Editing Executable and Linkable Format (section)

=== Program header ===

The program header table tells the system how to create a process image.  It is found at file offset {{mono|e_phoff}}, and consists of {{mono|e_phnum}} entries, each with size {{mono|e_phentsize}}.  The layout is slightly different in [[32-bit]] ELF vs [[64-bit]] ELF, because the {{mono|p_flags}} are in a different structure location for alignment reasons.  Each entry is structured as:

{| class="wikitable"
|+ Program header<ref>{{cite web|url=http://www.sco.com/developers/gabi/2000-07-17/ch5.pheader.html |title=Program Header |publisher=Sco.com |date=July 2000 |access-date=2017-04-05}}</ref>
|-
! colspan="2" | Offset!! colspan="2" | Size (bytes) !! rowspan="2" | Field !! rowspan="2" | Purpose
|-
! 32-bit !! 64-bit !! 32-bit !! 64-bit
|-
| colspan="2" | {{tt|0x00}} || colspan="2" | 4 
||{{mono|p_type}}||Identifies the type of the segment.
{| class="wikitable"
|-
!Value!!Name!!Meaning
|-
| {{tt|0x00000000}} ||{{mono|PT_NULL}}
| Program header table entry unused.
|-
| {{tt|0x00000001}} ||{{mono|PT_LOAD}}
| Loadable segment.
|-
| {{tt|0x00000002}} ||{{mono|PT_DYNAMIC}}
| Dynamic linking information.
|-
| {{tt|0x00000003}} ||{{mono|PT_INTERP}}
| Interpreter information.
|-
| {{tt|0x00000004}} ||{{mono|PT_NOTE}}
| Auxiliary information.
|-
| {{tt|0x00000005}} ||{{mono|PT_SHLIB}}
| Reserved.
|-
| {{tt|0x00000006}} ||{{mono|PT_PHDR}}
| Segment containing program header table itself.
|-
| {{tt|0x00000007}} ||{{mono|PT_TLS}}
| Thread-Local Storage template.
|-
| {{tt|0x60000000}} ||{{mono|PT_LOOS}}
| rowspan="2" | Reserved inclusive range. Operating system specific.
|-
| {{tt|0x6FFFFFFF}} ||{{mono|PT_HIOS}}
|-
| {{tt|0x70000000}} ||{{mono|PT_LOPROC}}
| rowspan="2" | Reserved inclusive range. Processor specific.
|-
| {{tt|0x7FFFFFFF}} ||{{mono|PT_HIPROC}}
|}
|-
|  || {{tt|0x04}} || || 4 ||{{mono|p_flags}}||Segment-dependent flags (position for 64-bit structure).
{| class="wikitable"
!Value
!Name
!Meaning
|-
| {{tt|0x1}}
|{{mono|PF_X}}
|Executable segment.
|-
| {{tt|0x2}}
|{{mono|PF_W}}
|Writeable segment.
|-
| {{tt|0x4}}
|{{mono|PF_R}}
|Readable segment.
|}
|-
| {{tt|0x04}} || {{tt|0x08}} || 4 || 8||{{mono|p_offset}}||Offset of the segment in the file image.
|-
| {{tt|0x08}} || {{tt|0x10}} || 4 || 8 ||{{mono|p_vaddr}}||Virtual address of the segment in memory.
|-
| {{tt|0x0C}} || {{tt|0x18}} || 4 || 8 ||{{mono|p_paddr}}||On systems where physical address is relevant, reserved for segment's physical address.
|-
| {{tt|0x10}} || {{tt|0x20}} || 4 || 8 ||{{mono|p_filesz}}||Size in bytes of the segment in the file image. May be 0.
|-
| {{tt|0x14}} || {{tt|0x28}} || 4 || 8 ||{{mono|p_memsz}}||Size in bytes of the segment in memory. May be 0.
|-
| {{tt|0x18}} ||  || 4 ||  ||{{mono|p_flags}}||Segment-dependent flags (position for 32-bit structure). See above <code>p_flags</code> field for flag definitions.
|-
| {{tt|0x1C}} || {{tt|0x30}} || 4 || 8 ||{{mono|p_align}}||<code>0</code> and <code>1</code> specify no alignment. Otherwise should be a positive, integral power of 2, with {{mono|p_vaddr}} equating {{mono|p_offset}} modulus {{mono|p_align}}.
|-
| {{tt|0x20}}
| {{tt|0x38}}
| colspan="3" |
|End of Program Header (size).
|}