections.
957 This section holds relocation entries with explicit addends, such
960 for the 32-bit class of object files.
961 An object may have multiple
965 This section holds a symbol hash table.
966 An object participating in
967 dynamic linking must contain a symbol hash table.
969 have only one hash table.
972 This section holds information for dynamic linking.
974 have only one dynamic section.
977 This section holds notes (ElfN_Nhdr).
980 A section of this type occupies no space in the file but otherwise
983 Although this section contains no bytes, the
985 member contains the conceptual file offset.
988 This section holds relocation offsets without explicit addends, such
991 for the 32-bit class of object files.
992 An object file may have multiple
996 This section is reserved but has unspecified semantics.
999 This section holds a minimal set of dynamic linking symbols.
1001 object file can also contain a
1005 .BR SHT_LOPROC ", " SHT_HIPROC
1006 Values in the inclusive range
1007 .RB [ SHT_LOPROC ", " SHT_HIPROC ]
1008 are reserved for processor-specific semantics.
1011 This value specifies the lower bound of the range of indices reserved for
1012 application programs.
1015 This value specifies the upper bound of the range of indices reserved for
1016 application programs.
1017 Section types between
1021 may be used by the application, without conflicting with current or future
1022 system-defined section types.
1026 Sections support one-bit flags that describe miscellaneous attributes.
1027 If a flag bit is set in
1032 Otherwise, the attribute is
1035 Undefined attributes are set to zero.
1039 This section contains data that should be writable during process
1043 This section occupies memory during process execution.
1045 sections do not reside in the memory image of an object file.
1047 attribute is off for those sections.
1050 This section contains executable machine instructions.
1053 All bits included in this mask are reserved for processor-specific
1058 If this section appears in the memory image of a process, this member
1059 holds the address at which the section's first byte should reside.
1060 Otherwise, the member contains zero.
1063 This member's value holds the byte offset from the beginning of the file
1064 to the first byte in the section.
1067 occupies no space in the file, and its
1069 member locates the conceptual placement in the file.
1072 This member holds the section's size in bytes.
1073 Unless the section type
1076 the section occupies
1081 may have a nonzero size, but it occupies no space in the file.
1084 This member holds a section header table index link, whose interpretation
1085 depends on the section type.
1088 This member holds extra information, whose interpretation depends on the
1092 Some sections have address alignment constraints.
1093 If a section holds a
1094 doubleword, the system must ensure doubleword alignment for the entire
1096 That is, the value of
1098 must be congruent to zero, modulo the value of
1100 Only zero and positive integral powers of two are allowed.
1101 The value 0 or 1 means that the section has no alignment constraints.
1104 Some sections hold a table of fixed-sized entries, such as a symbol table.
1105 For such a section, this member gives the size in bytes for each entry.
1106 This member contains zero if the section does not hold a table of
1109 Various sections hold program and control information:
1112 This section holds uninitialized data that contributes to the program's
1114 By definition, the system initializes the data with zeros
1115 when the program begins to run.
1116 This section is of type
1118 The attribute types are
1124 This section holds version control information.
1125 This section is of type
1127 No attribute types are used.
1130 This section holds initialized pointers to the C++ constructor functions.
1131 This section is of type
1133 The attribute types are
1139 This section holds initialized data that contribute to the program's
1141 This section is of type
1143 The attribute types are
1149 This section holds initialized data that contribute to the program's
1151 This section is of type
1153 The attribute types are
1159 This section holds information for symbolic debugging.
1162 This section is of type
1164 No attribute types are used.
1167 This section holds initialized pointers to the C++ destructor functions.
1168 This section is of type
1170 The attribute types are
1176 This section holds dynamic linking information.
1177 The section's attributes
1183 bit is set is processor-specific.
1184 This section is of type
1186 See the attributes above.
1189 This section holds strings needed for dynamic linking, most commonly
1190 the strings that represent the names associated with symbol table entries.
1191 This section is of type
1193 The attribute type used is
1197 This section holds the dynamic linking symbol table.
1198 This section is of type
1200 The attribute used is
1204 This section holds executable instructions that contribute to the process
1206 When a program exits normally the system arranges to
1207 execute the code in this section.
1208 This section is of type
1210 The attributes used are
1216 This section holds the version symbol table, an array of
1219 This section is of type
1220 .BR SHT_GNU_versym .
