From a6cd428f55ab4834bc4b05ad9ddb79ceb140e586 Mon Sep 17 00:00:00 2001
From: Pawel Wieczorkiewicz <wipawel@amazon.de>
Date: Mon, 16 Aug 2021 19:13:27 +0200
Subject: [PATCH] setup: add boot_flags with basic system configuration flags

First flag 'virt' indicates if transition to final page tables happened.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
---
 common/setup.c  | 4 ++++
 include/setup.h | 6 ++++++
 mm/vmm.c        | 4 ++++
 3 files changed, 14 insertions(+)

diff --git a/common/setup.c b/common/setup.c
index fb269bb4..0a525a12 100644
--- a/common/setup.c
+++ b/common/setup.c
@@ -72,6 +72,8 @@ bool_cmd("hpet", opt_hpet);
 
 io_port_t __data_rmode com_ports[2] = {COM1_PORT, COM2_PORT};
 
+boot_flags_t boot_flags;
+
 static unsigned bsp_cpu_id = 0;
 
 const char *kernel_cmdline;
@@ -240,6 +242,8 @@ void __noreturn __text_init kernel_start(uint32_t multiboot_magic,
     map_vga_area();
 
     write_cr3(cr3.paddr);
+    boot_flags.virt = true;
+
     WRITE_SP(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));
     if (opt_debug)
         dump_pagetables();
diff --git a/include/setup.h b/include/setup.h
index c8dfd68c..49a7f976 100644
--- a/include/setup.h
+++ b/include/setup.h
@@ -35,10 +35,16 @@
 
 #include <mm/pmm.h>
 
+struct boot_flags {
+    uint64_t virt : 1, rsvd : 63;
+};
+typedef struct boot_flags boot_flags_t;
+
 extern io_port_t com_ports[2];
 
 extern const char *kernel_cmdline;
 extern char cpu_identifier[49];
+extern boot_flags_t boot_flags;
 
 /* Static declarations */
 
diff --git a/mm/vmm.c b/mm/vmm.c
index a495f719..8a86acf8 100644
--- a/mm/vmm.c
+++ b/mm/vmm.c
@@ -25,6 +25,7 @@
 #include <ktf.h>
 #include <lib.h>
 #include <page.h>
+#include <setup.h>
 
 #include <mm/pmm.h>
 #include <mm/vmm.h>
@@ -34,6 +35,9 @@ void *get_free_pages(unsigned int order, uint32_t flags) {
     void *va = NULL;
     mfn_t mfn;
 
+    if (!boot_flags.virt)
+        panic("Unable to use %s() before final page tables are set\n", __func__);
+
     if (!frame)
         return NULL;