Add function to track free bytes in the coremap.

kern/arch/mips/vm/dumbvm.c

@@ -126,6 +126,15 @@ free_kpages(vaddr_t addr)
 	(void)addr;
 }
 
+unsigned
+int
+coremap_free_bytes() {
+
+	/* dumbvm doesn't track page allocations. Return 0 so that khu works. */
+
+	return 0;
+}
+
 void
 vm_tlbshootdown_all(void)
 {

kern/include/vm.h

@@ -55,6 +55,14 @@ int vm_fault(int faulttype, vaddr_t faultaddress);
 vaddr_t alloc_kpages(unsigned npages);
 void free_kpages(vaddr_t addr);
 
+/*
+ * Return amount of free memory (in bytes) available in unallocated coremap pages.
+ * If there are ongoing allocations, this value could change after it is
+ * returned to the caller. But it should have been correct at some point in
+ * time.
+ */
+unsigned int coremap_free_bytes(void);
+
 /* TLB shootdown handling called from interprocessor_interrupt */
 void vm_tlbshootdown_all(void);
 void vm_tlbshootdown(const struct tlbshootdown *);

kern/vm/kmalloc.c

@@ -827,16 +827,16 @@ kheap_printused(void)
 {
 	struct pageref *pr;
 	unsigned long total = 0;
+	char total_string[32];
+
 	/* print the whole thing with interrupts off */
 	spinlock_acquire(&kmalloc_spinlock);
-
 	for (pr = allbase; pr != NULL; pr = pr->next_all) {
 		total += subpage_stats(pr, true);
 	}
-
+	total += coremap_free_bytes();
 	spinlock_release(&kmalloc_spinlock);
 
-	char total_string[32];
 	snprintf(total_string, sizeof(total_string), "%lu", total);
 	secprintf(SECRET, total_string, "khu");
 }