From 3b0685a3f0b8a7a6d12ac02f24e979bfbcd043a9 Mon Sep 17 00:00:00 2001
From: Yury Popov <github@phoenix.dj>
Date: Thu, 23 May 2019 17:12:06 +0300
Subject: [PATCH] Multiboot VBE framebuffer support

---
 src/boot/bootstrap.s       |  5 +++--
 src/kernlib/display.cpp    | 11 +++++++++++
 src/platform/pagetable.cpp | 12 ++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/boot/bootstrap.s b/src/boot/bootstrap.s
index 6a3b1a9..2a8098d 100644
--- a/src/boot/bootstrap.s
+++ b/src/boot/bootstrap.s
@@ -12,8 +12,8 @@ _start:
   .align 4
 multiboot_header:
   .long 0x1BADB002
-  .long 0x00010003
-  .long -(0x1BADB002+0x00010003)
+  .long 0x00010005
+  .long -(0x1BADB002+0x00010005)
 
   .long multiboot_header
   .long __text_start__
@@ -21,6 +21,7 @@ multiboot_header:
   .long __bss_end__ + 0x80000
   .long multiboot_entry
 
+  .long 0, 800, 600, 8
 
 multiboot_entry:
   cli
diff --git a/src/kernlib/display.cpp b/src/kernlib/display.cpp
index 52c2755..26304d0 100644
--- a/src/kernlib/display.cpp
+++ b/src/kernlib/display.cpp
@@ -3,6 +3,7 @@
 
 #include "kernlib.hpp"
 #include "efi.hpp"
+#include "multiboot_info.hpp"
 #include "pagetable.hpp"
 #include "font-8x16.hpp"
 
@@ -203,6 +204,16 @@ void Display::setup() {
     instance = new FramebufferDisplay(fb->base, fb->width, fb->height, pixelFormat);
     return;
   }
+  const struct Multiboot::Payload *mb = Multiboot::getPayload();
+  if (mb && (mb->flags & Multiboot::FLAG_VBETAB)) {
+    const Multiboot::VBEModeInfo *mode = reinterpret_cast<const Multiboot::VBEModeInfo*>(mb->vbe.pmode_info);
+    if (mode && mode->lfb_ptr) {
+      instance = new FramebufferDisplay(
+          reinterpret_cast<void*>(mode->lfb_ptr),
+          mode->h_res, mode->v_res, PixelFormatBGRX);
+      return;
+    }
+  }
 
   // Fallback
   instance = new ConsoleDisplay();
diff --git a/src/platform/pagetable.cpp b/src/platform/pagetable.cpp
index 2d9705e..3baa6b7 100644
--- a/src/platform/pagetable.cpp
+++ b/src/platform/pagetable.cpp
@@ -348,6 +348,18 @@ void Pagetable::init() {
         mmap += ent->size + sizeof(ent->size);
       }
     }
+    if (multiboot->flags & Multiboot::FLAG_VBETAB) {
+      if (multiboot->vbe.pcontrol_info < 0x80000)
+        multiboot->vbe.pcontrol_info += bss_end;
+      if (multiboot->vbe.pmode_info < 0x80000)
+        multiboot->vbe.pmode_info += bss_end;
+      Multiboot::VBEInfo *vbe = reinterpret_cast<Multiboot::VBEInfo*>(multiboot->vbe.pcontrol_info);
+      map(vbe); map(vbe+1);
+      const char *vendor = reinterpret_cast<const char*>(vbe->vendor_string);
+      map(vendor);
+      Multiboot::VBEModeInfo *mode = reinterpret_cast<Multiboot::VBEModeInfo*>(multiboot->vbe.pmode_info);
+      map(mode); map(mode + 1);
+    }
   }
 }