From 7c056aa005ebf34e68944ddf1d0b8a7b5dbad9bc Mon Sep 17 00:00:00 2001
From: Mark <alnyan@airmail.cc>
Date: Tue, 17 Sep 2019 18:56:03 +0300
Subject: [PATCH] [amd64] Add amd64_phys_alloc/free_page()

---
 src/arch/amd64/mm/phys.c | 77 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 72 insertions(+), 5 deletions(-)

diff --git a/src/arch/amd64/mm/phys.c b/src/arch/amd64/mm/phys.c
index e478de0..0a978a0 100644
--- a/src/arch/amd64/mm/phys.c
+++ b/src/arch/amd64/mm/phys.c
@@ -1,19 +1,86 @@
 #include "arch/amd64/mm/phys.h"
+#include "arch/amd64/mm/pool.h"
+#include "sys/panic.h"
 #include "sys/debug.h"
+#include "sys/mm.h"
+
+// Roughly 36MiB of lower memory is occupied by kernel so far:
+// The rest is available for both kernel and user allocation
+#define PHYS_ALLOWED_BEGIN          (((/* Kernel image end */ 0x400000 + MM_POOL_SIZE) + 0xFFF) & ~0xFFF)
+
+// TODO: move to sys/util.h
+#define MAX(x, y)                   ((x) > (y) ? (x) : (y))
+
+// TODO: this could be a better allocator
+//     + Support more memory
+#define PHYS_MAX_PAGES              16384       // Gives exactly 4GiB available for allocation
+#define PHYS_TRACK_INDEX(page)      ((page) >> 18)
+#define PHYS_TRACK_BIT(page)        (((page) >> 12) & 0x3F)
+
+static uint64_t amd64_phys_memory_track[PHYS_MAX_PAGES];
+static uint64_t amd64_phys_last_index = 0;
+
+// Allocate a single 4K page
+uintptr_t amd64_phys_alloc_page(void) {
+    for (uint64_t i = amd64_phys_last_index; i < (PHYS_MAX_PAGES >> 6); ++i) {
+        for (uint64_t j = 0; j < 64; ++j) {
+            if (!(amd64_phys_memory_track[i] & (1ULL << j))) {
+                amd64_phys_memory_track[i] |= (1ULL << j);
+                amd64_phys_last_index = i;
+                return PHYS_ALLOWED_BEGIN + ((i << 18) | (j << 12));
+            }
+        }
+    }
+    for (uint64_t i = 0; i < amd64_phys_last_index; ++i) {
+        for (uint64_t j = 0; j < 64; ++j) {
+            if (!(amd64_phys_memory_track[i] & (1ULL << j))) {
+                amd64_phys_memory_track[i] |= (1ULL << j);
+                amd64_phys_last_index = i;
+                return PHYS_ALLOWED_BEGIN + ((i << 18) | (j << 12));
+            }
+        }
+    }
+    return MM_NADDR;
+}
+
+void amd64_phys_free(uintptr_t page) {
+    // Address is too low
+    if (page < PHYS_ALLOWED_BEGIN) {
+        panic("Tried to free kernel physical pages\n");
+    }
+    // Address is too high
+    if (PHYS_TRACK_INDEX(page) >= (PHYS_MAX_PAGES >> 6)) {
+        panic("Tried to free non-available physical page\n");
+    }
+
+    uint64_t bit = 1ULL << PHYS_TRACK_BIT(page);
+    uint64_t index = PHYS_TRACK_INDEX(page);
+
+    // Double free error
+    if (!(amd64_phys_memory_track[index] & bit)) {
+        panic("Tried to free non-allocated physical page\n");
+    }
+
+    amd64_phys_memory_track[index] &= ~bit;
+}
 
 void amd64_phys_memory_map(const multiboot_memory_map_t *mmap, size_t length) {
-    static const char *mmap_region_strings[6] = {
-        "Unknown", "Available", "Used", "ACPI", "Reserved", "Defective"
-    };
+    kdebug("Kernel table pool ends @ %p\n", PHYS_ALLOWED_BEGIN);
     kdebug("Memory map @ %p\n", mmap);
     uintptr_t curr_item = (uintptr_t) mmap;
     uintptr_t mmap_end = length + curr_item;
 
+    // Collect usable physical memory information
     while (curr_item < mmap_end) {
         const multiboot_memory_map_t *entry = (const multiboot_memory_map_t *) (curr_item);
-        size_t type_index = (entry->type >= (sizeof(mmap_region_strings) / sizeof(mmap_region_strings[0]))) ? 0 : entry->type;
 
-        kdebug("%p - %p: %s\n", entry->addr, entry->addr + entry->size, mmap_region_strings[type_index]);
+        uintptr_t page_aligned_begin = MAX((entry->addr + 0xFFF) & ~0xFFF, PHYS_ALLOWED_BEGIN);
+        uintptr_t page_aligned_end = (entry->addr + entry->len) & ~0xFFF;
+
+        if (entry->type == 1 && page_aligned_end > page_aligned_begin) {
+            // TODO: size pretty-printing
+            kdebug("+++ %uKiB @ %p\n", (page_aligned_end - page_aligned_begin) / 1024, page_aligned_begin);
+        }
 
         curr_item += entry->size + sizeof(uint32_t);
     }