stack/functions: Add functions lab.

[razvang0307]

Added functions lab based off old lab material.
Ignored throwback exercise 0.

Prerequisite Checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes against relevant architectures and platforms;
• Updated relevant documentation (if needed).

Description of changes

Added the lab materials for function calls in assembly.

[github-actions]

Published at https://cs-pub-ro.github.io/hardware-software-interface/21/

[teodutu]

Things are looking nice so far. I highlighted what needs to be done in my inline comments and besides those, you should also do the following globally:

• Add a .gitignore file to all support/ and solution/ folders. This file should only exclude the executable file and not the object file (.o) because object files are already excluded by the .gitignore in the root of the repo.
• Take a look at the linter errors and fix them [1]. To fix the Spellcheck errors you'll also have to add the false positives (correct words flagged as incorrect because they're missing from the action's wordlist) to the wordlists here. Create a PR in which you add the new words to the corresponding files here [2]. After changing a file, run sort -u -f <file_name.txt> <file_name.txt> to remove duplicates. Remember to add the conjugations and declinations of each word as well as the word itself.
• Squash your commits into a single one as described here [3]. For further modifications, use git commit --amend --no-edit to add them to the existing commit.

[1] https://github.com/cs-pub-ro/hardware-software-interface/pull/21/checks
[2] https://github.com/open-education-hub/actions/tree/main/spellcheck/config
[3] https://www.freecodecamp.org/news/git-squash-commits/

[teodutu]

Change the name of the folder to print-rev-string (using dashes -, not underscores _). Do the same for all folder names.

[teodutu]

Suggested change

	mov eax, dword [ebp+8]
	mov ecx, dword [ebp+12]
	add eax, ecx
	dec eax
	mov edx, dword [ebp+16]
	copy_one_byte:
	mov bl, byte [eax]
	mov byte [edx], bl
	mov eax, [ebp + 8]
	mov ecx, [ebp + 12]
	add eax, ecx
	dec eax
	mov edx, [ebp + 16]
	copy_one_byte:
	mov bl, [eax]
	mov [edx], bl

Using dword pr byte here is pointless because they can be inferred due to the other operand being a register.

[teodutu]

Suggested change

	In the file `print_rev_string.asm`, add the `reverse_string` function so that you have a listing similar to the one below:
	In the file `print_rev_string.asm`, add the `reverse_string()` function so that you have a listing similar to the one below:

Use () at the end of function names to distinguish them better from simple labels.

[teodutu]

Suggested change

	> **IMPORTANT:** When copying the `reverse_string` function into your program, remember that the function starts at the `reverse_string` label and ends at the `main` label. The `copy_one_byte` label is part of the `reverse_string` function.
	> **IMPORTANT:** When copying the `reverse_string()` function into your program, remember that the function starts at the `reverse_string` label and ends at the `main` label.
	> The `copy_one_byte` label is part of the `reverse_string` function.

Write one sentence per line. Everywhere. Also, notice the distinction I made above between the reverse_string() (with ()) function and the reverse_string label without (()).

[teodutu]

Suggested change

	mov eax, dword [ebp+8]
	mov ecx, dword [ebp+12]
	add eax, ecx
	dec eax
	mov edx, dword [ebp+16]
	copy_one_byte:
	mov bl, byte [eax]
	mov byte [edx], bl
	dec eax
	inc edx
	loopnz copy_one_byte
	inc edx
	mov byte [edx], 0
	leave
	ret
	main:
	push ebp
	mov ebp, esp
	mov eax, mystring
	xor ecx, ecx
	test_one_byte:
	mov bl, byte [eax]
	test bl, bl
	jz out
	inc eax
	inc ecx
	jmp test_one_byte
	out:
	; save ecx's value since it can be changed by printf
	push ecx
	mov eax, [ebp + 8]
	mov ecx, [ebp + 12]
	add eax, ecx
	dec eax
	mov edx, [ebp + 16]
	copy_one_byte:
	mov bl, [eax]
	mov [edx], bl
	dec eax
	inc edx
	loopnz copy_one_byte
	inc edx
	mov [edx], 0
	leave
	ret
	main:
	push ebp
	mov ebp, esp
	mov eax, mystring
	xor ecx, ecx
	test_one_byte:
	mov bl, [eax]
	test bl, bl
	jz out
	inc eax
	inc ecx
	jmp test_one_byte
	out:
	; Save ecx's value since it can be changed by printf.
	push ecx

