Implement disk read and error handling in VBR

CMakeLists.txt

@@ -60,12 +60,10 @@ file(RELATIVE_PATH _PATH_PREFIX ${EXECTOS_BINARY_DIR} ${EXECTOS_SOURCE_DIR})
 add_compiler_flags(-D__RELFILE__="&__FILE__[__FILE__[0] == '.' ? sizeof \\\"${_PATH_PREFIX}\\\" - 1 : sizeof XTOS_SOURCE_DIR]")
 
 # Set the virtual disk image size (in MiB)
-set_disk_image_size(32)
+set_disk_image_size(48)
 
 # Build all subprojects
 add_subdirectory(boot)
-add_subdirectory(bootdata)
 add_subdirectory(drivers)
 add_subdirectory(sdk)
-add_subdirectory(xtldr)
 add_subdirectory(xtoskrnl)

README.md

@@ -57,16 +57,18 @@ ExectOS is in very early development stage, thus its requirements have been not
 design, it requires a modern EFI enabled hardware. It is not possible currently to boot ExectOS on a legacy BIOS.
 
 # Source structure
-| Directory   | Description                                              |
-|-------------|----------------------------------------------------------|
-| bootdata    | default configuration and data needed to boot XTOS       |
-| drivers     | XT native drivers source code                            |
-| sdk/cmake   | Host toolchain configuration and build-related functions |
-| sdk/xtdk    | XT Software Development Kit headers                      |
-| services    | integral subsystems services source code                 |
-| subsystems  | environment subsystems source code                       |
-| xtoskrnl    | XTOS kernel source code                                  |
-| xtldr       | XTOS boot loader source code                             |
+| Directory        | Description                                                  |
+|------------------|--------------------------------------------------------------|
+| boot/bootdata    | default configuration and data needed to boot XTOS           |
+| boot/bootsect    | boot sector code (MBR & VBR) initializing the boot process   |
+| boot/xtldr       | XTOS boot loader source code                                 |
+| drivers          | XT native drivers source code                                |
+| sdk/cmake        | host toolchain configuration and build-related functions     |
+| sdk/firmware     | firmware enabling XTOS to boot on virtual machines           |
+| sdk/xtdk         | XT Software Development Kit headers                          |
+| services         | integral subsystems services source code                     |
+| subsystems       | environment subsystems source code                           |
+| xtoskrnl         | XTOS kernel source code                                      |
 
 # Build
 XTOS can only be built using [XTchain](https://git.codingworkshop.eu.org/xt-sys/xtchain), a dedicated toolchain designed

boot/CMakeLists.txt

@@ -1 +1,3 @@
+add_subdirectory(bootdata)
 add_subdirectory(bootsect)
+add_subdirectory(xtldr)

boot/bootsect/espboot.S

@@ -84,14 +84,145 @@ RealStart:
     leaw -16(%bp), %sp
     sti
 
-    /* Print message */
-    movw $msgUnavailable, %si
-    call Print
+    /* Get drive number */
+    cmpb $0xFF, DriveNumber - Start(%bp)
+    jne GetDriveParameters
+    movb %dl, DriveNumber - Start(%bp)
 
