setup, vga: map VGA memory area

This is needed to get rid of "Low memory" mappings.

Signed-off-by: Pawel Wieczorkiewicz <[email protected]>

Author: wipawel

common/setup.c

@@ -52,6 +52,7 @@
 #include <drivers/pic.h>
 #include <drivers/pit.h>
 #include <drivers/serial.h>
+#include <drivers/vga.h>
 
 bool opt_debug = false;
 bool_cmd("debug", opt_debug);
@@ -234,6 +235,7 @@ void __noreturn __text_init kernel_start(uint32_t multiboot_magic,
 
     map_multiboot_areas();
     map_bios_area();
+    map_vga_area();
 
     write_cr3(cr3.paddr);
     WRITE_SP(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));

drivers/vga.c

@@ -79,3 +79,11 @@ void vga_write(const char *buf, size_t len, vga_color_t color) {
     scroll_screen = screen;
     write_vga_buffer(screen);
 }
+
+void map_vga_area(void) {
+    for (mfn_t vga_mfn = paddr_to_mfn(VGA_START_ADDR);
+         vga_mfn < paddr_to_mfn(VGA_END_ADDR); vga_mfn++) {
+        vmap_4k(mfn_to_virt(vga_mfn), vga_mfn, L1_PROT);
+        kmap_4k(vga_mfn, L1_PROT);
+    }
+}

include/drivers/vga.h

@@ -59,4 +59,6 @@ extern void vga_scroll_up(void);
 extern void vga_scroll_down(void);
 
 extern void vga_write(const char *buf, size_t len, vga_color_t color);
+
+extern void map_vga_area(void);
 #endif /* KTF_DRV_VGA_H */