From cfcbb03e9b8d5f24069a212330075540161c8be0 Mon Sep 17 00:00:00 2001
From: John Hodge <tpg@mutabah.net>
Date: Thu, 8 Sep 2011 23:01:54 +0800
Subject: [PATCH] Kernel/x86_64 - Implemented SYSCALL in x86_64 port

- Seems to work
- I just love this code
---
 Kernel/arch/x86_64/desctab.asm    | 64 +++++++++++++++++++++++++++++++
 Kernel/arch/x86_64/include/arch.h | 15 +++-----
 Kernel/arch/x86_64/main.c         |  2 +-
 Kernel/arch/x86_64/proc.c         |  2 +
 4 files changed, 73 insertions(+), 10 deletions(-)

diff --git a/Kernel/arch/x86_64/desctab.asm b/Kernel/arch/x86_64/desctab.asm
index 8212773b..411cea3e 100644
--- a/Kernel/arch/x86_64/desctab.asm
+++ b/Kernel/arch/x86_64/desctab.asm
@@ -141,6 +141,28 @@ Desctab_Init:
 	
 	; Start interrupts
 	sti
+
+	; Initialise System Calls (SYSCALL/SYSRET)
+	; Set IA32_EFER.SCE
+	mov ecx, 0xC0000080
+	rdmsr
+	or eax, 1
+	wrmsr
+	; Set IA32_LSTAR (RIP of handler)
+	mov ecx, 0xC0000082	; IA32_LSTAR
+	mov eax, SyscallStub - 0xFFFFFFFF00000000
+	mov edx, 0xFFFFFFFF
+	wrmsr
+	; Set IA32_FMASK (flags mask)
+	mov ecx, 0xC0000084
+	rdmsr
+	mov eax, 0x202
+	wrmsr
+	; Set IA32_STAR (Kernel/User CS)
+	mov ecx, 0xC0000081
+	rdmsr
+	mov edx, 0x8 | (0x18 << 16)	; Kernel CS (and Kernel DS/SS - 8), User CS
+	wrmsr
 	
 	ret
 
@@ -387,6 +409,48 @@ SchedulerIRQ:
 	add rsp, 2*8	; Dummy error code and IRQ num
 	iretq
 
+[extern ci_offsetof_tThread_KernelStack]
+[extern SyscallHandler]
+[global SyscallStub]
+SyscallStub:
+	mov rbp, dr0
+	mov ebx, [rel ci_offsetof_tThread_KernelStack]
+	mov rbp, [rbp+rbx]	; Get kernel stack
+	xchg rbp, rsp	; Swap stacks
+
+	push rbp	; Save User RSP
+	push rcx	; RIP
+	push r11	; RFLAGS
+
+	; RDI
+	; RSI
+	; RDX
+	; R10 (RCX for non syscall)
+	; R8
+	; R9
+	sub rsp, (6+2)*8
+	mov [rsp+0x00], rax	; Number
+;	mov [rsp+0x08], rax	; Errno (don't care really)
+	mov [rsp+0x10], rdi	; Arg1
+	mov [rsp+0x18], rsi	; Arg2
+	mov [rsp+0x20], rdx	; Arg3
+	mov [rsp+0x28], r10	; Arg4
+	mov [rsp+0x30], r8	; Arg5
+	mov [rsp+0x38], r9	; Arg6
+	
+	mov rdi, rsp
+	sub rsp, 8
+	call SyscallHandler
+	add rsp, 8
+	mov ebx, [rsp+8]	; Get errno
+	mov rax, [rsp+0]	; Get return
+	add rsp, (6+2)*8
+
+	pop r11
+	pop rcx
+	pop rsp 	; Change back to user stack
+	sysret
+
 [section .data]
 gIDT:
 	; 64-bit Interrupt Gate, CS = 0x8, IST0 (Disabled)
diff --git a/Kernel/arch/x86_64/include/arch.h b/Kernel/arch/x86_64/include/arch.h
index d8b1124d..a0b3ba99 100644
--- a/Kernel/arch/x86_64/include/arch.h
+++ b/Kernel/arch/x86_64/include/arch.h
@@ -61,20 +61,17 @@ typedef struct sSyscallRegs
 		Uint    Num;
 		Uint    Return;
 	};      // RAX
-	Uint    Arg4;	// RCX
-	Uint	Arg3;	// RDX
 	Uint    Error;	// RBX
-	Uint    Resvd1[2];	// Kernel RSP, RBP
-	Uint	Arg2;	// RSI
 	Uint	Arg1;	// RDI
+	Uint	Arg2;	// RSI
+	Uint	Arg3;	// RDX
+	Uint    Arg4;	// RCX
 	Uint	Arg5;	// R8
 	Uint	Arg6;	// R9
-	Uint	Resvd2[6];	// R10 - R15
-	Uint	Resvd3[5];	// IntNum, ErrCode, RIP, CS, RFLAGS
-	
-	Uint	Resvd4[5];      // Int, Err, rip, CS, ...
+	Uint	_Flags;
+	Uint	_IP;
 	Uint	StackPointer;   // RSP
-	Uint	Resvd5[1];      // SS	
+	
 }	tSyscallRegs;
 
 /**
diff --git a/Kernel/arch/x86_64/main.c b/Kernel/arch/x86_64/main.c
index 044330a0..77df3628 100644
--- a/Kernel/arch/x86_64/main.c
+++ b/Kernel/arch/x86_64/main.c
@@ -27,7 +27,7 @@ void kmain(Uint MbMagic, void *MbInfoPtr)
 	tMBoot_Info	*mbInfo;
 	
 	Desctab_Init();
-	
+
 	MM_InitVirt();
 	*(Uint16*)(KERNEL_BASE|0xB8000) = 0x1F00|'C';
 	
diff --git a/Kernel/arch/x86_64/proc.c b/Kernel/arch/x86_64/proc.c
index 15c60b46..f7d6f92c 100644
--- a/Kernel/arch/x86_64/proc.c
+++ b/Kernel/arch/x86_64/proc.c
@@ -68,6 +68,8 @@ void	Proc_StartProcess(Uint16 SS, Uint Stack, Uint Flags, Uint16 CS, Uint IP);
 void	Proc_Scheduler(int CPU);
 
 // === GLOBALS ===
+//!\brief Used by desctab.asm in SyscallStub
+const int ci_offsetof_tThread_KernelStack = offsetof(tThread, KernelStack);
 // --- Multiprocessing ---
 #if USE_MP
 volatile int	giNumInitingCPUs = 0;
-- 
2.20.1