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 2021-03-22 "Linux man-pages (unreleased)"
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:
170 This array of bytes specifies how to interpret the file,
171 independent of the processor or the file's remaining contents.
172 Within this array everything is named by macros, which start with
175 and may contain values which start with the prefix
177 The following macros are defined:
181 The first byte of the magic number.
182 It must be filled with
187 The second byte of the magic number.
188 It must be filled with
193 The third byte of the magic number.
194 It must be filled with
199 The fourth byte of the magic number.
200 It must be filled with
205 The fifth byte identifies the architecture for this binary:
210 This class is invalid.
213 This defines the 32-bit architecture.
214 It supports machines with files
215 and virtual address spaces up to 4 Gigabytes.
218 This defines the 64-bit architecture.
223 The sixth byte specifies the data encoding of the processor-specific
225 Currently, these encodings are supported:
233 Two's complement, little-endian.
236 Two's complement, big-endian.
241 The seventh byte is the version number of the ELF specification:
256 The eighth byte identifies the operating system
257 and ABI to which the object is targeted.
258 Some fields in other ELF structures have flags
259 and values that have platform-specific meanings;
260 the interpretation of those fields is determined by the value of this byte.
266 Same as ELFOSABI_SYSV
272 .\" synonym: ELFOSABI_NONE
286 .\" .BR ELFOSABI_HURD
290 .\" .BR ELFOSABI_86OPEN
291 .\" 86Open Common IA32 ABI
298 .\" .BR ELFOSABI_MONTEREY
299 .\" Monterey project ABI
324 .B ELFOSABI_STANDALONE
325 Stand-alone (embedded) ABI
331 The ninth byte identifies the version of the ABI
332 to which the object is targeted.
333 This field is used to distinguish among incompatible versions of an ABI.
334 The interpretation of this version number
335 is dependent on the ABI identified by the
338 Applications conforming to this specification use the value 0.
342 These bytes are reserved and set to zero.
344 which read them should ignore them.
348 the future if currently unused bytes are given meanings.
349 .\" As reported by Yuri Kozlov and confirmed by Mike Frysinger, EI_BRAND is
350 .\" not in GABI (http://www.sco.com/developers/gabi/latest/ch4.eheader.html)
351 .\" It looks to be a BSDism
354 .\" Start of architecture identification.
363 This member of the structure identifies the object file type:
385 This member specifies the required architecture for an individual file.
399 Sun Microsystems SPARC
423 MIPS RS3000 (big-endian only)
428 .\" .BR EM_MIPS_RS4_BE
429 .\" MIPS RS4000 (big-endian only). Deprecated
431 .\" EM_MIPS_RS3_LE (MIPS R3000 little-endian)
439 SPARC with enhanced instruction set
455 Advanced RISC Machines
481 .\" Compaq [DEC] Alpha
484 .\" Compaq [DEC] Alpha with enhanced instruction set
489 This member identifies the file version:
502 This member gives the virtual address to which the system first transfers
503 control, thus starting the process.
504 If the file has no associated entry
505 point, this member holds zero.
508 This member holds the program header table's file offset in bytes.
510 the file has no program header table, this member holds zero.
513 This member holds the section header table's file offset in bytes.
515 file has no section header table, this member holds zero.
518 This member holds processor-specific flags associated with the file.
519 Flag names take the form EF_`machine_flag'.
520 Currently, no flags have been defined.
523 This member holds the ELF header's size in bytes.
526 This member holds the size in bytes of one entry in the file's
527 program header table; all entries are the same size.
530 This member holds the number of entries in the program header
536 gives the table's size
538 If a file has no program header,
540 holds the value zero.
542 If the number of entries in the program header table is
543 larger than or equal to
544 .\" This is a Linux extension, added in Linux 2.6.34.
546 (0xffff), this member holds
548 (0xffff) and the real number of entries in the program header table is held
551 member of the initial entry in section header table.
554 member of the initial entry contains the value zero.
558 This is defined as 0xffff, the largest number
560 can have, specifying where the actual number of program headers is assigned.
565 This member holds a sections header's size in bytes.
566 A section header is one
567 entry in the section header table; all entries are the same size.
