Kernel/Utilities: add a new get_top_of_stack convenience function

kernel/include/misc/utils.h

@@ -7,4 +7,5 @@ namespace Utilities
                                   uint64_t size); // Returns how many blocks of size blocksize does size occupy.
 
     uint64_t get_rflags();
+    uint64_t get_top_of_stack(uint64_t bottom, uint64_t stack_pages);
 }

kernel/src/misc/utils.cpp

@@ -1,5 +1,9 @@
 #include "misc/utils.h"
 
+#ifndef PAGE_SIZE
+#define PAGE_SIZE 4096
+#endif
+
 uint64_t Utilities::get_blocks_from_size(uint64_t blocksize, uint64_t size)
 {
     return (size + (blocksize - 1)) / blocksize;
@@ -9,4 +13,9 @@ extern "C" uint64_t asm_get_rflags();
 uint64_t Utilities::get_rflags()
 {
     return asm_get_rflags();
+}
+
+uint64_t Utilities::get_top_of_stack(uint64_t bottom, uint64_t stack_pages)
+{
+    return bottom + (stack_pages * PAGE_SIZE) - sizeof(uintptr_t);
 }