1221 The attribute type used is
1225 This section holds the version symbol definitions, a table of
1228 This section is of type
1229 .BR SHT_GNU_verdef .
1230 The attribute type used is
1234 This section holds the version symbol needed elements, a table of
1239 .BR SHT_GNU_versym .
1240 The attribute type used is
1244 This section holds the global offset table.
1245 This section is of type
1247 The attributes are processor-specific.
1250 This section holds a symbol hash table.
1251 This section is of type
1253 The attribute used is
1257 This section holds executable instructions that contribute to the process
1258 initialization code.
1259 When a program starts to run the system arranges to execute
1260 the code in this section before calling the main program entry point.
1261 This section is of type
1263 The attributes used are
1269 This section holds the pathname of a program interpreter.
1271 a loadable segment that includes the section, the section's attributes will
1275 Otherwise, that bit will be off.
1276 This section is of type
1280 This section holds line number information for symbolic debugging,
1281 which describes the correspondence between the program source and
1283 The contents are unspecified.
1284 This section is of type
1286 No attribute types are used.
1289 This section holds various notes.
1290 This section is of type
1292 No attribute types are used.
1295 This section is used to declare the expected run-time ABI of the ELF image.
1296 It may include the operating system name and its run-time versions.
1297 This section is of type
1299 The only attribute used is
1302 .IR .note.gnu.build-id
1303 This section is used to hold an ID that uniquely identifies
1304 the contents of the ELF image.
1305 Different files with the same build ID should contain the same executable
1309 option to the GNU linker (\fBld\fR (1)) for more details.
1310 This section is of type
1312 The only attribute used is
1316 This section is used in Linux object files for declaring stack attributes.
1317 This section is of type
1319 The only attribute used is
1321 This indicates to the GNU linker that the object file requires an
1324 .IR .note.openbsd.ident
1325 OpenBSD native executables usually contain this section
1326 to identify themselves so the kernel can bypass any compatibility
1327 ELF binary emulation tests when loading the file.
1330 This section holds the procedure linkage table.
1331 This section is of type
1333 The attributes are processor-specific.
1336 This section holds relocation information as described below.
1338 has a loadable segment that includes relocation, the section's attributes
1342 Otherwise, the bit will be off.
1345 is supplied by the section to which the relocations apply.
1349 normally would have the name
1351 This section is of type
1355 This section holds relocation information as described below.
1357 has a loadable segment that includes relocation, the section's attributes
1361 Otherwise, the bit will be off.
1364 is supplied by the section to which the relocations apply.
1368 normally would have the name
1370 This section is of type
1374 This section holds read-only data that typically contributes to a
1375 nonwritable segment in the process image.
1376 This section is of type
1378 The attribute used is
1382 This section holds read-only data that typically contributes to a
1383 nonwritable segment in the process image.
1384 This section is of type
1386 The attribute used is
1390 This section holds section names.
1391 This section is of type
1393 No attribute types are used.
1396 This section holds strings, most commonly the strings that represent the
1397 names associated with symbol table entries.
1398 If the file has a loadable
1399 segment that includes the symbol string table, the section's attributes
1403 Otherwise, the bit will be off.
1404 This section is of type
1408 This section holds a symbol table.
1409 If the file has a loadable segment
1410 that includes the symbol table, the section's attributes will include
1414 Otherwise, the bit will be off.
1415 This section is of type
1419 This section holds the
1421 or executable instructions, of a program.
1422 This section is of type
1424 The attributes used are
1429 .SS String and symbol tables
1430 String table sections hold null-terminated character sequences, commonly
1432 The object file uses these strings to represent symbol
1434 One references a string as an index into the string
1436 The first byte, which is index zero, is defined to hold
1437 a null byte (\(aq\e0\(aq).
1438 Similarly, a string table's last byte is defined to
1439 hold a null byte, ensuring null termination for all strings.
1441 An object file's symbol table holds information needed to locate and
1442 relocate a program's symbolic definitions and references.
1444 index is a subscript into this array.
1450 Elf32_Addr st_value;
1452 unsigned char st_info;
1453 unsigned char st_other;
1463 unsigned char st_info;
1464 unsigned char st_other;
1466 Elf64_Addr st_value;
1472 The 32-bit and 64-bit versions have the same members, just in a different
1476 This member holds an index into the object file's symbol string table,
1477 which holds character representations of the symbol names.
