vmm: allow changing page attributes after being mapped

Author: jewelcodes

src/include/kernel/memory.h

@@ -66,4 +66,6 @@ int vmmFree(uintptr_t, size_t);
 int vmmPageFault(uintptr_t, int);       // the platform-specific page fault handler must call this
 uintptr_t vmmMMIO(uintptr_t, bool);
 int vmmPageStatus(uintptr_t, uintptr_t *);
+uintptr_t vmmSetFlags(uintptr_t, size_t, int);
+
 void *sbrk(Thread *, intptr_t);

src/memory/virtual.c

@@ -211,4 +211,26 @@ uintptr_t vmmMMIO(uintptr_t phys, bool cache) {
     } else {
         return 0;
     }
+}
+
+/* vmmSetFlags(): sets the flags for a series of pages
+ * params: base - base address
+ * params: count - number of pages
+ * params: flags - page attributes to set
+ * returns: base address
+ */
+
+uintptr_t vmmSetFlags(uintptr_t base, size_t count, int flags) {
+    uintptr_t phys;
+    int parsedFlags = PLATFORM_PAGE_PRESENT;
+    if(flags & VMM_EXEC) parsedFlags |= PLATFORM_PAGE_EXEC;
+    if(flags & VMM_USER) parsedFlags |= PLATFORM_PAGE_USER;
+    if(flags & VMM_WRITE) parsedFlags |= PLATFORM_PAGE_WRITE;
+
+    for(size_t i = 0; i < count; i++) {
+        if(vmmPageStatus(base + (i*PAGE_SIZE), &phys) & PLATFORM_PAGE_PRESENT)
+            platformMapPage(base + (i*PAGE_SIZE), phys, parsedFlags);
+    }
+
+    return base;
 }