NSO: Difference between revisions

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NSO is the main executable format.
NSO is the main executable format.


It starts with a header:
It starts with the "NSO" header and mainly describes .text, .rodata, and .data segments (like a short-form of ELF program headers):
 
=== SegmentHeader ===
{| class="wikitable" border="1"
{| class="wikitable" border="1"
|-
|-
Line 10: Line 12:
| 0x0
| 0x0
| 4
| 4
| Magic "NSO0"
| file offset of data
|-
|-
| 0x4
| 0x4
| 4
| 4
|  
| memory offset loaded to
|-
|-
| 0x8
| 0x8
| 4
| 4
|  
| size of data copied to memory offset (i.e. size after decompression)
|-
|-
| 0xC
| 0xC
| 4
| 4
|  
| alignment used on memory size / size of .bss in the case of .data segment
|}
 
=== .rodata-relative extent ===
{| class="wikitable" border="1"
|-
|-
| 0x10
! Offset
| 4
! Size
| .text LZ4-compressed data start offset (0x101)
! Description
|-
|-
| 0x14
| 0x0
| 4
| 4
| .text offset? (0)
| offset (relative to .rodata)
|-
|-
| 0x18
| 0x4
| 4
| 4
| .text size
| size of region
|}
 
=== NSO Header ===
{| class="wikitable" border="1"
|-
|-
| 0x1C
! Offset
| 4
! Size
| .text required align? (0x1000)
! Description
|-
|-
| 0x20
| 0x0
| 4
| 4
| .rodata LZ4-compressed data start offset
| Magic "NSO0"
|-
|-
| 0x24
| 0x4
| 4
| 4
| .rodata offset
|  
|-
|-
| 0x28
| 0x8
| 4
| 4
| .rodata size
|  
|-
|-
| 0x2C
| 0xC
| 4
| 4
| .rodata required align? (1)
|  
|-
|-
| 0x30
| 0x10
| 4
| 0x10 * 3
| .data LZ4-compressed data start offset
| SegmentHeader for each segment
|-
| 0x34
| 4
| .data offset
|-
| 0x38
| 4
| .data size
|-
| 0x3C
| 4
| .bss size
|-
|-
| 0x40
| 0x40
| 0x14
| 0x14
| SHA1?
| Value of "build id" from ELF's GNU .note section
|-
|-
| 0x54
| 0x54
Line 81: Line 79:
|-
|-
| 0x60
| 0x60
| 4
| 0x4 * 3
| .rel.dyn compression offset?
| file size of each segment (i.e. LZ4-compressed size)
|-
| 0x6c
| 0x24
| Padding
|-
| 0x90
| 8
| .rodata-relative extents of .dynstr
|-
| 0x98
| 8
| .rodata-relative extents of .dynsym
|-
|-
| 0xA0
| 0xA0
| 0x60
| 0x20 * 3
| SHA256 hashes over the decompressed sections using the above byte-sizes: .text, .rodata, and .data.
| SHA256 hashes over the decompressed sections using the above byte-sizes: .text, .rodata, and .data.
|-
|-

Revision as of 01:27, 2 July 2017

NSO is the main executable format.

It starts with the "NSO" header and mainly describes .text, .rodata, and .data segments (like a short-form of ELF program headers):

SegmentHeader

Offset Size Description
0x0 4 file offset of data
0x4 4 memory offset loaded to
0x8 4 size of data copied to memory offset (i.e. size after decompression)
0xC 4 alignment used on memory size / size of .bss in the case of .data segment

.rodata-relative extent

Offset Size Description
0x0 4 offset (relative to .rodata)
0x4 4 size of region

NSO Header

Offset Size Description
0x0 4 Magic "NSO0"
0x4 4
0x8 4
0xC 4
0x10 0x10 * 3 SegmentHeader for each segment
0x40 0x14 Value of "build id" from ELF's GNU .note section
0x54 0xC Padding
0x60 0x4 * 3 file size of each segment (i.e. LZ4-compressed size)
0x6c 0x24 Padding
0x90 8 .rodata-relative extents of .dynstr
0x98 8 .rodata-relative extents of .dynsym
0xA0 0x20 * 3 SHA256 hashes over the decompressed sections using the above byte-sizes: .text, .rodata, and .data.
0x100 Compressed sections