1479 is nonzero, it represents a string table index that gives the symbol
1481 Otherwise, the symbol has no name.
1484 This member gives the value of the associated symbol.
1487 Many symbols have associated sizes.
1488 This member holds zero if the symbol
1489 has no size or an unknown size.
1492 This member specifies the symbol's type and binding attributes:
1496 The symbol's type is not defined.
1499 The symbol is associated with a data object.
1502 The symbol is associated with a function or other executable code.
1505 The symbol is associated with a section.
1506 Symbol table entries of
1507 this type exist primarily for relocation and normally have
1512 By convention, the symbol's name gives the name of the source file
1513 associated with the object file.
1516 bindings, its section index is
1518 and it precedes the other
1520 symbols of the file, if it is present.
1522 .BR STT_LOPROC ", " STT_HIPROC
1523 Values in the inclusive range
1524 .RB [ STT_LOPROC ", " STT_HIPROC ]
1525 are reserved for processor-specific semantics.
1528 Local symbols are not visible outside the object file containing their
1530 Local symbols of the same name may exist in multiple files
1531 without interfering with each other.
1534 Global symbols are visible to all object files being combined.
1536 definition of a global symbol will satisfy another file's undefined
1537 reference to the same symbol.
1540 Weak symbols resemble global symbols, but their definitions have lower
1543 .BR STB_LOPROC ", " STB_HIPROC
1544 Values in the inclusive range
1545 .RB [ STB_LOPROC ", " STB_HIPROC ]
1546 are reserved for processor-specific semantics.
1549 There are macros for packing and unpacking the binding and type fields:
1552 .BR ELF32_ST_BIND( \fIinfo\fP ) ", " ELF64_ST_BIND( \fIinfo\fP )
1553 Extract a binding from an
1557 .BR ELF32_ST_TYPE( \fIinfo ) ", " ELF64_ST_TYPE( \fIinfo\fP )
1558 Extract a type from an
1562 .BR ELF32_ST_INFO( \fIbind\fP ", " \fItype\fP ) ", " \
1563 ELF64_ST_INFO( \fIbind\fP ", " \fItype\fP )
1564 Convert a binding and a type into an
1570 This member defines the symbol visibility.
1575 Default symbol visibility rules.
1576 Global and weak symbols are available to other modules;
1577 references in the local module can be interposed
1578 by definitions in other modules.
1581 Processor-specific hidden class.
1584 Symbol is unavailable to other modules;
1585 references in the local module always resolve to the local symbol
1586 (i.e., the symbol can't be interposed by definitions in other modules).
1589 Symbol is available to other modules,
1590 but references in the local module always resolve to the local symbol.
1593 There are macros for extracting the visibility type:
1595 .BR ELF32_ST_VISIBILITY (other)
1597 .BR ELF64_ST_VISIBILITY (other)
1601 Every symbol table entry is
1603 in relation to some section.
1604 This member holds the relevant section
1607 .SS Relocation entries (Rel & Rela)
1608 Relocation is the process of connecting symbolic references with
1609 symbolic definitions.
1610 Relocatable files must have information that
1611 describes how to modify their section contents, thus allowing executable
1612 and shared object files to hold the right information for a process's
1614 Relocation entries are these data.
1616 Relocation structures that do not need an addend:
1621 Elf32_Addr r_offset;
1630 Elf64_Addr r_offset;
1636 Relocation structures that need an addend:
1641 Elf32_Addr r_offset;
1651 Elf64_Addr r_offset;
1659 This member gives the location at which to apply the relocation action.
1660 For a relocatable file, the value is the byte offset from the beginning
1661 of the section to the storage unit affected by the relocation.
1663 executable file or shared object, the value is the virtual address of
1664 the storage unit affected by the relocation.
1667 This member gives both the symbol table index with respect to which the
1668 relocation must be made and the type of relocation to apply.
1670 types are processor-specific.
1671 When the text refers to a relocation
1672 entry's relocation type or symbol table index, it means the result of
1674 .BR ELF[32|64]_R_TYPE
1676 .BR ELF[32|64]_R_SYM ,
1677 respectively, to the entry's
1682 This member specifies a constant addend used to compute the value to be
1683 stored into the relocatable field.
1685 .SS Dynamic tags (Dyn)
1688 section contains a series of structures that hold relevant
1689 dynamic linking information.
