* [PATCH] efi: Override runtime supported mask from a EFI variable if present
@ 2022-11-09 17:27 Ard Biesheuvel
2022-11-10 14:37 ` Alexandru Elisei
0 siblings, 1 reply; 3+ messages in thread
From: Ard Biesheuvel @ 2022-11-09 17:27 UTC (permalink / raw)
To: linux-efi; +Cc: linux-arm-kernel, alexandru.elisei, Ard Biesheuvel
For debugging purposes, allow the runtime override mask to be set from a
EFI variable if one exists. For instance, the RT supported mask can be
set to 0xfffd to disable the SetTime() runtime service, and enable all
others:
echo -ne "\x7\0\0\0\xfd\xff" \
> /sys/firmware/efi/efivars/LinuxRtMaskOverride-eb66918a-7eef-402a-842e-931d21c38ae9
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/efi.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index a46df5d1d0942751..faed1ef78c044924 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -367,7 +367,17 @@ static int __init efisubsys_init(void)
}
}
- if (efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
+ if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
+ unsigned long size = sizeof(efi.runtime_supported_mask);
+
+ if (efi.get_variable(L"LinuxRtMaskOverride",
+ &EFI_RT_PROPERTIES_TABLE_GUID, NULL, &size,
+ &efi.runtime_supported_mask) == EFI_SUCCESS)
+ pr_info("Overriding runtime_supported_mask to 0x%x\n",
+ efi.runtime_supported_mask);
+ }
+
+ if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_TIME))
platform_device_register_simple("rtc-efi", 0, NULL, 0);
/* We register the efi directory at /sys/firmware/efi */
--
2.35.1
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^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] efi: Override runtime supported mask from a EFI variable if present
2022-11-09 17:27 [PATCH] efi: Override runtime supported mask from a EFI variable if present Ard Biesheuvel
@ 2022-11-10 14:37 ` Alexandru Elisei
2022-11-11 7:51 ` Ard Biesheuvel
0 siblings, 1 reply; 3+ messages in thread
From: Alexandru Elisei @ 2022-11-10 14:37 UTC (permalink / raw)
To: Ard Biesheuvel; +Cc: linux-efi, linux-arm-kernel
Hi,
On Wed, Nov 09, 2022 at 06:27:50PM +0100, Ard Biesheuvel wrote:
> For debugging purposes, allow the runtime override mask to be set from a
> EFI variable if one exists. For instance, the RT supported mask can be
> set to 0xfffd to disable the SetTime() runtime service, and enable all
> others:
>
> echo -ne "\x7\0\0\0\xfd\xff" \
> > /sys/firmware/efi/efivars/LinuxRtMaskOverride-eb66918a-7eef-402a-842e-931d21c38ae9
I'm really sorry, I applied this patch, but I couldn't find the file
(LinuxRtMaskOverride*) under efivars, and couldn't find another way of
setting the variable.
Thanks,
Alex
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> drivers/firmware/efi/efi.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index a46df5d1d0942751..faed1ef78c044924 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -367,7 +367,17 @@ static int __init efisubsys_init(void)
> }
> }
>
> - if (efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
> + if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
> + unsigned long size = sizeof(efi.runtime_supported_mask);
> +
> + if (efi.get_variable(L"LinuxRtMaskOverride",
> + &EFI_RT_PROPERTIES_TABLE_GUID, NULL, &size,
> + &efi.runtime_supported_mask) == EFI_SUCCESS)
> + pr_info("Overriding runtime_supported_mask to 0x%x\n",
> + efi.runtime_supported_mask);
> + }
> +
> + if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_TIME))
> platform_device_register_simple("rtc-efi", 0, NULL, 0);
>
> /* We register the efi directory at /sys/firmware/efi */
> --
> 2.35.1
>
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] efi: Override runtime supported mask from a EFI variable if present
2022-11-10 14:37 ` Alexandru Elisei
@ 2022-11-11 7:51 ` Ard Biesheuvel
0 siblings, 0 replies; 3+ messages in thread
From: Ard Biesheuvel @ 2022-11-11 7:51 UTC (permalink / raw)
To: Alexandru Elisei; +Cc: linux-efi, linux-arm-kernel
On Thu, 10 Nov 2022 at 15:37, Alexandru Elisei <alexandru.elisei@arm.com> wrote:
>
> Hi,
>
> On Wed, Nov 09, 2022 at 06:27:50PM +0100, Ard Biesheuvel wrote:
> > For debugging purposes, allow the runtime override mask to be set from a
> > EFI variable if one exists. For instance, the RT supported mask can be
> > set to 0xfffd to disable the SetTime() runtime service, and enable all
> > others:
> >
> > echo -ne "\x7\0\0\0\xfd\xff" \
> > > /sys/firmware/efi/efivars/LinuxRtMaskOverride-eb66918a-7eef-402a-842e-931d21c38ae9
>
> I'm really sorry, I applied this patch, but I couldn't find the file
> (LinuxRtMaskOverride*) under efivars, and couldn't find another way of
> setting the variable.
>
The variable will be created by writing to the file.
But no worries, I think we have enough context now. I've queued up the
patch that checks the SMBIOS record for Altra machines.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > drivers/firmware/efi/efi.c | 12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index a46df5d1d0942751..faed1ef78c044924 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -367,7 +367,17 @@ static int __init efisubsys_init(void)
> > }
> > }
> >
> > - if (efi_rt_services_supported(EFI_RT_SUPPORTED_TIME_SERVICES))
> > + if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
> > + unsigned long size = sizeof(efi.runtime_supported_mask);
> > +
> > + if (efi.get_variable(L"LinuxRtMaskOverride",
> > + &EFI_RT_PROPERTIES_TABLE_GUID, NULL, &size,
> > + &efi.runtime_supported_mask) == EFI_SUCCESS)
> > + pr_info("Overriding runtime_supported_mask to 0x%x\n",
> > + efi.runtime_supported_mask);
> > + }
> > +
> > + if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_TIME))
> > platform_device_register_simple("rtc-efi", 0, NULL, 0);
> >
> > /* We register the efi directory at /sys/firmware/efi */
> > --
> > 2.35.1
> >
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2022-11-09 17:27 [PATCH] efi: Override runtime supported mask from a EFI variable if present Ard Biesheuvel
2022-11-10 14:37 ` Alexandru Elisei
2022-11-11 7:51 ` Ard Biesheuvel
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