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Get PC BIOS back on UEFI only system

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Re: Get PC BIOS back on UEFI only system

#41

Post by skissane »

rjst01 wrote: post #38
skissane wrote: post #17

Earlier quoted context omitted.

MBR and GPT can coexist on the same disk - MBR goes in sector 0, GPT starts in sector 1. Normally the MBR in sector 0 is “protective” (it just marks the whole disk as in use), but in theory you can create a “hybrid” disk in which the MBR and GPT both describe the same partitions. I suppose you could even reserve most of the disk as one big GPT partition and then split that up into multiple MBR partitions. You’d have…

In practice, whether or not this actually works can be very hit-or-miss. We've found several UEFI implementations will not consider a disk bootable if the pMBR doesn't exactly match the spec, which specifies that the 'protective' partition shouldn't be marked as bootable in the MBR partition table. Meanwhile, other implementations will not consider the disk bootable in BIOS mode if the partition in the pMBR is not ma…

I wonder… does the UEFI spec mandate any particular behaviour in these cases? Does the UEFI SCT test for it?

Seems like an inconsistency which could be addressed by adding it to the spec and/or test suite.

I guess the other thing I don’t know, is whether there is any actual real world pressure on firmware vendors to pass the test suite.

Re: Get PC BIOS back on UEFI only system

#42

Post by skissane »

rzzzt wrote: post #33
skissane wrote: post #12

Earlier quoted context omitted.

Microsoft owns GitHub, and GitHub is crawling with Windows source code leaks… and I’m wondering it anyone at Microsoft really cares? Is it possible they’ve even made an intentional decision just to ignore it? If it were an Oracle source code leak, I expect they’d have a crack team of lawyers suing people 24x7 until it was all gone… maybe that’s why there haven’t (to my knowledge) been any Oracle source code leaks (I…

MS offers (or offered back in the day of Win2000 and XP) access to source code for governments, system integrators and academic institutions as part of its Shared Source Initiative: - https://en.wikipedia.org/wiki/Shared_Source_Initiative#Overv... - https://news.microsoft.com/source/2002/02/21/microsoft-annou...

And it is pretty clear that’s where most or all of these leaks actually came from, not from within Microsoft. e.g. the NT4 and 2000 leaks apparently came from Mainsoft

I don’t know the current status of those source code access programs but I believe at least some of them are still in effect. IIRC, to stop the Chinese government from dumping Windows, they had to give them source code access, but I believe they are planning to dump it anyway, they see relying on US proprietary software for their government operations as too big a risk

Re: Get PC BIOS back on UEFI only system

#43

Post by adrian_b »

Kwpolska wrote: post #37
LukeShu wrote: post #30

Earlier quoted context omitted.

Too late to edit: non-GPT, non-MBR For instance, whole-disk btrfs. Or old BSD partition schemes.

How much benefit would there be in whole-disk btrfs? The space taken up by GPT and the FAT32 EFI partition is a rounding error compared to the sizes of modern disks.

I have used only whole-disk XFS SSDs and HDDs for more than a decade.

While the space wasted by GPT and partitions and by the arbitrary alignment rules used by various formatting tools is not great, I do not see any reason why it should exist. The space wasted now with GPT and UEFI is several orders of magnitude greater than it was with traditional partition tables, so eliminating it has become more attractive.

Such SSDs and HDDs are not bootable, but for me this is a desirable feature, not a bug. I boot my computers either from Ethernet (e.g. most of my servers) or from a removable USB memory.

The SSDs and HDDs with a whole-disk file system are also wholly encrypted. As in a proper encryption implementation, there is complete separation between the encrypted data and the encryption key. The encrypted disks or their hosting computers do not contain any information about decryption, unlike in many systems of disk encryption. The encrypted decryption keys can be found only on external or remote boot media, which are not normally associated with the hosting computers.

Re: Get PC BIOS back on UEFI only system

#45

Post by arccy »

bitwize wrote: post #31
kevinsync wrote: post #13

Earlier quoted context omitted.

