SysABI
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 |
The following calls should be implemented to some degree in noxos 1.0.
Categories
Files
| ID |
Name |
Description |
Arg1 |
Arg2 |
Arg3 |
Arg4 |
Result |
Status |
| 0x0001 |
nx_fs_open |
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 |
| 0x0002 |
nx_fs_close |
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 |
| 0x0003 |
nx_fs_read |
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 |
| 0x0004 |
nx_fs_write |
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 |
| 0x0005 |
nx_fs_delete |
Completely delete the file or folder at a given path path, which is len bytes long. |
path |
len |
|
|
status |
Implemented |
| 0x0006 |
nx_fs_list |
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 |
| 0x0007 |
nx_fs_info |
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 |
| 0x0101 |
nx_mem_alloc |
Maps n 4KB pages to address addr. You can provide a bitmap of flags with the flags argument. Which flags can be used, is described below. |
addr |
n |
flags |
|
status |
Implemented |
| 0x0102 |
nx_mem_free |
Unmaps n 4KB pages at address addr. |
addr |
n |
|
|
status |
Implemented |
| 0x0103 |
nx_mem_label |
Gives a memory region a file descriptor, called a label, which can then be used for example for executing executable data in that memory region in a new process |
addr |
len |
*fd |
|
status |
N/A |
| 0x0104 |
nx_mem_unlabel |
Takes the file descriptor away from a memory region. |
fd |
|
|
|
status |
N/A |
Processes
| ID |
Name |
Description |
Arg1 |
Arg2 |
Arg3 |
Arg4 |
Result |
Status |
| 0x0201 |
nx_proc_create |
Creates a new process with the configuration conf (which format is described below) and writes its process id to pid. |
conf |
*pid |
|
|
status |
N/A |
| 0x0202 |
nx_proc_signal_send |
Send the signal signal to pid. See below for a list of signals. |
pid |
signal |
|
|
status |
N/A |
| 0x0203 |
nx_proc_signal_set_handler |
Sets a handler for the signal signal in the process pid. Not all signals can have a handler. Look at the list for more information. |
pid |
signal |
*handler |
|
status |
N/A |
| 0x0204 |
nx_proc_thread_create |
Spawns a new thread for the current process. The starting point is defined by addr. The threads' ID is written into tid. |
addr |
*tid |
|
|
status |
N/A |
| 0x0205 |
nx_proc_thread_start |
Starts the current processes' thread with thread id tid. |
tid |
|
|
|
status |
N/A |
| 0x0206 |
nx_proc_thread_pause |
Pauses the current processes' thread with thread id tid. |
tid |
|
|
|
status |
N/A |
| 0x0207 |
nx_proc_thread_kill |
Kills the current processes' thread with thread id tid. |
tid |
|
|
|
status |
N/A |
Drivers
| 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 |
|
|
|
|
|
|
|
|
|
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. |
Process configuration
Process signals
- SIGSTART: starts the process
- SIGPAUSE: pauses the process
- SIGKILL: kills the process and destroys the processes data structures
- SIGEXIT: send by the kernel before stopping the process - handler implementation possible
- SIGPFAULT: sends when the process access memory it is not permitted to. Followed by SIGEXIT - handler implementation possible
- SIGMATHAULT: sends when the process does stuff like dividing by zero. Followed by SIGEXIT - handler implementation possible