From da99da2b36d98daeee72fc4de5fb147c1f65b047 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Thu, 18 Aug 2022 20:42:03 -0300
Subject: [PATCH] arch_ctl syscall

it controls architecture specific things such as the GSBASE in x86_64
---
 src/arch/x86_64/arch_ctl.c    | 29 +++++++++++++++++++++++++++++
 src/arch/x86_64/syscall.asm   |  4 +++-
 src/include/kernel/syscalls.h |  3 +++
 3 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 src/arch/x86_64/arch_ctl.c

diff --git a/src/arch/x86_64/arch_ctl.c b/src/arch/x86_64/arch_ctl.c
new file mode 100644
index 00000000..e04370ca
--- /dev/null
+++ b/src/arch/x86_64/arch_ctl.c
@@ -0,0 +1,29 @@
+#include <kernel/syscalls.h>
+#include <arch/msr.h>
+#include <errno.h>
+
+#define ARCH_CTL_GSBASE 0
+
+
+syscallret syscall_arch_ctl(int func, void* arg){
+	
+	syscallret retv;
+
+	retv.errno = 0;
+	retv.ret = 0;
+	
+	switch(func){
+		case ARCH_CTL_GSBASE:
+			wrmsr(MSR_KERNELGSBASE, (uint64_t)arg);
+			break;
+		default:
+			retv.errno = EINVAL;
+
+	}
+
+	if(retv.errno)
+		retv.ret = -1;
+
+	return retv;
+
+}
diff --git a/src/arch/x86_64/syscall.asm b/src/arch/x86_64/syscall.asm
index 6a9ad127..9d18b207 100644
--- a/src/arch/x86_64/syscall.asm
+++ b/src/arch/x86_64/syscall.asm
@@ -3,12 +3,14 @@ section .rodata
 
 extern syscall_libc_log
 extern syscall_mmap
-func_count equ 2
+extern syscall_arch_ctl
+func_count equ 3
 
 
 func_table:
 	dq syscall_libc_log
 	dq syscall_mmap
+	dq syscall_arch_ctl
 section .text
 global asm_syscall_entry
 
diff --git a/src/include/kernel/syscalls.h b/src/include/kernel/syscalls.h
index e1b93fdd..b40b9841 100644
--- a/src/include/kernel/syscalls.h
+++ b/src/include/kernel/syscalls.h
@@ -1,6 +1,9 @@
 #ifndef _SYSCALLS_H_INCLUDE
 #define _SYSCALLS_H_INCLUDE
 
+#include <stddef.h>
+#include <sys/types.h>
+
 typedef struct {
         long ret;
         long errno;