coreboot 4.13 was released on November 20th, 2020.
Since 4.12 there were 4200 new commits by over 234 developers. Of these, about 72 contributed to coreboot for the first time.
Thank you to all developers who again helped made coreboot better than ever, and a big welcome to our new contributors!
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Native refcode implementation for Bay Trail
Bay Trail no longer needs a refcode binary to function properly. The refcode was reimplemented as coreboot code, which should be functionally equivalent. Thus, coreboot only needs to run the MRC.bin to successfully boot Bay Trail.
Unusual config files to build test more code
There’s some new highly-unusual config files, whose only purpose is to coerce Jenkins into build-testing several disabled-by-default coreboot config options. This prevents them from silently decaying over time because of build failures.
Initial support for Intel Trusted eXecution Technology
coreboot now supports enabling Intel TXT. Though it’s not feature-complete yet, the code allows successfully launching tboot, a Measured Launch Environment. It was tested on Haswell using an Asrock B85M Pro4 mainboard with TPM 2.0 on LPC. Though support for other platforms is still not ready, it is being worked on. The Haswell MRC.bin needs to be patched so as to enable DPR. Given that the MRC binary cannot be redistributed, the best long-term solution is to replace it.
Hidden PCI devices
This new functionality takes advantage of the existing ‘hidden’ keyword in the devicetree. Since no existing boards were using the keyword, its usage was repurposed to make dealing with some unique PCI devices easier. The particular case here is Intel’s PMC (Power Management Controller). During the FSP-S run, the PMC device is made hidden, meaning that its config space looks as if there is no device there (Vendor ID reads as 0xFFFF_FFFF). However, the device does have fixed resources, both MMIO and I/O. These were previously recorded in different places (MMIO was typically an SA fixed resource, and I/O was treated as an LPC resource). With this change, when a device in the tree is marked as ‘hidden’, it is not probed (
pci_probe_dev()) but rather assumed to exist so that its resources can be placed in a more natural location. This also adds the ability for the device to participate in SSDT generation.
Tools for generating SPDs for LP4x memory on TGL and JSL
A set of new tools
gen_part_id.go are added to automate the process of generating SPDs for LP4x memory and assigning hardware strap IDs for memory parts used on TGL and JSL based boards. The SPD data obtained from memory part vendors has to be massaged to format it correctly as per JEDEC and Intel MRC expectations. These tools take a list of memory parts describing their physical attributes as per their datasheet and convert those attributes into SPD files for the platforms. More details about the tools are added in README.md.
New version of SMM loader
A new version of the SMM loader which accommodates platforms with over 32 CPU threads. The existing version of SMM loader uses a 64K code/data segment and only a limited number of CPU threads can fit into one segment (because of save state, STM, other features, etc). This loader extends beyond the 64K segment to accommodate additional CPUs and in theory allows as many CPU threads as possible limited only by SMRAM space and not by 64K. By default this loader version is disabled. Please see cpu/x86/Kconfig for more info.
coreboot now has an in-built Address Sanitizer, a runtime memory debugger designed to find out-of-bounds access and use-after-scope bugs. It is made available on all x86 platforms in ramstage and on QEMU i440fx, Intel Apollo Lake, and Haswell in romstage. Further, it can be enabled in romstage on other x86 platforms as well. Refer ASan documentation for more info.
Initial support for x86_64
The x86_64 code support has been revived and enabled for QEMU. While it started as PoC and the only supported platform is an emulator, there’s interest in enabling additional platforms. It would allow to access more than 4GiB of memory at runtime and possibly brings optimised code for faster execution times. It still needs changes in assembly, fixed integer to pointer conversions in C, wrappers for blobs, support for running Option ROMs, among other things.
Preparations to minimize enabling PCI bus mastering
For security reasons, bus mastering should be enabled as late as possible. In coreboot, it’s usually not necessary and payloads should only enable it for devices they use. Since not all payloads enable bus mastering properly yet, some Kconfig options were added as an intermediate step to give some sort of “backwards compatibility”, which allow enabling or disabling bus mastering by groups.
Currently available groups are:
- PCI bridges
- Any devices
For now, “Any devices” is enabled by default to keep the traditional behaviour, which also includes all other options. This is currently necessary, for instance, for libpayload-based payloads as the drivers don’t enable bus mastering for PCI bridges.
Exceptional cases, that may still need early bus master enabling in the future, should get their own per-reason Kconfig option. Ideally before the next release.
Early runtime configurability of the console log level
Traditionally, we didn’t allow the log level of the
romstage console to be changed at runtime (e.g. via
get_option()). It turned out that the technical constraints for this (no global variables in
romstage) vanished long ago, though. The new behaviour is to query
get_option() now from the second stage that uses the console on. In other words, if the
bootblock already enables the console, the
romstage log level can be changed via
get_option(). Keeping the log level of the first console static ensures that we can see console output even if there’s a bug in the more involved code to query options.
Resource allocator v4
A new revision of resource allocator v4 is now added to coreboot that supports mutiple ranges for allocating resources. Unlike the previous allocator (v3), it does not use the topmost available window for allocation. Instead, it uses the first window within the address space that is available and satisfies the resource request. This allows utilization of the entire available address space and also allows allocation above the 4G boundary. The old resource allocator v3 is still retained for some AMD platforms that do not conform to the requirements of the allocator.
PCI bus master configuration options
In order to minimize the usage of PCI bus mastering, the options we introduced in this release will be dropped in a future release again. For more details, please see Preparations to minimize enabling PCI bus mastering.
Resource allocator v3
Resource allocator v3 is retained in coreboot tree because the following platforms do not conform to the requirements of the resource allocation i.e. not all the fixed resources of the platform are provided during the
In order to have a single unified allocator in coreboot, this notice is being added to ensure that the platforms listed above are fixed before the next release. If there is interest in maintaining support for these platforms beyond the next release, please ensure that the platforms are fixed to conform to the expectations of resource allocation.
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