stos: mm: Add PMM groundwork

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

paw/stos/head/mm/pmm.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  Physical memory management
+ * Author:       Chloe M.
+ */
+
+#ifndef _MM_PMM_H_
+#define _MM_PMM_H_ 1
+
+#include <stdef.h>
+
+/*
+ * Initialize the physical memory management
+ */
+VOID MmInitPmm(VOID);
+
+#endif  /* !_MM_PMM_H_ */

paw/stos/init/init.c

@@ -11,6 +11,7 @@
 #include <ke/bpal.h>
 #include <hal/serial.h>
 #include <drivers/bootvid/fbio.h>
+#include <mm/pmm.h>
 #include <stdef.h>
 
 #define DTRACE(Fmt, ...) \
@@ -43,4 +44,7 @@ KiKernelEntry(VOID)
 
     /* Init bootcons */
     BootVidInitCons(NULL);
+
+    /* Initialize physical memory */
+    MmInitPmm();
 }

paw/stos/ke/Makefile

@@ -13,6 +13,7 @@ CFILES = $(shell find ../init -name "*.c")
 CFILES += $(shell find ../xt -name "*.c")
 CFILES += $(shell find ../lib -name "*.c")
 CFILES += $(shell find ../drivers -name "*.c")
+CFILES += $(shell find ../mm -name "*.c")
 CFILES += $(shell find bpal -name "*.c")
 DFILES = $(CFILES:.c=.d)
 OFILES = $(CFILES:.c=.o)

paw/stos/mm/pmm.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description:  Physical memory management
+ * Author:       Chloe M.
+ */
+
+#include <ex/trace.h>
+#include <ke/bpal.h>
+#include <mm/pmm.h>
+#include <units.h>
+
+#define DTRACE(Fmt, ...) \
+    TRACE("[ PMM ]: " Fmt, ##__VA_ARGS__)
+
+/* Use to convert type constants to strings */
+#define MEM_TYPE(TYPE)          \
+    ((TYPE) < NELEM(TypeTab))   \
+        ? TypeTab[(TYPE)]       \
+        : "invalid"
+
+/*
+ * Memory type constant to human readable
+ * string table.
+ */
+static const char *TypeTab[] = {
+    [MEMORY_USABLE]         = "usable",
+    [MEMORY_RESERVED]       = "reserved",
+    [MEMORY_ACPI_RECLAIM]   = "acpi reclaimable",
+    [MEMORY_ACPI_NVS]       = "acpi nvs",
+    [MEMORY_BAD]            = "bad*",
+    [MEMORY_BOOTLOADER]     = "bootloader",
+    [MEMORY_KERNEL]         = "stoskrnl.sys",
+    [MEMORY_FRAMEBUFFER]    = "framebuffer",
+    [MEMORY_ACPI_TABLES]    = "acpi tables"
+};
+
+/* Globals */
+static USIZE UsableMemory = 0;
+
+/*
+ * Print the units of a size in a pretty format
+ *
+ * @Length: Number of bytes
+ * @Title:  Title of units
+ */
+static inline VOID
+MmPrintUnits(USIZE Length, const CHAR *Title)
+{
+    if (Title == NULL) {
+        return;
+    }
+
+    if (Length >= UNIT_GIB) {
+        DTRACE("%d gib %s\n", Length / UNIT_GIB, Title);
+    } else if (Length >= UNIT_MIB) {
+        DTRACE("%d mib %s\n", Length / UNIT_MIB, Title);
+    } else {
+        DTRACE("%010d b %s\n", Length, Title);
+    }
+}
+
+static VOID
+MmProbeMemory(VOID)
+{
+    BPAL_HANDLE BpalHandle;
+    MEMMAP_ENTRY Entry;
+    UPTR EntryEnd;
+    USIZE Idx;
+    ST_STATUS Status;
+
+    KeBpalGetHandle(&BpalHandle);
+    for (Idx = 0;; ++Idx) {
+        Status = BpalHandle.MemEntryIdx(Idx, &Entry);
+        if (Status != STATUS_SUCCESS) {
+            break;
+        }
+
+        EntryEnd = Entry.Base + Entry.Length;
+        DTRACE("[%p - %p) ~ %s\n", Entry.Base, EntryEnd, MEM_TYPE(Entry.Type));
+
+        /* Only usable entries from this point on */
+        if (Entry.Type != MEMORY_USABLE) {
+            continue;
+        }
+
+        UsableMemory += Entry.Length;
+    }
+
+    MmPrintUnits(UsableMemory, "avl");
+}
+
+VOID
+MmInitPmm(VOID)
+{
+    DTRACE("sniffing out installed ram...\n");
+    MmProbeMemory();
+}