kernel.md

Kernel instructions

These instructions are used to manipulate with the kernel and access its functions. Following instructions will be covered in the article:

1. sysenter and syscall
2. int
3. sysreq

sysenter and syscall

You use sysenter to expose a specific kernel module to the program, and syscall to call a specific function from the exposed module.

.start
    mov fdx, 1 ; fdx = 1
    sysenter "ios" ; enter the module used for text input-output, "ios" = input-output-string
    syscall ; call function 1, which is `sys_ios_write`

syscall list

Module	ID	Arguments	Description
ios	1	tlr, bos	Prints exclusively text with the size of bos (byte output size). Uses stl as a help argument.
ios	2	tlr	Prints integers and floating point numbers. Uses stl as a help argument.
ios	3	-	Requests textual user input and stores the value in tlr.
ios	4	-	Requests numeric (including floats) user input and stores the value in tlr.
ios	5	tlr	Prints the textual value of a built-in operand.
ios	6	tlr	Prints the name of a symbol a reference is pointing to.
ios	7	tlr	Prints a single character.
ios	8	-	Requests a single character input from the user and stores the value in tlr.
fs/host	1	tlr	Create a directory; with tlr being a string containing the directory name.
fs/host	2	tlr	Remove a directory; with tlr being a string containing the directory name.
fs/host	3	tlr	Create a file; with tlr being a string containing the file name.
fs/host	4	tlr	Remove a file; with tlr being a string containing the file name.
fs/host	5	tlr, stl	Overwrite file content; with tlr being a string containing the file name, and stl being a string containing the new content.
fs/host	6	tlr, stl	Append content to file; with tlr being a string containing the file name, and stl being a string containing the content to append.
fs/host	7	tlr	Remove all file content; with tlr being a string containing the file name.
fs/host	8	tlr, stl	Read a file line; with tlr being a string containing the file name, and stl being the line number. Read content is subsequently stored in tlr.
cmanip	1	cpt	Clear the bit array, with cpt being a pointer holding the address of your bit array.
cmanip	2	cpt	Flip the bit array, with cpt being a pointer holding the address of your bit array.
cmanip	3	cpt	Reverse the bit array, with cpt being a pointer holding the address of your bit array.
cmanip	4	cpt, tlr, stl	Set a value at a specific index, with cpt being a pointer holding the address of your bit array, tlr an index and stl either 0 or 1 as a value.
cmanip	5	cpt, tlr	Get value stored at the bit array, with cpt being a pointer holding the address of your bit array and tlr being the index. After the syscall, the function will store the value in tlr.
cmanip	6	cpt, tlr, stl	Set-at-parent-of function, with cpt being a pointer holding the address of your binary tree, tlr being the index and stl the value.
cmanip	7	cpt, tlr, stl	Set-at-right child-of function, with cpt being a pointer holding the address of your binary tree, tlr being the index and stl the value.
cmanip	8	cpt, tlr, stl	Set-at-left child-of function, with cpt being a pointer holding the address of your binary tree, tlr being the index and stl the value.
cmanip	9	cpt, tlr, stl	Get-at function, with cpt being a pointer holding the address of your binary tree and tlr being the index. After the syscall, the function will store the value in tlr.
net	1	tlr, stl	Download a file, with tlr being a link to the file and stl being the output destination.
mem	1	tlr	Gets memory usage in bytes and stores it inside the rax register.
txtop	1	tlr, stl	Concatenate 2 textual values, with these registers holding the two values.
txtop	2	tlr	Remove whitespaces from string ends.
txtop	3	tlr	Tokenizes the string stored inside the tlr register.
txtop	4	tlr	Formats the string stored inside the tlr register.
txtop	5	tlr	Turns a string stored in tlr into an integer and stores it in rax.
txtop	6	tlr	Turns a string stored in tlr into a float and stores it in rbx.
txtop	7	tlr, rax	Gets a character stored in string stored in tlr at index rax and stores it into tlr.
chrono	1	/	Gets the current year and stores it in tlr.
chrono	2	/	Gets the current month and stores it in tlr.
chrono	3	/	Gets the current day in a month and stores it in tlr.
chrono	4	/	Gets the current hour and stores it in tlr.
chrono	5	/	Gets the current minute and stores it in tlr.
chrono	6	/	Gets the current second and stores it in tlr.
thread	1	tlr	Prints the thread output, with tlr being a thread pointer.
thread	2	tlr	Gets the thread return and stores it in tlr, with tlr firstly being a thread pointer as well.
ext	/	/	Call a system call from a specific extension (dynamic library).
tcp	1	tlr, stl	tlr is the IP, and stl the data we are sending.
tcp	2	tlr	Receive data from the IP address stored inside tlr.
http	1	tlr	tlr is the address. Used to get HTTP data.
http	2	tlr, stl	Send data, with tlr being the URL and stl the data.
math	1	tlr	Finds sin() of the number inside tlr. Stores the result inside tlr.
math	2	tlr	Finds cos() of the number inside tlr. Stores the result inside tlr.
math	3	tlr	Finds tan() of the number inside tlr. Stores the result inside tlr.
math	4	tlr	Finds sqrt() of the number inside tlr. Stores the result inside tlr.
math	5	tlr	Finds abs() of the number inside tlr. Stores the result inside tlr.
math	6	tlr	Finds cbrt() of the number inside tlr. Stores the result inside tlr.
misc	1	tlr, stl	Returns a random number, with tlr being the minimum, and stl being the maximum.
crypto	1	tlr	Performs SHA256 hash on a string stored in tlr. The result is stored in tlr.
crypto	2	tlr, stl	Performs XOR encryption on a string stored in tlr. The result is stored in tlr. Store a specific key into stl.
crypto	3	tlr, stl	Performs XOR decryption on a string stored in tlr. The result is stored in tlr. Store a specific key into stl.
tuple	1	tlr	Get tuple size, tlr is a reference to a tuple. Result is stored in tlr.
ctx	1	tlr	Get context size, tlr is a reference to a context. Result is stored in tlr.
fs/vdsk	1	tlr, stl	Create a file named tlr, with content in stl.
fs/vdsk	2	tlr	Remove a file named tlr.
fs/vdsk	3	tlr	Check if a file named tlr exists.
fs/vdsk	4	tlr	Create a directory or advance into that directory, go back with ...
fs/vdsk	5	tlr	Reads a file named in tlr and stores the data in tlr.
fs/vdsk	6	tlr, stl	Opens a file named in tlr and stores the data stored in stl into the file.
fs/vdsk	7	tlr, stl	Reads a file named in tlr and appends the data stored in stl into the file.
fs/vdsk	8	tlr	Reads a file named in tlr and prints the contents of the file.

int

This instruction is used to directly talk to the system.

int 0x3 ; tells the system to manually calculate the `bos` size for output

System interrupt	Description
0x3	Toggles the automatic bos calculation when printing text.
0x4	Toggles the offline mode. When offline mode is on, host service calls that require internet connection are blocked.

sysreq

Use this instruction to check if a symbol exists!

.data
    intg myData: 0
.start
    sysreq &myData -> intg ; checks if an integer named myData exists

Works also for procedures and threads.