Add FDF lesson draft

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

1 files changed, 669 insertions, 0 deletions

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+When we build OVMF image the final result is a flash image.
+
+Last messages in the build log provide some information about image generation:
+```
+$ build --platform=OvmfPkg/OvmfPkgX64.dsc --arch=X64 --buildtarget=RELEASE --tagname=GCC5
+
+<...>
+
+Fd File Name:OVMF (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x40000
+   Region Name = DATA
+
+Generate Region at Offset 0x40000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x41000
+   Region Size = 0x1000
+   Region Name = DATA
+
+Generate Region at Offset 0x42000
+   Region Size = 0x42000
+   Region Name = None
+
+Generate Region at Offset 0x84000
+   Region Size = 0x348000
+   Region Name = FV
+
+Generating FVMAIN_COMPACT FV
+
+Generating PEIFV FV
+###
+Generating DXEFV FV
+########
+Generate Region at Offset 0x3CC000
+   Region Size = 0x34000
+   Region Name = FV
+
+Generating SECFV FV
+#
+Fd File Name:OVMF_VARS (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x40000
+   Region Name = DATA
+
+Generate Region at Offset 0x40000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x41000
+   Region Size = 0x1000
+   Region Name = DATA
+
+Generate Region at Offset 0x42000
+   Region Size = 0x42000
+   Region Name = None
+
+Fd File Name:OVMF_CODE (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x348000
+   Region Name = FV
+
+Generate Region at Offset 0x348000
+   Region Size = 0x34000
+   Region Name = FV
+
+Fd File Name:MEMFD (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/MEMFD.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x6000
+   Region Name = None
+
+Generate Region at Offset 0x6000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x7000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x8000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x9000
+   Region Size = 0x2000
+   Region Name = None
+
+Generate Region at Offset 0xB000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0xC000
+   Region Size = 0x1000
+   Region Name = None
+Padding region starting from offset 0xD000, with size 0x3000
+
+Generate Region at Offset 0xD000
+   Region Size = 0x3000
+   Region Name = None
+
+Generate Region at Offset 0x10000
+   Region Size = 0x10000
+   Region Name = None
+
+Generate Region at Offset 0x20000
+   Region Size = 0xE0000
+   Region Name = FV
+
+Generate Region at Offset 0x100000
+   Region Size = 0xC00000
+   Region Name = FV
+
+GUID cross reference file can be found at /<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/Guid.xref
+
+FV Space Information
+SECFV [13%Full] 212992 (0x34000) total, 27904 (0x6d00) used, 185088 (0x2d300) free
+PEIFV [11%Full] 917504 (0xe0000) total, 102824 (0x191a8) used, 814680 (0xc6e58) free
+DXEFV [22%Full] 12582912 (0xc00000) total, 2879400 (0x2befa8) used, 9703512 (0x941058) free
+FVMAIN_COMPACT [27%Full] 3440640 (0x348000) total, 935208 (0xe4528) used, 2505432 (0x263ad8) free
+
+- Done -
+```
+
+This image process is initiated because the package DSC file `OvmfPkg/OvmfPkgX64.dsc` has `FLASH_DEFINITION` identifier defined:
+```
+[Defines]
+  ...
+  FLASH_DEFINITION               = OvmfPkg/OvmfPkgX64.fdf
+```
+
+The referenced FDF file should be formatted according to the [EDK II Flash Description (FDF) File Specification](https://edk2-docs.gitbook.io/edk-ii-fdf-specification/).
+This file defines the flash images generated in the end of the build.
+
+Each image is called `Flash Device Image` and is defined by the `[FD.<name>]` section.
