physical mem manager

Makefile

@@ -20,7 +20,7 @@ ISO := Hazel.iso
 CFLAGS    := -ffreestanding -Wall -Wextra -Werror -I $(INCLUDEDIR) -I lib
 LDFLAGS   := -ffreestanding -nostdlib -lgcc -T kernel/kernel.ld
 QEMUFLAGS := -cdrom $(BUILDDIR)/$(ISO) \
-			 -d int \
+	     -m 512M \
 	     -serial stdio
 
 $(BUILDDIR)/$(KIMG): $(KOBJ) $(LOBJ)

include/kernel/kernel.h

@@ -8,8 +8,10 @@
 #define CHECK_FLAG(x, n) (x & (1<<n))
 
 typedef struct {
-   multiboot_memory_map_t *mem_map;
-   uint32_t mem_map_len;
+   multi_mmap_t *multi_mmap;
+   uint32_t multi_mmap_size;
+   uint32_t *mmap;
+   uint32_t mmap_size;
    log_method_t log_method;
    uint64_t ticks;
 } kernel_ctx_t;

include/kernel/mem.h

@@ -0,0 +1,26 @@
+#ifndef HAZEL_MEM_H_
+#define HAZEL_MEM_H_
+
+#include <kernel/kernel.h>
+#include <stdint.h>
+
+#define KERNEL_START 0x1000000 // 1 MiB
+#define KERNEL_SIZE  0xC800    // 50 KiB
+#define BLOCK_SIZE 4096
+#define BITS 32
+
+uint8_t mmap_init(void);
+void mmap_set_block(int block);
+void mmap_free_block(int block);
+void *mmap_find_first_free_block(void);
+void *mmap_block_to_physical(int block);
+
+void memset(void *s, int c, uint32_t len);
+void memcpy(void *dest, void *src, int n);
+
+typedef struct {
+    void *data;
+    void *next;
+} linked_mem_t;
+
+#endif

include/kernel/multiboot.h

@@ -40,7 +40,7 @@ struct multiboot_mmap_entry
 #define MULTIBOOT_MEMORY_BADRAM                 5
     uint32_t type;
 } __attribute__((packed));
-typedef struct multiboot_mmap_entry multiboot_memory_map_t;
+typedef struct multiboot_mmap_entry multi_mmap_t;
 
 
 #endif

kernel/init.asm

@@ -43,7 +43,6 @@ _start:
     mov esp, stack_bottom
     mov ebp, esp
     push ebx 
-    and esp, 0xfffffff0
     extern kernel
     call kernel
     cli

kernel/kernel.c

@@ -1,5 +1,6 @@
 #include <kernel/kernel.h>
 #include <kernel/multiboot.h>
+#include <kernel/mem.h>
 #include <kernel/serial.h>
 #include <kernel/idt.h>
 #include <kernel/pic.h>
@@ -28,13 +29,15 @@ void sleep(int delay) {
 void kernel(multiboot_info_t *info) {
     if (!CHECK_FLAG(info->flags, 6)) goto halt;  // Memory map
     if (!CHECK_FLAG(info->flags, 12)) goto halt; // VBE data 
-    ctx.mem_map = (multiboot_memory_map_t *)info->memmapaddress;
-    ctx.mem_map_len = info->memmaplength;
+    ctx.multi_mmap = (multi_mmap_t *)info->memmapaddress;
+    ctx.multi_mmap_size = info->memmaplength;
 
     if (serial_port_init(COM1)) ctx.log_method = LOG_COM1;
-
     LOG("Kernel log being sent to COM1\n");
 
+    if (!mmap_init()) goto halt;
+    LOG("%d bytes of RAM detected\nCreated a %d byte large physical memory map at 0x%08X\n", ctx.mmap_size*BLOCK_SIZE*8, ctx.mmap_size, ctx.mmap);
+
     for (int i = 0; i < 32; i++) {
         idt_encode_entry(idt, i, isr_stub_table[i], GDT_SEGMENT_SELECTOR(1, 0), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
     }

