![]() In order to extract the FVM there are two open source options: We are primarily interested in the Firmware Volume at this time. The Firmware Volume contains a complete image while the Firmware Capsule contains incremental updates. scap (Signed Capsule) which contains a Firmware Capsule. fd (Flash Descriptor) which contains a Firmware Volume (FVM), and. Like other vendors, Apple tends to use two file extensions for UEFI firmware. Alternatively, maintains a repository of firmware images on Github. the firmware for an iMac is located at EFI/APPLE/FIRMWARE/IM171_0110_B00.fd). Apple has been nice to us by leaving a copy on the ESP under the path EFI/APPLE/FIRMWARE (e.g. The first step to working with UEFI firmware is to get the firmware (obvious, I know). I plan to cover that work in a future blog post but for now suffice it to say that I was interested in better understanding what happens before macOS is executed hence the need to investigate UEFI. My target for this work is a MacBook Pro with TouchBar. ![]() Another point of note is that UEFI may expose services during boot, at runtime, or both. Through this paradigm, vendors are able to use the same set of custom interfaces from all of their applications since the protocols are defined in a global namespace. Vendors (operating system, hardware, or platform) may also expose functionality in addition to that provided by UEFI through a protocol-interface paradigm. This is a large, and much appreciated, departure from the interrupt driven programming interface used by BIOS. The UEFI specification states that the ESP should be formatted as a FAT-32 partition.įrom a developers perspective, UEFI manifests itself as a C API designed around tables. Typically the ESP is where you’ll find an OS loader but you may also find other assets such as firmware images, configuration files, and custom UEFI applications. The first partition on the device is referred to as the EFI System Partition (ESP) and may contain almost anything. UEFI is natively capable of reading from devices, such as hard drives and flash drives, partitioned using the GPT scheme. The UEFI specification borrows heavily from concepts and constructs present in the Microsoft Windows environment for example, UEFI binaries are very closely related to Microsoft’s PE-32/64 binary format. A Crash Course in UEFIĪs mentioned previously, UEFI is intended to replace the BIOS as well as provide an environment for developers to create pre-OS applications and drivers. ![]() This blog post discusses some of the basics of UEFI and tools available. In order to better understand another target I am reversing it became clear that I needed to learn more about UEFI and reverse some aspects of it. UEFI is defined as a specification with a corresponding reference implementation named Tianocore. It was developed as a replacement for the BIOS and provides an environment where developers can create applications and drivers for use before the operating system is loaded. Drop your BIOS(es) where needed.As Wikipedia and its own Forum says, UEFI (Unified Extensible Firmware Interface) is a software layer situated between the operating system and platform firmware.
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