+
+For example `OvmfPkg/OvmfPkgX64.fdf` has 4 such sections:
+```
+[FD.OVMF]
+[FD.OVMF_VARS]
+[FD.OVMF_CODE]
+[FD.MEMFD]
+```
+Each of these sections leads to the `Flash Device Image` generation:
+```
+$ find Build/OvmfX64/RELEASE_GCC5/FV/ -name "*.fd"
+Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd
+Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd
+Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd
+Build/OvmfX64/RELEASE_GCC5/FV/MEMFD.fd
+```
+You can see how they are generated in the log above:
+```
+$ build --platform=OvmfPkg/OvmfPkgX64.dsc --arch=X64 --buildtarget=RELEASE --tagname=GCC5
+
+<...>
+
+Fd File Name:OVMF (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd)
+
+<...>
+
+Fd File Name:OVMF_VARS (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd)
+
+<...>
+
+Fd File Name:OVMF_CODE (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd)
+
+<...>
+
+Fd File Name:MEMFD (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/MEMFD.fd)
+
+<...>
+
+GUID cross reference file can be found at /<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/Guid.xref
+
+FV Space Information
+SECFV [13%Full] 212992 (0x34000) total, 27904 (0x6d00) used, 185088 (0x2d300) free
+PEIFV [11%Full] 917504 (0xe0000) total, 102824 (0x191a8) used, 814680 (0xc6e58) free
+DXEFV [22%Full] 12582912 (0xc00000) total, 2879400 (0x2befa8) used, 9703512 (0x941058) free
+FVMAIN_COMPACT [27%Full] 3440640 (0x348000) total, 935208 (0xe4528) used, 2505432 (0x263ad8) free
+
+- Done -
+```
+
+The `Flash Device Image` is intendend for usage on a specific flash device, therefore the following tokens are mandatory for each FD section:
+```
+BaseAddress   = <...>
+Size          = <...>
+ErasePolarity = <...>
+```
+- `BaseAddress` field defines an address at which flash image would be mapped to the CPU memory
+- `Size` field defines the size of the flash image
+- `ErasePolarity` field defines how to fill not used space in flash image (with 0 or 1)
+
+Most often the following two tokens are also defined:
+```
+BlockSize = <...>
+NumBlocks = <...>
+```
+This tokens define block structure of a flash chip. If they are present this rule should be satisfied:
+```
+BlockSize * NumBlocks = Size
+```
+
+Let's look at the values for these tokens in the `OvmfPkg/OvmfPkgX64.fdf` file. Most of the tokens there are defined via defines. For their definition we should look in the `[Defines]` section:
+```
+[Defines]
+!include OvmfPkgDefines.fdf.inc
+```
+As you can see this section uses `!include` directive to abstract all defines in the separate file. If you look at this file, you'll see that it contains some `if...endif` logic depending on the value of `FD_SIZE_IN_KB` variable for various configurations. In our case `OvmfPkg/OvmfPkgX64.dsc` defines `FD_SIZE_IN_KB = 4096`:
+```
+[Defines]
+  ...
+  !ifdef $(FD_SIZE_1MB)
+    DEFINE FD_SIZE_IN_KB           = 1024
+  !else
+  !ifdef $(FD_SIZE_2MB)
+    DEFINE FD_SIZE_IN_KB           = 2048
+  !else
+  !ifdef $(FD_SIZE_4MB)
+    DEFINE FD_SIZE_IN_KB           = 4096
+  !else
+    DEFINE FD_SIZE_IN_KB           = 4096
+  !endif
+```
+Therefore we use the following defines from the `OvmfPkg/OvmfPkgDefines.fdf.inc` file:
+```
+DEFINE BLOCK_SIZE        = 0x1000
+
+!if $(FD_SIZE_IN_KB) == 4096
+DEFINE VARS_SIZE         = 0x84000
+DEFINE VARS_BLOCKS       = 0x84
+DEFINE VARS_LIVE_SIZE    = 0x40000
+DEFINE VARS_SPARE_SIZE   = 0x42000
+
+DEFINE FW_BASE_ADDRESS   = 0xFFC00000
+DEFINE FW_SIZE           = 0x00400000
+DEFINE FW_BLOCKS         = 0x400
+DEFINE CODE_BASE_ADDRESS = 0xFFC84000
+DEFINE CODE_SIZE         = 0x0037C000
+DEFINE CODE_BLOCKS       = 0x37C
+DEFINE FVMAIN_SIZE       = 0x00348000
+DEFINE SECFV_OFFSET      = 0x003CC000
+DEFINE SECFV_SIZE        = 0x34000
+!endif
+
+DEFINE MEMFD_BASE_ADDRESS = 0x800000
+```
+
+Now we can calculate the token values for each `Flash Device Image` in the `OvmfPkg/OvmfPkgX64.fdf`:
+```
+[FD.OVMF]
+BaseAddress   = $(FW_BASE_ADDRESS)   # 0xFFC00000
+Size          = $(FW_SIZE)           # 0x00400000
+ErasePolarity = 1
+BlockSize     = $(BLOCK_SIZE)        # 0x1000
+NumBlocks     = $(FW_BLOCKS)         # 0x400
+
+...
+
+[FD.OVMF_VARS]
+BaseAddress   = $(FW_BASE_ADDRESS)   # 0xFFC00000
+Size          = $(VARS_SIZE)         # 0x84000
+ErasePolarity = 1
+BlockSize     = $(BLOCK_SIZE)        # 0x1000
+NumBlocks     = $(VARS_BLOCKS)       # 0x84
+
+...
