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Date: Fri, 31 Jul 2020 16:15:03 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Daniel Gutson <daniel@...ypsium.com>
Cc: Derek Kiernan <derek.kiernan@...inx.com>,
Tudor Ambarus <tudor.ambarus@...rochip.com>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Arnd Bergmann <arnd@...db.de>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
linux-kernel@...r.kernel.org, Richard Hughes <hughsient@...il.com>,
Alex Bazhaniuk <alex@...ypsium.com>
Subject: Re: [PATCH] Platform lockdown information in SYSFS
On Fri, Jul 31, 2020 at 10:30:43AM -0300, Daniel Gutson wrote:
> On Fri, Jul 31, 2020 at 4:01 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Thu, Jul 30, 2020 at 06:41:36PM -0300, Daniel Gutson wrote:
> > > This patch exports information about the platform lockdown
> > > firmware configuration in the sysfs filesystem.
> > > In this initial patch, I include some configuration attributes
> > > for the system SPI chip.
> > >
> > > This initial version exports the BIOS Write Enable (bioswe),
> > > BIOS Lock Enable (ble), and the SMM Bios Write Protect (SMM_BWP)
> > > fields of the Bios Control register. The idea is to keep adding more
> > > flags, not only from the BC but also from other registers in following
> > > versions.
> > >
> > > The goal is that the attributes are avilable to fwupd when SecureBoot
> > > is turned on.
> > >
> > > The patch provides a new misc driver, as proposed in the previous patch,
> > > that provides a registration function for HW Driver devices to register
> > > class_attributes.
> > > In this case, the intel SPI flash chip (intel-spi) registers three
> > > class_attributes corresponding to the fields mentioned above.
> >
> > Better, but you are abusing sysfs (note, no CAPS) a lot here...
> >
> >
> > >
> > > Signed-off-by: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > ---
> > > .../ABI/stable/sysfs-class-platform-lockdown | 23 +++++++
> > > MAINTAINERS | 7 +++
> > > drivers/misc/Kconfig | 9 +++
> > > drivers/misc/Makefile | 1 +
> > > drivers/misc/platform-lockdown-attrs.c | 57 +++++++++++++++++
> > > drivers/mtd/spi-nor/controllers/Kconfig | 1 +
> > > .../mtd/spi-nor/controllers/intel-spi-pci.c | 49 +++++++++++++++
> > > drivers/mtd/spi-nor/controllers/intel-spi.c | 62 +++++++++++++++++++
> > > .../platform_data/platform-lockdown-attrs.h | 19 ++++++
> > > 9 files changed, 228 insertions(+)
> > > create mode 100644 Documentation/ABI/stable/sysfs-class-platform-lockdown
> > > create mode 100644 drivers/misc/platform-lockdown-attrs.c
> > > create mode 100644 include/linux/platform_data/platform-lockdown-attrs.h
> > >
> > > diff --git a/Documentation/ABI/stable/sysfs-class-platform-lockdown b/Documentation/ABI/stable/sysfs-class-platform-lockdown
> > > new file mode 100644
> > > index 000000000000..6034d6cbefac
> > > --- /dev/null
> > > +++ b/Documentation/ABI/stable/sysfs-class-platform-lockdown
> > > @@ -0,0 +1,23 @@
> > > +What: /sys/class/platform-lockdown/bioswe
> > > +Date: July 2020
> > > +KernelVersion: 5.8.0
> > > +Contact: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > +Description: If the system firmware set BIOS Write Enable.
> > > + 0: writes disabled, 1: writes enabled.
> > > +Users: https://github.com/fwupd/fwupd
> > > +
> > > +What: /sys/class/platform-lockdown/ble
> > > +Date: July 2020
> > > +KernelVersion: 5.8.0
> > > +Contact: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > +Description: If the system firmware set Bios Lock Enable.
> > > + 0: SMM lock disabled, 1: SMM lock enabled.
> > > +Users: https://github.com/fwupd/fwupd
> > > +
> > > +What: /sys/class/platform-lockdown/smm_bwp
> > > +Date: July 2020
> > > +KernelVersion: 5.8.0
> > > +Contact: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > +Description: If the system firmware set SMM Bios Write Protect.
> > > + 0: writes disabled unless in SMM, 1: writes enabled.