570 This member holds the number of entries in the section header table.
576 gives the section header table's size in bytes.
577 If a file has no section
580 holds the value of zero.
582 If the number of entries in the section header table is
583 larger than or equal to
587 holds the value zero and the real number of entries in the section header
590 member of the initial entry in section header table.
593 member of the initial entry in the section header table holds
597 This member holds the section header table index of the entry associated
598 with the section name string table.
599 If the file has no section name string
600 table, this member holds the value
603 If the index of section name string table section is
604 larger than or equal to
606 (0xff00), this member holds
608 (0xffff) and the real index of the section name string table section
611 member of the initial entry in section header table.
614 member of the initial entry in section header table contains the value zero.
616 .SS Program header (Phdr)
617 An executable or shared object file's program header table is an array of
618 structures, each describing a segment or other information the system needs
619 to prepare the program for execution.
624 Program headers are meaningful only for executable and shared object files.
625 A file specifies its own program header size with the ELF header's
630 The ELF program header is described by the type
634 depending on the architecture:
666 The main difference between the 32-bit and the 64-bit program header lies
667 in the location of the
669 member in the total struct.
672 This member of the structure indicates what kind of segment this array
673 element describes or how to interpret the array element's information.
677 The array element is unused and the other members' values are undefined.
678 This lets the program header have ignored entries.
681 The array element specifies a loadable segment, described by
685 The bytes from the file are mapped to the beginning of the memory
687 If the segment's memory size
689 is larger than the file size
693 bytes are defined to hold the value 0 and to follow the segment's
695 The file size may not be larger than the memory size.
696 Loadable segment entries in the program header table appear in ascending
702 The array element specifies dynamic linking information.
705 The array element specifies the location and size of a null-terminated
706 pathname to invoke as an interpreter.
707 This segment type is meaningful
708 only for executable files (though it may occur for shared objects).
709 However it may not occur more than once in a file.
710 If it is present, it must precede any loadable segment entry.
713 The array element specifies the location of notes (ElfN_Nhdr).
716 This segment type is reserved but has unspecified semantics.
718 contain an array element of this type do not conform to the ABI.
721 The array element, if present,
722 specifies the location and size of the program header table itself,
723 both in the file and in the memory image of the program.
724 This segment type may not occur more than once in a file.
726 occur only if the program header table is part of the memory image of the
728 If it is present, it must precede any loadable segment entry.
730 .BR PT_LOPROC ", " PT_HIPROC
731 Values in the inclusive range
734 are reserved for processor-specific semantics.
737 GNU extension which is used by the Linux kernel to control the state of the
738 stack via the flags set in the
744 This member holds the offset from the beginning of the file at which
745 the first byte of the segment resides.
748 This member holds the virtual address at which the first byte of the
749 segment resides in memory.
752 On systems for which physical addressing is relevant, this member is
753 reserved for the segment's physical address.
757 not used and must be zero.
760 This member holds the number of bytes in the file image of the segment.
764 This member holds the number of bytes in the memory image of the segment.
768 This member holds a bit mask of flags relevant to the segment:
773 An executable segment.
783 A text segment commonly has the flags
787 A data segment commonly has
793 This member holds the value to which the segments are aligned in memory
795 Loadable process segments must have congruent values for
799 modulo the page size.
800 Values of zero and one mean no alignment is required.
803 should be a positive, integral power of two, and
810 .SS Section header (Shdr)
811 A file's section header table lets one locate all the file's sections.
813 section header table is an array of
821 member gives the byte offset from the beginning of the file to the section
824 holds the number of entries the section header table contains.
826 holds the size in bytes of each entry.
828 A section header table index is a subscript into this array.
830 header table indices are reserved:
831 the initial entry and the indices between
835 The initial entry is used in ELF extensions for
840 in other cases, each field in the initial entry is set to zero.
841 An object file does not have sections for
842 these special indices:
845 This value marks an undefined, missing, irrelevant,
846 or otherwise meaningless section reference.
849 This value specifies the lower bound of the range of reserved indices.
851 .BR SHN_LOPROC ", " SHN_HIPROC
852 Values greater in the inclusive range
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
1009 are reserved for processor-specific semantics.