1692 member controls the interpretation
1705 extern Elf32_Dyn _DYNAMIC[];
1718 extern Elf64_Dyn _DYNAMIC[];
1723 This member may have any of the following values:
1727 Marks end of dynamic section
1730 String table offset to name of a needed library
1733 Size in bytes of PLT relocation entries
1736 Address of PLT and/or GOT
1739 Address of symbol hash table
1742 Address of string table
1745 Address of symbol table
1748 Address of Rela relocation table
1751 Size in bytes of the Rela relocation table
1754 Size in bytes of a Rela relocation table entry
1757 Size in bytes of string table
1760 Size in bytes of a symbol table entry
1763 Address of the initialization function
1766 Address of the termination function
1769 String table offset to name of shared object
1772 String table offset to library search path (deprecated)
1775 Alert linker to search this shared object before the executable for symbols
1778 Address of Rel relocation table
1781 Size in bytes of Rel relocation table
1784 Size in bytes of a Rel table entry
1787 Type of relocation entry to which the PLT refers (Rela or Rel)
1790 Undefined use for debugging
1793 Absence of this entry indicates that no relocation entries should
1794 apply to a nonwritable segment
1797 Address of relocation entries associated solely with the PLT
1800 Instruct dynamic linker to process all relocations before
1801 transferring control to the executable
1804 String table offset to library search path
1806 .BR DT_LOPROC ", " DT_HIPROC
1807 Values in the inclusive range
1808 .RB [ DT_LOPROC ", " DT_HIPROC ]
1809 are reserved for processor-specific semantics
1813 This member represents integer values with various interpretations.
1816 This member represents program virtual addresses.
1818 these addresses, the actual address should be computed based on the
1819 original file value and memory base address.
1820 Files do not contain
1821 relocation entries to fixup these addresses.
1824 Array containing all the dynamic structures in the
1827 This is automatically populated by the linker.
1828 .\" GABI ELF Reference for Note Sections:
1829 .\" http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section
1831 .\" Note that it implies the sizes and alignments of notes depend on the ELF
1832 .\" size (e.g. 32-bit ELFs have three 4-byte words and use 4-byte alignment
1833 .\" while 64-bit ELFs use 8-byte words & alignment), but that is not the case
1834 .\" in the real world. Notes always have three 4-byte words as can be seen
1835 .\" in the source links below (remember that Elf64_Word is a 32-bit quantity).
1836 .\" glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=9e59b3275917549af0cebe1f2de9ded3b7b10bf2#l1173
1837 .\" binutils: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=binutils/readelf.c;h=274ddd17266aef6e4ad1f67af8a13a21500ff2af#l15943
1838 .\" Linux: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/elf.h?h=v4.8#n422
1839 .\" Solaris: https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-18048.html
1840 .\" FreeBSD: https://svnweb.freebsd.org/base/head/sys/sys/elf_common.h?revision=303677&view=markup#l33
1841 .\" NetBSD: https://www.netbsd.org/docs/kernel/elf-notes.html
1842 .\" OpenBSD: https://github.com/openbsd/src/blob/master/sys/sys/exec_elf.h#L533
1845 ELF notes allow for appending arbitrary information for the system to use.
1846 They are largely used by core files
1850 but many projects define their own set of extensions.
1852 the GNU tool chain uses ELF notes to pass information from
1853 the linker to the C library.
1855 Note sections contain a series of notes (see the
1858 Each note is followed by the name field (whose length is defined in
1859 \fIn_namesz\fR) and then by the descriptor field (whose length is defined in
1860 \fIn_descsz\fR) and whose starting address has a 4 byte alignment.
1861 Neither field is defined in the note struct due to their arbitrary lengths.
1863 An example for parsing out two consecutive notes should clarify their layout
1868 void *memory, *name, *desc;
1869 Elf64_Nhdr *note, *next_note;
1871 /* The buffer is pointing to the start of the section/segment */
1874 /* If the name is defined, it follows the note */
1875 name = note->n_namesz == 0 ? NULL : memory + sizeof(*note);
1877 /* If the descriptor is defined, it follows the name
1880 desc = note->n_descsz == 0 ? NULL :
1881 memory + sizeof(*note) + ALIGN_UP(note->n_namesz, 4);
1883 /* The next note follows both (with alignment) */
1884 next_note = memory + sizeof(*note) +
1885 ALIGN_UP(note->n_namesz, 4) +
1886 ALIGN_UP(note->n_descsz, 4);
1890 Keep in mind that the interpretation of
1892 depends on the namespace defined by the
1897 field is not set (e.g., is 0), then there are two sets of notes:
1898 one for core files and one for all other ELF types.
