Move lessons to separate folder

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>

3 files changed, 681 insertions, 0 deletions

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+The latest ACPI specification can be found under UEFI specifications page https://uefi.org/specifications
+
+The current latest specification is "ACPI Specification Version 6.4 (released January 2021)" (https://uefi.org/specs/ACPI/6.4/)
+
+
+Use the same tactic we used for SMBIOS tables to print ACPI entry point table address:
+```
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiLib.h>
+
+#include <Library/BaseMemoryLib.h>
+
+EFI_STATUS
+EFIAPI
+UefiMain (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  )
+{
+  for (UINTN i=0; i<SystemTable->NumberOfTableEntries; i++) {
+    if (CompareGuid(&(SystemTable->ConfigurationTable[i].VendorGuid), &gEfiAcpi20TableGuid)) {
+      Print(L"ACPI table is placed at %p\n\n", SystemTable->ConfigurationTable[i].VendorTable);
+    }
+  }
+  return EFI_SUCCESS;
+}
+```
+
+Use `dmem` to peak inside ACPI table memory:
+```
+FS0:\> AcpiInfo.efi
+ACPI table is placed at 7B7E014
+
+FS0:\> dmem 7B7E014 30
+Memory Address 0000000007B7E014 30 Bytes
+  07B7E014: 52 53 44 20 50 54 52 20-4E 42 4F 43 48 53 20 02  *RSD PTR NBOCHS .*
+  07B7E024: 74 D0 B7 07 24 00 00 00-E8 D0 B7 07 00 00 00 00  *t...$...........*
+  07B7E034: 66 00 00 00 AF AF AF AF-AF AF AF AF AF AF AF AF  *f...............*
+FS0:\>
+```
+
+The signature `RSP PTR` stands for `Root System Description Pointer (RSDP) Structure` (https://uefi.org/specs/ACPI/6.4/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html#root-system-description-pointer-rsdp-structure).
+
+It contains addresses for `RSDT` and `XSDT` tables. If you calculate offsets, you'll get these addresses from our memory dump:
+```
+XSDT=0x07B7D0E8
+RSDT=0x07B7D074
+```
+These tables in turn would cointain pointers to other ACPI tables that actualy contain data useful to OS.
+
+According to the spec "platforms provide the RSDT to enable compatibility with ACPI 1.0 operating systems. The XSDT supersedes RSDT functionality". So if you peak these addresses with `dmem`, table contents would be pretty much the same except table signatures. Therefore in our app code we would be parsing XSDT table data.
+
+Ok, it's time to write some code. ACPI structures are defined in the following header files:
+```
+$ ls -1 MdePkg/Include/IndustryStandard/Acpi*
+MdePkg/Include/IndustryStandard/Acpi.h
+MdePkg/Include/IndustryStandard/Acpi10.h
+MdePkg/Include/IndustryStandard/Acpi20.h
+MdePkg/Include/IndustryStandard/Acpi30.h
+MdePkg/Include/IndustryStandard/Acpi40.h
+MdePkg/Include/IndustryStandard/Acpi50.h
+MdePkg/Include/IndustryStandard/Acpi51.h
+MdePkg/Include/IndustryStandard/Acpi60.h
+MdePkg/Include/IndustryStandard/Acpi61.h
+MdePkg/Include/IndustryStandard/Acpi62.h
+MdePkg/Include/IndustryStandard/Acpi63.h
+MdePkg/Include/IndustryStandard/AcpiAml.h
+```
+
+Keep in mind that headers for latter standards include headers for earlier standards in itself.
+```
+Acpi.h > Acpi63.h > Acpi62.h > ... > Acpi10.h > AcpiAml.h
+```
+
+Let's look at RSDP structure definition at the most latest ACPI standard header file
+https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandard/Acpi63.h
+```
+///
+/// Root System Description Pointer Structure
+///
+typedef struct {
+  UINT64  Signature;
+  UINT8   Checksum;
+  UINT8   OemId[6];
+  UINT8   Revision;
+  UINT32  RsdtAddress;
+  UINT32  Length;
+  UINT64  XsdtAddress;
+  UINT8   ExtendedChecksum;
+  UINT8   Reserved[3];
+} EFI_ACPI_6_3_ROOT_SYSTEM_DESCRIPTION_POINTER;
+```
+
+We can use it to print addresses of RSDT/XSDT tables.