The little bit I perused is very readable code.. like enjoyable to read. There are a lot of stylistic decisions that always felt "right" to me (general spacing, commenting style, horizontal alignment of equals signs, etc) -- but FWIW the first codebase I ever read (and probably imprinted on me indelibly) was DikuMUD, which is kind of in the same ballpark. Anyways, very cool to see.

I... wouldn't confess to having perused illegally leaked Windows source, as it could taint you and make you ineligible to contribute to certain projects, like Wine.

if you read it but didn't confess, you'd still be ineligible, you'd be harming rather than helping wine if you did sneak in contributions.

Re: Get PC BIOS back on UEFI only system

#46

Post by sdflhasjd »

axiolite wrote: post #9
ehutch79 wrote: post #2

Why?

From the project page: "Boot FreeDOS, Windows XP, and Windows 7" Additionally, it was just 3 years ago that memtest86plus finally got a UEFI version. That was painful for a few years there. (Though the 4GB RAM limit would have made this not an ideal solution.) I'm sure there are other such self-hosting utilities that haven't been and may not be ported/rewritten to work under UEFI.

I think I remember Windows 7 (and maybe even Vista) supported UEFI natively.

Re: Get PC BIOS back on UEFI only system

#47

Post by 3036e4 »

Amazing! I thought all hope of ever running FreeDOS on the bare metal again on new hardware was lost, but maybe using this code (or something similar) a future FreeDOS installer can fix this at least on some systems.

Re: Get PC BIOS back on UEFI only system

#49

Post by superkuh »

mintsuki wrote: post #34
LukeShu wrote: post #30

Earlier quoted context omitted.

Too late to edit: non-GPT, non-MBR For instance, whole-disk btrfs. Or old BSD partition schemes.

That is a very niche use case, and also won't really work on most real BIOS machines as they actually check for a proper MBR and/or BPB (and no GPT), which is also why GPT on BIOS support is very spotty, since a lot of BIOSes will detect the GPT and refuse to boot, or refuse to boot in legacy (CSM) mode. In any case that is far beyond the original scope of booting old PC OSes, which MBR support alone serves really we…

GPT is not UEFI. It's just the format of the storage device. I have many computers with GPT formatted disks with actual master boot records at the start of the disk that boot MBR on both original BIOS machines and CSM BIOS machines.

MBR is two things with the same name. It is both the format of the storage device and describes a booting mode using a master boot record and up to 4 partitions.

GPT is one thing. It is a format for a storage device. It is the alternative to the MBR format for storage devices. It has nothing to do with (U)EFI.

BIOS or BIOS/csm are not types of formats for storage devices. They are types of boot processes. (U)EFI is another type of boot process.

You can easily mix and match boot types (BIOS/csm vs UEFI) and storage device format types (GPT vs MBR). As others have said, there may be some slight incompatibilities on some rare hardware/software configs, but mostly it just works.

Re: Get PC BIOS back on UEFI only system

#50

Post by joshuaissac »

AStonesThrow wrote: post #21
skissane wrote: post #12

Earlier quoted context omitted.

Microsoft owns GitHub, and GitHub is crawling with Windows source code leaks… and I’m wondering it anyone at Microsoft really cares? Is it possible they’ve even made an intentional decision just to ignore it? If it were an Oracle source code leak, I expect they’d have a crack team of lawyers suing people 24x7 until it was all gone… maybe that’s why there haven’t (to my knowledge) been any Oracle source code leaks (I…

When I started college in 1989, my Pascal programming class used a cluster of AT&T 3B2 systems running SVR3. I poked around those systems like crazy over the course of two quarters. I don't remember if there was any significant source code exposed to unprivileged users. During the mid-90s, the Unix Wars were raging and Unix System Labs was suing U.C. Berkeley over the intellectual property of Unix source code. Unix h…

This type of restriction is still applied to contributors to the ReactOS project, in that contributions are not accepted from those who have seen any leaked Windows source code or have worked for Microsoft.
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