> > > +Users: https://github.com/fwupd/fwupd
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index f0569cf304ca..771ed1693d28 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -13608,6 +13608,13 @@ S: Maintained
> > > F: Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.yaml
> > > F: drivers/iio/chemical/pms7003.c
> > >
> > > +PLATFORM LOCKDOWN ATTRIBUTES MODULE
> > > +M: Daniel Gutson <daniel.gutson@...ypsium.com>
> > > +S: Supported
> > > +F: Documentation/ABI/sysfs-class-platform-lockdown
> > > +F: drivers/misc/platform-lockdown-attrs.c
> > > +F: include/linux/platform_data/platform-lockdown-attrs.h
> > > +
> > > PLX DMA DRIVER
> > > M: Logan Gunthorpe <logang@...tatee.com>
> > > S: Maintained
> > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > > index e1b1ba5e2b92..058d4ba3cefd 100644
> > > --- a/drivers/misc/Kconfig
> > > +++ b/drivers/misc/Kconfig
> > > @@ -456,6 +456,15 @@ config PVPANIC
> > > a paravirtualized device provided by QEMU; it lets a virtual machine
> > > (guest) communicate panic events to the host.
> > >
> > > +config PLATFORM_LOCKDOWN_ATTRS
> > > + tristate "Platform lockdown information in the SYSFS"
> >
> > "Platform lockdown information for some hardware information displayed
> > in sysfs" ?
> >
> > > + depends on SYSFS
> > > + help
> > > + This kernel module is a helper driver to provide information about
> > > + platform lockdown settings and configuration.
> >
> > Is that what this really is?
> >
> > > + This module is used by other device drivers -such as the intel-spi-
> > > + to publish the information in /sys/class/platform-lockdown.
> > > +
> > > source "drivers/misc/c2port/Kconfig"
> > > source "drivers/misc/eeprom/Kconfig"
> > > source "drivers/misc/cb710/Kconfig"
> > > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> > > index c7bd01ac6291..e29b45c564f9 100644
> > > --- a/drivers/misc/Makefile
> > > +++ b/drivers/misc/Makefile
> > > @@ -57,3 +57,4 @@ obj-$(CONFIG_PVPANIC) += pvpanic.o
> > > obj-$(CONFIG_HABANA_AI) += habanalabs/
> > > obj-$(CONFIG_UACCE) += uacce/
> > > obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
> > > +obj-$(CONFIG_PLATFORM_LOCKDOWN_ATTRS) += platform-lockdown-attrs.o
> > > diff --git a/drivers/misc/platform-lockdown-attrs.c b/drivers/misc/platform-lockdown-attrs.c
> > > new file mode 100644
> > > index 000000000000..d08b3d895064
> > > --- /dev/null
> > > +++ b/drivers/misc/platform-lockdown-attrs.c
> > > @@ -0,0 +1,57 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Platform lockdown attributes kernel module
> > > + *
> > > + * Copyright (C) 2020 Daniel Gutson <daniel.gutson@...ypsium.com>
> > > + * Copyright (C) 2020 Eclypsium Inc.
> > > + */
> > > +#include <linux/kobject.h>
> > > +#include <linux/sysfs.h>
> > > +#include <linux/module.h>
> > > +#include <linux/init.h>
> > > +#include <linux/list.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/platform_data/platform-lockdown-attrs.h>
> > > +
> > > +static struct class platform_lockdown_class = {
> > > + .name = "platform-lockdown",
> > > + .owner = THIS_MODULE,
> > > +};
> > > +
> > > +int register_platform_lockdown_attribute(
> > > + struct class_attribute *lockdown_attribute)
> > > +{
> > > + /* attempt to create the file: */
> > > + return class_create_file(&platform_lockdown_class,
> > > + lockdown_attribute);
> > > +}
> > > +EXPORT_SYMBOL_GPL(register_platform_lockdown_attribute);
> >
> > nit, global symbols should put the noun first:
> > platform_lockdown_attribute_register()
> >
> > But, this all is not ok.
> >
> > You are trying to create/remove random sysfs files that end up in a
> > single class. What you want to do is create a device that is associated
> > with this class, and make that device a child of the device you are
> > registering these attributes for.
> >
> > Think of this as an input device. You don't put the random input
> > attributes all in one place, you create a new device that represents the
> > input interface and register that. Then userspace can iterate over all
> > devices that are of the input class and see the individual attributes of
> > them.
>
> So I create the child device.
> And these attributes, will be class attributes or device attributes of
> the child device?
Device attributes of course :)
greg k-h
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