UEFI-Lessons/Lessons/Lesson_12 at master · Kostr/UEFI-Lessons

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Let's investigate final protocol that was attached to our ImageHandle - EFI_SHELL_PARAMETERS_PROTOCOL

https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/ShellParameters.h

typedef struct _EFI_SHELL_PARAMETERS_PROTOCOL {
  ///
  /// Points to an Argc-element array of points to NULL-terminated strings containing
  /// the command-line parameters. The first entry in the array is always the full file
  /// path of the executable. Any quotation marks that were used to preserve
  /// whitespace have been removed.
  ///
  CHAR16 **Argv;

  ///
  /// The number of elements in the Argv array.
  ///
  UINTN Argc;

  ///
  /// The file handle for the standard input for this executable. This may be different
  /// from the ConInHandle in EFI_SYSTEM_TABLE.
  ///
  SHELL_FILE_HANDLE StdIn;

  ///
  /// The file handle for the standard output for this executable. This may be different
  /// from the ConOutHandle in EFI_SYSTEM_TABLE.
  ///
  SHELL_FILE_HANDLE StdOut;

  ///
  /// The file handle for the standard error output for this executable. This may be
  /// different from the StdErrHandle in EFI_SYSTEM_TABLE.
  ///
  SHELL_FILE_HANDLE StdErr;
} EFI_SHELL_PARAMETERS_PROTOCOL;

As we see, we can access command line arguments that was passed to our program through this protocol. Let's use it in our MemoryInfo program.

In the last lesson we've printed our EFI memory map. It had >100 entries. When you boot Linux kernel, you can see some info about the current memory map, but this table is much shorter. It happens because of two facts:

Kernel differentiate EFI memory types much less granular. Instead of EfiReservedMemoryType/EfiLoaderCode/EfiLoaderData/...it simply has only 4 types:usable/ACPI NVS/ACPI data/reserved`
Kernel glues adjacent regions together

I've generated kernel image for EFI x86-64 with buildroot:

cd ~
git clone https://github.com/buildroot/buildroot.git
cd buildroot
make pc_x86_64_efi_defconfig
make

If we try to boot this kernel with:

qemu-system-x86_64 -drive if=pflash,format=raw,file=Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd \
                   -drive format=raw,file=fat:rw:~/UEFI_disk \
                   -nographic \
                   -kernel ~/buildroot/output/images/bzImage \
                   -append "console=ttyS0"

In kernel boot log we can see:

BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable
BIOS-e820: [mem 0x0000000000100000-0x00000000007fffff] usable
BIOS-e820: [mem 0x0000000000800000-0x0000000000807fff] ACPI NVS
BIOS-e820: [mem 0x0000000000808000-0x000000000080ffff] usable
BIOS-e820: [mem 0x0000000000810000-0x00000000008fffff] ACPI NVS
BIOS-e820: [mem 0x0000000000900000-0x00000000078eefff] usable
BIOS-e820: [mem 0x00000000078ef000-0x0000000007b6efff] reserved
BIOS-e820: [mem 0x0000000007b6f000-0x0000000007b7efff] ACPI data
BIOS-e820: [mem 0x0000000007b7f000-0x0000000007bfefff] ACPI NVS
BIOS-e820: [mem 0x0000000007bff000-0x0000000007ef3fff] usable
BIOS-e820: [mem 0x0000000007ef4000-0x0000000007f77fff] reserved
BIOS-e820: [mem 0x0000000007f78000-0x0000000007ffffff] ACPI NVS
BIOS-e820: [mem 0x00000000ffc00000-0x00000000ffffffff] reserved

Let's modify our MemoryInfo program:

if full option is passed, we print memory map as we do now
if no option is passed, we print memory map in a "Linux kernel way"

First, add full boolean flag. If argument "full" is passed to our program, we'll set this flag, else it would be equal to false.

EFI_SHELL_PARAMETERS_PROTOCOL* ShellParameters;

Status = gBS->HandleProtocol(
  ImageHandle,
  &gEfiShellParametersProtocolGuid,
  (VOID **) &ShellParameters
);

BOOLEAN full=FALSE;
if (Status == EFI_SUCCESS) {
  if (ShellParameters->Argc == 2) {
    if (!StrCmp(ShellParameters->Argv[1], L"full")) {
      full=TRUE;
    }
  }
}

To use EFI_SHELL_PARAMETERS_PROTOCOL we need to add include file:

#include <Protocol/ShellParameters.h>

And add GUID to the application *.inf file:

[Protocols]
  gEfiShellParametersProtocolGuid

Now to the next problem. Create a function for OS memory type mapping:

const CHAR16 *memory_types_OS_view[] = {
    L"reserved", // L"EfiReservedMemoryType",
    L"usable",   // L"EfiLoaderCode",
    L"usable",   // L"EfiLoaderData",
    L"usable",   // L"EfiBootServicesCode",
    L"usable",   // L"EfiBootServicesData",
    L"reserved", // L"EfiRuntimeServicesCode",
    L"reserved", // L"EfiRuntimeServicesData",
    L"usable",   // L"EfiConventionalMemory",
    L"reserved", // L"EfiUnusableMemory",
    L"ACPI data",// L"EfiACPIReclaimMemory",
    L"ACPI NVS", // L"EfiACPIMemoryNVS",
    L"reserved", // L"EfiMemoryMappedIO",
    L"reserved", // L"EfiMemoryMappedIOPortSpace",
    L"reserved", // L"EfiPalCode",
    L"usable",   // L"EfiPersistentMemory",
    L"usable",   // L"EfiMaxMemoryType"
};

const CHAR16 *
memory_type_to_str_OS_view(UINT32 type)
{
    if (type > sizeof(memory_types_OS_view)/sizeof(CHAR16 *))
        return L"Unknown";

    return memory_types_OS_view[type];
}

And finally we need to modify our program to glue adjacent regions with the same type together if the full flag is not set:

EFI_MEMORY_DESCRIPTOR* desc = MemoryMap;
EFI_MEMORY_DESCRIPTOR* next_desc;
int i = 0;
while ((UINT8 *)desc < (UINT8 *)MemoryMap + MemoryMapSize) {
  UINTN PAGE_SIZE = 4096;
  UINTN mapping_size =(UINTN) desc->NumberOfPages * PAGE_SIZE;

  UINT64 Start = desc->PhysicalStart;

  next_desc = (EFI_MEMORY_DESCRIPTOR *)((UINT8 *)desc + DescriptorSize);
  if (!full) {
    while ((UINT8 *)next_desc < (UINT8 *)MemoryMap + MemoryMapSize) {
      mapping_size =(UINTN) desc->NumberOfPages * PAGE_SIZE;
      if ((desc->PhysicalStart + mapping_size) == (next_desc->PhysicalStart)) {

        if (desc->Type != next_desc->Type) {
          if (StrCmp(memory_type_to_str_OS_view(desc->Type),
                     memory_type_to_str_OS_view(next_desc->Type)))
            break;
          }

          desc=next_desc;
          next_desc = (EFI_MEMORY_DESCRIPTOR *)((UINT8 *)next_desc + DescriptorSize);
      } else {
          break;
      }
    }
  }

  if (full) {
    CHAR16 str[ATTRIBUTE_STR_SIZE];
    Print(L"[#%02d] Type: %s  Attr: %s\n", i++,
      memory_type_to_str(desc->Type), memory_attrs_to_str(str, desc->Attribute));
    Print(L"      Phys: %016llx-%016llx\n", Start, Start + mapping_size - 1);
  }
  else {
    Print(L" [mem: %016llx-%016llx] %s\n", Start, desc->PhysicalStart + mapping_size - 1,
      memory_type_to_str_OS_view(desc->Type) );
  }

  desc = next_desc;
}

Build program and copy it to UEFI folder. If we run in with the full option, everything would be like the last time:

FS0:\> MemoryInfo.efi full
[#00] Type: EfiBootServicesCode  Attr:  UC WC WT WB
      Phys: 0000000000000000-0000000000000FFF
[#01] Type: EfiConventionalMemory  Attr:  UC WC WT WB
      Phys: 0000000000001000-000000000009FFFF
[#02] Type: EfiConventionalMemory  Attr:  UC WC WT WB
      Phys: 0000000000100000-00000000007FFFFF
[#03] Type: EfiACPIMemoryNVS  Attr:  UC WC WT WB
      Phys: 0000000000800000-0000000000807FFF
[#04] Type: EfiConventionalMemory  Attr:  UC WC WT WB
      Phys: 0000000000808000-000000000080FFFF
[#05] Type: EfiACPIMemoryNVS  Attr:  UC WC WT WB
      Phys: 0000000000810000-00000000008FFFFF
...

But if we run it without the full option, we will get a map similar to the that kernel displays in its boot log:

FS0:\> MemoryInfo.efi
 [mem: 0000000000000000-000000000009FFFF] usable
 [mem: 0000000000100000-00000000007FFFFF] usable
 [mem: 0000000000800000-0000000000807FFF] ACPI NVS
 [mem: 0000000000808000-000000000080FFFF] usable
 [mem: 0000000000810000-00000000008FFFFF] ACPI NVS
 [mem: 0000000000900000-00000000078EEFFF] usable
 [mem: 00000000078EF000-0000000007B6EFFF] reserved
 [mem: 0000000007B6F000-0000000007B7EFFF] ACPI data
 [mem: 0000000007B7F000-0000000007BFEFFF] ACPI NVS
 [mem: 0000000007BFF000-0000000007EF3FFF] usable
 [mem: 0000000007EF4000-0000000007F77FFF] reserved
 [mem: 0000000007F78000-0000000007FFFFFF] ACPI NVS
 [mem: 00000000FFC00000-00000000FFFFFFFF] reserved

Compare it with the actual kernel output:

BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable
BIOS-e820: [mem 0x0000000000100000-0x00000000007fffff] usable
BIOS-e820: [mem 0x0000000000800000-0x0000000000807fff] ACPI NVS
BIOS-e820: [mem 0x0000000000808000-0x000000000080ffff] usable
BIOS-e820: [mem 0x0000000000810000-0x00000000008fffff] ACPI NVS
BIOS-e820: [mem 0x0000000000900000-0x00000000078eefff] usable
BIOS-e820: [mem 0x00000000078ef000-0x0000000007b6efff] reserved
BIOS-e820: [mem 0x0000000007b6f000-0x0000000007b7efff] ACPI data
BIOS-e820: [mem 0x0000000007b7f000-0x0000000007bfefff] ACPI NVS
BIOS-e820: [mem 0x0000000007bff000-0x0000000007ef3fff] usable
BIOS-e820: [mem 0x0000000007ef4000-0x0000000007f77fff] reserved
BIOS-e820: [mem 0x0000000007f78000-0x0000000007ffffff] ACPI NVS
BIOS-e820: [mem 0x00000000ffc00000-0x00000000ffffffff] reserved

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