Friday, February 24, 2017

This one is for 20, or Anniversary.Next^5

As I reach my 20 year anniversary with Intel today, I reflect upon advice that resonates with me. I especially like the posting http://perspectives.mvdirona.com/2016/11/advice-to-someone-just-entering-our-industry/, including the admonition to "Play the Long Game."

20 years. And all doing firmware. Several different firmware architectures and many instances of EFI-style firmware (e.g., Release 1-Release 8.1/2/3/4/5/6, Release 9 "aka EDKII").....


Hopefully this won't encourage me to abuse logical fallacies like argument from authority, saying 'In my 20 years at Intel we.....' Instead you're only as good as the last game you've played, not your record of games.

Or having a Whiggish view of tech history. Instead it's more Kolmogorov probability that monotonically increasing (or decreasing) progress and determinism.

Speaking of history, my original badge from February 24, 1997 can be found below, with the drop-e logo and, gasp, a suit and tie.


And now

Ah, the thick head of hair that I had in the 90's. And my Harry Potter glasses. I recall visiting Shanghai and Suzhou in '01. In the latter city the locals pointed at me in those crazy glasses and a scratch on my forehead from my two year old daughter (that resembled the lightning bolt), reinforcing the Potter doppelganger experience. Pre-SARs in Shanghai, so it was still possible to eat snake, drunken shrimp, and dining colleague from the south China province whose restaurant jaunt truly lived up to the saying "... the Chinese eat anything with four legs except a table, and anything that flies that isn't an airplane..." http://simonlesser.blogspot.com/2009/06/food.html.

So my journey at Intel started in 1996 after contact from an Intel recruiter while I lived in Houston,TX. He exhorted me to join Intel, especially given the 'imminent' Merced CPU development. I interviewed in Hillsboro, OR in October 1996 and was told that I could go to Oregon for IA32 Xeon, or DuPont, WA for IA-64 Merced. Having grown up in Houston, Texas and not realizing that the Pacific Northwest even existed prior to this conversation, I naturally chose DuPont in order to be part of the 64-bit revolution.

Fast forward to February 1997. My wife and I moved to Olympia, WA. Given some of the, er, delay in Merced, I had the opportunity to pick up a Masters at the University of Washington

and at the same time work on developing getting our Itanium firmware ready. This included working on the System Abstraction Layer (SAL) http://www.intel.com/content/www/us/en/processors/itanium/itanium-system-abstraction-layer-specification.html with my BIOS hero/guru Sham D. in Hillsboro, along with Mani and Suresh in Santa Clara. The original boot flow entailed SAL-A for memory initialization, SAL-B for platform initialization and the "SAL_PROC" for the OS-visible API's to enable boot-loaders. The loader API into the firmware was a direct mapping of the PC/AT BIOS calls, with examples including instances like SAL_PROC 0x13 having a similar command set to int13h https://en.wikipedia.org/wiki/BIOS_interrupt_call.

As an arbitrary pedantic sidebar, you definitely see a pattern in firmware for 'phases' that typically include 'turn on memory,' 'turn on platform', and 'provide the boot loader environment.' Itanium had SAL-A, SAL-B, EFI. UEFI PI has SEC, PEI, DXE, BDS/TSL/UEFI API's. coreboot has bootblock, rom stage, ram stage, payload (including Seabios or UEFI or Depthcharge or ...). Power8 has hostboot, skiboot, and Petitboot (or EDKII UEFI). The workstation BIOS for IA-32 below had VM0, VM1, VM2, Furball. PC/AT BIOS has bootblock, POST, BIOS runtime. You see a pattern here?

Writing SAL_PROC code was pretty exciting. It could be invoked in virtual or physical mode. With hand-crafted Itanium assembly it was pretty reasonable to write position independent code (PIC) and use the GP register to discern where to find global data. But in moving to C, writing portable C code to abstract the SAL services was quite a feat. This is distinct from the UEFI runtime where were are callable in 1:1 mapping and then non-1:1 after the invocation of the SetVirtualAddress call by the OS kernel.

Regarding gaps with SAL_PROC as a boot firmware interface, as chronicled in page 8 of http://www.intel.com/content/dam/www/public/us/en/documents/research/2011-vol15-iss-1-intel-technology-journal.pdf, Intel created the Intel Boot Initiative (IBI) as a C-callable alternative. The original IBI specification looked a lot like ARC http://www.netbsd.org/docs/Hardware/Machines/ARC/riscspec.pdf. Ken R., a recent join to Intel from an MS (where he had a lot of DNA for ACPI), helped turn IBI into what we know as EFI 1.02, namely evolving IBI to have discoverable interfaces like protocols (think COM IUnknown::QueryInterface) and Task Priority Levels (think NT IRQLs), and of course the Camelcase coding style and use of CONTAINING_RECORD macro for information hiding of private data in our public protocol interface C structures. Many thanks to Ken.