[teodutu]

Suggested change

	## Bonus: toupper Only for Lowercase Letters
	## `toupper()` Only for Lowercase Letters

[teodutu]

Suggested change

	# Implementing the toupper Function
	# Implementing the `toupper()` Function

[teodutu]

Suggested change

	mov eax, dword [ebp+8]
	check_one_byte:
	mov bl, byte [eax]
	test bl, bl
	je out
	sub bl, 0x20
	mov byte [eax], bl
	mov eax, [ebp + 8]
	check_one_byte:
	mov bl, [eax]
	test bl, bl
	je out
	sub bl, 0x20
	mov [eax], bl

[teodutu]

Increase the font of all text to 20 instead of 12.

[teodutu]

Suggested change

	mov eax, dword [ebp+8] ; first argument in eax
	mov ebx, dword [ebp+12] ; second argument in ebx
	mov ecx, dword [ebp+16] ; third argument in ecx
	mov eax, [ebp + 8] ; first argument in eax
	mov ebx, [ebp + 12] ; second argument in ebx
	mov ecx, [ebp + 16] ; third argument in ecx

[george-cosma]

I slightly disagree. While not necessary, I feel it does decently illustrate the point that we are extracting the arguments from memory.

[george-cosma]

Yhea, most of it is fine. Good work! I left some comments though that I'd like your input on. Feel free to disagree.

[george-cosma]

AFAIK in 64-bit you pass a handful of arguments by registers, but after you run out, registers are put on the stack. Do double-check me though.

[george-cosma]

I think mentioning what leave actually does (and mentioning the enter commands too) could be helpful to understand what is happening both in "lower-level" assembly, and to highlight the existence of more complexx commands.

https://stackoverflow.com/a/29790275

[george-cosma]

I slightly disagree. While not necessary, I feel it does decently illustrate the point that we are extracting the arguments from memory.

[george-cosma]

I would encourage to mention pusha and popa (and their downsides -- fucks up the eax register).

[george-cosma]

I suggest moving this information (what registers we can ovewrite and not) to main-body contents, maybe beneath 5.. It's important info. Though this is more of an aesthetics change - so I don't feel strongly about it.

[george-cosma]

Suggested change

	extern puts
	extern puts ; we need to mark "puts()" as an external function, not one found in this file

I'd add even more details than what I sugested. Make sure that the students understan what extern is. Perhaps even add a section about it in the main content?

[george-cosma]

Oh, and one more comment: Do we need to put the content under Lab9/Functions/{Reading/Guides/...}. Shouldn't it be just Lab9/{Reading/Guides/...}, skip on the unnecessary sub-heading? This is a question to everyone - how do we want to handle this case?

[teodutu]

Oh, and one more comment: Do we need to put the content under Lab9/Functions/{Reading/Guides/...}. Shouldn't it be just Lab9/{Reading/Guides/...}, skip on the unnecessary sub-heading? This is a question to everyone - how do we want to handle this case?

Let's keep them all like this for now so all labs (with or without multiple subchapters) are consistent. It's easy to change this in the future so this isn't that big of an issue.

[savacezarmarian14]

Maybe add some explanation comments if this is the solution. I think students should read the comments rather than copy the code

[savacezarmarian14]

Students will not understand why this add esp, 4 is needed when the call returns

[savacezarmarian14]

I strongly recommand a new line at the end of file. See [1]
[1] https://gist.github.com/OleksiyRudenko/d51388345ea55767b7672307fe35adf3

[savacezarmarian14]

Please check my comments. Also keep in mind that i didn't comment at all files that should have changes. IT LOOKS GOOD FROM MY POINT OF VIEW.

[teodutu]

ping @razvang0307