25 lines
1.1 KiB
Markdown
25 lines
1.1 KiB
Markdown
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gitea: none
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include_toc: true
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---
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# Executables
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Sentinel 65X's firmware is designed to load and execute binaries in the `PGZ` format. This is a multi-segment binary file format which can load data into any number of areas of memory from a compact binary.
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## PGZ Format
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The first byte of a PGZ file is always an ASCII "Z".
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This is followed by one or more segments, packed with no padding or separator. Each such segment has the following format:
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| Offset | Length | Description |
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| :----: | :----: | :------------: |
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| 0 | 3 bytes | Target address |
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| 3 | 3 bytes | Length of data |
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| 6 | ... | Data |
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This enables the binary loader to be extremely simple, as the data to be read into memory is always read from a contiguous region of memory, and the information provided is sufficient to make use of the C standard library `memcpy()` function.
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The final segment is special: its target address represents the entry point to the executable, and its length of data value is always `0x000000`. The loader can easily detect this to identify when loading is done and where to enter the program.
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