-    /* Wait for key press and reboot */
-    xorw %ax, %ax
-    int $0x16
-    int $0x19
+GetDriveParameters:
+    /* Get drive parameters from the BIOS */
+    movb DriveNumber - Start(%bp), %dl
+    movb $0x08, %ah
+    movb $0x00, %al
+    int $0x13
+    jnc GetDriveSize
+    movw $0xFFFF, %cx
+    movb %cl, %dh
+
+GetDriveSize:
+    /* Get drive size from the BIOS */
+    movzbl %dh, %eax
+    incw %ax
+    movzbl %cl, %edx
+    andb $0x3F, %dl
+    mulw %dx
+    xchgb %cl, %ch
+    shrb $0x06, %ch
+    incw %cx
+    movzwl %cx, %ecx
+    mull %ecx
+    movl %eax, %edi
+
+VerifyBiosParameterBlock:
+    /* Verify the FAT32 BPB */
+    cmpw $0x00, SectorsPerFat - Start(%bp)
+    jne FsError
+    cmpw $0x00, FsVersion - Start(%bp)
+    ja FsError
+
+ReadExtraCode:
+    /* Read second VBR sector with extra boot code */
+    movl HiddenSectors - Start(%bp), %eax
+    addl $0x02, %eax
+    movw $0x01, %cx
+    xorw %bx, %bx
+    movw %bx, %es
+    movw $0x7E00, %bx
+    call ReadSectors
+    jmp StartSectors
+
+ReadSectors:
+    /* Check for extended BIOS functions and use it only if available */
+    pushw %es
+    pushal
+    movb $0x41, %ah
+    movw $0x55AA, %bx
+    movb DriveNumber - Start(%bp), %dl
+    int $0x13
+    jc ReadCHS
+    cmpw $0xAA55, %bx
+    jne ReadCHS
+    testb $0x01, %cl
+    jz ReadCHS
+
+    /* Verify drive size and determine whether to use CHS or LBA */
+    cmpl %edi, %eax
+    jnb ReadLBA
+
+ReadCHS:
+    /* Read sectors using CHS */
+    popal
+    pushal
+    xorl %edx, %edx
+    movzwl SectorsPerTrack - Start(%bp), %ecx
+    divl %ecx
+    incb %dl
+    movb %dl, %cl
+    movl %eax, %edx
+    shrl $0x10, %edx
+    divw NumberOfHeads - Start(%bp)
+    movb %dl, %dh
+    movb DriveNumber - Start(%bp), %dl
+    movb %al, %ch
+    rorb $0x01, %ah
+    rorb $0x01, %ah
+    orb %ah, %cl
+    movw $0x0201, %ax
+    int $0x13
+    jc DiskError
+    popal
+    incl %eax
+    movw %es, %dx
+    addw $0x20, %dx
+    movw %dx, %es
+    loop ReadCHS
+    popw %es
+    ret
+
+ReadLBA:
+    /* Prepare DAP packet and read sectors using LBA */
+    popal
+    pushw %cx
+    pushal
+    pushw $0x00
+    pushw $0x00
+    pushl %eax
+    pushw %es
+    pushw %bx
+    pushw %cx
+    pushw $0x10
+    movw %sp, %si
+    movb DriveNumber - Start(%bp), %dl
+    movb $0x42, %ah
+    int $0x13
+    jc DiskError
+    addw $0x10, %sp
+    popal
+    popw %si
+    pushw %bx
+    movzwl %si, %ebx
+    addl %ebx, %eax
+    shll $0x05, %ebx
+    movw %es, %dx
+    addw %bx, %dx
+    movw %dx, %es
+    popw %bx
+    subw %si, %cx
+    jnz ReadLBA
+    popw %es
+    ret
+
+DiskError:
+    /* Display disk error message and reboot */
+    movw $msgDiskError, %si
+    call Print
+    jmp Reboot
+
+FsError:
+    /* Display FS error message and reboot */
+    movw $msgFsError, %si
+    call Print
+    jmp Reboot
 
 Print:
     /* Simple routine to print messages */
@@ -105,9 +236,40 @@ Print:
 DonePrint:
     retw
 
-msgUnavailable:
-    .ascii "XTLDR requires EFI-based system!\r\nPress any key to restart\r\n"
+Reboot:
+    /* Display a message, wait for a key press and reboot */
+    movw $msgAnyKey, %si
+    call Print
+    xorw %ax, %ax
+    int $0x16
+    int $0x19
+
+msgAnyKey:
+    .ascii "Press any key to restart\r\n"
+
+msgDiskError:
+    .ascii "Disk error\r\n"
+
+msgFsError:
+    .ascii "File system error\r\n"
 
 /* Fill the rest of the VBR with zeros and add VBR signature at the end */
 .fill (510 - (. - Start)), 1, 0
 .word 0xAA55
+
+
+StartSectors:
+    /* Print message */
+    movw $msgUnavailable, %si
+    call Print
+
+    /* Wait for key press and reboot */
+    xorw %ax, %ax
+    int $0x16
+    int $0x19
+
+msgUnavailable:
+    .ascii "XTLDR requires EFI-based system!\r\nPress any key to restart\r\n"
+
+/* Fill the rest of the extra VBR with zeros */
+.fill (1024 - (. - Start)), 1, 0

sdk/xtdk/amd64/artypes.h

@@ -394,13 +394,6 @@ typedef struct _CPU_IDENTIFICATION
     USHORT Stepping;
     CPU_VENDOR Vendor;
     UCHAR VendorName[13];
-    UINT32 StandardFeaturesEcx;
-    UINT32 StandardFeaturesEdx;
-    UINT32 ExtendedFeaturesEcx;
-    UINT32 ExtendedFeaturesEdx;
-    UINT32 Standard7FeaturesEbx;
-    UINT32 Standard7FeaturesEcx;
-    UINT32 Standard7FeaturesEdx;
 } CPU_IDENTIFICATION, *PCPU_IDENTIFICATION;
 
 /* CPUID registers */

sdk/xtdk/i686/artypes.h

@@ -359,10 +359,6 @@ typedef struct _CPU_IDENTIFICATION
     USHORT Stepping;
     CPU_VENDOR Vendor;
     UCHAR VendorName[13];
-    UINT32 StandardFeaturesEcx;
-    UINT32 StandardFeaturesEdx;
-    UINT32 ExtendedFeaturesEcx;
-    UINT32 ExtendedFeaturesEdx;
 } CPU_IDENTIFICATION, *PCPU_IDENTIFICATION;
 