+
+[FD.OVMF_CODE]
+BaseAddress   = $(CODE_BASE_ADDRESS) # 0xFFC84000
+Size          = $(CODE_SIZE)         # 0x0037C000
+ErasePolarity = 1
+BlockSize     = $(BLOCK_SIZE)        # 0x1000
+NumBlocks     = $(CODE_BLOCKS)       # 0x37C
+
+...
+
+[FD.MEMFD]
+BaseAddress   = $(MEMFD_BASE_ADDRESS) # 0x800000
+Size          = 0xD00000
+ErasePolarity = 1
+BlockSize     = 0x10000
+NumBlocks     = 0xD0
+```
+
+Here you can see that `BlockSize * NumBlocks = Size` formula is correct for every FD.
+
+And you can verify that size of the files matches the `Size` field values:
+```
+$ printf "%x\n" `stat -c "%s"  Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd`
+400000
+$ printf "%x\n" `stat -c "%s"  Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd`
+37c000
+$ printf "%x\n" `stat -c "%s"  Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd`
+84000
+$ printf "%x\n" `stat -c "%s"  Build/OvmfX64/RELEASE_GCC5/FV/MEMFD.fd`
+d00000
+```
+
+Couple of words about the images itself. Remember what commands we've used to launch QEMU:
+```
+qemu-system-x86_64 \
+  -drive if=pflash,format=raw,file=Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd \
+  ...
+
+qemu-system-x86_64 \
+  -drive if=pflash,format=raw,readonly,file=Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd \
+  -drive if=pflash,format=raw,file=Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd \
+  ...
+```
+If you look closely to the `OVMF_CODE.fd` and `OVMF_VARS.fd` you could notice that 
+```
+[FD.OVMF_VARS].BaseAddress + [FD.OVMF_VARS].Size = [FD.OVMF_CODE].BaseAddress
+[FD.OVMF_CODE].BaseAddress + [FD.OVMF_CODE].Size = 0x100000000
+
+[FD.OVMF].BaseAddress + [FD.OVMF].Size = 0x100000000
+
+[FD.OVMF].BaseAddress == [FD.OVMF_VARS].BaseAddress
+```
+Simply speaking the `[FD.OVMF]` image is just the `[FD.OVMF_VARS]` image followed by the `[FD.OVMF_CODE]` image.
+
+# Regions
+
+`Flash Device Image` consists of regions. It is necessary to have at least one region in a `Flash Device Image`.
+
+The most simple definition of region is:
+```
+Offset|Size
+```
+For example:
+```
+0x500|0x600
+```
+This is a region that starts at offset 0x500 with a size of 0x600. It is important to note that the final `Flash Device Image` size is defined by its regions and not by the `Size` token value.
+
+If we want to, we can assign PCDs to the region offset/size values:
+```
+Offset|Size
+TokenSpaceGuidCName.PcdOffsetCName | TokenSpaceGuidCName.PcdSizeCName
+```
+For example:
+```
+0x500|0x600
+gEfiMyTokenSpaceGuid.PcdFlashRegionBaseAddress | gEfiMyTokenSpaceGuid.PcdFlashRegionSize
+```
+This way the build system will automatically override these PCD with our values. Off course these PCDs `gEfiMyTokenSpaceGuid.PcdFlashRegionBaseAddress` and `gEfiMyTokenSpaceGuid.PcdFlashRegionSize` must be defined in the DEC file.
+They can be of types `PcdsFixedAtBuild` or `PcdsPatchableInModule`, but not dynamic!
+
+Another thing that we would want to add to our region definition is a region type:
+```
+Offset|Size
+TokenSpaceGuidCName.PcdOffsetCName | TokenSpaceGuidCName.PcdSizeCName
+  RegionType
+```
+
+If `RegionType` is not present, it is considered `None` and edk2 doesn't touch this region data. It can be usefull, for example, if we define a space in flash reserved for logs.
+If `RegionType` is present, it can be one of the following types: `FV`, `DATA`, `FILE`, `INF` or `CAPSULE`.
+
+Here are some exmplanation for the most common ones: `FV`, `DATA`, `FILE`:
+
+## FV region
+
+The `FV` region type is a pointer to some `Firmware Volume`. `Firmware Volume` (`FV`) is a data block next level lower than `Flash Device Image` (`FD`).
