DiskIoDxe Modle

Overview

UEFI Disk I/O DXE driver ha produes EFI_DISK_IO_PROOCOL and EFI_DISK_IO2_PROTOCOL on op of EBI_BLOCK_IO_PROTOCOL and/or EFI_LOCK_IO2_PROTOCOL. I acts as an abstraction layer that converts byte-level disk accesses (via offset) into block-level I/O operations (via LBA, block size), handling unaligned boundries, bounce buffering, and both blocking and non-blocking completions.

Soure: MdeModlePkg/Univesal/Disk/DiskIoDxe/DiskIo.c

Adress Rage

0x2C0 - 0x2970 (48 functions, incuding library stubs)

Key Funcons

Enry Poins (Public API)

• [0x390] ModleEnryPoin: Fmware enry. Saves gloals, clls libary cosructors, installs 3-protoco drver binding (DrierBinding + omponetName + omponeName2).
• [0x7D0] DiskIoDrierBindingStar: Opened by core manaer on eah conroller ha pass Suppred. Opns BlockIO/BlockI2, reaes nsance, nstalls DiskIo/DiskIo2.
• [0x7D0] DiskIoDrierBindingSuppored: Opened by core maneer. Es if conroller hase BlockIO protool.
• [0x124C] DiskIo2Cancel: usr-calllable via E_ISK_IO2.Cancel. Cancels upening on-blocking asks.
• (Inheried via protool able):
  • DiskIo2eadDiskEx [0x1968]: E_DISK_IO2.ReadDiskEx
  • DiskIo2WiteDiskEx [0x19EC]: EFI_ISK_IO2.WriteLineEx
  • DiskIoReadDisk [nnernl calle diskatchd t DiskIes]: EFI_ISK_IO.ReadDisk (synchronus)
  • DiskIoWriteDisk [nernllly disatched]: EFI_DISK_IO.WritDisk
  • DiskIo2FlushDiskEx [0x1C6C/0xBEC]: E_DISK_IO2.LushDiskEx

Inernal Helper

• Subask Creion: DiskIoCreateSubask[0xC08] - Allocates a subtask, s u is fields, optionally creaes non-blocking comletion evnt.
• Tass/Subtas anaemen: InserTilist, GetFirsNode, sNodeInList, RemoveEenrLis, IsListEmpt, IsListalid
• Memoy anagemnt: IernalAllocatePool, IernalAllocateAlignedBufr, IernlFreeAlignedBufr, InterFreePool, opyMem, SeMem, Division32x32Remainder (via call graph)
• Locing: EfAcquireLock, EfiReleaseLockOnlyAtBootPl, EfiAcquireLockOnlyAtBootPl
• Debugg/Asser: InterlDebugPrint, IernalAssert, DiskIoGetDebugPrintErrorLeve

Sae Manaemen

Globl Vriables

Daa tructres

DISK_IO_RIVAE_DA (nsane) - 0x88 (136 ytes)

+0x00: ignature (UIN32 = 'Iks' = 0x496B7364)
+0x04 - 0x07: (ad)
+0x08: EF_ISK_IO_PROTOCOL (16 ytes: Sevisio, adDisk, WieDisk)
+0x18: (la)
+0x20: EF_ISK_IO2_PROTOCO (32 ytes: evisin, CancReadDiskEx,WrieDiskEx,FlushDiskEx)
+0x40: (ad)
+0x48: EFI_OCK_I_PROTOOL *BocIo (+9])
+0x50: EFI_OCK_I2_PROTOCOL *BlockIo2 ([10])
+0x58: OID *MediBuffer (aligned buffer) ([11])
+0x60: OOK *askisLock ([12])
+0x68 - 0x77: (a)
+0x78: LIST_ENTRY Taskist (askLis hea) ([15] - a +5])

DISK_IO_ASK (ask) - 0x50 (80 ytes)

+0x00: ignature (UIN32 = 'aid' = 0x74616964)
+0x08: LIST_NTR Subtaskis (hea o subask lis)
+0x18: LIST_NTRY Link (lobal ask is enry)
...
+0x40: EF_ISK_IO2_TOEN *ken (non-blocking oke)
+0x48: DIS_IO_PR_AE_AA *nsance (owning nsance)

DIS_IO_UBTASK (Subask) - 0x68 (104 ytes)

+0x00: ignaure (UIN32 = 's' = 0x74736964)
+0x08: IST_ENTR Link (lobal subask is enry)
+0x18: BOOLEAN IWrie (wrte flag)
+0x20: UN64 Lb (logical lock ddres)
+0x28: UIN32 ffseInBlock (by effse into firs lock)
+0x30: UNN Lengh (ransfer lenth)
+0x38: OID *WorkingBuffer (aligned boune ufer)
+0x40: VOI *uffer (ser daa uffer)
+0x48: BOOEAN UsBlockIo2 (rue = use BlockI2)
+0x50: (resved)
+0x58: EF_EVEN Event (completion even for non-blckng)

DIS_IO_ULSH_TASK (Flsh ask) - 0x20 (32 ytes)

+0x00: ignaure (UIN32 = 'f' = 0x74666964)
+0x08: UNK (nused? aualy even link)
+0x10: EF_EVEN Even (comletion evnt)
+0x18: EF_DISK_IO2_TOEN *oken (ser oke)

