Messages in this thread | | | Date | Tue, 30 Jun 2020 17:32:23 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] SPI LPC information kernel module |
| |
On Tue, Jun 30, 2020 at 05:28:32PM +0200, Greg Kroah-Hartman wrote: > On Tue, Jun 30, 2020 at 11:42:58AM -0300, Daniel Gutson wrote: > > On Tue, Jun 30, 2020 at 5:56 AM Greg Kroah-Hartman < > > gregkh@linuxfoundation.org> wrote: > > > > > On Mon, Jun 29, 2020 at 07:59:32PM -0300, Daniel Gutson wrote: > > > > This kernel module exports 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. > > > > > > > > A technical note: I check if *ppos == BUFFER_SIZE in the reading function > > > > to exit early and avoid an extra access to the HW, for example when using > > > > the 'cat' command, which causes two read operations. > > > > > > Why not use the simple_* functions which should prevent that type of > > > thing? > > > > > > > a hint please? I don't see how to do it with simple_read_from_buffer, I > > need to return in the read fop the amount of read bytes, but don't know > > how to mark EOF. Because of that, 'cat' reads again just for me to tell it > > there's nothing else to read. > > That's fine, the kernel does not tell userspace "EOF", that is up to the > libc to determine. If you read the data from the hardware once, and > keep it in your buffer, simple_read_from_buffer() will handle all of > that logic for you, please let it do that. > > > > > Signed-off-by: Daniel Gutson <daniel.gutson@eclypsium.com> > > > > --- > > > > Documentation/ABI/stable/securityfs-spi-lpc | 23 + > > > > > > Why is this going in securityfs at all? Why not just sysfs as it is a > > > CPU attribute, right? > > > > > > > Richard already discussed that, but "it" is not only (one) CPU attribute, > > are SPI chip settings and attributes coming from the firmware. > > All hardware things, please use sysfs, that is what it is designed for. > > > Please note that I wanted to submit the minimum patch, but I need to add > > more attributes. > > A patch series is great to create and send showing all of that. > > > > > diff --git a/Documentation/ABI/stable/securityfs-spi-lpc > > > b/Documentation/ABI/stable/securityfs-spi-lpc > > > > new file mode 100644 > > > > index 000000000000..22660a7fd914 > > > > --- /dev/null > > > > +++ b/Documentation/ABI/stable/securityfs-spi-lpc > > > > @@ -0,0 +1,23 @@ > > > > +What: /sys/kernel/security/firmware/bioswe > > > > +Date: June 2020 > > > > +KernelVersion: 5.8.0 > > > > +Contact: daniel.gutson@eclypsium.com > > > > +Description: If the system firmware set BIOS Write Enable. > > > > + 0: writes disabled, 1: writes enabled. > > > > > > THis is very x86-specific, what about ARM/MIPS/anything else? Perhaps a > > > cpu/arch-specific thing instead? > > > > > > > We debated this but didn't find a better match, since cpu/arch-specific > > seemed too core to put informational drivers. > > Do you have a suggestion? > > Make it explicitly hardware specific in your userspace location. > Otherwise you just defined this for all hardware types, with what you > used above, and I do not think you wanted to do that. > > > > Again, which makes it seem like securityfs is not the thing for this, as > > > it describes the hardware, not a security model which is what securityfs > > > has been for in the past, right? > > > > > > > I prefer to leave this to the other discussion with Richard. It's fine for > > me too to use sysfs. > > FWIW, the driver provides information related to firmware security. > > It provides information on what is going on with the firmware, it's up > to userspace to know/determine/care if that means anything with regards > to "security" or not :)
Also, you seem to have missed /sys/firmware/ on your system :)
| |