NRO

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NRO is the executable format for non-ExeFS binaries.

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

NRO Start

Offset Size Description
0x0 0x4 Unused
0x4 0x4 MOD0 offset
0x8 0x8 Padding

NRO Header

Offset Size Description
0x0 0x4 Magic "NRO0"
0x4 0x4 NRO Format Version (Always 0)
0x8 4 size (Total NRO filesize)
0xC 0x4 Flags (Unused)
0x10 0x8 * 3 SegmentHeader[3] {.text, .ro, .data}
0x28 0x4 bssSize
0x2C 0x4 Reserved (Unused)
0x30 0x20 Value of "build id" from ELF's GNU .note section. Contains variable sized digest, up to 32bytes.
0x50 0x08 Reserved (Unused)
0x58 0x8 * 3 SegmentHeader[3] {.apiInfo, .dynstr, .dynsym}

SegmentHeader

Offset Size Description
0x0 0x4 FileOffset
0x4 0x4 Size

Assets

This is an optional custom assets section for homebrew, this is located at file offset {NroHeader.size}. See also switch-tools for implementation.

The below offsets are relative to the beginning of the assets section (AssetHeader).

AssetHeader

Offset Size Description
0x0 0x4 Magic "ASET"
0x4 0x4 Format version, currently 0.
0x8 0x10 AssetSection icon. Used by the Homebrew Launcher. Like official icons, this is a 256x256 JPEG.
0x18 0x10 AssetSection NACP. Used by the Homebrew Launcher.
0x28 0x10 AssetSection romfs. Can be used by the application.

AssetSection

Offset Size Description
0x0 0x8 Offset
0x8 0x8 Size, 0 indicates this section is empty.