+
+Example:
+```
+0x000000|0x0C0000
+FV = FVMAIN
+```
+In this case FDF must define the section `[FV.FVMAIN]`.
+
+We will look at the `Firmware Volumes` in the next lesson.
+
+## DATA region
+
+In the case of a `DATA` region we immediately define the data inside the region via initialized array:
+```
+0x0|0x50
+DATA = {
+  0xDE, 0xAD, 0xBE, 0xEF
+}
+```
+This would give us a region with such data:
+```
+00000000  de ad be ef ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
+00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
+*
+00000050
+```
+
+If you don't want to pollute FDF file, you can create some file and put data text into it:
+```
+0x0|0x50
+DATA = {
+  !include mydata.txt
+}
+```
+```
+$ cat mydata.txt
+0xDE, 0xAD, 0xBE, 0xEF
+```
+
+## FILE region
+
+FILE region is a pointer to a binary file that will be loaded into the flash device.
+
+For example create a simple file with text:
+```
+$ cat "hello!" > hello.txt
+```
+And define this region:
+```
+0x0|0x50
+FILE = hello.txt
+```
+In the final flash image it would look like this:
+```
+00000000  68 65 6c 6c 6f 21 0a ff  ff ff ff ff ff ff ff ff  |hello!..........|
+00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
+*
+00000050
+```
+
+# OVMF `Flash Device Image` regions
+
+Let's look closely to the OVMF `Flash Device Image` regions.
+
+Start with `[FD.OVMF_VARS]` Flash Device Image:
+```
+[FD.OVMF_VARS]
+...
+!include VarStore.fdf.inc
+```
+As you can see all of its regions are defined in the `OvmfPkg/VarStore.fdf.inc` file.
+
+If we remember that `FD_SIZE_IN_KB` is equal to `4096` in our case we can simplify `OvmfPkg/VarStore.fdf.inc` content to this:
+```
+0x00000000|0x00040000 # NV_VARIABLE_STORE
+DATA = {
+  ...
+}
+0x00040000|0x00001000 # NV_EVENT_LOG
+0x00041000|0x00001000 # NV_FTW_WORKING
+DATA = {
+  ...
+}
+0x00042000|0x00042000 # NV_FTW_SPARE
+```
+
+Here we have two empty regions, and two regions initialized with DATA arrays.
+
+Now we can see how FDF content corresponds to build log output:
+```
+Fd File Name:OVMF_VARS (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_VARS.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x40000
+   Region Name = DATA
+
+Generate Region at Offset 0x40000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x41000
+   Region Size = 0x1000
+   Region Name = DATA
+
+Generate Region at Offset 0x42000
+   Region Size = 0x42000
+   Region Name = None
+```
+
+The `[FD.OVMF_CODE]` flash device image consists of two Firmware Volumes (for the defines definition look at the `OvmfPkg/OvmfPkgDefines.fdf.inc` content):
+```
+[FD.OVMF_CODE]
+...
+0x00000000|$(FVMAIN_SIZE)        # 0x00000000|0x00348000
+FV = FVMAIN_COMPACT
+
+$(FVMAIN_SIZE)|$(SECFV_SIZE)     # 0x00348000|0x34000
+FV = SECFV
+```
+And here is example of build log output for this FD from the start of the lesson:
+```
+Fd File Name:OVMF_CODE (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF_CODE.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x348000
+   Region Name = FV
+
+Generate Region at Offset 0x348000
+   Region Size = 0x34000
+   Region Name = FV
+```
+
+Finally `[FD.OVMF]`:
+```
+[FD.OVMF]
+...
+!include VarStore.fdf.inc
+
+$(VARS_SIZE)|$(FVMAIN_SIZE)
+FV = FVMAIN_COMPACT
+
+$(SECFV_OFFSET)|$(SECFV_SIZE)
+FV = SECFV
+```
+Which means:
+```
+0x00000000|0x00040000 # NV_VARIABLE_STORE
+DATA = {
+  ...
+}
+0x00040000|0x00001000 # NV_EVENT_LOG
+0x00041000|0x00001000 # NV_FTW_WORKING
+DATA = {
+  ...
