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SmmAccessPei Module Analysis

Module Information

Field Value
Module Name SmmAccessPei.efi
Index 0358
MD5 c85821f577b2bd2503af9491efa78481
SHA256 ee3db7e65870c79bb4d463ea5eb90951965d62f6d030cfd49c19c6cbf422a006
Architecture IA32 (32-bit)
Base Address 0xffd6bc7c
Image Size 0x1060 (4,192 bytes)

Segment Layout

Segment Start End Size Permissions
HEADER 0xffd6bc7c 0xffd6bedc 0x260 (608) ---
.text 0xffd6bedc 0xffd6c73c 0x860 (2,144) rx
.rdata 0xffd6c73c 0xffd6cbfc 0x4c0 (1,216) r
.data 0xffd6cbfc 0xffd6cc5c 0x60 (96) rw
.reloc 0xffd6cc5c 0xffd6ccdc 0x80 (128) r
GAP 0xffd6ccdc 0xffd6dc7c 0xfa0 (4,000) rw

Functions (18 total, 1 named, 17 unnamed originally)

Address Name Size Type
0xffd6bedc InternalCopyMemBackwards 0x3f Overlapping-safe memory copy
0xffd6bf3c SetMem 0x15 memset wrapper
0xffd6bf5c SetMem32Loop 0x1f Internal SetMem32 loop
0xffd6bf7c SetMem32 0x15 memset32 wrapper
0xffd6bf91 _ModuleEntryPoint 0x465 Module entry point / dispatcher
0xffd6c3f6 GetFirstHob 0x6e Get first HOB from PEI services
0xffd6c464 GetNextHobByType 0x45 Find next HOB by type (GUID extension)
0xffd6c4a9 GetNextGuidHob 0x3a Find next HOB by GUID
0xffd6c4e3 GetDebugInterface 0x31 Get debug protocol interface
0xffd6c514 DebugPrint 0x2a Debug message print
0xffd6c53e DebugAssert 0x1e Debug assert handler
0xffd6c55c AllocatePool 0x2a PEI pool allocation
0xffd6c586 CopyMem 0x71 CopyMem with validation
0xffd6c5f7 CompareGuid 0x5f GUID comparison
0xffd6c656 GetDebugErrorLevel 0x4f Get debug level from CMOS (0x4A)
0xffd6c6a5 ReadUnaligned64 0x2c 64-bit unaligned read
0xffd6c6d1 GetPeiServicesTable 0x32 Get PEI services from IDT
0xffd6c703 ReadIdtr 0x23 Read IDT register (SIDT)

Purpose

This PEIM provides the SMM Access PPI for Purley platforms. It performs the following:

  1. HOB Discovery: Locates two GUID HOBs:

    • gSmmAccessPrivateGuid -- contains TSEG reserved region descriptors
    • gSmmBaseHobGuid -- contains TSEG size, IED base/size, SMM base info

  2. SMM Region Management: Copies SMM reserved region descriptors from HOBs into private context and validates region count (max 4).

  3. PPI Installation: Installs EFI_PEI_SMM_ACCESS_PPI which exposes:

    • Open -- opens a specific SMRAM descriptor for access
    • Close -- closes a specific SMRAM descriptor
    • Lock -- locks a specific SMRAM descriptor permanently
    • GetCapabilities -- returns SMRAM descriptor capabilities

  4. Debug Output: Logs TSEG/IED/SMM base and size information.

Key Data

CMOS Debug Level Register (0x4A)

The debug error level is read from CMOS register 0x4A (via port 0x70/0x71):

  • 0x00: No debug output
  • 0x01: EFI_D_INFO / EFI_D_ERROR output
  • Values read through a special mechanism at memory 0xFDAF0490

Build Information

  • Platform: PurleySktPkg
  • Build: HR6N0XMLK / DEBUG_VS2015 / IA32
  • PDB: PurleySktPkg/Smm/SmmAccessPei/SmmAccessPei/DEBUG/SmmAccessPei.pdb

Source Files

File Description
SmmAccessPei.c Main module source
SmmAccessPei.h Module header with data structure definitions

IDA Database

IDB saved to original location:
/private/ajax/bios/HR650X_3647_AJAX_BIOS_ORIGINAL.pe_structured/pe_files/0358_SmmAccessPei_ee3db7e65870/SmmAccessPei.efi.i64