Fix embarassing bug in paging impl that caused crashes..

This replaces the old way of appending the memory bitmap to the end of the kernel, which started causing problems with expansion..

I hardcoded the value to 0x1440, which is the start of the first FREE block of memory given to SeaBIOS in QEMU. This should be changed in the future..

chroma.json

@@ -3,13 +3,12 @@
     "config": "img/boot/config",
     "initrd": {
         "type": "tar",
-        "file": "img/boot/exe"
+        "directory": "img/boot"
     },
     "partitions": [
         {
             "type": "boot",
-            "size": 4,
-            "directory": "img/boot/loader"
+            "size": 4
         },
         {
             "type": "Microsoft basic data",

chroma/inc/kernel/boot/boot.h

@@ -14,8 +14,7 @@ extern "C" {
 #define BOOT_MAGIC "BOOT"
 
 /* minimum protocol level:
- *  hardcoded kernel name, static kernel memory addresses 
- * this is the default */
+ *  hardcoded kernel name, static kernel memory addresses */
 #define PROTOCOL_MINIMAL 0
 /* static protocol level:
  *  kernel name parsed from environment, static kernel memory addresses */
@@ -28,7 +27,6 @@ extern "C" {
 
 /* loader types, just informational */
 #define LOADER_BIOS (0<<2)
-/* unless we get to a weird stage, these should never be used. */
 #define LOADER_UEFI (1<<2)
 #define LOADER_RPI  (2<<2)
 
@@ -108,31 +106,6 @@ typedef struct {
 } __attribute__((packed)) bootinfo;
 
 
-typedef struct {
-  uint32_t Magic;
-  uint8_t Class;
-  uint8_t Endianness;
-  uint8_t Version;
-  uint8_t ABI;
-  uint8_t ABIVersion;
-  uint8_t Unused[7];
-  uint16_t Type;
-  uint16_t TargetArchitecture;
-  uint32_t ELFVersion;
-  size_t EntryPoint;
-  size_t ProgramHeadersTable;
-  size_t SectionHeadersTable;
-  uint32_t Flags;
-  uint16_t ELFHeaderSize;
-  uint16_t ProgramHeadersEntrySize;
-  uint16_t ProgramHeaderEntries;
-  uint16_t SectionHeadersEntrySize;
-  uint16_t SectionHeaderEntries;
-  uint16_t SectionHeaderNameEntry;
-  uint8_t End;
-} __attribute__((packed)) ELF64Header_t;
-
-
 #ifdef  __cplusplus
 }
 #endif

chroma/inc/kernel/chroma.h

@@ -28,7 +28,6 @@ extern bootinfo bootldr;
 extern unsigned char* environment;
 extern uint8_t fb;
 extern volatile unsigned char _binary_font_psf_start;
-extern volatile size_t* _kernel_text_start;
 
 extern address_space_t KernelAddressSpace;
 

chroma/inc/kernel/system/memory.h

@@ -8,8 +8,6 @@
  ***     Chroma       ***
  ***********************/
 
-size_t KernelLocation;
-
 
 /************************************************
 *    C O N S T A N T S   A N D   M A C R O S
@@ -54,8 +52,6 @@ size_t KernelLocation;
 #define ERR_RESERVED 0x8
 #define ERR_INST     0x10
 
-#define ELF64MAGIC 0x7F454c46
-
 
 /*
  * The way we boot, using BOOTBOOT, and the static hard drive images, means 
@@ -108,6 +104,8 @@ size_t KernelLocation;
 #define FB_REGION           0xFFFFFFFFFC000000ull // Cannot move!
 #define FB_PHYSICAL         0x00000000E0000000ull // Physical location of the Framebuffer
 #define KERNEL_REGION       0xFFFFFFFFFFE00000ull // -2MiB, from bootloader
+#define KERNEL_PHYSICAL     0x0000000000008000ull // Physical location of the kernel
+#define KERNEL_PHYSICAL_2   0x000000000011C000ull // For some reason the kernel is split in half
 
 #define USER_REGION         0x00007FFFFFFFFFFFull // Not needed yet, but we're higher half so we might as well be thorough
 

chroma/kernel.c

@@ -20,48 +20,9 @@ address_space_t KernelAddressSpace;
 
 int Main(void) {
     KernelAddressSpace = (address_space_t) {0};
-    KernelLocation = 0x112600;
 
