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cannon: Update fcntl documentation #449

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Nov 4, 2024
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cannon: Update fcntl documentation #449

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18 changes: 9 additions & 9 deletions specs/fault-proof/cannon-fault-proof-vm.md
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Expand Up @@ -130,15 +130,15 @@ syscall calling conventions and general syscall handling behavior.
However, the FPVM supports a subset of Linux/MIPS syscalls with slightly different behaviors.
The following table list summarizes the supported syscalls and their behaviors.

| \$v0 | system call | \$a0 | \$a1 | \$a2 | Effect |
| ---- | ----------- | --------------- | ---------- | ------------ | -------------------------------------------------------------------------------------------------------------------- |
| 4090 | mmap | uint32 addr | uint32 len | 🚫 | Allocates a page from the heap. See [heap](#heap) for details. |
| 4045 | brk | 🚫 | 🚫 | 🚫 | Returns a fixed address for the program break at `0x40000000` |
| 4120 | clone | 🚫 | 🚫 | 🚫 | Returns 1 |
| 4246 | exit_group | uint8 exit_code | 🚫 | 🚫 | Sets the Exited and ExitCode states to `true` and `$a0` respectively. |
| 4003 | read | uint32 fd | char \*buf | uint32 count | Similar behavior as Linux/MIPS with support for unaligned reads. See [I/O](#io) for more details. |
| 4004 | write | uint32 fd | char \*buf | uint32 count | Similar behavior as Linux/MIPS with support for unaligned writes. See [I/O](#io) for more details. |
| 4055 | fcntl | uint32 fd | int32 cmd | 🚫 | Similar behavior as Linux/MIPS. Only the `F_GETFL` (3) cmd is supported. Sets errno to `0x16` for all other commands |
| \$v0 | system call | \$a0 | \$a1 | \$a2 | Effect |
| ---- | ----------- | --------------- | ---------- | ------------ |------------------------------------------------------------------------------------------------------------------------------------------|
| 4090 | mmap | uint32 addr | uint32 len | 🚫 | Allocates a page from the heap. See [heap](#heap) for details. |
| 4045 | brk | 🚫 | 🚫 | 🚫 | Returns a fixed address for the program break at `0x40000000` |
| 4120 | clone | 🚫 | 🚫 | 🚫 | Returns 1 |
| 4246 | exit_group | uint8 exit_code | 🚫 | 🚫 | Sets the Exited and ExitCode states to `true` and `$a0` respectively. |
| 4003 | read | uint32 fd | char \*buf | uint32 count | Similar behavior as Linux/MIPS with support for unaligned reads. See [I/O](#io) for more details. |
| 4004 | write | uint32 fd | char \*buf | uint32 count | Similar behavior as Linux/MIPS with support for unaligned writes. See [I/O](#io) for more details. |
| 4055 | fcntl | uint32 fd | int32 cmd | 🚫 | Similar behavior as Linux/MIPS. Only the `F_GETFD`(1) and `F_GETFL` (3) cmds are supported. Sets errno to `0x16` for all other commands. |

For all of the above syscalls, an error is indicated by setting the return
register (`$v0`) to `0xFFFFFFFF` (-1) and `errno` (`$a3`) is set accordingly.
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