adds a little bit of memory protection

kernel/arch/pmm/pmm.c

@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <string.h>
+#include <stdlib.h>
 
 #ifdef __TESTING__
 #include <stdio.h>
@@ -41,29 +42,29 @@ struct pmm_mem_info {
 
 struct pmm_mem_info main_mem;
 
-void pmm_set(int bit);
-void pmm_unset(int bit);
-bool pmm_test(int bit);
+void pmm_set(uint32_t bit);
+void pmm_unset(uint32_t bit);
+bool pmm_test(uint32_t bit);
 int pmm_first_free(void);
 void pmm_init(void);
 void* pmm_alloc_block(void);
 void pmm_free_block(void* p);
 
-void __pmm_set(int bit, struct pmm_mem_info* mem_block)
+void __pmm_set(uint32_t bit, struct pmm_mem_info* mem_block)
 {
 	(mem_block->bitmap)[bit / 32] |= (1 << (bit % 32));
 	mem_block->used_blocks++;
 	mem_block->free_blocks--;
 }
 
-void __pmm_unset(int bit, struct pmm_mem_info* mem_block)
+void __pmm_unset(uint32_t bit, struct pmm_mem_info* mem_block)
 {
 	(mem_block->bitmap)[bit / 32] &= ~(1 << (bit % 32));
 	mem_block->used_blocks--;
 	mem_block->free_blocks++;
 }
 
-bool __pmm_test(int bit, struct pmm_mem_info* mem_block)
+bool __pmm_test(uint32_t bit, struct pmm_mem_info* mem_block)
 {
 	return (mem_block->bitmap)[bit / 32] & (1 << (bit % 32));
 }
@@ -84,7 +85,7 @@ int __pmm_first_free(struct pmm_mem_info* mem_block)
 
 void __pmm_add_mem_block(uint32_t addr, int32_t len, struct pmm_mem_info* mem_block)
 {
-	mem_block->startaddr = addr; // main_mem isn't properly being set like this... TODO
+	mem_block->startaddr = addr; 
 	mem_block->len = len;
 	mem_block->bitmap = 0;
 }
@@ -125,12 +126,20 @@ void* __pmm_alloc_block(struct pmm_mem_info* mem_block)
 void __pmm_free_block(void* p, struct pmm_mem_info* mem_block)
 {
 	uint64_t* addr = (uint64_t*) &p;
-	int idx = ((*addr) - mem_block->startaddr) / PMM_PAGE_SIZE;
+	uint32_t idx = ((*addr) - mem_block->startaddr) / PMM_PAGE_SIZE;
+
+	// TODO this might still be a little flaky
+	// should we be able to free any pointer? or just ones that we've given out?
+	if (idx == 0)
+		panic("Trying to free reserved memory!");
+
+	if (pmm_test(idx) == 0)
+		panic("Trying to free a block that was already free!");
 
 	__pmm_unset(idx, mem_block);
 }
 
-void pmm_set(int bit)
+void pmm_set(uint32_t bit)
 {
 	/**
 	 * Here we want to calculate if the bit is over the length
@@ -145,13 +154,13 @@ void pmm_set(int bit)
 	__pmm_set(bit, &main_mem); 
 }
 
-void pmm_unset(int bit)
+void pmm_unset(uint32_t bit)
 {
 	 // TODO: same as above
 	 __pmm_unset(bit, &main_mem);
 }
 
-bool pmm_test(int bit)
+bool pmm_test(uint32_t bit)
 {
 	// TODO: same as above
 	return __pmm_test(bit, &main_mem);
@@ -175,18 +184,12 @@ void pmm_init(void)
 
 void* pmm_alloc_block(void)
 {
-#ifdef __TESTING__
-	printf("PMM: Alloc'd a block!\n");
-#endif
 	return __pmm_alloc_block(&main_mem);
 }
 
 void pmm_free_block(void* p)
 {
 	__pmm_free_block(p, &main_mem);
-#ifdef __TESTING__
-	puts("PMM: Free'd a block!");
-#endif
 }
 
 void pmm_add_mem_block(uint32_t addr, uint32_t len)

kernel/kmain.c

@@ -68,7 +68,6 @@ void _main(multiboot_info_t* mbd, uint32_t magic)
 
 	print_main_mem();
 
-
 	pmm_free_block(a);
 
 	print_main_mem();