     SerialPrintf("\r\n[ boot] Booting Chroma..\r\n");
     SerialPrintf("[ boot] Kernel loaded at 0x%p, ends at 0x%p, is %d bytes long.\r\n", KernelAddr, KernelEnd, KernelEnd - KernelAddr);
-    SerialPrintf("[ boot] Initrd is physically at 0x%p, and is %d bytes long.\r\n", bootldr.initrd_ptr, bootldr.initrd_size);
-
-    SerialPrintf("[ boot] Searching for kernel... Constants start at 0x%p\r\n", &_kernel_text_start);
-    // We stop at the constants in the kernel, otherwise we'll read the constant ELF64MAGIC which is stored inside the kernel...
-    
-    size_t headerLoc = 0;
-    for(size_t i = KernelAddr; i < KernelEnd; i++) {
-        if(i < (size_t) (&_kernel_text_start) - KernelAddr) {
-            if(*((volatile uint32_t*)(i)) == ELF64MAGIC) {
-                SerialPrintf("[ boot] Matched kernel header at 0x%p.\r\n", i);
-            }
-        }
-    }
-
-    int flag = 0;
-
-    if(headerLoc) {
-        ELF64Header_t* PotentialKernelHeader = (ELF64Header_t*) &headerLoc;
-        SerialPrintf(
-            "[ boot] Considering ELF with:\r\n\tBitness %d\r\n\tEntry point 0x%p\r\n\tFile type %s : %d\r\n\tArchitecture %s : %d\r\n",
-            PotentialKernelHeader->Class == 2 ? 64 : 32, PotentialKernelHeader->EntryPoint, PotentialKernelHeader->Type == 0x02 ? "EXECUTABLE" : "OTHER", PotentialKernelHeader->Type, PotentialKernelHeader->TargetArchitecture == 0x3E ? "AMD64" : "OTHER", PotentialKernelHeader->TargetArchitecture);
-        if(PotentialKernelHeader->EntryPoint == KernelAddr) {
-            SerialPrintf("[ boot] Header at 0x%p matches kernel header.\r\n", headerLoc);
-            flag = 1;
-        }
-
-        if(!flag) {
-
-            for(size_t i = 0; i < 8; i++) {
-                SerialPrintf("[ boot] Header dump part %d: 0x%x\r\n", i, *((volatile uint32_t*)(headerLoc + i)));
-            }
-        }
-    }
-
-    if(!flag) {
-        SerialPrintf("[ boot] Unable to find kernel in memory. Fatal error.\r\n");
-        //for(;;) {}
-    }
 
     SerialPrintf("[ boot] The bootloader has put the paging tables at 0x%p.\r\n", ReadControlRegister(3));
 

chroma/system/memory/paging.c

@@ -48,7 +48,7 @@
  * 
  */ 
 
-//extern size_t _kernel_text_start;
+extern size_t _kernel_text_start;
 extern size_t _kernel_rodata_start;
 extern size_t _kernel_data_start;
 
@@ -138,10 +138,10 @@ void InitPaging() {
 
     SerialPrintf("[  Mem] Identity mapping higher half complete.\n");
 
-    MMapEnt* TopEntry = (MMapEnt*)(((size_t) (&bootldr) + bootldr.size) - sizeof(MMapEnt));
+    MMapEnt* TopEntry = (MMapEnt*)(((&bootldr) + bootldr.size) - sizeof(MMapEnt));
     size_t LargestAddress = TopEntry->ptr + TopEntry->size;
 
-    SerialPrintf("[  Mem] About to map lower memory into the Direct Region. Highest address = 0x%p\n", AlignUpwards(LargestAddress, PAGE_SIZE));
+    SerialPrintf("[  Mem] About to map lower memory into the Direct Region.\n");
     for(size_t Address = 0; Address < AlignUpwards(LargestAddress, PAGE_SIZE); Address += PAGE_SIZE) {
         MapVirtualMemory(&KernelAddressSpace, (size_t*)(((char*)Address) + DIRECT_REGION), Address, MAP_WRITE);
     }
@@ -151,16 +151,16 @@ void InitPaging() {
 
     //TODO: Disallow execution of rodata and data, and bootldr/environment
     for(void* Address = CAST(void*, KERNEL_REGION);
-            Address < CAST(void*, KERNEL_REGION + (KernelEnd - KernelAddr)); // Lower half of Kernel
+            Address < CAST(void*, KERNEL_REGION + 0x2000); // Lower half of Kernel
             Address = CAST(void*, CAST(char*, Address) + PAGE_SIZE)) {
-                MapVirtualMemory(&KernelAddressSpace, Address, (CAST(size_t, Address) - KERNEL_REGION) + KernelLocation, MAP_EXEC);
+                MapVirtualMemory(&KernelAddressSpace, Address, (CAST(size_t, Address) - KERNEL_REGION) + KERNEL_PHYSICAL, MAP_EXEC);
     }
 
-    /*for(void* Address = CAST(void*, KERNEL_REGION + 0x2000);
+    for(void* Address = CAST(void*, KERNEL_REGION + 0x2000);
             Address < CAST(void*, KERNEL_REGION + 0x12000); // Higher half of kernel
             Address = CAST(void*, CAST(char*, Address) + PAGE_SIZE)) {
                 MapVirtualMemory(&KernelAddressSpace, Address, (CAST(size_t, Address) - KERNEL_REGION) + KERNEL_PHYSICAL_2, MAP_EXEC);
-    }*/
+    }
 
     for(void* Address = CAST(void*, FB_REGION);
             Address < CAST(void*, 0x200000);     // TODO: Turn this into a calculation with bootldr.fb_size
@@ -169,9 +169,6 @@ void InitPaging() {
     }
 
     SerialPrintf("[  Mem] Kernel mapped into pagetables. New PML4 at 0x%p\r\n", KernelAddressSpace.PML4);
-    SerialPrintf("[  Mem] About to move into our own pagetables.\r\n");
-    WriteControlRegister(3, (size_t) KernelAddressSpace.PML4);
-    SerialPrintf("[  Mem] We survived!\r\n");
     //ASSERT(Allocator != NULL);
 }