+```
+EFI_ACPI_6_3_ROOT_SYSTEM_DESCRIPTION_POINTER* RSDP = NULL;
+
+for (UINTN i=0; i<SystemTable->NumberOfTableEntries; i++) {
+  if (CompareGuid(&(SystemTable->ConfigurationTable[i].VendorGuid), &gEfiAcpi20TableGuid)) {
+    Print(L"RSDP table is placed at %p\n\n", SystemTable->ConfigurationTable[i].VendorTable);
+    RSDP = SystemTable->ConfigurationTable[i].VendorTable;
+  }
+}
+
+if (!RSDP) {
+  Print(L"No ACPI2.0 table was found in the system\n");
+  return EFI_SUCCESS;
+}
+
+if (((CHAR8)((RSDP->Signature >>  0) & 0xFF) != 'R') ||
+    ((CHAR8)((RSDP->Signature >>  8) & 0xFF) != 'S') ||
+    ((CHAR8)((RSDP->Signature >> 16) & 0xFF) != 'D') ||
+    ((CHAR8)((RSDP->Signature >> 24) & 0xFF) != ' ') ||
+    ((CHAR8)((RSDP->Signature >> 32) & 0xFF) != 'P') ||
+    ((CHAR8)((RSDP->Signature >> 40) & 0xFF) != 'T') ||
+    ((CHAR8)((RSDP->Signature >> 48) & 0xFF) != 'R') ||
+    ((CHAR8)((RSDP->Signature >> 56) & 0xFF) != ' ')) {
+  Print(L"Error! RSDP signature is not valid!\n");
+  return EFI_SUCCESS;
+}
+
+Print(L"System description tables:\n");
+Print(L"\tRSDT table is placed at address %p\n", RSDP->RsdtAddress);
+Print(L"\tXSDT table is placed at address %p\n", RSDP->XsdtAddress);
+Print(L"\n");
+```
+
+In the same file (https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandard/Acpi63.h) you can find description for XSDT structure:
+```
+//
+// Extended System Description Table
+// No definition needed as it is a common description table header, the same with
+// EFI_ACPI_DESCRIPTION_HEADER, followed by a variable number of UINT64 table pointers.
+//
+```
+
+The definition for `EFI_ACPI_DESCRIPTION_HEADER` can be found here https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandard/Acpi10.h:
+```
+#pragma pack(1)
+///
+/// The common ACPI description table header.  This structure prefaces most ACPI tables.
+///
+typedef struct {
+  UINT32  Signature;
+  UINT32  Length;
+  UINT8   Revision;
+  UINT8   Checksum;
+  UINT8   OemId[6];
+  UINT64  OemTableId;
+  UINT32  OemRevision;
+  UINT32  CreatorId;
+  UINT32  CreatorRevision;
+} EFI_ACPI_DESCRIPTION_HEADER;
+#pragma pack()
+```
+
+Let's check information about other ACPI tables that are present in the system:
+```
+EFI_ACPI_DESCRIPTION_HEADER* XSDT = (EFI_ACPI_DESCRIPTION_HEADER*)RSDP->XsdtAddress;
+if (((CHAR8)((XSDT->Signature >>  0) & 0xFF) != 'X') ||
+    ((CHAR8)((XSDT->Signature >>  8) & 0xFF) != 'S') ||
+    ((CHAR8)((XSDT->Signature >> 16) & 0xFF) != 'D') ||
+    ((CHAR8)((XSDT->Signature >> 24) & 0xFF) != 'T')) {
+  Print(L"Error! XSDT signature is not valid!\n");
+  return EFI_SUCCESS;
+}
+
+Print(L"Main ACPI tables:\n");
+UINT64 offset = sizeof(EFI_ACPI_DESCRIPTION_HEADER);
+while (offset < XSDT->Length) {
+  UINT64* table_address = (UINT64*)((UINT8*)XSDT + offset);
+  EFI_ACPI_6_3_COMMON_HEADER* table = (EFI_ACPI_6_3_COMMON_HEADER*)(*table_address);
+  TableName[0] = (CHAR16)((table->Signature>> 0)&0xFF);
+  TableName[1] = (CHAR16)((table->Signature>> 8)&0xFF);
+  TableName[2] = (CHAR16)((table->Signature>>16)&0xFF);
+  TableName[3] = (CHAR16)((table->Signature>>24)&0xFF);
+  TableName[4] = 0;
+
+  Print(L"\t%s table is placed at address %p with length 0x%x\n",
+                                           TableName,
+                                           table,
+                                           table->Length);
+  offset += sizeof(UINT64);
