Improve region allocator with an idea to break dependency cycle

2 files changed, 8 insertions, 2 deletions

diff --git a/kernel/include/paging.h b/kernel/include/paging.h
index 5766e65..7082e2e 100644
--- a/kernel/include/paging.h
+++ b/kernel/include/paging.h
@@ -13,6 +13,8 @@ pagedir_t *get_kernel_pagedir();
 
 void switch_pagedir(pagedir_t *pd);
 
+// The three functions below DO NOT DEPEND on argument pd for
+// addresses above K_HIGHHALF_ADDR, so just pass 0 to map/unmap in kernel space.
 uint32_t pd_get_frame(pagedir_t *pd, size_t vaddr);		// get physical frame for virtual address
 int pd_map_page(pagedir_t *pd,
 				size_t vaddr, uint32_t frame_id,
diff --git a/kernel/include/region.h b/kernel/include/region.h
index 701e2d9..3c64081 100644
--- a/kernel/include/region.h
+++ b/kernel/include/region.h
@@ -8,8 +8,7 @@
 // Region types
 #define REGION_T_KERNEL_BASE	0x00000001		// base kernel code & data
 #define REGION_T_DESCRIPTORS	0x00000002		// contains more region descriptors
-#define REGION_T_PAGEDIR		0x00000010		// used to map a page directory
-#define REGION_T_PAGETABLE		0x00000020		// used to map a page table
+#define REGION_T_PAGETABLE		0x00000010		// used to map a page table/page directory
 #define REGION_T_CORE_HEAP		0x00000100		// used for the core kernel heap
 #define REGION_T_PROC_HEAP		0x00000200		// used for a kernel process' heap
 #define REGION_T_CACHE			0x00001000		// used for cache
@@ -30,4 +29,9 @@ size_t region_alloc(size_t size, uint32_t type, page_fault_handler_t pf);	// ret
 region_info_t *find_region(size_t addr);
 void region_free(size_t addr);
 
+#define N_PAGES_IN_PT_REGION 4
+// special call for use by paging code
+// allocates a region of N_PAGES_IN_PT_REGION pages
+size_t region_alloc_for_pt();	
+
 void dbg_print_region_stats();