x86/pmap: directmap update

This module is probably the most impacted by the direct physical
mapping.

First, it establishes the direct physical mapping before paging is
enabled, and uses the largest available page size when doing so.

In addition, the recursive mapping of PTEs is removed, since all
page table pages are allocated from the direct physical mapping.
This changes the way mapping requests are processed.

The ability to access any page table page at any time removes the
need for virtual addresses reserved for temporary mappings.

Since it's now perfectly possible to return physical address 0 for
a kernel mapping, change the interface of the pmap_extract function
and rename it to pmap_kextract to stress the fact that it should
only be used for kernel mappings.

2 files changed, 3 insertions, 0 deletions

diff --git a/kern/error.c b/kern/error.c
index f448b4d9..a86e913c 100644
--- a/kern/error.c
+++ b/kern/error.c
@@ -32,6 +32,8 @@ error_str(int error)
         return "invalid argument";
     case ERROR_BUSY:
         return "device or resource busy";
+    case ERROR_FAULT:
+        return "Bad address";
     default:
         return "unknown error";
     }
diff --git a/kern/error.h b/kern/error.h
index cf88775d..eb11cda0 100644
--- a/kern/error.h
+++ b/kern/error.h
@@ -22,6 +22,7 @@
 #define ERROR_AGAIN 2
 #define ERROR_INVAL 3
 #define ERROR_BUSY  4
+#define ERROR_FAULT 5
 
 /*
  * Return a string describing the given error.