1012 This value specifies the lower bound of the range of indices reserved for
1013 application programs.
1016 This value specifies the upper bound of the range of indices reserved for
1017 application programs.
1018 Section types between
1022 may be used by the application, without conflicting with current or future
1023 system-defined section types.
1027 Sections support one-bit flags that describe miscellaneous attributes.
1028 If a flag bit is set in
1033 Otherwise, the attribute is
1036 Undefined attributes are set to zero.
1040 This section contains data that should be writable during process
1044 This section occupies memory during process execution.
1046 sections do not reside in the memory image of an object file.
1048 attribute is off for those sections.
1051 This section contains executable machine instructions.
1054 All bits included in this mask are reserved for processor-specific
1059 If this section appears in the memory image of a process, this member
1060 holds the address at which the section's first byte should reside.
1061 Otherwise, the member contains zero.
1064 This member's value holds the byte offset from the beginning of the file
1065 to the first byte in the section.
1068 occupies no space in the file, and its
1070 member locates the conceptual placement in the file.
1073 This member holds the section's size in bytes.
1074 Unless the section type
1077 the section occupies
1082 may have a nonzero size, but it occupies no space in the file.
1085 This member holds a section header table index link, whose interpretation
1086 depends on the section type.
1089 This member holds extra information, whose interpretation depends on the
1093 Some sections have address alignment constraints.
1094 If a section holds a
1095 doubleword, the system must ensure doubleword alignment for the entire
1097 That is, the value of
1099 must be congruent to zero, modulo the value of
1101 Only zero and positive integral powers of two are allowed.
1102 The value 0 or 1 means that the section has no alignment constraints.
1105 Some sections hold a table of fixed-sized entries, such as a symbol table.
1106 For such a section, this member gives the size in bytes for each entry.
1107 This member contains zero if the section does not hold a table of
1110 Various sections hold program and control information:
1113 This section holds uninitialized data that contributes to the program's
1115 By definition, the system initializes the data with zeros
1116 when the program begins to run.
1117 This section is of type
1119 The attribute types are
1125 This section holds version control information.
1126 This section is of type
1128 No attribute types are used.
1131 This section holds initialized pointers to the C++ constructor functions.
1132 This section is of type
1134 The attribute types are
1140 This section holds initialized data that contribute to the program's
1142 This section is of type
1144 The attribute types are
1150 This section holds initialized data that contribute to the program's
1152 This section is of type
1154 The attribute types are
1160 This section holds information for symbolic debugging.
1163 This section is of type
1165 No attribute types are used.
1168 This section holds initialized pointers to the C++ destructor functions.
1169 This section is of type
1171 The attribute types are
1177 This section holds dynamic linking information.
1178 The section's attributes
1184 bit is set is processor-specific.
1185 This section is of type
1187 See the attributes above.
1190 This section holds strings needed for dynamic linking, most commonly
1191 the strings that represent the names associated with symbol table entries.
1192 This section is of type
1194 The attribute type used is
1198 This section holds the dynamic linking symbol table.
1199 This section is of type
1201 The attribute used is
1205 This section holds executable instructions that contribute to the process
1207 When a program exits normally the system arranges to
1208 execute the code in this section.
1209 This section is of type
1211 The attributes used are
1217 This section holds the version symbol table, an array of
1220 This section is of type
1221 .BR SHT_GNU_versym .
1222 The attribute type used is
1226 This section holds the version symbol definitions, a table of
1229 This section is of type
1230 .BR SHT_GNU_verdef .
1231 The attribute type used is
1235 This section holds the version symbol needed elements, a table of
1240 .BR SHT_GNU_versym .
1241 The attribute type used is
1245 This section holds the global offset table.
1246 This section is of type
1248 The attributes are processor-specific.
1251 This section holds a symbol hash table.
1252 This section is of type
1254 The attribute used is
1258 This section holds executable instructions that contribute to the process
1259 initialization code.
1260 When a program starts to run the system arranges to execute
1261 the code in this section before calling the main program entry point.