Building out EFI was definitely evolutionary. It started from the 'top down' with EFI acting as that final phase/payload in the first instances with alternative platform initialization instances underneath. This view even informed the thema of 'booting from the top down' that informed how we sequenced the chapters in the 2006 Beyond BIOS book, for example. The initial usage of EFI was the 'sample implementation' built on top of the reference SAL code and a PC/AT BIOS invoked by the EFI 'thunk' drivers.

As we moved into the 2000's, the Intel Framework Specifications were defined in order to replace the SAL for Itanium and PC/AT BIOS for Itanium and IA-32, respectively. We internally referred to things like SAL + BIOS + EFI Sample as a "Franken-BIOS." The associated code base moved from the EFI Sample to the EFI Developer Kit, or EDKI, to distinguish it from the EDKII done in the later 2000's. This internal code-base was called 'Tiano', thus the name of community sites like http://www.tianocore.org.  Someone said the name came from the sailor with Columbus who first noticed America, but the only citation I could find publicly is the "Taino" tribe with whom Columbus engaged.

As a funny sidebar, I do recall the meeting where someone found "Tiano Island" http://pf.geoview.info/tiano,4033365 on the web. At the time it cost some number of millions of dollars. The original director of our team, numbering just a few engineers in the room, said 'let's each pool a couple percent of our stock options and buy the island.' I guess Stu had a much more significant equity position than I did, as a lowly grade 7 engineer.



In late 90's at DuPont, SAL and EFI sample were not the only code base activities. While in DuPont the erstwhile workstation group also created a clean-room replacement for the early boot flow. This started on IA32 and the OS interface was the PC/AT BIOS. For this effort we didn't have an image loader and instead just used non-1:1 GDT settings in order to run the protected mode code. For booting the protected mode code provisioned the 16-bit BIOS blob with information like the disk parameters, etc, so that the 16-bit code was just the 'runtime interface.' The 16-bit BIOS blob was called the 'furball' since we hoped to 'cough it up' once the industry had transitioned into a modern bootload erenvironment, such as EFI.

I still recall colleagues in the traditional business units yelling 'you'll never pass WHQL' with the above solution, but it did work. In fact, the work informed the subsequent interfaces and development with the Intel Framework Compatibility Support Module http://www.intel.com/content/www/us/en/architecture-and-technology/unified-extensible-firmware-interface/efi-compatibility-support-module-specification-v096.html.

We then ported the workstation code to boot the first Itanium workstation. I left that effort and joined the full EFI effort afterward. I recall the specific event which precipitated the decision. I was chatting with Sham and the workstation BIOS lead in the latter's cube. The lead said 'Now that we have our BIOS in modular code code "Plug-In Modules" (PIM's) we can tackle the option ROM problem. I thought to myself that just refactoring code into separate entities isn't the challenge in moving from PC/AT 16-bit option ROM's into a native format, it's all about the 'interfaces, namely how would a 'new' option ROM snap into a modern firmware infrastructure. IBI (now called EFI) was on that path to a solution, whereas a chunk of 'yet another codebase with PIM's' wasn't. Thus I was off to chatting with my friend Andrew, then lunch with Mark D, and onto the EFI quest in 1999. Quite the firmware long-game.

Next we're of finishing the first EFI, going from IBI to EFI .98 to EFI 1.02.

Next we're off on a cross-divisional team to create the '20 year BIOS replacement' called Tiano and the Intel Framework Specifications are born.

Next we solve the option ROM and driver problem with EFI 1.10.  Along the way between 1.10 and UEFI 2.0 we incubate a lot of future technology with the never release 'EFI 1.20' work.

Next Andrew Fish and I ported EDK to Intel 64. And I had fun with a port to XScale back in 2001. I have always enjoyed firmware bring-up on new CPU's.

Fast forward to 2005. The EFI specification became the UEFI 2.0 specification, and many of the Intel Framework Specifications became the UEFI Platform Initialization specification. Wrote the first EFI interface and platform spec for TPM measured boot https://github.com/vincentjzimmer/Documents/blob/master/EFIS004Fall06.pdf.

Fast forward to the 2010's.  More open source. More device types. More CPU ports. Continue to evolve network booting, such as IPV6 https://tools.ietf.org/rfc/rfc5970.txt and HTTP https://github.com/vincentjzimmer/Documents/blob/master/UEFI-Recovery-Options-002-1.pdf. Good stuff. Helped deliver UEFI Secure Boot https://github.com/vincentjzimmer/Documents/blob/master/SAM4542.pdf https://github.com/vincentjzimmer/Documents/blob/master/UEFI-Networking-and-Pre-OS-Security.pdf.

In parallel, I often had side firmware engagements, including a fun tour of duty helping our the solid state disk (SSD) team on firmware.

I still believe in better living through tools, too, whether they have landed in the community http://www.uefi.org/sites/default/files/resources/2014_UEFI_Plugfest_04_Intel.pdf, almost made it https://github.com/vincentjzimmer/Documents/blob/master/Vij_KRHZRWL_13.pdf https://github.com/termite2/Termite, or are in incubation https://www.usenix.org/system/files/conference/woot15/woot15-paper-bazhaniuk.pdf.

Fast forward to 2017. Year 20. It's still a lot of fun solving crossword puzzles with hardware and firmware.