+}
+```
+
+If you build our app and execute it under OVMF now you would get:
+```
+FS0:\> AcpiInfo.efi
+RSDP table is placed at 7B7E014
+
+System description tables:
+        RSDT table is placed at address 7B7D074
+        XSDT table is placed at address 7B7D0E8
+
+Main ACPI tables:
+        FACP table is placed at address 7B7A000 with length 0x74
+        APIC table is placed at address 7B79000 with length 0x78
+        HPET table is placed at address 7B78000 with length 0x38
+        BGRT table is placed at address 7B77000 with length 0x38
+```
+
+Pretty neat, our system has 4 ACPI data tables:
+- Fixed ACPI Description Table (`FACP`) - https://uefi.org/specs/ACPI/6.4/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html#fixed-acpi-description-table-fadt
+- Multiple APIC Description Table (`MADT`) - https://uefi.org/specs/ACPI/6.4/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html#multiple-apic-description-table-madt
+- IA-PC High Precision Event Timer Table (`HPET`) - http://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/software-developers-hpet-spec-1-0a.pdf - This one is not present in ACPI spec, but in a separate document from the page https://uefi.org/acpi
+- Boot Graphics Resource Table (`BGRT`) - https://uefi.org/specs/ACPI/6.4/05_ACPI_Software_Programming_Model/ACPI_Software_Programming_Model.html#boot-graphics-resource-table-bgrt
+
+
+Keep in mind that as with SMBIOS tables we could use a protocol to get the same data. `GetAcpiTable()` function of a `EFI_ACPI_SDT_PROTOCOL` can help to get the same information. This protocol also is defined by UEFI PI specification.
+
+In edk2 it is defined under https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/AcpiSystemDescriptionTable.h
+
+# Use `EFI_SHELL_PROTOCOL` to save table data
+
+Now let's try to save ACPI tables from memory to files.
+
+To do this we can utilize `EFI_SHELL_PROTOCOL` that is defined in UEFI Shell specification (https://uefi.org/sites/default/files/resources/UEFI_Shell_2_2.pdf). It has many functions for File I/O.
+
+The necessary header in edk2 is https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/Shell.h
+```
+typedef struct _EFI_SHELL_PROTOCOL {
+  EFI_SHELL_EXECUTE                         Execute;
+  EFI_SHELL_GET_ENV                         GetEnv;
+  EFI_SHELL_SET_ENV                         SetEnv;
+  EFI_SHELL_GET_ALIAS                       GetAlias;
+  EFI_SHELL_SET_ALIAS                       SetAlias;
+  EFI_SHELL_GET_HELP_TEXT                   GetHelpText;
+  EFI_SHELL_GET_DEVICE_PATH_FROM_MAP        GetDevicePathFromMap;
+  EFI_SHELL_GET_MAP_FROM_DEVICE_PATH        GetMapFromDevicePath;
+  EFI_SHELL_GET_DEVICE_PATH_FROM_FILE_PATH  GetDevicePathFromFilePath;
+  EFI_SHELL_GET_FILE_PATH_FROM_DEVICE_PATH  GetFilePathFromDevicePath;
+  EFI_SHELL_SET_MAP                         SetMap;
+  EFI_SHELL_GET_CUR_DIR                     GetCurDir;
+  EFI_SHELL_SET_CUR_DIR                     SetCurDir;
+  EFI_SHELL_OPEN_FILE_LIST                  OpenFileList;
+  EFI_SHELL_FREE_FILE_LIST                  FreeFileList;
+  EFI_SHELL_REMOVE_DUP_IN_FILE_LIST         RemoveDupInFileList;
+  EFI_SHELL_BATCH_IS_ACTIVE                 BatchIsActive;
+  EFI_SHELL_IS_ROOT_SHELL                   IsRootShell;
+  EFI_SHELL_ENABLE_PAGE_BREAK               EnablePageBreak;
+  EFI_SHELL_DISABLE_PAGE_BREAK              DisablePageBreak;
