homepage/content/projects/noxos/docs/sysabi.md

title	summary	date
Sysabi	The noxos `Application Binary Interface`.	2023-03-14T21:00:40+01:00

Syscalls are a way for programms to communicate with the kernel.

To perform a syscall, you need to populate the following registers:

Register	Value
rax	The syscalls ID
rdi	Argument 1
rsi	Argument 2
rdx	Argument 3
rcx	Argument 4

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The following calls should be implemented to some degree in noxos 1.0.

Categories

Files

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status
0x0101	nx_fopen	Opens the file at the len bytes long path path and writes a file descriptor to the referenced file into fd (which needs to be a pointer).	path	len	*fd		status	Implemented
0x0102	nx_fclose	Closes the file which is indicated by descriptor fd. This should always be called, otherwise the OS will have to unload files without knowledge of usage.	fd				status	Implemented
0x0103	nx_fread	Reads at most n bytes from a file given as descriptor fd and at a specific position offset into a given memory region mem.	fd	offset	mem	n	status	Implemented
0x0104	nx_fwrite	Writes n bytes from a given memory region mem into the file referenced by fd at the given position offset, not inserting but either overwriting existing content or appending to the file.	fd	offset	mem	n	status	Implemented
0x0105	nx_fdelete	Completely delete the file or folder at a given path path, which is len bytes long.	path	len			status	Implemented
0x0106	nx_flist	List all files and/or directories at the len bytes long path path and write their NULL-separated names into mem. When mem is NULL, needed_mem (which needs to be a pointer to an 32-bit integer) is filled with the appropriate value.	path	len	mem	*needed_mem	status	Implemented
0x0107	nx_finfo	Writes the information about the files attribute attr into mem. Types of attributes are described below.	fd	attr	mem		status	N/A

Note: The len argument of paths isn't used at the moment, rather than using len, path needs to be Null-Terminated.

Memory

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status
0x0201	nx_mmap	Maps n 4KB pages to address addr. You can provide a bitmap of flags with the flags argument. Which flags can be is described below.	addr	n	flags		status	N/A
0x0202	nx_munmap	Unmaps n 4KB pages at address addr.	addr	n			status	N/A

Processes

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status

Runtime / Dynamic Linker

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status

Compatibility & Safety

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status

Kernel

The kernel syscalls can only be called from the kernels main process [link to processing article needed]. If another process calls them, they will just return without doing anything.

ID	Name	Description	Arg1	Arg2	Arg3	Arg4	Result	Status

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Appendixes

Types of file attributes

ID	Name	Description	Data Type	Status
0	permissions	Who has what permission to access the file	uint16_t	N/A
1	size	The files size in bytes	uint64_t	N/A

Memory mapping flags

Bit	Name	Description
0	write	Enables write access to the mapped pages.
1	no_exec	Prevents execution of the mapped pages.