+}
+0x00042000|0x00042000 # NV_FTW_SPARE
+
+$(VARS_SIZE)|$(FVMAIN_SIZE)      # 0x84000 | 0x00348000
+FV = FVMAIN_COMPACT
+
+$(SECFV_OFFSET)|$(SECFV_SIZE)    # 0x003CC000 | 0x34000
+FV = SECFV
+```
+The build log for this FD:
+```
+Fd File Name:OVMF (/<...>/edk2/Build/OvmfX64/RELEASE_GCC5/FV/OVMF.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x40000
+   Region Name = DATA
+
+Generate Region at Offset 0x40000
+   Region Size = 0x1000
+   Region Name = None
+
+Generate Region at Offset 0x41000
+   Region Size = 0x1000
+   Region Name = DATA
+
+Generate Region at Offset 0x42000
+   Region Size = 0x42000
+   Region Name = None
+
+Generate Region at Offset 0x84000
+   Region Size = 0x348000
+   Region Name = FV
+
+...
+
+Generate Region at Offset 0x3CC000
+   Region Size = 0x34000
+   Region Name = FV
+```
+
+# Creating `UefiLessonsPkg.fdf`
+
+If you want to, you can experiment with FDF in our `UefiLessonsPkg` package.
+
+For this add `FLASH_DEFINITION` define to the `UefiLessonsPkg/UefiLessonsPkg.dsc` file:
+```
+[Defines]
+  ...
+  FLASH_DEFINITION               = UefiLessonsPkg/UefiLessonsPkg.fdf
+
+...
+```
+And create file `UefiLessonsPkg/UefiLessonsPkg.fdf`. For example fill it with this content:
+```
+[FD.SimpleImage]
+BaseAddress   = 0x0
+Size          = 0x1000
+ErasePolarity = 1
+
+0x00|0x50
+```
+This would produce the following FD as a build result:
+```
+Fd File Name:SIMPLEIMAGE (/home/aladyshev/tiano/2021/edk2/Build/UefiLessonsPkg/RELEASE_GCC5/FV/SIMPLEIMAGE.fd)
+
+Generate Region at Offset 0x0
+   Region Size = 0x50
+   Region Name = None
+```
+You can look at its content with a help of `hexdump` utility:
+```
+$ hexdump /home/aladyshev/tiano/2021/edk2/Build/UefiLessonsPkg/RELEASE_GCC5/FV/SIMPLEIMAGE.fd
+0000000 ffff ffff ffff ffff ffff ffff ffff ffff
+*
+0000050
+```
+
+If regions would start not from the 0x0, the build system will automatically create a padding region. For example this config:
+```
+[FD.SimpleImage]
+BaseAddress   = 0x0
+Size          = 0x1000
+ErasePolarity = 1
+
+0x60|0x300
+```
+Would produce the following log:
+```
+Fd File Name:SIMPLEIMAGE (/home/aladyshev/tiano/2021/edk2/Build/UefiLessonsPkg/RELEASE_GCC5/FV/SIMPLEIMAGE.fd)
+Padding region starting from offset 0x0, with size 0x60
+
+Generate Region at Offset 0x0
+   Region Size = 0x60
+   Region Name = None
+
+Generate Region at Offset 0x60
+   Region Size = 0x300
+   Region Name = None
+```
+And hexdump output would look like this:
+```
+$ hexdump /home/aladyshev/tiano/2021/edk2/Build/UefiLessonsPkg/RELEASE_GCC5/FV/SIMPLEIMAGE.fd
+0000000 ffff ffff ffff ffff ffff ffff ffff ffff
+*
+0000360
+```
+
+You can define PCDs in the DEC file `UefiLessonsPkg/UefiLessonsPkg.dec`:
+```
+[PcdsFixedAtBuild]
+  ...
+  gUefiLessonsPkgTokenSpaceGuid.Region1Offset|0|UINT32|0x00000005
+  gUefiLessonsPkgTokenSpaceGuid.Region1Size|0|UINT32|0x00000006
+```
+And initialize them in FDF:
+```
+[FD.SimpleImage]
+BaseAddress   = 0x0
+Size          = 0x1000
+ErasePolarity = 1
+
+0x0|0x50
+gUefiLessonsPkgTokenSpaceGuid.Region1Offset | gUefiLessonsPkgTokenSpaceGuid.Region1Size
+```
+
+
+As a final example let's declare the region as DATA and initialize it:
+```
+[FD.SimpleImage]
+BaseAddress   = 0x0
+Size          = 0x1000
+ErasePolarity = 1
+
+0x0|0x50
+DATA = {
+  0xDE, 0xAD, 0xBE, 0xEF
+}
+```
+
+This would give us the following content in the final image:
+```
+$ hexdump /home/aladyshev/tiano/2021/edk2/Build/UefiLessonsPkg/RELEASE_GCC5/FV/SIMPLEIMAGE.fd -C
+00000000  de ad be ef ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
+00000010  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
+*
+00000050
+```