kernel/mem.c

@@ -0,0 +1,127 @@
+#include <kernel/mem.h>
+
+extern kernel_ctx_t ctx;
+
+// TODO: Fix this, it wastes memory when switching regions because the previous offset isnt being subtracted
+// Should work fine for now?
+void *mmap_block_to_physical(int block) {
+    uint32_t offset = block * BLOCK_SIZE;
+
+    for (uint32_t i = 0; i < ctx.multi_mmap_size; i++) {
+        struct multiboot_mmap_entry entry = ctx.multi_mmap[i];
+        if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
+
+        uint32_t len  = (uint32_t)(entry.len_low | entry.len_high);
+        uint32_t addr = (uint32_t)(entry.addr_low | entry.addr_high);
+        if (len > offset)
+           return (void *)(addr + offset);
+    }
+
+    return 0;
+}
+
+void memset(void *s, int c, uint32_t len) {
+    unsigned char *dst = s;
+    while (len > 0) {
+        *dst = (unsigned char) c;
+        dst++;
+        len--;
+    }
+}
+
+void memcpy(void *dest, void *src, int n) {  
+    for (int i=0; i<n; i++)  
+        ((char *)dest)[i] = ((char *)src)[i];  
+}
+
+
+uint8_t mmap_init(void) {
+    // Calculate the number of bytes available to us
+    uint64_t available_bytes = 0;
+    for (uint32_t i = 0; i < ctx.multi_mmap_size; i++) {
+	struct multiboot_mmap_entry entry = ctx.multi_mmap[i];
+	if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
+
+	uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
+	available_bytes += len;
+    }
+
+    ctx.mmap_size = available_bytes / BLOCK_SIZE / 8;
+
+    // Loop again to find the first region with enough space to hold the memory map
+    int index = -1;
+    for (uint32_t i = 0; i < ctx.multi_mmap_size; i++) {
+        struct multiboot_mmap_entry entry = ctx.multi_mmap[i];
+        if (entry.type != MULTIBOOT_MEMORY_AVAILABLE) continue;
+
+        uint32_t len = (uint32_t)(entry.len_low | entry.len_high);
+        if (len > ctx.mmap_size) {
+            index = i;
+            break;
+        }
+    }
+
+    if (index == -1) return 0; // Failed
+
+    // Create map
+    struct multiboot_mmap_entry entry = ctx.multi_mmap[index];
+    uint32_t addr = (uint32_t)(entry.addr_low | entry.addr_high);
+    ctx.mmap = (uint32_t *)addr;
+    // Zero the map
+    memset(ctx.mmap, 0, ctx.mmap_size);
+    // Reserve the blocks that hold the memory map + 1
+    uint32_t blocks_to_set = ctx.mmap_size / BLOCK_SIZE + 1;
+    for (uint32_t i = 0; i < blocks_to_set; i++)
+        mmap_set_block(i);
+    // Reserve the kernel space
+    int bits = ctx.mmap_size * 8;
+    for (int i = 0; i < bits; i++) {
+        uint32_t phys = (uint32_t)mmap_block_to_physical(i);
+        if (phys > KERNEL_START && phys < KERNEL_START + KERNEL_SIZE)
+            mmap_set_block(i);
+    }
+
+    return 1;
+}
+
+void mmap_set_block(int block) {
+    int index = block / BITS;
+    int bit = block;
+    if (block >= BITS)
+        bit -= BITS;
+
+    uint32_t mask = 1 << bit;
+    if (!(ctx.mmap[index] & mask))
+        ctx.mmap[index] |= mask;
+}
+
+void mmap_free_block(int block) {
+    int index = block / BITS;
+    int bit = block;
+    if (block >= BITS)
+        bit -= BITS;
+
+    uint32_t mask = 1 << bit;
+    if (ctx.mmap[index] & mask)
+        ctx.mmap[index] ^= mask;
+}
+
+void *mmap_find_first_free_block(void) {
+    int bits = ctx.mmap_size * 8;
+    for (int i = 0; i < bits; i++) {
+        int index = i / BITS;
+        int bit = i;
+        if (i >= BITS)
+            bit -= BITS;
+
+        uint32_t mask = 1 << bit;
+
+        uint32_t dword = ctx.mmap[index];
+        if (!(dword & mask)) {
+            mmap_set_block(i);
+            return mmap_block_to_physical(i);
+        }
+    }
+    
+    return 0;
+}