Revert "Remove page frame allocator"

This reverts commit db8a61a779.

kernelmq/Makefile

@@ -14,6 +14,7 @@ OBJS += main.c.o
 OBJS += init.c.o
 OBJS += multiboot.c.o
 OBJS += panic.c.o  panic.asm.cpp.o
+OBJS += pfa.c.o
 OBJS += paging.c.o paging.asm.cpp.o
 OBJS += page_dir.c.o
 

kernelmq/init.c

@@ -1,4 +1,5 @@
 #include "panic.h"
+#include "pfa.h"
 #include "protected.h"
 #include "paging.h"
 
@@ -18,6 +19,8 @@ void init(const struct KernelMQ_Info *const kinfo_ptr)
 
     assert(kernelmq_info_validate_and_copy(&kinfo, kinfo_ptr), "Invalid kernel information.");
 
+    pfa_initialize(&kinfo);
+
     protected_initialize(&kinfo);
 
     // Set up a new post-relocate bootstrap pagetable so that

kernelmq/pfa.c

@@ -0,0 +1,111 @@
+#include "pfa.h"
+
+#include "config.h"
+#include "panic.h"
+#include "logger.h"
+
+#include "stdlib.h"
+
+#define FRAMES_COUNT (PAGE_DIR_LENGTH * PAGE_TABLE_LENGTH)
+
+static unsigned char frames[FRAMES_COUNT];
+
+static void mark_used(unsigned long base, unsigned long limit);
+
+void pfa_initialize(const struct KernelMQ_Info *const kinfo)
+{
+    logger_info_from("pfa", "Initialize page frame allocator.");
+
+    kmemset(frames, 0, sizeof(frames));
+
+    mark_used(0, MEM_UPPER_BASE - 1);
+
+    mark_used(kinfo->kernel_phys_base, kinfo->kernel_phys_limit);
+
+    for (unsigned int i = 0; i < kinfo->modules_count; ++i) {
+        const struct KernelMQ_Info_Module *const module = &kinfo->modules[i];
+
+        mark_used(module->base, module->limit);
+    }
+
+    for (unsigned int i = 0; i < kinfo->areas_count; ++i) {
+        const struct KernelMQ_Info_Area *const area = &kinfo->areas[i];
+
+        if (!area->is_available) {
+            mark_used(area->base, area->limit);
+        }
+    }
+}
+
+unsigned long pfa_alloc_page()
+{
+    for (unsigned int i = 0; i < FRAMES_COUNT; ++i) {
+        if (!frames[i]) {
+            frames[i] = 0xFF;
+            return i * PAGE_SIZE;
+        }
+    }
+
+    return 0;
+}
+
+unsigned long pfa_alloc_big_page()
+{
+    unsigned int start = 0;
+
+    for (unsigned int i = 0; i < FRAMES_COUNT; ++i) {
+        if (frames[i]) {
+            start = i + 1;
+            continue;
+        }
+
+        if (start % (PAGE_BIG_SIZE / PAGE_SIZE)) {
+            continue;
+        }
+
+        if (i - start + 1 == PAGE_BIG_SIZE / PAGE_SIZE) {
+            for (unsigned int j = start; j <= i; ++j) {
+                frames[j] = 0xFF;
+            }
+
+            return start * PAGE_SIZE;
+        }
+    }
+
+    return 0;
+}
+
+void pfa_free_page(const unsigned long base)
+{
+    assert(!(base % PAGE_SIZE), "Small page address to free is not aligned.");
+
+    const unsigned long i = base / PAGE_SIZE;
+
+    if (i >= FRAMES_COUNT) {
+        return;
+    }
+
+    frames[i] = 0;
+}
+
+void pfa_free_big_page(const unsigned long base)
+{
+    assert(!(base % PAGE_BIG_SIZE), "Big page address to free is not aligned.");
+
+    const unsigned long start = base / PAGE_SIZE;
+    const unsigned long end   = start + PAGE_BIG_SIZE / PAGE_SIZE;
+
+    for (unsigned int i = start; i <= end && i < FRAMES_COUNT; ++i) {
+        frames[i] = 0;
+    }
+}
+
+void mark_used(const unsigned long base, const unsigned long limit)
+{
+    const unsigned int start = base  / PAGE_SIZE;
+    const unsigned int end   = limit / PAGE_SIZE;
+
+    for (unsigned int i = start; i <= end; ++i) {
+        frames[i] = 0xFF;
+    }
+}

kernelmq/pfa.h

@@ -0,0 +1,14 @@
+#ifndef KERNELMQ_INCLUDED_PFA
+#define KERNELMQ_INCLUDED_PFA 1
+
+#include "info.h"
+
+void pfa_initialize(const struct KernelMQ_Info *kinfo);
+
+unsigned long pfa_alloc_page();
+unsigned long pfa_alloc_big_page();
+
+void pfa_free_page(unsigned long base);
+void pfa_free_big_page(unsigned long base);
+
+#endif