From 84e4c1c51c5f91301518d5ad07e66d7375108e2f Mon Sep 17 00:00:00 2001
From: antifallobst <antifallobst@systemausfall.org>
Date: Fri, 17 Feb 2023 15:18:12 +0100
Subject: [PATCH] feature (kernel): Implemented syscall architecture

---
 kernel/inc/platform/syscall.h       | 36 +++++++++++++++++++++++
 kernel/src/platform/interrupts.c    |  7 ++++-
 kernel/src/platform/syscall.c       | 45 +++++++++++++++++++++++++++++
 kernel/src/platform/x86/syscall.asm |  5 ++++
 4 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 kernel/inc/platform/syscall.h
 create mode 100644 kernel/src/platform/syscall.c
 create mode 100644 kernel/src/platform/x86/syscall.asm

diff --git a/kernel/inc/platform/syscall.h b/kernel/inc/platform/syscall.h
new file mode 100644
index 0000000..0b6f00a
--- /dev/null
+++ b/kernel/inc/platform/syscall.h
@@ -0,0 +1,36 @@
+/* Copyright (C) Antifallobst <antifallobst@systemausfall.org>
+ *
+ * NoxOS is free software:
+ * you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of the License,
+ * or (at your option) any later version.
+ *
+ * NoxOS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef NOX_SYSCALL_H
+#define NOX_SYSCALL_H
+
+#include "platform/cpu.h"
+
+typedef enum {
+    SYSCALLS_MISC   = 0x00,
+    SYSCALLS_FILE   = 0x01,
+    SYSCALLS_PROC   = 0x02,
+    SYSCALLS_KERNEL = 0xFF,
+}syscall_group_E;
+
+typedef enum {
+    SYSCALL_KERNEL_START_SCHEDULER  = 0xFF00
+} syscall_E;
+
+extern void syscall_perform(syscall_E id);
+
+cpu_state_T* syscall_handle(cpu_state_T* state);
+
+#endif //NOX_SYSCALL_H
diff --git a/kernel/src/platform/interrupts.c b/kernel/src/platform/interrupts.c
index b811375..146e4f7 100644
--- a/kernel/src/platform/interrupts.c
+++ b/kernel/src/platform/interrupts.c
@@ -17,6 +17,7 @@
 #include "platform/cpu.h"
 #include "platform/gdt.h"
 #include "platform/exceptions.h"
+#include "platform/syscall.h"
 #include "mm/page_frame.h"
 #include "utils/logger.h"
 #include "utils/io.h"
@@ -231,7 +232,7 @@ cpu_state_T* irq_handle(cpu_state_T* state, pic_irq_E irq) {
 
     switch (irq) {
         case IRQ_PIT: {
-            log(LOG_DEBUG, "PIT -> Tick");
+//            log(LOG_DEBUG, "PIT -> Tick");
             break;
         }
         default: {
@@ -253,6 +254,10 @@ cpu_state_T* interrupts_handle(cpu_state_T* state) {
         return irq_handle(state, state->interrupt_id - IRQ_MASTER_OFFSET);
     }
 
+    if (state->interrupt_id == 0x80) {
+        return syscall_handle(state);
+    }
+
     log(LOG_WARNING, "Unhandled interrupt: 0x%xb", state->interrupt_id);
 
     return state;
diff --git a/kernel/src/platform/syscall.c b/kernel/src/platform/syscall.c
new file mode 100644
index 0000000..fa8dc9b
--- /dev/null
+++ b/kernel/src/platform/syscall.c
@@ -0,0 +1,45 @@
+/* Copyright (C) Antifallobst <antifallobst@systemausfall.org>
+ *
+ * NoxOS is free software:
+ * you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of the License,
+ * or (at your option) any later version.
+ *
+ * NoxOS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "platform/syscall.h"
+#include "utils/logger.h"
+#include "proc/scheduler.h"
+
+cpu_state_T* syscall_handle(cpu_state_T* state) {
+    cpu_state_T*    return_state = state;
+    syscall_group_E group_id     = (state->rax & 0xFF00) >> 8;
+
+    if (group_id == SYSCALLS_KERNEL &&
+        scheduler_is_initialized() &&
+        scheduler_get_current_process() != PROC_KERNEL)
+    {
+        log(LOG_WARNING, "non kernel process[%d:%d] tried to perform a kernel syscall (permission denied)", scheduler_get_current_process(), scheduler_get_current_thread());
+        return return_state;
+    }
+
+    switch (state->rax) {
+        case SYSCALL_KERNEL_START_SCHEDULER: {
+            scheduler_start(state);
+            break;
+        }
+
+        default: {
+            log(LOG_WARNING, "Unhandled syscall: 0x%xw    RAX[0x%x]", state->rax, state->rax);
+            break;
+        }
+    }
+
+    return return_state;
+}
\ No newline at end of file
diff --git a/kernel/src/platform/x86/syscall.asm b/kernel/src/platform/x86/syscall.asm
new file mode 100644
index 0000000..3f6016a
--- /dev/null
+++ b/kernel/src/platform/x86/syscall.asm
@@ -0,0 +1,5 @@
+syscall_perform:
+    mov rax, rdi
+    int 0x80
+    ret
+GLOBAL syscall_perform
\ No newline at end of file