+  EFI_SHELL_GET_PAGE_BREAK                  GetPageBreak;
+  EFI_SHELL_GET_DEVICE_NAME                 GetDeviceName;
+  EFI_SHELL_GET_FILE_INFO                   GetFileInfo;
+  EFI_SHELL_SET_FILE_INFO                   SetFileInfo;
+  EFI_SHELL_OPEN_FILE_BY_NAME               OpenFileByName;
+  EFI_SHELL_CLOSE_FILE                      CloseFile;
+  EFI_SHELL_CREATE_FILE                     CreateFile;
+  EFI_SHELL_READ_FILE                       ReadFile;
+  EFI_SHELL_WRITE_FILE                      WriteFile;
+  EFI_SHELL_DELETE_FILE                     DeleteFile;
+  EFI_SHELL_DELETE_FILE_BY_NAME             DeleteFileByName;
+  EFI_SHELL_GET_FILE_POSITION               GetFilePosition;
+  EFI_SHELL_SET_FILE_POSITION               SetFilePosition;
+  EFI_SHELL_FLUSH_FILE                      FlushFile;
+  EFI_SHELL_FIND_FILES                      FindFiles;
+  EFI_SHELL_FIND_FILES_IN_DIR               FindFilesInDir;
+  EFI_SHELL_GET_FILE_SIZE                   GetFileSize;
+  EFI_SHELL_OPEN_ROOT                       OpenRoot;
+  EFI_SHELL_OPEN_ROOT_BY_HANDLE             OpenRootByHandle;
+  EFI_EVENT                                 ExecutionBreak;
+  UINT32                                    MajorVersion;
+  UINT32                                    MinorVersion;
+  // Added for Shell 2.1
+  EFI_SHELL_REGISTER_GUID_NAME              RegisterGuidName;
+  EFI_SHELL_GET_GUID_NAME                   GetGuidName;
+  EFI_SHELL_GET_GUID_FROM_NAME              GetGuidFromName;
+  EFI_SHELL_GET_ENV_EX                      GetEnvEx;
+} EFI_SHELL_PROTOCOL;
+```
+
+We will use 3 functions from this protocol `OpenFileByName`/`WriteFile`/`CloseFile`:
+```
+EFI_SHELL_PROTOCOL.OpenFileByName()
+
+Summary:
+Opens a file or a directory by file name.
+
+Prototype:
+typdef
+EFI_STATUS
+(EFIAPI *EFI_SHELL_OPEN_FILE_BY_NAME) (
+ IN CONST CHAR16 *FileName,
+ OUT SHELL_FILE_HANDLE *FileHandle,
+ IN UINT64 OpenMode
+ );
+
+Parameters:
+FileName	Points to the null-terminated UCS-2 encoded file name.
+FileHandle	On return, points to the file handle.
+OpenMode	File open mode.
+
+Description:
+This function opens the specified file in the specified OpenMode and returns a file handle.
+```
+```
+EFI_SHELL_PROTOCOL.WriteFile()
+
+Summary:
+Writes data to the file.
+
+Prototype:
+typedef
+EFI_STATUS
+(EFIAPI EFI_SHELL_WRITE_FILE)(
+ IN SHELL_FILE_HANDLE FileHandle,
+ IN OUT UINTN *BufferSize,
+ OUT VOID *Buffer
+ );
+
+Parameters:
+FileHandle 	The opened file handle for writing.
+BufferSize	On input, size of Buffer.
+Buffer		The buffer in which data to write.
+
+Description:
+This function writes the specified number of bytes to the file at the current file position. The current file position is advanced the actual number of bytes
+written, which is returned in BufferSize. Partial writes only occur when there has been a data error during the write attempt (such as “volume space full”).
+The file automatically grows to hold the data, if required.
+```
+```
+EFI_SHELL_PROTOCOL.CloseFile()
+
+Summary:
+Closes the file handle.
+
+Prototype:
+typedef
+EFI_STATUS
+(EFIAPI *EFI_SHELL_CLOSE_FILE)(
+ IN SHELL_FILE_HANDLE FileHandle
+ );
+
+Parameters:
+FileHandle	The file handle to be closed
+Description	This function closes a specified file handle. All “dirty” cached file data is flushed
+		to the device, and the file is closed. In all cases, the handle is closed.
