From 43c10da9cf77bb7676db3733499c1b578826dca9 Mon Sep 17 00:00:00 2001
From: Ada Christine <adachristine18@gmail.com>
Date: Sun, 13 Feb 2022 13:10:49 +0000
Subject: splitting out descriptor declarations

---
 kc/core/cpu/cpu.c        | 65 +++++++++---------------------------------------
 kc/core/cpu/descriptor.h | 55 ++++++++++++++++++++++++++++++++++++++++
 kc/core/panic.c          |  8 +++---
 3 files changed, 72 insertions(+), 56 deletions(-)
 create mode 100644 kc/core/cpu/descriptor.h

(limited to 'kc')

diff --git a/kc/core/cpu/cpu.c b/kc/core/cpu/cpu.c
index 28b69ff..7b48e30 100644
--- a/kc/core/cpu/cpu.c
+++ b/kc/core/cpu/cpu.c
@@ -5,6 +5,7 @@
 #include "msr.h"
 #include "task.h"
 #include "memory.h"
+#include "descriptor.h"
 
 #include <stddef.h>
 #include <stdint.h>
@@ -25,58 +26,6 @@
 #define MSR_CSTAR 0xc0000083
 #define MSR_SFMASK 0xc0000084
 
-struct dtr64
-{
-    uint16_t limit;
-    uint64_t base;
-} __attribute__((packed));
-
-struct segment_descriptor
-{
-    uint16_t limit0;
-    uint16_t base0;
-    uint8_t base16;
-    uint8_t access;
-    uint8_t flags_limit16;
-    uint8_t base24;
-} __attribute__((packed));
-
-enum segment_descriptor_type
-{
-    CODE64_SUPER_SEG,
-    CODE64_USER_SEG,
-    DATA_SEG,
-    TASK64_SEG,
-};
-
-struct gate_descriptor
-{
-    uint16_t offset0;
-    uint16_t selector;
-    uint8_t ist;
-    uint8_t access;
-    uint16_t offset16;
-    uint64_t offset32;
-} __attribute__((packed));
-
-enum gate_descriptor_type
-{
-    INT64_GATE,
-    TRAP64_GATE,
-};
-
-struct task64_segment
-{
-    uint32_t reserved0;
-    uint64_t rsp0;
-    uint64_t rsp1;
-    uint64_t rsp2;
-    uint64_t reserved1;
-    uint64_t ist[7];
-    uint16_t reserved2;
-    uint16_t iomap_base;
-};
-
 static struct segment_descriptor gdt[GDT_ENTRIES];
 static struct gate_descriptor idt[IDT_ENTRIES];
 static struct task64_segment tss;
@@ -126,11 +75,18 @@ static void set_gdt(int index,
     };
 }
 
-static void set_idt(int vec,
+static void set_idt(
+        int vec,
         uint16_t selector,
         uint64_t offset,
         enum gate_descriptor_type type)
 {
+    // TODO: panic() on attempt to set an idte outside of bounds?
+    if (vec >= IDT_ENTRIES)
+    {
+        return;
+    }
+
     idt[vec].offset0 = offset & 0xffff;
     idt[vec].selector = selector;
     idt[vec].offset16 = (offset >> 16) & 0xffff;
@@ -138,6 +94,9 @@ static void set_idt(int vec,
 
     switch (type)
     {
+        case EMPTY_GATE:
+            idt[vec].access = 0x0;
+            break;
         case INT64_GATE:
             idt[vec].access = 0x8e;
             break;
diff --git a/kc/core/cpu/descriptor.h b/kc/core/cpu/descriptor.h
new file mode 100644
index 0000000..802c09c
--- /dev/null
+++ b/kc/core/cpu/descriptor.h
@@ -0,0 +1,55 @@
+#pragma once
+
+struct dtr64
+{
+    uint16_t limit;
+    uint64_t base;
+} __attribute__((packed));
+
+struct segment_descriptor
+{
+    uint16_t limit0;
+    uint16_t base0;
+    uint8_t base16;
+    uint8_t access;
+    uint8_t flags_limit16;
+    uint8_t base24;
+} __attribute__((packed));
+
+enum segment_descriptor_type
+{
+    CODE64_SUPER_SEG,
+    CODE64_USER_SEG,
+    DATA_SEG,
+    TASK64_SEG,
+};
+
+struct gate_descriptor
+{
+    uint16_t offset0;
+    uint16_t selector;
+    uint8_t ist;
+    uint8_t access;
+    uint16_t offset16;
+    uint64_t offset32;
+} __attribute__((packed));
+
+enum gate_descriptor_type
+{
+    EMPTY_GATE,
+    INT64_GATE,
+    TRAP64_GATE,
+};
+
+struct task64_segment
+{
+    uint32_t reserved0;
+    uint64_t rsp0;
+    uint64_t rsp1;
+    uint64_t rsp2;
+    uint64_t reserved1;
+    uint64_t ist[7];
+    uint16_t reserved2;
+    uint16_t iomap_base;
+};
+
diff --git a/kc/core/panic.c b/kc/core/panic.c
index b0d9daf..6fd5581 100644
--- a/kc/core/panic.c
+++ b/kc/core/panic.c
@@ -12,9 +12,11 @@ static char const *reason_strings[] = {
 noreturn void panic(enum panic_reason reason)
 {
     // TODO: kprintf() and friends
-    kputs("kernel panic: ");
-    kputs(reason_strings[reason]);
-    kputs("\n");
+    if (reason > sizeof(reason_strings) / sizeof(*reason_strings))
+    {
+        reason = 0;
+    }
+    kprintf("kernel panic: %s\n", reason_strings[reason]);
     halt();
 }
 
-- 
cgit v1.3.1-1-g115d