From 8d63b96ad929f4ff2607cc63a89cda4a537eb9a9 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Tue, 8 Sep 2026 15:16:44 +0200
Subject: [PATCH] feat: add FreeObj, Slab and spinLockInit

---
 src/slab.c     | 130 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/spinlock.c |  40 +++++++++++++++
 2 files changed, 170 insertions(+)
 create mode 100644 src/slab.c
 create mode 100644 src/spinlock.c

diff --git a/src/slab.c b/src/slab.c
new file mode 100644
index 0000000..59fcea8
--- /dev/null
+++ b/src/slab.c
@@ -0,0 +1,130 @@
+#include "slab.h"
+#include "pmm.h"
+
+typedef struct FreeObj {
+    struct FreeObj* next;
+} FreeObj;
+
+typedef struct Slab {
+    struct Slab* next;
+    FreeObj* freeList;
+    usize freeCount;
+} Slab;
+
+static usize alignUp(usize value, usize alignment)
+{
+    return (value + alignment - 1) & ~(alignment - 1);
+}
+
+static Slab* growSlab(KmemCache* cache)
+{
+    uint64 frame = pmmAlloc();
+    if (frame == 0)
+        return nullptr;
+
+    Slab* slab = (Slab*)frame;
+    slab->next = cache->slabs;
+    slab->freeCount = cache->objsPerSlab;
+
+    uint8* base = (uint8*)frame + alignUp(sizeof(Slab), sizeof(void*));
+    FreeObj* prev = nullptr;
+    for (usize i = 0; i < cache->objsPerSlab; i++) {
+        FreeObj* obj = (FreeObj*)(base + i * cache->objSize);
+        obj->next = prev;
+        prev = obj;
+    }
+    slab->freeList = prev;   /* built back-to-front; order does not matter */
+
+    cache->slabs = slab;
+    cache->slabCount++;
+    return slab;
+}
+
+bool kmemCacheInit(KmemCache* cache, const char* name, usize objSize)
+{
+    cache->name = name;
+    cache->slabs = nullptr;
+    cache->slabCount = 0;
+    cache->usedObjs = 0;
+
+    usize size = objSize < sizeof(FreeObj) ? sizeof(FreeObj) : objSize;
+    size = alignUp(size, sizeof(void*));
+    cache->objSize = size;
+
+    usize headerSize = alignUp(sizeof(Slab), sizeof(void*));
+    if (headerSize + size > frameSize) {
+        cache->objsPerSlab = 0;
+        return false;
+    }
+    cache->objsPerSlab = (frameSize - headerSize) / size;
+    return true;
+}
+
+void kmemCacheDestroy(KmemCache* cache)
+{
+    Slab* slab = cache->slabs;
+    while (slab != nullptr) {
+        Slab* next = slab->next;
+        pmmFree((uint64)slab);
+        slab = next;
+    }
+
+    cache->name = nullptr;
+    cache->objSize = 0;
+    cache->objsPerSlab = 0;
+    cache->slabs = nullptr;
+    cache->slabCount = 0;
+    cache->usedObjs = 0;
+}
+
+void* kmemCacheAlloc(KmemCache* cache)
+{
+    if (cache->objsPerSlab == 0)
+        return nullptr;
+
+    Slab* slab = cache->slabs;
+    while (slab != nullptr && slab->freeList == nullptr)
+        slab = slab->next;
+
+    if (slab == nullptr) {
+        slab = growSlab(cache);
+        if (slab == nullptr)
+            return nullptr;
+    }
+
+    FreeObj* obj = slab->freeList;
+    slab->freeList = obj->next;
+    slab->freeCount--;
+    cache->usedObjs++;
+    return (void*)obj;
+}
+
+void kmemCacheFree(KmemCache* cache, void* obj)
+{
+    Slab* slab = (Slab*)((uintptr)obj & ~(uintptr)(frameSize - 1));
+    FreeObj* fo = (FreeObj*)obj;
+    fo->next = slab->freeList;
+    slab->freeList = fo;
+    slab->freeCount++;
+    cache->usedObjs--;
+}
+
+usize kmemCacheUsed(const KmemCache* cache)
+{
+    return cache->usedObjs;
+}
+
+usize kmemCacheCapacity(const KmemCache* cache)
+{
+    return cache->slabCount * cache->objsPerSlab;
+}
+
+usize kmemCacheSlabCount(const KmemCache* cache)
+{
+    return cache->slabCount;
+}
+
+usize kmemCacheObjsPerSlab(const KmemCache* cache)
+{
+    return cache->objsPerSlab;
+}
diff --git a/src/spinlock.c b/src/spinlock.c
new file mode 100644
index 0000000..86c11da
--- /dev/null
+++ b/src/spinlock.c
@@ -0,0 +1,40 @@
+#include "spinlock.h"
+#include "ports.h"
+
+void spinLockInit(SpinLock* lock)
+{
+    lock->locked = 0;
+}
+
+uint64 spinLockAcquire(SpinLock* lock)
+{
+    uint64 flags = saveAndDisableInterrupts();
+    while (__atomic_exchange_n(&lock->locked, 1, __ATOMIC_ACQUIRE) != 0) {
+        /* single-core: a lock held across this spin can only be released by
+           an interrupt handler, but interrupts are off -- callers must never
+           acquire a lock they (or a handler nested under them) already hold */
+    }
+    return flags;
+}
+
+bool spinLockTryAcquire(SpinLock* lock, uint64* savedFlags)
+{
+    uint64 flags = saveAndDisableInterrupts();
+    if (__atomic_exchange_n(&lock->locked, 1, __ATOMIC_ACQUIRE) != 0) {
+        restoreInterrupts(flags);
+        return false;
+    }
+    *savedFlags = flags;
+    return true;
+}
+
+void spinLockRelease(SpinLock* lock, uint64 flags)
+{
+    __atomic_store_n(&lock->locked, 0, __ATOMIC_RELEASE);
+    restoreInterrupts(flags);
+}
+
+bool spinLockIsLocked(const SpinLock* lock)
+{
+    return __atomic_load_n(&lock->locked, __ATOMIC_ACQUIRE) != 0;
+}