+
+```
+
+Now let's start coding. Add necessary include to our *.c file:
+```
+#include <Protocol/Shell.h>
+```
+And necessary protocol guid to our *.inf file:
+```
+[Protocols]
+  gEfiShellProtocolGuid
+```
+
+In our program we need to acquire `EFI_SHELL_PROTOCOL`, this can be done via `LocateProtocol` function from the BootServices:
+```
+EFI_SHELL_PROTOCOL* ShellProtocol;
+EFI_STATUS Status = gBS->LocateProtocol(
+  &gEfiShellProtocolGuid,
+  NULL,
+  (VOID **)&ShellProtocol
+);
+
+if (EFI_ERROR(Status)) {
+  Print(L"Can't open EFI_SHELL_PROTOCOL: %r\n", Status);
+  return EFI_SUCCESS;
+}
+```
+
+Then use `EFI_SHELL_PROTOCOL` functions in our while loop to create files with ACPI table data. For every table we will create a file "<signature>.aml". We use `.aml` extension for our files because in ACPI language source files usually have *.asl/*.dsl extension (ACPI Source Language), and compiled files have *.aml extension (ACPI Machine Language):
+```
+CHAR16 FileName[9] = {0};
+StrCpyS(FileName, 9, TableName);
+StrCatS(FileName, 9, L".aml");
+Print(L"%s\n", FileName);
+SHELL_FILE_HANDLE FileHandle;
+Status = ShellProtocol->OpenFileByName(FileName,
+                                       &FileHandle,
+                                       EFI_FILE_MODE_CREATE | EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ);
+
+if (!EFI_ERROR(Status)) {
+  UINTN size = table->Length;
+  Status = ShellProtocol->WriteFile(FileHandle, &size, (VOID*)table);
+  if (EFI_ERROR(Status)) {
+    Print(L"Error in WriteFile: %r\n", Status);
+  }
+  Status = ShellProtocol->CloseFile(FileHandle);
+  if (EFI_ERROR(Status)) {
+    Print(L"Error in CloseFile: %r\n", Status);
+  }
+} else {
+  Print(L"Error in OpenFileByName: %r\n", Status);
+}
+```
+
+To create a string with a file name we use `StrCatS` and `StrCpyS` functions. They are safe versions of string concatention/string copy functions similar to their C++ analogs `strcat_s`/`strcpy_s`. You can check out them in a library https://github.com/tianocore/edk2/blob/master/MdePkg/Library/BaseLib/SafeString.c
+
+With a help of `EFI_SHELL_PROTOCOL` file operation functions writing data to a file is pretty similar to standard system programming. We open handle, write data to it, and finally close handle.
+
+If you build our app and execute it under OVMF you would get 4 files in our `UEFI_disk` shared folder:
+```
+$ ls -1 ~/UEFI_disk/*.aml
+/home/kostr/UEFI_disk/apic.aml
+/home/kostr/UEFI_disk/bgrt.aml
+/home/kostr/UEFI_disk/facp.aml
+/home/kostr/UEFI_disk/hpet.aml
+```
+
+You can use `iasl` compiler to disassemle ACPI table data:
+```
+$ iasl -d ~/UEFI_disk/*.aml
+
+Intel ACPI Component Architecture
+ASL+ Optimizing Compiler/Disassembler version 20190509
+Copyright (c) 2000 - 2019 Intel Corporation
+
+File appears to be binary: found 81 non-ASCII characters, disassembling
+Binary file appears to be a valid ACPI table, disassembling
+Input file /home/kostr/UEFI_disk/apic.aml, Length 0x78 (120) bytes
+ACPI: APIC 0x0000000000000000 000078 (v01 BOCHS  BXPCAPIC 00000001 BXPC 00000001)
+Acpi Data Table [APIC] decoded
+Formatted output:  /home/kostr/UEFI_disk/apic.dsl - 4935 bytes
+File appears to be binary: found 32 non-ASCII characters, disassembling
+Binary file appears to be a valid ACPI table, disassembling
+Input file /home/kostr/UEFI_disk/bgrt.aml, Length 0x38 (56) bytes
+ACPI: BGRT 0x0000000000000000 000038 (v01 INTEL  EDK2     00000002      01000013)
+Acpi Data Table [BGRT] decoded
+Formatted output:  /home/kostr/UEFI_disk/bgrt.dsl - 1628 bytes
+File appears to be binary: found 91 non-ASCII characters, disassembling
+Binary file appears to be a valid ACPI table, disassembling
+Input file /home/kostr/UEFI_disk/facp.aml, Length 0x74 (116) bytes
+ACPI: FACP 0x0000000000000000 000074 (v01 BOCHS  BXPCFACP 00000001 BXPC 00000001)
+Acpi Data Table [FACP] decoded
+Formatted output:  /home/kostr/UEFI_disk/facp.dsl - 4892 bytes
+File appears to be binary: found 33 non-ASCII characters, disassembling
+Binary file appears to be a valid ACPI table, disassembling
+Input file /home/kostr/UEFI_disk/hpet.aml, Length 0x38 (56) bytes
+ACPI: HPET 0x0000000000000000 000038 (v01 BOCHS  BXPCHPET 00000001 BXPC 00000001)
+Acpi Data Table [HPET] decoded
+Formatted output:  /home/kostr/UEFI_disk/hpet.dsl - 1887 bytes
+```
+
+Now you have *.dsl files in the same `UEFI_disk` shared folder.