1262 This section is of type
1264 The attributes used are
1270 This section holds the pathname of a program interpreter.
1272 a loadable segment that includes the section, the section's attributes will
1276 Otherwise, that bit will be off.
1277 This section is of type
1281 This section holds line number information for symbolic debugging,
1282 which describes the correspondence between the program source and
1284 The contents are unspecified.
1285 This section is of type
1287 No attribute types are used.
1290 This section holds various notes.
1291 This section is of type
1293 No attribute types are used.
1296 This section is used to declare the expected run-time ABI of the ELF image.
1297 It may include the operating system name and its run-time versions.
1298 This section is of type
1300 The only attribute used is
1303 .I .note.gnu.build\-id
1304 This section is used to hold an ID that uniquely identifies
1305 the contents of the ELF image.
1306 Different files with the same build ID should contain the same executable
1310 option to the GNU linker (\fBld\fR (1)) for more details.
1311 This section is of type
1313 The only attribute used is
1317 This section is used in Linux object files for declaring stack attributes.
1318 This section is of type
1320 The only attribute used is
1322 This indicates to the GNU linker that the object file requires an
1325 .I .note.openbsd.ident
1326 OpenBSD native executables usually contain this section
1327 to identify themselves so the kernel can bypass any compatibility
1328 ELF binary emulation tests when loading the file.
1331 This section holds the procedure linkage table.
1332 This section is of type
1334 The attributes are processor-specific.
1337 This section holds relocation information as described below.
1339 has a loadable segment that includes relocation, the section's attributes
1343 Otherwise, the bit will be off.
1346 is supplied by the section to which the relocations apply.
1350 normally would have the name
1352 This section is of type
1356 This section holds relocation information as described below.
1358 has a loadable segment that includes relocation, the section's attributes
1362 Otherwise, the bit will be off.
1365 is supplied by the section to which the relocations apply.
1369 normally would have the name
1371 This section is of type
1375 This section holds read-only data that typically contributes to a
1376 nonwritable segment in the process image.
1377 This section is of type
1379 The attribute used is
1383 This section holds read-only data that typically contributes to a
1384 nonwritable segment in the process image.
1385 This section is of type
1387 The attribute used is
1391 This section holds section names.
1392 This section is of type
1394 No attribute types are used.
1397 This section holds strings, most commonly the strings that represent the
1398 names associated with symbol table entries.
1399 If the file has a loadable
1400 segment that includes the symbol string table, the section's attributes
1404 Otherwise, the bit will be off.
1405 This section is of type
1409 This section holds a symbol table.
1410 If the file has a loadable segment
1411 that includes the symbol table, the section's attributes will include
1415 Otherwise, the bit will be off.
1416 This section is of type
1420 This section holds the
1422 or executable instructions, of a program.
1423 This section is of type
1425 The attributes used are
1430 .SS String and symbol tables
1431 String table sections hold null-terminated character sequences, commonly
1433 The object file uses these strings to represent symbol
1435 One references a string as an index into the string
1437 The first byte, which is index zero, is defined to hold
1438 a null byte (\(aq\e0\(aq).
1439 Similarly, a string table's last byte is defined to
1440 hold a null byte, ensuring null termination for all strings.
1442 An object file's symbol table holds information needed to locate and
1443 relocate a program's symbolic definitions and references.
1445 index is a subscript into this array.
1451 Elf32_Addr st_value;
1453 unsigned char st_info;
1454 unsigned char st_other;
1464 unsigned char st_info;
1465 unsigned char st_other;
1467 Elf64_Addr st_value;
1473 The 32-bit and 64-bit versions have the same members, just in a different
1477 This member holds an index into the object file's symbol string table,
1478 which holds character representations of the symbol names.
1480 is nonzero, it represents a string table index that gives the symbol
1482 Otherwise, the symbol has no name.
1485 This member gives the value of the associated symbol.
1488 Many symbols have associated sizes.
1489 This member holds zero if the symbol
1490 has no size or an unknown size.
1493 This member specifies the symbol's type and binding attributes:
1497 The symbol's type is not defined.
1500 The symbol is associated with a data object.
1503 The symbol is associated with a function or other executable code.
1506 The symbol is associated with a section.
1507 Symbol table entries of
1508 this type exist primarily for relocation and normally have
1513 By convention, the symbol's name gives the name of the source file
1514 associated with the object file.
