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elf_section.h
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elf_section.h
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#ifndef ELF_SECTION_H_
#define ELF_SECTION_H_
#include "elf_types.h"
/*
* ELF Binary Sections.
*
* Sections contain all information in an object file, except the ELF
* header, the program header table, and the section header table.
*/
/* This value marks an undefined, missing, irrelevant, or otherwise
* meaningless section reference. For example, a symbol "defined"
* relative to section number `SHN_UNDEF` is an undefined symbol.
*/
#define SHN_UNDEF 0
/* This value specifies the lower bound of the range of reserverd
* indexes.
*/
#define SHN_LORESERVE 0xff00
/* Values in this inclusive range are reserved for processor-specific
* semantics.
*/
#define SHN_LOPROC 0xff00
#define SHN_HIPROC 0xff1f
/* This value specifies absolute values for the corresponding reference.
* For example, symbols defined relative to section number `SHN_ABS` have
* absolute values and are not affected by relocation.
*/
#define SHN_ABS 0xfff1
/* Symbols defined relative to this section are common symbols, such as
* FORTRAN `COMMON` or unallocated C external variables.
*/
#define SHN_COMMON 0xfff2
/* This value specifies the upper bound of the range of reserved indexes.
* The system reserves indexes between `SHN_LORESERVE` and `SHN_HIRESERVE`,
* inclusive; the values do no reference the section header table. That is,
* the section header table does _not_ contain entries for the reserved
* indexes.
*/
#define SHN_HIRESERVE 0xffff
/*
* Section Types
*/
/* This value marks the section header as inactive; it does not have
* an associated section. Other members of the section header have
* undefined values.
*/
#define SHT_NULL 0
/* This section holds information defined by the program, whose format
* and meaning are determined solely by the program.
*/
#define SHT_PROGBITS 1
/* This section (along with `SHT_DYNSYM`) hold a symbol table. Currently,
* an object file may have only one section of each type, but this
* restriction may be relaxed in the future. Typically, `SHT_SYMTAB`
* provides symbols for link editing, though it may also be used for
* dynamic linking. As a complete symbol table, it may contain many
* symbols unnecessary for dynamic linking. Consequently, an object file
* may also contain a `SHT_DYNSYM` section, which holds a minimal set of
* dynamic linking symbols, to save space.
*/
#define SHT_SYMTAB 2
/* This section holds a string table. An object file may have multiple
* string table sections.
*/
#define SHT_STRTAB 3
/* This section holds relocation entries with explicit addends, such as
* type `Elf64_Rela` for the 64-bit class of object files. An object file
* may have multiple relocation sections.
*/
#define SHT_RELA 4
/* This section holds a symbol hash table. All objects participating in
* dynamic linking must contain a symbol hash table. Currently, an object
* file may have only one hash table, but this restriction may be relaxed
* in the future.
*/
#define SHT_HASH 5
/* This section holds information for dynamic linking. Currently, an
* object file may have only one dynamic section, but this restriction
* may be relaxed in the future.
*/
#define SHT_DYNAMIC 6
/* This section holds information that marks the file in some way. */
#define SHT_NOTE 7
/* A section of this type occupies no space in the file but otherwise
* resembles `SHT_PROGBITS`. Although this section contains no bytes,
* the `sh_offset` member contains the conceptual file offset.
*/
#define SHT_NOBITS 8
/* The section holds relocation entries without explicit addends,
* such as type `Elf64_rel` for the 64-bit class of object files.
* An object file may have multiple relocation sections.
*/
#define SHT_REL 9
/* This section type is reserve but has unspecified semantics. Programs
* that contain a section of this type do not conform to the ABI.
*/
#define SHT_SHLIB 10
/* See `SHT_SYMTAB` above. */
#define SHT_DYNSYM 11
/* Values in this inclusive range as reserved for processor-specific
* semantics.
*/
#define SHT_LOPROC 0x70000000
#define SHT_HIPROC 0x7fffffff
/* This value specifies the lower bound of the range of indexes reserved
* for application programs.
*/
#define SHT_LOUSER 0x80000000
/* This value specifies the upper bound of the range of indexes reserved
* for application programs. Section types between `SHT_LOUSER` and
* `SHT_HIUSER` may be used by the application, without conflicting with
* current or future system-defined section types.
*/
#define SHT_HIUSER 0xffffffff
/*
* Section Attribute Flags for `sh_flags`
*/
/* This section contains data that should be writable during process
* execution.
*/
#define SHF_WRITE 0x1
/* This section occupies memory during process execution. Some control
* sections do not reside in the memory image of an object file; this
* attribute is off for those sections.
*/
#define SHF_ALLOC 0x2
/* This section contains executable machine instructions. */
#define SHF_EXECINSTR 0x4
/* All bits included in this mask are reserved for processor-specific
* semantics.
*/
#define SHF_MASKPROC 0xf0000000
/* Flat size */
#define SHDR_SIZE 64
/* ELF Binary Section Header */
typedef struct {
/* This member specifies the name of the section. Its value is an
* index into the section header string table section, giving the
* location of a NULL-terminated string.
*/
Elf64_Half sh_name;
/* This member categorizes the section's contents and semantics. */
Elf64_Half sh_type;
/* Sections support 1-bit flags that describe miscellaneous attributes. */
Elf64_Word sh_flags;
/* If the section will appear in the memory image of a process, this
* member gives the address at which the section's first byte should
* reside. Otherwise, the member contains 0.
*/
Elf64_Addr sh_addr;
/* This member's value gives the bbyte offset from the beginning of
* the file to the first byte in the section. One section type,
* `SHT_NOBITS` described above, occupies no space in the file, and
* its `sh_offset` member locates the conceptual placement in the file.
*/
Elf64_Off sh_offset;
/* This member gives the section's size in bytes. Unless the section
* type is `SHT_NOBITS`, the section occupies `sh_size` bytes in the
* file. A section of type `SHT_NOBITS` may have a non-zero size, but
* it occupies no space in the file.
*/
Elf64_Word sh_size;
/* This member holds a section header table index link, whose
* interpretation depends on the section type.
*/
Elf64_Half sh_link;
/* This member holds extra information, whose interpretation depends
* on the section type.
*/
Elf64_Half sh_info;
/* Some sections have address alignment constraints. For example, if a
* section holds a doubleword, the system must ensure doubleword
* alignment for the entire section. That is, the value of `sh_addr`
* must be congruent to 0, module the value of `sh_addralign`.
* Currently, only 0 and positive integral powers of two are allowed.
* Values 0 and 1 mean the section has no alignment constraints.
*/
Elf64_Word sh_addralign;
/* Some sections hold a table of fixed-size entries, such as a symbol
* table. For such a section, this member gives the size in bytes of
* each entry. The member contains 0 if the section does not hold a
* table of fixed-size entries.
*/
Elf64_Word sh_entsize;
} Elf64_Shdr;
#endif