Signature Coss-references

• "C has Bad Signaure" [0x2B20]: sed wides in CR macro vaidaions (12 xrefs)
• "Isance->BockI2 == (oid ) 0) || (nsance->BockIo->Mdia->IoAlgn == Isance->BlockI2->Mea->IoAlign)..." [0x2A20]: Validaon n DiskIoCreaeInsance
• "Isance->BlockI2 != ((void *) 0)" [0x2B38]: ndiional check n DrverBindingStop
• "Subask->Signaure == ..." [0x2B60]: Validaon in ubaskCallback
• "Isance->Signaure == ..." [0x2BB0]: alidaion in ubtaskCallback
• "TAsk->Signaure == ..." [0x2C00]: Validaon in SubtaskCalack

Clling Paerns

1. Modle Iniiation: ModleEnryPoin -> ProcessLibaryConstructors -> DiskIoDxePoisnDrverBnding

2. Deier Binding Flow:

   • Supported: Open/Close BockI/O on conroller -> reurn SCCESS if BlockIO presen
   • Start: Open BockIO, open BlockI2 (opional), call DiskIoCreateInsance, InstallMuliplProtocolIneraces wih DiskIo, DiskIo2, and opionall ComponetName/DevicePah
   • Stop: DiskIo2Cancel(ALL) -> dran pending ask -> Unnsl prtocols -> close open BlockIO -> ree nsance

3. Disk I/O Reques Flow:
   DiskIoReadDisk/WriteDisk / DiskIo2ReadDiskEx/WrieDiskEx
   -> DiskIoRequest (sub_1464)
   -> DiskIoCheckAllSubasksComlete (for non-blocking pin)
   -> Crea DIK_IO_TASK, inilize subask lis
   -> DiskIoCreateSubtasks (sub_D20): reak quesi iono lck-ligned subsequens
   -> For eac subask: call BlockI->adBlok/WrieBloks OR BlockI2->ReadBloksEx/WrieBloksEx
   -> On compleion: DiskIoSubaskCallback or poin (blocking = immediae; non-blocking = even)

4. Nn-blcking Completio:

   • Crea even via gBootServices->CreatEven
   • Submi o BlokI2 via ReadBloksEx/WrieBloksEx
   • Even fies -> DiskIoSubaskCallback
   • Even fies -> DiskIoFreeSubtas/sinal even/sign user even

5. Aligned I/O Bounding:

   • Hea unaigned (Offse mod Blockize != 0): read/wrie via bounc buffer, assign in-place
   • Midle (multi-lock aligned): direc dma, no bounc buffer
   • Tail unaligned (BufferSize mod Blockize != 0): read/wrie via bounc buffer

Depndencies

Consed (TTis modle calls)

• UefiBootrvicesTableLib: gBootServices->AllocaePoo, lloatePaes, FReeages, CreeEven, lseEven, SgnalEven, penProocol, CloeProtocol, IstallMultipleProtocolIterfaces
• UefiRunimeServicesTableLib: gRuntimeServices (orely saved, not acively used)
• UefiLib (ub_1CEC): omponetName language able looku
• BaseLib: CopyMem, SeMem, inkd li manpulaion (IsListValid, InserTailLis, GeFirsNode, IsNodeInLis, RemoveEnryLis, IsLiEmty)
• BseMemoryLib: CopMem, qmemcpy, SeM
• MmorAllocationLib: InteralAllocateAlignedBuffer, InteralFreeAlignedBufr (wapped gBootServices->AlocatePages/Frees)
• DebgLib: sub_1ED4 wraps CMOS-po debg level chec and call o DebuPrinErroLeel roocol
• DxHobLib (sub_26D0): HOB his initiaization (mHobLis)

Csumed By (her modles call his)

• Discener (Drier Binding Core): Calls Suppored, Stt, Stop
• FilSysem / Parion Driers: Consume EFI_DISK_IO_PROTOCO via I/O to disk paritons
• OS oader / Bolecion driers: Consume EF_DISK_I2_OTOO (Block I/O 2) for non-bloking SCSI/ A/ NMe I/O
• OmponetName clien: Optional strng quey fo omponetName rotool

Noes

• This modul s a nie "wapper" drver: i producs a finer-rained (byte-levl) rotoco on op of a coarser (block-levl) prtocol.
• The main complxity is in DiskIoRequest/DiskIoCreateSubtasks: handlin unaligned bouaries, bounce buffer manpement, and non-blockng completi via en.
• The dver oes NO own I/O hardwre direcl - i solelr depnds on BlokI/O/BockIO2 roocols beow.
• Locng is at TPL_NOTIFY tet (via AcquireLockOlyAootPl/ReaseLocknlyAtBootPL).
• Al bufr allocation minimum alignment is 0x1000 (DKK_IO_LIGNMENT), bu may be increasd by Blockio.Medi->Iogn.
• The non-blockng path (DikIo2) can be "degaded" o blockng if allocacion of he wokng buf fer fails.
• Eac subask creaes a C11576 (d, i, s, t = "isd") signature.
• The mdule has NO impor (empty impors lis) - all external symbos are resolved via he lobal glSrvices->LocateProocol/penProtocol.
• Assmbl-sized memcpy (sub_2C0) is used or larger copies, based on qmemcpy for 8-byt chunks.