From 34775633b23e79c3d99196ef84575d3e5f463640 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Fri, 17 Jan 2025 16:11:13 +0200
Subject: [PATCH] Kernel: Clear DF on every interrupt handler

I was missing this and it lead to UB with my new mem* functions that
were implemented with `rep`
---
 kernel/arch/i686/Syscall.S      | 1 +
 kernel/arch/i686/interrupts.S   | 5 +++++
 kernel/arch/x86_64/Syscall.S    | 1 +
 kernel/arch/x86_64/interrupts.S | 6 +++++-
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/arch/i686/Syscall.S b/kernel/arch/i686/Syscall.S
index 4edf07cc..6cf888d2 100644
--- a/kernel/arch/i686/Syscall.S
+++ b/kernel/arch/i686/Syscall.S
@@ -14,6 +14,7 @@ asm_syscall_handler:
 	pushl %edi
 	pushl %esi
 	pushl %ebp
+	cld
 
 	# align stack
 	movl %esp, %ebp
diff --git a/kernel/arch/i686/interrupts.S b/kernel/arch/i686/interrupts.S
index 3f2b6bb7..c0b9089d 100644
--- a/kernel/arch/i686/interrupts.S
+++ b/kernel/arch/i686/interrupts.S
@@ -27,6 +27,7 @@
 isr_stub:
 	push_userspace
 	load_kernel_segments
+	cld
 
 	movl %cr0, %eax; pushl %eax
 	movl %cr2, %eax; pushl %eax
@@ -58,6 +59,7 @@ isr_stub:
 irq_stub:
 	push_userspace
 	load_kernel_segments
+	cld
 
 	movl 40(%esp), %eax # interrupt number
 
@@ -79,6 +81,7 @@ irq_stub:
 asm_yield_handler:
 	# This can only be called from kernel, so no segment saving is needed
 	pushal
+	cld
 
 	movl %esp,     %eax # interrupt registers ptr
 	leal 32(%esp), %ebx # interrupt stack ptr
@@ -101,6 +104,7 @@ asm_yield_handler:
 asm_ipi_handler:
 	push_userspace
 	load_kernel_segments
+	cld
 
 	movl %esp, %ebp
 	subl $15, %esp
@@ -118,6 +122,7 @@ asm_ipi_handler:
 asm_timer_handler:
 	push_userspace
 	load_kernel_segments
+	cld
 
 	movl %esp, %ebp
 	subl $15, %esp
diff --git a/kernel/arch/x86_64/Syscall.S b/kernel/arch/x86_64/Syscall.S
index 878e24c6..ac447607 100644
--- a/kernel/arch/x86_64/Syscall.S
+++ b/kernel/arch/x86_64/Syscall.S
@@ -16,6 +16,7 @@ asm_syscall_handler:
 	pushq %r13
 	pushq %r14
 	pushq %r15
+	cld
 
 	movq %rsi, %r8
 	movq %rdi, %r9
diff --git a/kernel/arch/x86_64/interrupts.S b/kernel/arch/x86_64/interrupts.S
index c394d5c0..8f6effb2 100644
--- a/kernel/arch/x86_64/interrupts.S
+++ b/kernel/arch/x86_64/interrupts.S
@@ -36,7 +36,7 @@
 
 isr_stub:
 	pushaq
-
+	cld
 	movq %cr0, %rax; pushq %rax
 	movq %cr2, %rax; pushq %rax
 	movq %cr3, %rax; pushq %rax
@@ -55,6 +55,7 @@ isr_stub:
 
 irq_stub:
 	pushaq
+	cld
 	movq 120(%rsp), %rdi	# irq number
 	call cpp_irq_handler
 	popaq
@@ -64,6 +65,7 @@ irq_stub:
 .global asm_yield_handler
 asm_yield_handler:
 	pushaq
+	cld
 	leaq 120(%rsp), %rdi # interrupt stack ptr
 	movq     %rsp,  %rsi # interrupt register ptr
 	call cpp_yield_handler
@@ -73,6 +75,7 @@ asm_yield_handler:
 .global asm_ipi_handler
 asm_ipi_handler:
 	pushaq
+	cld
 	call cpp_ipi_handler
 	popaq
 	iretq
@@ -80,6 +83,7 @@ asm_ipi_handler:
 .global asm_timer_handler
 asm_timer_handler:
 	pushaq
+	cld
 	call cpp_timer_handler
 	popaq
 	iretq