From 6eea8a6272c5d81e8d821bddb12c92d86ea041fd Mon Sep 17 00:00:00 2001
From: Amelia Coutard <eliottulio.coutard@gmail.com>
Date: Sun, 9 Oct 2022 20:30:21 +0200
Subject: [PATCH] Changed the order of the info in the GDT, to make it possible
 to use syscall/sysret

---
 src/boot.S         | 19 ++++++++++---------
 src/interrupts.hpp |  2 +-
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/boot.S b/src/boot.S
index ef9fce4..d63fb7d 100644
--- a/src/boot.S
+++ b/src/boot.S
@@ -29,13 +29,6 @@ multiboot_header_end:
 GDT:
 .set GDT.NULL, . - GDT
 	.quad 0
-.set GDT.KERNEL_CODE, . - GDT
-	.short 0xFFFF # Limit[0:16]
-	.short 0x0000 # Base[0:16]
-	.byte 0x00 # Base[16:24]
-	.byte 0b10011010 # Access: present | readable | ring0
-	.byte 0b10101111 # Flags: page_gran | long_mode, Limit[16:20]
-	.byte 0x00 # Base[24:32]
 .set GDT.KERNEL_DATA, . - GDT
 	.short 0xFFFF # Limit[0:16]
 	.short 0x0000 # Base[0:16]
@@ -43,11 +36,11 @@ GDT:
 	.byte 0b10010010 # Access: present | writeable | ring0
 	.byte 0b11001111 # Flags: page_gran | d_b, Limit[16:20]
 	.byte 0x00 # Base[24:32]
-.set GDT.USER_CODE, . - GDT
+.set GDT.KERNEL_CODE, . - GDT
 	.short 0xFFFF # Limit[0:16]
 	.short 0x0000 # Base[0:16]
 	.byte 0x00 # Base[16:24]
-	.byte 0b11111010 # Access: present | readable | ring3
+	.byte 0b10011010 # Access: present | readable | ring0
 	.byte 0b10101111 # Flags: page_gran | long_mode, Limit[16:20]
 	.byte 0x00 # Base[24:32]
 .set GDT.USER_DATA, . - GDT
@@ -57,6 +50,13 @@ GDT:
 	.byte 0b11110010 # Access: present | writeable | ring3
 	.byte 0b11001111 # Flags: page_gran | d_b, Limit[16:20]
 	.byte 0x00 # Base[24:32]
+.set GDT.USER_CODE, . - GDT
+	.short 0xFFFF # Limit[0:16]
+	.short 0x0000 # Base[0:16]
+	.byte 0x00 # Base[16:24]
+	.byte 0b11111010 # Access: present | readable | ring3
+	.byte 0b10101111 # Flags: page_gran | long_mode, Limit[16:20]
+	.byte 0x00 # Base[24:32]
 .set GDT.TSS, . - GDT
 	.short TSS_SIZE & 0xFFFF # Limit[0:16]
 	.short 0x0000 # Base[0:16] # TSS & 0xFFFF
@@ -68,6 +68,7 @@ GDT.PTR:
 	.short . - GDT - 1
 	.quad GDT - KERNEL_VMA
 
+.globl TSS
 TSS:
 	.skip 4
 	RSP0: .quad 0
diff --git a/src/interrupts.hpp b/src/interrupts.hpp
index 9cbf48e..af4cb6d 100644
--- a/src/interrupts.hpp
+++ b/src/interrupts.hpp
@@ -56,7 +56,7 @@ void enable_interrupts(const isr_info (&ISRs)[interrupt_nb], os::idt<interrupt_n
 	for (std::size_t i = 0; i < interrupt_nb; i++) {
 		idt[i] = {
 			.offset_low  = uint16_t(ISRs[i].addr & 0xFFFF),
-			.kernel_cs   = 0x08,
+			.kernel_cs   = 0x10,
 			.ist_offset  = 0,
 			.gate_type   = std::uint8_t(ISRs[i].type), // Trap gate.
 			.dpl         = ISRs[i].dpl,
-- 
2.47.0