During my time at Intel I've also appreciated the wisdom of others, whether through the mentoring of direct interaction or the written word. For the latter I heartily recommend keeping the following close at hand.



So am I done this morning? Let's do a final rewind to February 1992 when I jumped into industry in Houston. First I wrote firmware for embedded systems attached to natural gas pipelines http://www.emerson.com/resource/blob/133882/bb9c3232256dfab98cc6a20a27d43c1f/document-3-9000-309-data.pdf - sensors, serial protocols with radio interfaces to SCADA host, control algorithms, I2c pluggable expansion cards, loaders in microcontroller mask ROM's, porting a lot of evil assembly to C code...  fun stuff. The flow computer/Remote Telemetry Unit (RUT) work was an instance of the Internet of Things before the IOT was invented. Then on to industrial PC BIOS and management controller firmware. Then on to hardware RAID controllers and server BIOS. And then Intel in February 1997. 5 years of excitement in Houston prior to my Intel journey.

So I guess that sums out to 25. Now I feel tired. Time to stop blogging and playing the rewinding history game. Here's looking to the next 25.

Cheers.

Thursday, February 9, 2017

Specifications and a New Book

I recently came across http://electronicdesign.com/embedded/what-s-difference-between-de-jure-and-de-facto-standards which reminded me of the world of firmware. Specifically, there is an interplay of de jure standards, such as the UEFI 2.6 specification, and then de facto standards, including open and closed source behaviors.

I'll give a quick example where these two venues collided. Specifically, during the drafting of the UEFI 2.5 specification, there was an operating system request to make the UEFI run time code produced in a way such that the hypervisor or OS could apply page protection. Recall that UEFI runtime code and data are co-located in ring 0 with the OS kernel. This change entailed several things, including the OS making the UEFI run time code read-only and the data pages non-executable. To that end, the EDKII was updated to align the UEFI runtime driver sections on a 4KiB boundary and not merge the code and data pages. In addition, the UEFI memory map was updated to have a memory descriptor for each code and data page, creating several descriptors for each UEFI runtime image, versus the former behavior of having one memory descriptor for the entire set of PE images.

We codified this behavior in UEFI 2.5 with the memory properties table

This bit let the OS know that the code was factored into these separate pages and validated by the firmware producer to be truly pure code and data (e.g., no self-modifying code). This was a de jure UEFI 2.5 specification addition.

What happened?  Namely, why did we move to the EFI_MEMORY_ATTRIBUTES_TABLE in UEFI 2.6 and add language to the specification?

After publishing the 2.5 specification and upstreaming patches responsive to this properties table, many OS kernels started to crash. Uh oh.



What we learned was that when OS kernels invoke SetVirtualAddress to map the UEFI runtime entries from a 1:1 pre-OS setting to a non-1:1 OS kernel mapping, the relative distance between entries were not preserved. This didn't appear in earlier implementations since one memory descriptor covered a single image. In fracturing the single descriptor covering the PE image into multiple entries, the un-documented requirement to keep relative offsets between sections of a PE/COFF image during the SetVa call was surfaced.  We essentially discovered a de facto requirement to have a single descriptor covering a single PE/COFF image.

Thus the change in the UEFI 2.6 de jure specification to have an 'alternate' table to the UEFI memory map (e.g.,  EFI_MEMORY_ATTRIBUTES_TABLE) and maintain the single descriptor per image given the circa 1999 and beyond OS's and their SetVa expectations.

This new attributes table is also called out in some OS requirements https://msdn.microsoft.com/windows/hardware/commercialize/design/minimum/device-guard-and-credential-guard.

This doesn't moot the value of the de jure specification, of course. OS and device vendors appreciate standards so that long-term support (LTS) variants of the OS can have an expectation that platforms produced during the support lifetime, such as 10 years, will be compatible. Given the complexity of modern system, the de jure specification cannot always cover all of the system details. Thus the value of open source and products providing some de facto standardization, too, to complement the formal standard.

Speaking of industry standard firmware and code, I'd also like to let people know that the "Beyond BIOS" book is now available at https://www.amazon.com/Beyond-BIOS-Developing-Extensible-Interface/dp/1501514784 and https://www.degruyter.com/view/product/484468. Since the original publication in 2006, many things have changed, including scaling of the industry standards efforts, but the basics remain the same.  And those areas that have evolved are deftly treated in the updated text.


This book serves as a good launching point for someone just diving into the world of industry standard firmware. I was happy to have the opportunity to work with my old friends and co-authors Mike Rothman and Suresh, along with new friends like Jeffrey, Megan, and others from De Gruyter. De Gruyter also allowed for me to share a sample chapter https://github.com/vincentjzimmer/Documents/blob/master/Beyond_BIOS_3rd_Ed_Chapter-7-9781501505690.pdf, too.

If you have the time please take a look.

And interactions of modern systems don't always behave as expected, too.



You can learn more about the UEFI Shell, which is nicely staged in the picture above, in a update of the UEFI Shell book later this year https://www.degruyter.com/view/product/484477.