[kernel] Move slab_allocated items to the heap

Allocate the slabs for slab-allocated items to the heap, now that heap
regions are aligned. This also lets the slab sizes be non-page-sized.

src/kernel/memory_bootstrap.cpp

@@ -24,8 +24,6 @@ using bootproto::allocation_register;
 
 using obj::vm_flags;
 
-uintptr_t g_slabs_bump_pointer;
-
 // These objects are initialized _before_ global constructors are called,
 // so we don't want them to have global constructors at all, lest they
 // overwrite the previous initialization.
@@ -56,10 +54,6 @@ obj::vm_area_guarded g_kernel_buffers {
     mem::buffers_size,
     vm_flags::write};
 
-obj::vm_area_open g_kernel_slabs {
-    mem::slabs_size,
-    vm_flags::write};
-
 void * operator new(size_t size)           { return g_kernel_heap.allocate(size); }
 void * operator new [] (size_t size)       { return g_kernel_heap.allocate(size); }
 void operator delete (void *p) noexcept    { return g_kernel_heap.free(p); }
@@ -135,8 +129,6 @@ memory_initialize_post_ctors(bootproto::args &kargs)
 {
     vm_space &vm = vm_space::kernel_space();
     vm.add(mem::buffers_offset, &g_kernel_buffers);
-    vm.add(mem::slabs_offset, &g_kernel_slabs);
-    g_slabs_bump_pointer = mem::slabs_offset;
 
     g_frame_allocator.free(
         get_physical_page(kargs.page_tables.pointer),

src/kernel/objects/mailbox.h

@@ -7,6 +7,7 @@
 #include <util/map.h>
 #include <util/spinlock.h>
 
+#include "memory.h"
 #include "objects/kobject.h"
 #include "slab_allocated.h"
 #include "wait_queue.h"
@@ -79,7 +80,7 @@ private:
 
 
 struct mailbox::message :
-    public slab_allocated<message, 1>
+    public slab_allocated<message, mem::frame_size>
 {
     uint64_t tag;
     uint64_t subtag;

src/kernel/slab_allocated.h

@@ -8,14 +8,11 @@
 
 #include "memory.h"
 
-extern uintptr_t g_slabs_bump_pointer;
-
-template <typename T, unsigned N = 1>
+template <typename T, size_t N>
 class slab_allocated
 {
 public:
-    constexpr static unsigned slab_pages = N;
-    constexpr static unsigned slab_size = N * mem::frame_size;
+    static constexpr size_t slab_size = N;
 
     void * operator new(size_t size)
     {
@@ -37,9 +34,7 @@ private:
     {
         s_free.ensure_capacity(per_block);
 
-        uintptr_t start = __atomic_fetch_add(
-                &g_slabs_bump_pointer, slab_size,
-                __ATOMIC_SEQ_CST);
+        uint8_t *start = new uint8_t [slab_size];
 
         T *current = reinterpret_cast<T*>(start);
         T *end = util::offset_pointer(current, slab_size);
@@ -50,8 +45,8 @@ private:
     static util::vector<T*> s_free;
 };
 
-template <typename T, unsigned N>
+template <typename T, size_t N>
 util::vector<T*> slab_allocated<T,N>::s_free;
 
 #define DEFINE_SLAB_ALLOCATOR(type) \
-    template<> util::vector<typename type*> slab_allocated<typename type, type::slab_pages>::s_free {};
+    template<> util::vector<typename type*> slab_allocated<typename type, type::slab_size>::s_free {};