1517 bindings, its section index is
1519 and it precedes the other
1521 symbols of the file, if it is present.
1523 .BR STT_LOPROC ", " STT_HIPROC
1524 Values in the inclusive range
1527 are reserved for processor-specific semantics.
1530 Local symbols are not visible outside the object file containing their
1532 Local symbols of the same name may exist in multiple files
1533 without interfering with each other.
1536 Global symbols are visible to all object files being combined.
1538 definition of a global symbol will satisfy another file's undefined
1539 reference to the same symbol.
1542 Weak symbols resemble global symbols, but their definitions have lower
1545 .BR STB_LOPROC ", " STB_HIPROC
1546 Values in the inclusive range
1549 are reserved for processor-specific semantics.
1552 There are macros for packing and unpacking the binding and type fields:
1555 .BR ELF32_ST_BIND( \fIinfo\fP ) ", " ELF64_ST_BIND( \fIinfo\fP )
1556 Extract a binding from an
1560 .BR ELF32_ST_TYPE( \fIinfo ) ", " ELF64_ST_TYPE( \fIinfo\fP )
1561 Extract a type from an
1565 .BR ELF32_ST_INFO( \fIbind\fP ", " \fItype\fP ) ", " \
1566 ELF64_ST_INFO( \fIbind\fP ", " \fItype\fP )
1567 Convert a binding and a type into an
1573 This member defines the symbol visibility.
1578 Default symbol visibility rules.
1579 Global and weak symbols are available to other modules;
1580 references in the local module can be interposed
1581 by definitions in other modules.
1584 Processor-specific hidden class.
1587 Symbol is unavailable to other modules;
1588 references in the local module always resolve to the local symbol
1589 (i.e., the symbol can't be interposed by definitions in other modules).
1592 Symbol is available to other modules,
1593 but references in the local module always resolve to the local symbol.
1596 There are macros for extracting the visibility type:
1598 .BR ELF32_ST_VISIBILITY (other)
1600 .BR ELF64_ST_VISIBILITY (other)
1604 Every symbol table entry is
1606 in relation to some section.
1607 This member holds the relevant section
1610 .SS Relocation entries (Rel & Rela)
1611 Relocation is the process of connecting symbolic references with
1612 symbolic definitions.
1613 Relocatable files must have information that
1614 describes how to modify their section contents, thus allowing executable
1615 and shared object files to hold the right information for a process's
1617 Relocation entries are these data.
1619 Relocation structures that do not need an addend:
1624 Elf32_Addr r_offset;
1633 Elf64_Addr r_offset;
1639 Relocation structures that need an addend:
1644 Elf32_Addr r_offset;
1654 Elf64_Addr r_offset;
1662 This member gives the location at which to apply the relocation action.
1663 For a relocatable file, the value is the byte offset from the beginning
1664 of the section to the storage unit affected by the relocation.
1666 executable file or shared object, the value is the virtual address of
1667 the storage unit affected by the relocation.
1670 This member gives both the symbol table index with respect to which the
1671 relocation must be made and the type of relocation to apply.
1673 types are processor-specific.
1674 When the text refers to a relocation
1675 entry's relocation type or symbol table index, it means the result of
1677 .B ELF[32|64]_R_TYPE
1679 .BR ELF[32|64]_R_SYM ,
1680 respectively, to the entry's
1685 This member specifies a constant addend used to compute the value to be
1686 stored into the relocatable field.
1688 .SS Dynamic tags (Dyn)
1691 section contains a series of structures that hold relevant
1692 dynamic linking information.