+
+For example here is a content for `APIC` table:
+```
+$ cat ~/UEFI_disk/apic.dsl
+/*
+ * Intel ACPI Component Architecture
+ * AML/ASL+ Disassembler version 20190509 (64-bit version)
+ * Copyright (c) 2000 - 2019 Intel Corporation
+ *
+ * Disassembly of /home/kostr/UEFI_disk/apic.aml, Sat Jul  3 00:09:16 2021
+ *
+ * ACPI Data Table [APIC]
+ *
+ * Format: [HexOffset DecimalOffset ByteLength]  FieldName : FieldValue
+ */
+
+[000h 0000   4]                    Signature : "APIC"    [Multiple APIC Description Table (MADT)]
+[004h 0004   4]                 Table Length : 00000078
+[008h 0008   1]                     Revision : 01
+[009h 0009   1]                     Checksum : ED
+[00Ah 0010   6]                       Oem ID : "BOCHS "
+[010h 0016   8]                 Oem Table ID : "BXPCAPIC"
+[018h 0024   4]                 Oem Revision : 00000001
+[01Ch 0028   4]              Asl Compiler ID : "BXPC"
+[020h 0032   4]        Asl Compiler Revision : 00000001
+
+[024h 0036   4]           Local Apic Address : FEE00000
+[028h 0040   4]        Flags (decoded below) : 00000001
+                         PC-AT Compatibility : 1
+
+[02Ch 0044   1]                Subtable Type : 00 [Processor Local APIC]
+[02Dh 0045   1]                       Length : 08
+[02Eh 0046   1]                 Processor ID : 00
+[02Fh 0047   1]                Local Apic ID : 00
+[030h 0048   4]        Flags (decoded below) : 00000001
+                           Processor Enabled : 1
+                      Runtime Online Capable : 0
+
+[034h 0052   1]                Subtable Type : 01 [I/O APIC]
+[035h 0053   1]                       Length : 0C
+[036h 0054   1]                  I/O Apic ID : 00
+[037h 0055   1]                     Reserved : 00
+[038h 0056   4]                      Address : FEC00000
+[03Ch 0060   4]                    Interrupt : 00000000
+
+[040h 0064   1]                Subtable Type : 02 [Interrupt Source Override]
+[041h 0065   1]                       Length : 0A
+[042h 0066   1]                          Bus : 00
+[043h 0067   1]                       Source : 00
+[044h 0068   4]                    Interrupt : 00000002
+[048h 0072   2]        Flags (decoded below) : 0000
+                                    Polarity : 0
+                                Trigger Mode : 0
+
+[04Ah 0074   1]                Subtable Type : 02 [Interrupt Source Override]
+[04Bh 0075   1]                       Length : 0A
+[04Ch 0076   1]                          Bus : 00
+[04Dh 0077   1]                       Source : 05
+[04Eh 0078   4]                    Interrupt : 00000005
+[052h 0082   2]        Flags (decoded below) : 000D
+                                    Polarity : 1
+                                Trigger Mode : 3
+
+[054h 0084   1]                Subtable Type : 02 [Interrupt Source Override]
+[055h 0085   1]                       Length : 0A
+[056h 0086   1]                          Bus : 00
+[057h 0087   1]                       Source : 09
+[058h 0088   4]                    Interrupt : 00000009
+[05Ch 0092   2]        Flags (decoded below) : 000D
+                                    Polarity : 1
+                                Trigger Mode : 3
+
+[05Eh 0094   1]                Subtable Type : 02 [Interrupt Source Override]
+[05Fh 0095   1]                       Length : 0A
