From a6c1174b3fb598cd59c1668cfc4d4746ab688079 Mon Sep 17 00:00:00 2001
From: aqua <aqua@iserlohn-fortress.net>
Date: Fri, 1 Apr 2022 11:38:00 +0300
Subject: lidt

---
 arch/i686/include/gdt.h         |  5 -----
 arch/i686/include/idt.h         | 18 ++++++++++++++++
 arch/i686/include/sys/control.h |  9 ++++++++
 arch/i686/lgdt.c                |  8 +++++--
 arch/i686/lidt.c                | 46 +++++++++++++++++++++++++++++++++++++++++
 arch/i686/meson.build           |  7 +++++--
 6 files changed, 84 insertions(+), 9 deletions(-)
 create mode 100644 arch/i686/include/idt.h
 create mode 100644 arch/i686/include/sys/control.h
 create mode 100644 arch/i686/lidt.c

(limited to 'arch')

diff --git a/arch/i686/include/gdt.h b/arch/i686/include/gdt.h
index 6badf84..9148c3d 100644
--- a/arch/i686/include/gdt.h
+++ b/arch/i686/include/gdt.h
@@ -47,11 +47,6 @@ _Static_assert(sizeof(struct SegmentDescriptor_t) == 8);
 
 void SegmentDescriptor(struct SegmentDescriptor_t *self, unsigned base, unsigned limit, uint8_t access);
 
-struct __attribute__((packed)) Pointer {
-  uint16_t limit;
-  uint32_t base;
-};
-
 void gdt_install();
 
 enum SegmentIndex {
diff --git a/arch/i686/include/idt.h b/arch/i686/include/idt.h
new file mode 100644
index 0000000..22dc6de
--- /dev/null
+++ b/arch/i686/include/idt.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <stdint.h>
+
+struct interrupt_frame {
+  uint32_t ip;
+  uint32_t cs;
+  uint32_t flags;
+  uint32_t sp;
+  uint32_t ss;
+};
+
+void abort_handler(struct interrupt_frame *frame);
+void interrupt_handler(struct interrupt_frame *frame);
+void interrupt_handler_e(struct interrupt_frame *frame, uint32_t error);
+void syscall_handler(struct interrupt_frame *frame);
+
+void idt_install();
diff --git a/arch/i686/include/sys/control.h b/arch/i686/include/sys/control.h
new file mode 100644
index 0000000..a40a67f
--- /dev/null
+++ b/arch/i686/include/sys/control.h
@@ -0,0 +1,9 @@
+#pragma once
+
+static void
+abort()
+{
+  asm volatile(R"(cli
+h: hlt
+jmp h)");
+}
diff --git a/arch/i686/lgdt.c b/arch/i686/lgdt.c
index 2d35e8d..2be5d30 100644
--- a/arch/i686/lgdt.c
+++ b/arch/i686/lgdt.c
@@ -1,5 +1,10 @@
 #include <gdt.h>
 
+struct __attribute__((packed)) Pointer {
+  uint16_t limit;
+  uint32_t base;
+};
+
 static struct SegmentDescriptor_t segments[8] __attribute__((aligned(32)));
 
 void
@@ -9,8 +14,7 @@ gdt_install()
   SegmentDescriptor(&segments[2], 0, 0xffffffff, 0x9a);         // ktext
   SegmentDescriptor(&segments[3], 0, 0xffffffff, 0x92);         // kdata
 
-  struct Pointer ptr = {.limit = sizeof(segments) - 1, .base = (unsigned)&segments};
-
+  const struct Pointer ptr = {.limit = sizeof(segments) - 1, .base = (unsigned)&segments};
   asm volatile("lgdt (%0)" : : "a"(&ptr));
 
   // load the kernel data segment
diff --git a/arch/i686/lidt.c b/arch/i686/lidt.c
new file mode 100644
index 0000000..efbade3
--- /dev/null
+++ b/arch/i686/lidt.c
@@ -0,0 +1,46 @@
+#include <idt.h>
+#include <stdint.h>
+
+struct __attribute__((packed)) Pointer {
+  uint16_t limit;
+  uint32_t base;
+};
+
+enum Type {
+  Null = 0,
+  Intr = 0b10001110, // 32-bit interrupt
+};
+
+struct __attribute__((packed)) Gate_t {
+  uint16_t offset_15_0;  // segment offset low
+  uint16_t selector;     // code segment selector
+  uint8_t __unused;      // unused in protected mode
+  uint8_t type;          // interrupt type
+  uint16_t offset_31_16; // segment offset high
+};
+_Static_assert(sizeof(struct Gate_t) == 8);
+
+void
+Gate(struct Gate_t *entry, void *f, uint16_t selector)
+{
+  uint32_t f_addr = (uint32_t)f;
+  entry->offset_15_0 = f_addr & 0xffff;
+  entry->offset_31_16 = (f_addr >> 16) & 0xffff;
+  entry->selector = selector;
+  entry->__unused = 0;
+  entry->type = Intr;
+}
+
+static struct Gate_t interrupt_table[256] __attribute((aligned(4096)));
+
+void
+idt_install()
+{
+  for (int i = 0; i <= 0x2f; ++i) Gate(&interrupt_table[i], &interrupt_handler, 0x10);
+  Gate(&interrupt_table[0x80], &abort_handler, 0x10);
+
+  const struct Pointer ptr = {.limit = sizeof(interrupt_table) - 1, .base = (unsigned)&interrupt_table};
+  asm volatile("lidt (%0)" : : "a"(&ptr));
+
+  asm volatile("sti");
+}
diff --git a/arch/i686/meson.build b/arch/i686/meson.build
index 25eebee..f6bed8e 100644
--- a/arch/i686/meson.build
+++ b/arch/i686/meson.build
@@ -1,6 +1,9 @@
 arch = declare_dependency(
-  sources: ['boot.S', 'init.s', 'gdt.c', 'lgdt.c'],
-  include_directories: 'include'
+  sources: ['boot.S', 'init.s',
+    'gdt.c', 'lgdt.c', 'lidt.c'
+  ],
+  include_directories: 'include',
+  compile_args: '-mgeneral-regs-only'
 )
 
 test('GDT', executable('gdt', ['test/gdt.c', 'gdt.c'], include_directories: 'include', native: true))
-- 
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