From 01e14d418abee460e41c0782d68e56c42c689edf Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Wed, 25 Jun 2025 16:23:59 +0200
Subject: [PATCH] FIX: No longer allow exceeding printf buffer, instead print
 an error to stdout. Temporary fix

Later, if buffer is full, print current buffer and reset buffer so that there is no limit.
---
 console.asm | 44 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/console.asm b/console.asm
index b1ef2f3..6990b3e 100644
--- a/console.asm
+++ b/console.asm
@@ -5,8 +5,11 @@ extern	itoa
 
 section .rodata
 	NL		db	0xA
+	bufferLength	equ	4096
+	ERR_buffLen	db	"<!> ERROR: Failed to complete printf(), reached buffer length!",0xA,0x0
+	lERR_buffLen	equ	$-ERR_buffLen-1
 section .bss
-	printfBuff	resb	4096
+	printfBuff	resb	bufferLength
 	printfNBuff	resb	32
 section .text
 	global	print
@@ -52,18 +55,25 @@ printf:
 	push	rbp
 	mov	rbp, rsp
 
-	push	r12
-	push	r13
+	push	rbx ; used to check if error must be sent (reached buff len)
+	push	r12 ; used for writing byted to printBuff
+	push	r13 ; (also) used for writing bytes to printBuff (why again? gotta check that out - probably not needed, just lost count of register usage at some point)
+	push	r14 ; count length of printBuff
 
+	xor	rbx, rbx
 	xor	r10, r10
+	xor	r14, r14
 	lea	r11, [rel printfBuff]
 	.makeStr:
 		cmp	byte [rdi], 0x0
 		je	.finish
+		cmp	r14, bufferLength-1
+		je	.finish_L
 		cmp	byte [rdi], '%'
 		je	.replaceArg
 		mov	r12b, byte [rdi]
 		mov	byte [r11], r12b
+		inc	r14
 		jmp	.continue
 		.replaceArg:
 			cmp	byte [rdi+1], 0x0
@@ -80,6 +90,7 @@ printf:
 			
 			;--- invalid specifier ---;
 			mov	byte [r11], '%'
+			inc	r14
 			inc	r10 ;assuming args were passed for invalid specifiers !
 			jmp	.continue
 
@@ -172,8 +183,15 @@ printf:
 
 			.charToStr:
 			mov	[printfNBuff], dil
+			inc	r14
+			cmp	r14, bufferLength-1
+			; Print error to stdout
+			je	.finish_L
 			mov	dil, 0
 			mov	[printfNBuff+1], dil
+			inc	r14
+			cmp	r14, bufferLength-1
+			je	.finish_L
 			lea	rsi, [rel printfNBuff]
 			jmp	.insertLoop
 
@@ -208,10 +226,13 @@ printf:
 
 			;--- Move fetched data to buffer ---;
 			.insertLoop:
+				cmp	r14, bufferLength-1
+				je	.finish_L
 				cmp	byte [rsi], 0x0
 				je	.s0f
 				mov	r13b, byte [rsi]
 				mov	byte [r11], r13b
+				inc	r14
 				inc	rsi
 				inc	r11
 				jmp	.insertLoop
@@ -224,15 +245,32 @@ printf:
 		inc	rdi
 		inc	r11
 		jmp	.makeStr
+	
+	.finish_L:
+	mov	rbx, 1
+
 	.finish:
 	mov	byte [r11], 0x0
 	lea	rdi, [rel printfBuff]
 	call	print
 	lea	rdi, [rel printfBuff]
 	call	strlen
+	test	rbx, rbx
+	jz	.final
 
+	push	r11
+	mov	rax, NR_write
+	mov	rdi, 2
+	lea	rsi, [rel ERR_buffLen]
+	mov	rdx, lERR_buffLen
+	syscall
+
+	.final:
+	pop	r11
+	pop	r14
 	pop	r13
 	pop	r12
+	pop	rbx
 
 	leave
 	ret