+[060h 0096   1]                          Bus : 00
+[061h 0097   1]                       Source : 0A
+[062h 0098   4]                    Interrupt : 0000000A
+[066h 0102   2]        Flags (decoded below) : 000D
+                                    Polarity : 1
+                                Trigger Mode : 3
+
+[068h 0104   1]                Subtable Type : 02 [Interrupt Source Override]
+[069h 0105   1]                       Length : 0A
+[06Ah 0106   1]                          Bus : 00
+[06Bh 0107   1]                       Source : 0B
+[06Ch 0108   4]                    Interrupt : 0000000B
+[070h 0112   2]        Flags (decoded below) : 000D
+                                    Polarity : 1
+                                Trigger Mode : 3
+
+[072h 0114   1]                Subtable Type : 04 [Local APIC NMI]
+[073h 0115   1]                       Length : 06
+[074h 0116   1]                 Processor ID : FF
+[075h 0117   2]        Flags (decoded below) : 0000
+                                    Polarity : 0
+                                Trigger Mode : 0
+[077h 0119   1]         Interrupt Input LINT : 01
+
+Raw Table Data: Length 120 (0x78)
+
+    0000: 41 50 49 43 78 00 00 00 01 ED 42 4F 43 48 53 20  // APICx.....BOCHS
+    0010: 42 58 50 43 41 50 49 43 01 00 00 00 42 58 50 43  // BXPCAPIC....BXPC
+    0020: 01 00 00 00 00 00 E0 FE 01 00 00 00 00 08 00 00  // ................
+    0030: 01 00 00 00 01 0C 00 00 00 00 C0 FE 00 00 00 00  // ................
+    0040: 02 0A 00 00 02 00 00 00 00 00 02 0A 00 05 05 00  // ................
+    0050: 00 00 0D 00 02 0A 00 09 09 00 00 00 0D 00 02 0A  // ................
+    0060: 00 0A 0A 00 00 00 0D 00 02 0A 00 0B 0B 00 00 00  // ................
+    0070: 0D 00 04 06 FF 00 00 01                          // ........
+```
+
+
diff --git a/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.c b/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.c
new file mode 100644
index 0000000..0511f59
--- /dev/null
+++ b/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.c
@@ -0,0 +1,106 @@
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/UefiLib.h>
+
+#include <Library/BaseMemoryLib.h>
+#include <Protocol/Shell.h>
+
+EFI_STATUS
+EFIAPI
+UefiMain (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  )
+{
+  EFI_SHELL_PROTOCOL* ShellProtocol;
+  EFI_STATUS Status = gBS->LocateProtocol(
+    &gEfiShellProtocolGuid,
+    NULL,
+    (VOID **)&ShellProtocol
+  );
+
+  if (EFI_ERROR(Status)) {
+    Print(L"Can't open EFI_SHELL_PROTOCOL: %r\n", Status);
+    return EFI_SUCCESS;
+  }
+
+  EFI_ACPI_6_3_ROOT_SYSTEM_DESCRIPTION_POINTER* RSDP = NULL;
+
+  for (UINTN i=0; i<SystemTable->NumberOfTableEntries; i++) {
+    if (CompareGuid(&(SystemTable->ConfigurationTable[i].VendorGuid), &gEfiAcpi20TableGuid)) {
+      Print(L"RSDP table is placed at %p\n\n", SystemTable->ConfigurationTable[i].VendorTable);
+      RSDP = SystemTable->ConfigurationTable[i].VendorTable;
+    }
+  }
+
+  if (!RSDP) {
+    Print(L"No ACPI2.0 table was found in the system\n");
+    return EFI_SUCCESS;
+  }
+
+  if (((CHAR8)((RSDP->Signature >>  0) & 0xFF) != 'R') ||
+      ((CHAR8)((RSDP->Signature >>  8) & 0xFF) != 'S') ||
+      ((CHAR8)((RSDP->Signature >> 16) & 0xFF) != 'D') ||
+      ((CHAR8)((RSDP->Signature >> 24) & 0xFF) != ' ') ||
+      ((CHAR8)((RSDP->Signature >> 32) & 0xFF) != 'P') ||
