On Fri, 2016-03-18 at 16:15 +0000, Matt Fleming wrote: > On Fri, 18 Mar, at 12:11:50PM, Daniel Baluta wrote: > > > > From: Matt Gumbel <matthew.k.gumbel@xxxxxxxxx> > > > > This driver intercepts system reboot requests and populates the > > LoaderEntryOneShot EFI variable with the user-supplied reboot > > argument. EFI bootloaders such as Gummiboot will consume this > > variable and use it to control which OS is booted next. > > > > We use this with Android where reboot() tells the kernel that > > we want to boot into recovery or other non-default OS environment. > > > > It is the bootloader's job to guard against this variable being > > uninitialzed or containing invalid data, and just boot normally > > if that is the case. > > > > Signed-off-by: Matt Gumbel <matthew.k.gumbel@xxxxxxxxx> > > Signed-off-by: Mohamed Abbas <mohamed.abbas@xxxxxxxxx> > > Signed-off-by: Constantin Musca <constantin.musca@xxxxxxxxx> > > Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx> > > --- > > Changes since v1: > > * updated Makefile after changing source name from efibc.c -> > > efi-bc.c > > to comply with naming rules in drivers/firmware/efi/ > > > > drivers/firmware/efi/Kconfig | 11 ++ > > drivers/firmware/efi/Makefile | 1 + > > drivers/firmware/efi/efi-bc.c | 251 > > ++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 263 insertions(+) > > create mode 100644 drivers/firmware/efi/efi-bc.c > Why does this require a driver? Why is it not possible to solve this > problem by creating the variable in userspace before invoking > reboot(2)? Hi Matt, It is possible, but that means modifying those userspace apps :) There are reboot implementations that do "reboot <reason>", such as Android's reboot command [1] and Upstart's reboot replacement [2], which pass the reason as an argument to the reboot syscall. Probably your first question will be - "Why don't you modify those apps?" Well, I don't see platform-agnostic way how those could be modified to pass the reason to the bootloader, regardless of platform or bootloader. Other non-EFI platforms use a driver as well: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/dri vers/soc/tegra/pmc.c#n382 [1] https://android.googlesource.com/platform/system/core/+/master/libcu tils/android_reboot.c#228 [2] https://bazaar.launchpad.net/~upstart-devel/upstart/trunk/view/head: /util/reboot.c#L259 Cheers, Stefan ��.n��������+%������w��{.n�����{����* jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
