Stay updated with the latest U-Boot development news, features, tutorials, and community highlights.
We’ve just merged a fix in Concept for a particularly tricky memory corruption bug in the U-Boot sandbox environment. This bug was difficult to track down, so we wanted to share the story of the investigation and the solution. The Symptom: Mysterious Heap Corruption The problem first appeared as random and hard-to-reproduce memory corruption in […]
For a while now, U-Boot’s EFI application (efi_app) has been a handy tool, but with one noticeable difference between architectures: x86 could show things on the screen, while ARM was stuck in the dark. If you wanted a splash screen or a graphical boot menu in your ARM EFI app, you were out of luck. […]
Continuous Integration (CI) is the backbone of a large project like U-Boot, ensuring that every change is tested against a huge matrix of boards and configurations. While this comprehensive testing is vital for quality, it can also be time-consuming. When you’re focused on a specific feature, waiting for a full “world build” to complete can […]
The Flattened Image Tree (FIT) is at the heart of modern U-Boot booting, providing a flexible and verifiable way to package kernels, ramdisks, and devicetrees. A new series introduces a significant enhancement to how U-Boot processes FITs, enabling a powerful two-stage boot process. This allows a “load-only” FIT to configure the system (like setting up […]
As U-Boot’s support for hardware grows, so does the complexity of managing build configurations. A single board might require several build variations—for example, one with network support and one without, or a standard build versus one tailored for Android booting. Historically, managing these variations often meant duplicating large defconfig files, a maintenance headache waiting to […]
In the world of embedded systems, a Flattened Image Tree (FIT) is the standard way to package a bootable OS, typically bundling the kernel, a ramdisk, and the necessary devicetree (FDT) into a single, verifiable file. While convenient, this approach tightly couples the OS with its hardware description. But what if the OS and the […]
We’re excited to announce a significant new feature in U-Boot: a virtio-scsi driver. While U-Boot has long supported virtio-blk for block device access in virtualized environments, virtio-scsi offers greater flexibility, allowing a single virtio device to host multiple disks (LUNs) and supporting features like hotplug. This comprehensive 27-patch series, does more than just add a […]
The U-Boot boot process relies heavily on the Flattened Image Tree (FIT) format to package kernels, ramdisks, device trees, and other components. At the heart of this lies the fit_image_load() function, which is responsible for parsing the FIT, selecting the right images, and loading them into memory. Over the years, as more features like the […]
The integration of pytest with real boards (test.py) was written by Stephen Warren of Nvidia, some 9 years ago. It has certainly stood the test of time. The original code has been tweaked for various purposes over the years, but considering the number of tests added in that time, the changes are very small. Here […]
U-Boot has a new continuous integration (CI) lab page that provides a real-time look at the status of various development boards. The page, located at https://lab.u-boot.org/, offers a simple and clean interface that allows developers and curious people to quickly check on the health and activity of each board in the lab. When you first […]
U-Boot makes extensive use of linker-generated lists to discover everything from drivers to commands at runtime. This clever mechanism allows developers to add new features with a single macro, and the linker automatically assembles them into a contiguous array. The C code can then iterate through this array by finding its start and end markers, which are also provided by the linker. For this to work, there’s a critical assumption: the array of structs is perfectly contiguous, with each element having the exact same size. But what happens when the linker, in its quest for optimisation, breaks this assumption? A Little Wrinkle We have known for a while about a subtle issue where the linker, in certain cases, would insert a few bytes of padding between elements in these lists. This is usually done to align the next element to a more efficient memory boundary (like 8 or 16 bytes). […]
What is virtio-fs? For those unfamiliar, virtio-fs is a modern shared filesystem designed specifically for virtualised environments. It allows a virtual machine (the “guest”) to access a directory on the host system, but it does so with a focus on performance and providing local filesystem semantics. Unlike traditional methods like network filesystems (e.g., NFS, Samba) or even the older virtio-9p protocol, virtio-fs is engineered to take advantage of the fact that the guest and host are running on the same machine. By leveraging shared memory and a design based on FUSE (Filesystem in Userspace), it bypasses much of the communication overhead that can slow down other solutions. The result is a faster, more seamless file sharing experience that is ideal for development, testing, and booting from a root filesystem located on the host. virtio-fs arrives in U-Boot Concept The recent merge request in U-Boot Concept introduces a new virtio-fs driver […]
U-Boot Concept now supports the EFI Boot Graphics Resource Table (BGRT) feature. This enhancement allows for a more seamless and branded boot experience on devices that use EFI_LOADER, i.e. the Unified Extensible Firmware Interface (UEFI). What is BGRT? The BGRT is a table in the ACPI (Advanced Configuration and Power Interface) that allows the firmware to pass a logo or image to the operating system during the boot process. This means that instead of a generic boot screen, users can be greeted with a custom logo, such as a company or product brand. This creates a more professional and polished user experience. Why is this important for U-Boot? By supporting BGRT, U-Boot can now provide a more consistent and visually appealing boot experience on a wider range of devices, particularly those running operating systems like Windows or Linux that support UEFI. This is especially valuable in embedded systems and custom […]
What happens in the final moments before U-Boot hands control over to the operating system? Until recently, the answer was, “it’s complicated.” Each architecture like ARM, x86, and RISC-V had its own way of handling the final pre-boot cleanup, leading to a maze of slightly different functions and duplicated code. It was difficult to know what was really happening just before the kernel started. Thanks to a recent series of commits in Concept, this critical part of the boot process has been significantly cleaned up and unified. A Simpler, Centralized Approach The core of this effort is the introduction of a new generic function: bootm_final(). This function’s purpose is to consolidate all the common steps that must happen right before booting an OS. By moving to this centralized model, we’ve replaced various architecture-specific functions, like bootm_announce_and_cleanup(), with a single, unified call. This new approach has been adopted across the x86, […]
Since 2018 U-Boot has had a good selection of features for running on top of QEMU, including: Most of this was written by Bin Meng. It uses driver model and is nicely implemented. What’s new? More recently a few more features have been added: The `virtio list` command can be useful for seeing what paravirtualised devices are available and whether U-Boot has a driver for them. Here you can see U-Boot running on an x86 host. Here you can see how the random-number driver can be used: SCSI is accessed by scanning it first. Note that standard boot does this automatically, if you are just booting an OS. You can also inspect some of the qfw tables directly. The qfw list command has been around for a while, although some minor updates were added recently. It shows the files that QEMU presents to U-Boot: Low-level features The new qfw table […]
