From c4ce3212e797cbe617aea30c057756916f4ae99b Mon Sep 17 00:00:00 2001
From: Kwarde <kevin@kwarde.com>
Date: Wed, 25 Jun 2025 10:02:59 +0200
Subject: [PATCH] Assure fwrite() and fclose() only work if FD>=3, exit with -9
 (EBADF) otherwise

---
 file.asm | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/file.asm b/file.asm
index db0a611..c2acbef 100644
--- a/file.asm
+++ b/file.asm
@@ -86,9 +86,17 @@ fclose:
 	push	rbp
 	mov	rbp, rsp
 
+	cmp	rdi, 3
+	jl	.ebadf
+
 	mov	rax, NR_close
 	syscall
+	jmp	.quit
 
+	.ebadf:
+	mov	rax, -9
+
+	.quit:
 	leave
 	ret
 ;----- fwrite(FILE* fp, char* str) -----;
@@ -98,6 +106,9 @@ fwrite:
 	push	rbp
 	mov	rbp, rsp
 
+	cmp	rdi, 3
+	jl	.ebadf
+
 	mov	r9, rdi
 	mov	rdi, rsi
 	call	strlen
@@ -105,6 +116,11 @@ fwrite:
 	mov	rax, NR_write
 	mov	rdi, r9
 	syscall
+	jmp	.quit
 
+	.ebadf:
+	mov	rax, -9
+
+	.quit:
 	leave
 	ret