x86_64: pmap: map all of physical memory starting at VM_PAGEMAP_BASE

arch/x86_64/include/socks/machine/vm.h

@@ -1,8 +1,16 @@
 #ifndef SOCKS_X86_64_VM_H_
 #define SOCKS_X86_64_VM_H_
 
+/* kernel higher-half base virtual address. */
 #define VM_KERNEL_VOFFSET 0xFFFFFFFF80000000
 
+/* direct page-mapping region.
+   NOTE that these are the maximum bounds of this region.
+   the actual size depends on the amount of physical
+   memory present. */
+#define VM_PAGEMAP_BASE   0xFFFF888000000000
+#define VM_PAGEMAP_LIMIT  0xFFFFC87FFFFFFFFF
+
 #define VM_PAGE_SIZE  0x1000
 #define VM_PAGE_MASK  (VM_PAGE_SIZE-1)
 #define VM_PAGE_SHIFT 12

arch/x86_64/pmap.c

@@ -247,6 +247,23 @@ void pmap_bootstrap(void)
 			    hugepage);
 	}
 
+	phys_addr_t pmem_limit = 0x0;
+	memblock_iter_t it;
+	for_each_mem_range(&it, 0x00, UINTPTR_MAX) {
+		if (it.it_limit > pmem_limit) {
+			pmem_limit = it.it_limit;
+		}
+	}
+
+	printk("pmap: initialising direct physical memory mappings");
+	vbase = VM_PAGEMAP_BASE;
+	for (size_t i = 0; i < pmem_limit; i += hugepage_sz) {
+		do_pmap_add(kernel_pmap,
+			    (void *)(vbase + i),
+			    PFN(i),
+			    VM_PROT_READ | VM_PROT_WRITE | VM_PROT_SVR, hugepage);
+	}
+
 	pmap_switch(kernel_pmap);
 	printk("pmap: kernel pmap initialised");
 }