1899 If the namespace is unknown, then tools will usually fallback to these sets
1905 Elf32_Word n_namesz;
1906 Elf32_Word n_descsz;
1915 Elf64_Word n_namesz;
1916 Elf64_Word n_descsz;
1923 The length of the name field in bytes.
1924 The contents will immediately follow this note in memory.
1925 The name is null terminated.
1926 For example, if the name is "GNU", then
1931 The length of the descriptor field in bytes.
1932 The contents will immediately follow the name field in memory.
1935 Depending on the value of the name field, this member may have any of the
1939 .B Core files (e_type = ET_CORE)
1940 Notes used by all core files.
1941 These are highly operating system or architecture specific and often require
1942 close coordination with kernels, C libraries, and debuggers.
1943 These are used when the namespace is the default (i.e.,
1945 will be set to 0), or a fallback when the namespace is unknown.
1965 String from sysinfo(SI_PLATFORM)
1998 siginfo_t (size might increase over time)
2001 Contains information about mapped files
2007 PowerPC Altivec/VMX registers
2010 PowerPC SPE/EVR registers
2013 PowerPC VSX registers
2016 i386 TLS slots (struct user_desc)
2019 x86 io permission bitmap (1=deny)
2022 x86 extended state using xsave
2024 .B NT_S390_HIGH_GPRS
2025 s390 upper register halves
2031 s390 time-of-day (TOD) clock comparator register
2034 s390 time-of-day (TOD) programmable register
2037 s390 control registers
2040 s390 prefix register
2042 .B NT_S390_LAST_BREAK
2043 s390 breaking event address
2045 .B NT_S390_SYSTEM_CALL
2046 s390 system call restart data
2049 s390 transaction diagnostic block
2052 ARM VFP/NEON registers
2058 ARM hardware breakpoint registers
2061 ARM hardware watchpoint registers
2063 .B NT_ARM_SYSTEM_CALL
2064 ARM system call number
2069 Extensions used by the GNU tool chain.
2073 Operating system (OS) ABI information.
2074 The desc field will be 4 words:
2079 word 0: OS descriptor
2080 (\fBELF_NOTE_OS_LINUX\fR, \fBELF_NOTE_OS_GNU\fR, and so on)`
2082 word 1: major version of the ABI
2084 word 2: minor version of the ABI
2086 word 3: subminor version of the ABI
2091 Synthetic hwcap information.
2092 The desc field begins with two words:
2097 word 0: number of entries
2099 word 1: bit mask of enabled entries
2103 Then follow variable-length entries, one byte followed by a null-terminated
2105 The byte gives the bit number to test if enabled, (1U << bit) & bit mask.
2108 Unique build ID as generated by the GNU
2112 The desc consists of any nonzero number of bytes.
2114 .B NT_GNU_GOLD_VERSION
2115 The desc contains the GNU Gold linker version used.
2118 .B Default/unknown namespace (e_type != ET_CORE)
2119 These are used when the namespace is the default (i.e.,
2121 will be set to 0), or a fallback when the namespace is unknown.
2126 A version string of some sort.
2129 Architecture information.
2136 .\" ELF support first appeared in
2138 .\" although not all supported platforms use it as the native
2139 .\" binary file format.
2140 ELF first appeared in
2142 The ELF format is an adopted standard.
2151 Sun, BSD and AMD64 also support them; for further information,
2152 look under SEE ALSO.
2154 .\" The original version of this manual page was written by
2155 .\" .An Jeroen Ruigrok van der Werven
2156 .\" .Aq asmodai@FreeBSD.org
2157 .\" with inspiration from BSDi's
2174 .BR dl_iterate_phdr (3),
2179 .IR "Elf-64 Object File Format" .
2181 Santa Cruz Operation,
2182 .IR "System V Application Binary Interface" .
2184 UNIX System Laboratories,
2186 .IR "Executable and Linking Format (ELF)" .
2189 .IR "Linker and Libraries Guide" .
2192 .IR "System V Application Binary Interface AMD64 Architecture Processor Supplement" .
projects / thirdparty / man-pages.git / blob