On Wed, 2013-01-23 at 07:52 +0000, Matt Fleming wrote: > On Wed, 2013-01-23 at 04:16 +0000, Ben Hutchings wrote: > > On Mon, 2013-01-21 at 21:12 +0000, Matt Fleming wrote: > > [...] > > > From 92e73f936e40a8c6562e47425d434a4e62d2b8e2 Mon Sep 17 00:00:00 2001 > > > From: Matt Fleming <matt.fleming@xxxxxxxxx> > > > Date: Wed, 14 Nov 2012 09:42:35 +0000 > > > Subject: [PATCH] efi: Make 'efi_enabled' a function to query EFI facilities > > > > > > Originally 'efi_enabled' indicated whether a kernel was booted from > > > EFI firmware. Over time its semantics have changed, and it now > > > indicates whether or not we are booted on an EFI machine with > > > bit-native firmware, e.g. 64-bit kernel with 64-bit firmware. > > > > > > The immediate motivation for this patch is the bug report at, > > > > > > https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557 > > > > > > which details how running a platform driver on an EFI machine that is > > > designed to run under BIOS can cause the machine to become > > > bricked. Also, the following report, > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=47121 > > > > > > details how running said driver can also cause Machine Check > > > Exceptions. Drivers need a new means of detecting whether they're > > > running on an EFI machine, as sadly the expression, > > > > > > if (!efi_enabled) > > > > > > hasn't been a sufficient condition for quite some time. > > [...] > > > > This patch maps the old efi_enabled flag to efi_enabled(EFI_BOOT). Your > > second patch adds a test for efi_enabled(EFI_BOOT) to the samsung-laptop > > driver. So the samsung-laptop driver could be fixed by adding a check > > for the old flag; it doesn't depend on the addition of new flags at all. > > The changes elsewhere may well be important, but the cited motivation > > here just doesn't make sense. > > If we instead check for the old flag then the samsung-laptop driver > would run if booting a 32-bit kernel with 64-bit EFI firmware, or vice > versa, because efi_enabled == 0 in that case. > > It's not sufficient to just check the old flag, the samsung-laptop > driver really can't be allowed to run at all if booting from EFI, and > the old flag doesn't provide us with that guarantee. OK, yes, I misread this. Sorry to waste your time. Ben. -- Ben Hutchings Q. Which is the greater problem in the world today, ignorance or apathy? A. I don't know and I couldn't care less.
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