From 0d594ecd85aaf654b815ce983852d464ed4efc0d Mon Sep 17 00:00:00 2001
From: tkchia <tkchia-cosmo@gmx.com>
Date: Sun, 25 Sep 2022 13:17:33 +0000
Subject: [PATCH] Bare metal VGA: allow for 64-bit video frame buffer address

---
 libc/runtime/mman.internal.h | 5 +++--
 libc/vga/rlinit-vga.S        | 3 +++
 libc/vga/writev-vga.c        | 6 +++---
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/libc/runtime/mman.internal.h b/libc/runtime/mman.internal.h
index 0af3bb84e..9f96ed695 100644
--- a/libc/runtime/mman.internal.h
+++ b/libc/runtime/mman.internal.h
@@ -26,8 +26,9 @@ struct mman {
                                                      or pixels (graphics) */
   unsigned short pc_video_height;        /* 0x1d2e — height in chars. (text)
                                                      or pixels (graphics) */
-  uint32_t pc_video_framebuffer;         /* 0x1d30 */
-  uint32_t pc_video_framebuffer_size;    /* 0x1d34 */
+  uint64_t pc_video_framebuffer;         /* 0x1d30 — physical address of
+                                                     video frame buffer */
+  uint64_t pc_video_framebuffer_size;    /* 0x1d38 */
 };
 
 COSMOPOLITAN_C_END_
diff --git a/libc/vga/rlinit-vga.S b/libc/vga/rlinit-vga.S
index 914b2a4fa..e61b6b438 100644
--- a/libc/vga/rlinit-vga.S
+++ b/libc/vga/rlinit-vga.S
@@ -66,6 +66,9 @@
 	movw	$25,mm+"struct mman::pc_video_height"
 	movl	$0xb8000,mm+"struct mman::pc_video_framebuffer"
 	movl	$0x8000,mm+"struct mman::pc_video_framebuffer_size"
+	xor	%eax,%eax
+	mov	%eax,mm+"struct mman::pc_video_framebuffer"+4
+	mov	%eax,mm+"struct mman::pc_video_framebuffer_size"+4
 	mov	$0x1003,%ax		# enable/disable VGA text blinking
 #ifdef VGA_USE_BLINK
 	mov	$1,%bx
diff --git a/libc/vga/writev-vga.c b/libc/vga/writev-vga.c
index 4eb6650c2..894120fbb 100644
--- a/libc/vga/writev-vga.c
+++ b/libc/vga/writev-vga.c
@@ -62,7 +62,8 @@ __attribute__((__constructor__)) static textstartup void _vga_init(void) {
   if (IsMetal()) {
     struct mman *mm = (struct mman *)(BANE + 0x0500);
     unsigned short height = mm->pc_video_height, width = mm->pc_video_width;
-    void * vid_buf = (void *)(BANE + mm->pc_video_framebuffer);
+    uint64_t vid_buf_phy = mm->pc_video_framebuffer;
+    void *vid_buf = (void *)(BANE + vid_buf_phy);
     size_t vid_buf_sz = mm->pc_video_framebuffer_size;
     /*
      * Get the initial cursor position from the BIOS data area.  Also get
@@ -78,8 +79,7 @@ __attribute__((__constructor__)) static textstartup void _vga_init(void) {
     if (chr_ht_hi != 0 || chr_ht > 32)
       chr_ht = 32;
     /* Make sure the video buffer is mapped into virtual memory. */
-    __invert_memory_area(mm, __get_pml4t(), (uint64_t)vid_buf, vid_buf_sz,
-                         PAGE_RW);
+    __invert_memory_area(mm, __get_pml4t(), vid_buf_phy, vid_buf_sz, PAGE_RW);
     /*
      * Initialize our tty structure from the current screen contents,
      * current cursor position, & character height.