1695 member controls the interpretation
1708 extern Elf32_Dyn _DYNAMIC[];
1721 extern Elf64_Dyn _DYNAMIC[];
1726 This member may have any of the following values:
1730 Marks end of dynamic section
1733 String table offset to name of a needed library
1736 Size in bytes of PLT relocation entries
1739 Address of PLT and/or GOT
1742 Address of symbol hash table
1745 Address of string table
1748 Address of symbol table
1751 Address of Rela relocation table
1754 Size in bytes of the Rela relocation table
1757 Size in bytes of a Rela relocation table entry
1760 Size in bytes of string table
1763 Size in bytes of a symbol table entry
1766 Address of the initialization function
1769 Address of the termination function
1772 String table offset to name of shared object
1775 String table offset to library search path (deprecated)
1778 Alert linker to search this shared object before the executable for symbols
1781 Address of Rel relocation table
1784 Size in bytes of Rel relocation table
1787 Size in bytes of a Rel table entry
1790 Type of relocation entry to which the PLT refers (Rela or Rel)
1793 Undefined use for debugging
1796 Absence of this entry indicates that no relocation entries should
1797 apply to a nonwritable segment
1800 Address of relocation entries associated solely with the PLT
1803 Instruct dynamic linker to process all relocations before
1804 transferring control to the executable
1807 String table offset to library search path
1809 .BR DT_LOPROC ", " DT_HIPROC
1810 Values in the inclusive range
1813 are reserved for processor-specific semantics
1817 This member represents integer values with various interpretations.
1820 This member represents program virtual addresses.
1822 these addresses, the actual address should be computed based on the
1823 original file value and memory base address.
1824 Files do not contain
1825 relocation entries to fixup these addresses.
1828 Array containing all the dynamic structures in the
1831 This is automatically populated by the linker.
1832 .\" GABI ELF Reference for Note Sections:
1833 .\" http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section
1835 .\" Note that it implies the sizes and alignments of notes depend on the ELF
1836 .\" size (e.g. 32-bit ELFs have three 4-byte words and use 4-byte alignment
1837 .\" while 64-bit ELFs use 8-byte words & alignment), but that is not the case
1838 .\" in the real world. Notes always have three 4-byte words as can be seen
1839 .\" in the source links below (remember that Elf64_Word is a 32-bit quantity).
1840 .\" glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=9e59b3275917549af0cebe1f2de9ded3b7b10bf2#l1173
1841 .\" binutils: https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=binutils/readelf.c;h=274ddd17266aef6e4ad1f67af8a13a21500ff2af#l15943
1842 .\" Linux: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/elf.h?h=v4.8#n422
1843 .\" Solaris: https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-18048.html
1844 .\" FreeBSD: https://svnweb.freebsd.org/base/head/sys/sys/elf_common.h?revision=303677&view=markup#l33
1845 .\" NetBSD: https://www.netbsd.org/docs/kernel/elf-notes.html
1846 .\" OpenBSD: https://github.com/openbsd/src/blob/master/sys/sys/exec_elf.h#L533
1849 ELF notes allow for appending arbitrary information for the system to use.
1850 They are largely used by core files
1854 but many projects define their own set of extensions.
1856 the GNU tool chain uses ELF notes to pass information from
1857 the linker to the C library.
1859 Note sections contain a series of notes (see the
1862 Each note is followed by the name field (whose length is defined in
1863 \fIn_namesz\fR) and then by the descriptor field (whose length is defined in
1864 \fIn_descsz\fR) and whose starting address has a 4 byte alignment.
1865 Neither field is defined in the note struct due to their arbitrary lengths.
1867 An example for parsing out two consecutive notes should clarify their layout
1872 void *memory, *name, *desc;
1873 Elf64_Nhdr *note, *next_note;
1875 /* The buffer is pointing to the start of the section/segment. */
1878 /* If the name is defined, it follows the note. */
1879 name = note\->n_namesz == 0 ? NULL : memory + sizeof(*note);
1881 /* If the descriptor is defined, it follows the name
1882 (with alignment). */
1884 desc = note\->n_descsz == 0 ? NULL :
1885 memory + sizeof(*note) + ALIGN_UP(note\->n_namesz, 4);
1887 /* The next note follows both (with alignment). */
1888 next_note = memory + sizeof(*note) +
1889 ALIGN_UP(note\->n_namesz, 4) +
1890 ALIGN_UP(note\->n_descsz, 4);
1894 Keep in mind that the interpretation of
1896 depends on the namespace defined by the
1901 field is not set (e.g., is 0), then there are two sets of notes:
1902 one for core files and one for all other ELF types.
