stos: ex: Add per-cpu pool allocator groundwork

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/arch/amd64/cpu/init.c

@@ -9,6 +9,8 @@
 #include <hal/kpcr.h>
 #include <hal/intr.h>
 #include <ex/trace.h>
+#include <ex/pool.h>
+#include <ke/knot.h>
 #include <machine/cpuid.h>
 #include <machine/idt.h>
 #include <stdef.h>
@@ -131,3 +133,22 @@ HalKpcrP1Init(KPCR *Kpcr)
         : "memory"
     );
 }
+
+VOID
+HalKpcrP2Init(KPCR *Kpcr)
+{
+    ST_STATUS Status;
+
+    if (Kpcr == NULL) {
+        return;
+    }
+
+    Status = ExPoolInit(&Kpcr->AllocPool);
+    if (Status != STATUS_SUCCESS) {
+        KeKnot(
+            KNOT_MISC,
+            "failed to initialize pool for cpu%d\n",
+            Kpcr->CoreId
+        );
+    }
+}

paw/stos/ex/pool.c

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Pool allocator
+ * Author:      Chloe M.
+ */
+
+#include <ex/pool.h>
+#include <ex/trace.h>
+#include <mm/vmm.h>
+#include <string.h>
+
+#define DTRACE(Fmt, ...) \
+    TRACE("[ POOL ]: " Fmt, ##__VA_ARGS__)
+
+/* Globals */
+static USIZE PoolCount = 0;
+
+static ST_STATUS
+PoolInitBlock(MEMORY_BLOCK *Block)
+{
+    if (Block == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    Block->FirstPage = MmAllocPages(1);
+    if (Block->FirstPage == NULL) {
+        return STATUS_NO_MEMORY;
+    }
+
+    Block->LastPage = Block->FirstPage;
+    Block->PageCount = 1;
+    RtlMemSet(Block->FirstPage, 0, PAGESIZE);
+    return STATUS_SUCCESS;
+}
+
+ST_STATUS
+ExPoolInit(MEMORY_POOL *Pool)
+{
+    UCHAR LevelIdx;
+    MEMORY_BLOCK *Block;
+    ST_STATUS Status;
+
+    if (Pool == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    /* Initialize the pools */
+    DTRACE("bringing up pool #%d\n", PoolCount);
+    for (LevelIdx = 0; LevelIdx < LEVEL_COUNT; ++LevelIdx) {
+        Block = &Pool->BlockLevels[LevelIdx];
+        Status = PoolInitBlock(Block);
+
+        /* XXX: We may wanna clean up our mess we made */
+        if (Status != STATUS_SUCCESS) {
+            DTRACE("critical: failed to initialize pool\n");
+            return STATUS_NO_MEMORY;
+        }
+    }
+
+    DTRACE("brought up %d levels for pool #%d : ok\n", LEVEL_COUNT, PoolCount);
+    ++PoolCount;
+    return STATUS_SUCCESS;
+}

paw/stos/head/ex/pool.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Pool allocator
+ * Author:      Chloe M.
+ */
+
+#ifndef _EX_POOL_H_
+#define _EX_POOL_H_ 1
+
+#include <hal/page.h>
+#include <stapi/status.h>
+#include <stdef.h>
+
+/* Compute the granularity of a specific level */
+#define LEVEL_GRAN(LEVEL) \
+    (1 << (3 + (LEVEL)))
+
+/* Maximum levels per pool */
+#define LEVEL_COUNT 8
+
+/*
+ * When allocating pages, we sacrifice a little bit of its
+ * first bytes to store some metadata. This is the true size
+ * of unreserved / usable data.
+ */
+#define POOL_REAL_PAGESZ \
+    (PAGESIZE - sizeof(MEMORY_PAGE))
+
+/*
+ * Page data structure used internally to link together page
+ * lists
+ *
+ * @Bitmap: Bitmap to data [0 : free, 1 : allocated]
+ * @Next:   Next page in list
+ */
+typedef struct _MEMORY_PAGE {
+    UQUAD Bitmap;
+    struct _MEMORY_PAGE *Next;
+} MEMORY_PAGE;
+
+/*
+ * A memory block holds a list of memory chunks of a specific
+ * granularity.
+ *
+ * @FirstPage:  First page in list
+ * @LastPage:   Last page in list
+ * @PageCount:  Number of pages total
+ */
+typedef struct {
+    MEMORY_PAGE *FirstPage;
+    MEMORY_PAGE *LastPage;
+    USIZE PageCount;
+} MEMORY_BLOCK;
+
+/*
+ * A memory pool holds blocks of varying granularities
+ *
+ * @BlockLevels: Block levels [granularity : GRAN(level)]
+ */
+typedef struct {
+    MEMORY_BLOCK BlockLevels[LEVEL_COUNT];
+} MEMORY_POOL;
+
+/*
+ * Initialize a memory pool
+ *
+ * @Pool: Memory pool to initialize
+ */
+ST_STATUS ExPoolInit(MEMORY_POOL *Pool);
+
+#endif  /* !_EX_POOL_H_ */

paw/stos/head/hal/kpcr.h

@@ -11,17 +11,20 @@
 
 #include <stdef.h>
 #include <machine/mcb.h>
+#include <ex/pool.h>
 
 /*
  * The kernel processor control region contains MI
  * information about the processor.
  *
- * @CoreId:  Processor core ID assigned by us
- * @Mcb:     Machine-core block
+ * @CoreId:     Processor core ID assigned by us
+ * @Mcb:        Machine-core block
+ * @AllocPool:  Memory-allocation pool
  */
 typedef struct {
     USHORT CoreId;
     MCB Mcb;
+    MEMORY_POOL AllocPool;
 } KPCR;
 
 /*
@@ -31,4 +34,11 @@ typedef struct {
  */
 VOID HalKpcrP1Init(KPCR *Kpcr);
 
+/*
+ * Phase 2 initialization of processor
+ *
+ * @Kpcr: KPCR to initialize
+ */
+VOID HalKpcrP2Init(KPCR *Kpcr);
+
 #endif  /* !_HAL_KPCR_H_ */

paw/stos/init/init.c

@@ -75,4 +75,7 @@ KiKernelEntry(VOID)
 
     /* Initialize ACPI */
     AcpiInit();
+
+    /* Phase 2 initialization of the bootstrap core */
+    HalKpcrP2Init(&BootstrapCore);
 }