![]() EFI Pre-EFI Initialization Core Interface Specification v0.91.EFI Firmware File System Specification v0.9.EFI Driver Execution Environment Core Interface Spec v0.91.EFI S3 Resume Boot Path Specification v0.9.The most relevant EFI documents for this post are: Recent OS X versions are 64-bit only so this feature is not used anymore. It was followed by the UEFI (Unified Extensible Firmware Interface) managed by the Unified EFI Forum ( Apple forked from EFI v1.10 (Dec 2002) and introduced some changes, for example support for fat EFI binaries (support for both 32-bit and 64-bit systems). 1 – Relevant documentationĮFI (Extensible Firmware Interface) specification was published by Intel. ![]() The script is stored in physical memory and this is the main reason why the Dark Jedi attack described at CCC 2014 is possible. It is on the DXE phase that the boot script is created on normal boot path, meaning that the script is created once on a normal boot. The DXE phase is where most of the initialization work is performed (there are some 150 DXE drivers in EFI firmware), so this is the main reason why the boot script is important for a fast resume from sleep cycle (EFI documents from 2003 describe that Microsoft requires a maximum of 0.5 seconds for the S3 resume). The following picture from the EFI documentation describes the differences between the normal and S3 boot phases.Ī description of each phase – SEC (Security), PEI (Pre-EFI Initialization), DXE (Driver Execution Environment), BDS (Boot Device Selection) – can be found here. ![]() Sample contents of a boot script will be shown later. Script execution will be faster than restarting and reinitializing all the necessary drivers, as it happens in a regular boot path. Instead of reinitializing everything again, the boot script will restore the machine to the same configuration without executing again the whole DXE phase, which is time consuming.
0 Comments
Leave a Reply. |