1903 If the namespace is unknown, then tools will usually fallback to these sets
1909 Elf32_Word n_namesz;
1910 Elf32_Word n_descsz;
1919 Elf64_Word n_namesz;
1920 Elf64_Word n_descsz;
1927 The length of the name field in bytes.
1928 The contents will immediately follow this note in memory.
1929 The name is null terminated.
1930 For example, if the name is "GNU", then
1935 The length of the descriptor field in bytes.
1936 The contents will immediately follow the name field in memory.
1939 Depending on the value of the name field, this member may have any of the
1943 .B Core files (e_type = ET_CORE)
1944 Notes used by all core files.
1945 These are highly operating system or architecture specific and often require
1946 close coordination with kernels, C libraries, and debuggers.
1947 These are used when the namespace is the default (i.e.,
1949 will be set to 0), or a fallback when the namespace is unknown.
1969 String from sysinfo(SI_PLATFORM)
2002 siginfo_t (size might increase over time)
2005 Contains information about mapped files
2011 PowerPC Altivec/VMX registers
2014 PowerPC SPE/EVR registers
2017 PowerPC VSX registers
2020 i386 TLS slots (struct user_desc)
2023 x86 io permission bitmap (1=deny)
2026 x86 extended state using xsave
2028 .B NT_S390_HIGH_GPRS
2029 s390 upper register halves
2035 s390 time-of-day (TOD) clock comparator register
2038 s390 time-of-day (TOD) programmable register
2041 s390 control registers
2044 s390 prefix register
2046 .B NT_S390_LAST_BREAK
2047 s390 breaking event address
2049 .B NT_S390_SYSTEM_CALL
2050 s390 system call restart data
2053 s390 transaction diagnostic block
2056 ARM VFP/NEON registers
2062 ARM hardware breakpoint registers
2065 ARM hardware watchpoint registers
2067 .B NT_ARM_SYSTEM_CALL
2068 ARM system call number
2073 Extensions used by the GNU tool chain.
2077 Operating system (OS) ABI information.
2078 The desc field will be 4 words:
2083 word 0: OS descriptor
2084 (\fBELF_NOTE_OS_LINUX\fR, \fBELF_NOTE_OS_GNU\fR, and so on)`
2086 word 1: major version of the ABI
2088 word 2: minor version of the ABI
2090 word 3: subminor version of the ABI
2095 Synthetic hwcap information.
2096 The desc field begins with two words:
2101 word 0: number of entries
2103 word 1: bit mask of enabled entries
2107 Then follow variable-length entries, one byte followed by a null-terminated
2109 The byte gives the bit number to test if enabled, (1U << bit) & bit mask.
2112 Unique build ID as generated by the GNU
2116 The desc consists of any nonzero number of bytes.
2118 .B NT_GNU_GOLD_VERSION
2119 The desc contains the GNU Gold linker version used.
2122 .B Default/unknown namespace (e_type != ET_CORE)
2123 These are used when the namespace is the default (i.e.,
2125 will be set to 0), or a fallback when the namespace is unknown.
2130 A version string of some sort.
2133 Architecture information.
2139 .\" ELF support first appeared in
2141 .\" although not all supported platforms use it as the native
2142 .\" binary file format.
2143 ELF first appeared in
2145 The ELF format is an adopted standard.
2154 Sun, BSD, and AMD64 also support them; for further information,
2155 look under SEE ALSO.
2157 .\" The original version of this manual page was written by
2158 .\" .An Jeroen Ruigrok van der Werven
2159 .\" .Aq asmodai@FreeBSD.org
2160 .\" with inspiration from BSDi's
2178 .BR dl_iterate_phdr (3),
2183 .IR "Elf-64 Object File Format" .
2185 Santa Cruz Operation,
2186 .IR "System V Application Binary Interface" .
2188 UNIX System Laboratories,
2190 .IR "Executable and Linking Format (ELF)" .
2193 .IR "Linker and Libraries Guide" .
2196 .IR "System V Application Binary Interface AMD64 Architecture Processor Supplement" .
projects / thirdparty / man-pages.git / blob