 /* CPUID registers */

xtoskrnl/ar/amd64/procsup.cc

@@ -64,6 +64,9 @@ AR::ProcSup::IdentifyProcessor(VOID)
     CPUID_REGISTERS CpuRegisters;
     CPUID_SIGNATURE CpuSignature;
 
+    /* Not fully implemented yet */
+    UNIMPLEMENTED;
+
     /* Get current processor control block */
     Prcb = KE::Processor::GetCurrentProcessorControlBlock();
 
@@ -119,42 +122,7 @@ AR::ProcSup::IdentifyProcessor(VOID)
         Prcb->CpuId.Vendor = CPU_VENDOR_UNKNOWN;
     }
 
-    /* Get CPU standard features */
-    RtlZeroMemory(&CpuRegisters, sizeof(CPUID_REGISTERS));
-    CpuRegisters.Leaf = CPUID_GET_STANDARD1_FEATURES;
-    CpuFunc::CpuId(&CpuRegisters);
-
-    /* Store CPU standard features in processor control block */
-    Prcb->CpuId.StandardFeaturesEcx = CpuRegisters.Ecx;
-    Prcb->CpuId.StandardFeaturesEdx = CpuRegisters.Edx;
-
-    /* Get CPU extended features */
-    RtlZeroMemory(&CpuRegisters, sizeof(CPUID_REGISTERS));
-    CpuRegisters.Leaf = 0x80000001;
-    CpuFunc::CpuId(&CpuRegisters);
-
-    /* Store CPU extended features in processor control block */
-    Prcb->CpuId.ExtendedFeaturesEcx = CpuRegisters.Ecx;
-    Prcb->CpuId.ExtendedFeaturesEdx = CpuRegisters.Edx;
-
-    /* Get CPU leaf 7 features (subleaf 0) */
-    RtlZeroMemory(&CpuRegisters, sizeof(CPUID_REGISTERS));
-    CpuRegisters.Leaf = CPUID_GET_STANDARD7_FEATURES;
-    CpuRegisters.SubLeaf = 0;
-    CpuFunc::CpuId(&CpuRegisters);
-
-    /* Store CPU leaf 7 features in processor control block */
-    Prcb->CpuId.Standard7FeaturesEbx = CpuRegisters.Ebx;
-    Prcb->CpuId.Standard7FeaturesEcx = CpuRegisters.Ecx;
-    Prcb->CpuId.Standard7FeaturesEdx = CpuRegisters.Edx;
-    
-    /* Print CPU information */
-    DebugPrint(L"CPU: Vendor %hs, Family 0x%X, Model 0x%X, Stepping 0x%X\n",
-               Prcb->CpuId.VendorName,
-               Prcb->CpuId.Family,
-               Prcb->CpuId.Model,
-               Prcb->CpuId.Stepping);
-               
+    /* TODO: Store a list of CPU features in processor control block */
 }
 
 /**

xtoskrnl/ar/i686/procsup.cc

@@ -59,6 +59,9 @@ AR::ProcSup::IdentifyProcessor(VOID)
     CPUID_REGISTERS CpuRegisters;
     CPUID_SIGNATURE CpuSignature;
 
+    /* Not fully implemented yet */
+    UNIMPLEMENTED;
+
     /* Get current processor control block */
     Prcb = KE::Processor::GetCurrentProcessorControlBlock();
 
@@ -114,30 +117,7 @@ AR::ProcSup::IdentifyProcessor(VOID)
         Prcb->CpuId.Vendor = CPU_VENDOR_UNKNOWN;
     }
 
-    /* Get CPU standard features */
-    RtlZeroMemory(&CpuRegisters, sizeof(CPUID_REGISTERS));
-    CpuRegisters.Leaf = CPUID_GET_STANDARD1_FEATURES;
-    CpuFunc::CpuId(&CpuRegisters);
-
-    /* Store CPU standard features in processor control block */
-    Prcb->CpuId.StandardFeaturesEcx = CpuRegisters.Ecx;
-    Prcb->CpuId.StandardFeaturesEdx = CpuRegisters.Edx;
-
-    /* Get CPU extended features */
-    RtlZeroMemory(&CpuRegisters, sizeof(CPUID_REGISTERS));
-    CpuRegisters.Leaf = 0x80000001;
-    CpuFunc::CpuId(&CpuRegisters);
-
-    /* Store CPU extended features in processor control block */
-    Prcb->CpuId.ExtendedFeaturesEcx = CpuRegisters.Ecx;
-    Prcb->CpuId.ExtendedFeaturesEdx = CpuRegisters.Edx;
-
-    /* Print CPU information */
-    DebugPrint(L"CPU: Vendor %hs, Family 0x%X, Model 0x%X, Stepping 0x%X\n",
-               Prcb->CpuId.VendorName,
-               Prcb->CpuId.Family,
-               Prcb->CpuId.Model,
-               Prcb->CpuId.Stepping);
+    /* TODO: Store a list of CPU features in processor control block */
 }
 
 /**