+      ((CHAR8)((RSDP->Signature >> 40) & 0xFF) != 'T') ||
+      ((CHAR8)((RSDP->Signature >> 48) & 0xFF) != 'R') ||
+      ((CHAR8)((RSDP->Signature >> 56) & 0xFF) != ' ')) {
+    Print(L"Error! RSDP signature is not valid!\n");
+    return EFI_SUCCESS;
+  }
+
+  Print(L"System description tables:\n");
+  Print(L"\tRSDT table is placed at address %p\n", RSDP->RsdtAddress);
+  Print(L"\tXSDT table is placed at address %p\n", RSDP->XsdtAddress);
+  Print(L"\n");
+
+  EFI_ACPI_DESCRIPTION_HEADER* XSDT = (EFI_ACPI_DESCRIPTION_HEADER*)RSDP->XsdtAddress;
+  if (((CHAR8)((XSDT->Signature >>  0) & 0xFF) != 'X') ||
+      ((CHAR8)((XSDT->Signature >>  8) & 0xFF) != 'S') ||
+      ((CHAR8)((XSDT->Signature >> 16) & 0xFF) != 'D') ||
+      ((CHAR8)((XSDT->Signature >> 24) & 0xFF) != 'T')) {
+    Print(L"Error! XSDT signature is not valid!\n");
+    return EFI_SUCCESS;
+  }
+
+  Print(L"Main ACPI tables:\n");
+  UINT64 offset = sizeof(EFI_ACPI_DESCRIPTION_HEADER);
+  while (offset < XSDT->Length) {
+    UINT64* table_address = (UINT64*)((UINT8*)XSDT + offset);
+    EFI_ACPI_6_3_COMMON_HEADER* table = (EFI_ACPI_6_3_COMMON_HEADER*)(*table_address);
+    CHAR16 TableName[5];
+    TableName[0] = (CHAR16)((table->Signature>> 0)&0xFF);
+    TableName[1] = (CHAR16)((table->Signature>> 8)&0xFF);
+    TableName[2] = (CHAR16)((table->Signature>>16)&0xFF);
+    TableName[3] = (CHAR16)((table->Signature>>24)&0xFF);
+    TableName[4] = 0;
+
+    Print(L"\t%s table is placed at address %p with length 0x%x\n",
+                                             TableName,
+                                             table,
+                                             table->Length);
+    CHAR16 FileName[9] = {0};
+    StrCpyS(FileName, 9, TableName);
+    StrCatS(FileName, 9, L".aml");
+    SHELL_FILE_HANDLE FileHandle;
+    Status = ShellProtocol->OpenFileByName(FileName,
+                                           &FileHandle,
+                                           EFI_FILE_MODE_CREATE | EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ);
+    if (!EFI_ERROR(Status)) {
+      UINTN size = table->Length;
+      Status = ShellProtocol->WriteFile(FileHandle, &size, (VOID*)table);
+      if (EFI_ERROR(Status)) {
+        Print(L"Error in WriteFile: %r\n", Status);
+      }
+      Status = ShellProtocol->CloseFile(FileHandle);
+      if (EFI_ERROR(Status)) {
+        Print(L"Error in CloseFile: %r\n", Status);
+      }
+    } else {
+      Print(L"Error in OpenFileByName: %r\n", Status);
+    }
+    offset += sizeof(UINT64);
+  }
+
+  return EFI_SUCCESS;
+}
diff --git a/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.inf b/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.inf
new file mode 100644
index 0000000..53d0356
--- /dev/null
+++ b/Lessons/Lesson_28/UefiLessonsPkg/AcpiInfo/AcpiInfo.inf
@@ -0,0 +1,24 @@
+[Defines]
+  INF_VERSION                    = 1.25
+  BASE_NAME                      = AcpiInfo
+  FILE_GUID                      = 18998798-69a2-4ab5-9ffc-a8ee2494b029
+  MODULE_TYPE                    = UEFI_APPLICATION
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = UefiMain
+
+[Sources]
+  AcpiInfo.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  UefiApplicationEntryPoint
+  UefiLib
+
+[Guids]
+  gEfiAcpi20TableGuid
+
+[Protocols]
+  gEfiShellProtocolGuid
+