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[v2,11/57,X] Annotate hardware config module parameters in drivers/clocksource/

Message ID 20200619165010.645925-12-seth.forshee@canonical.com
State New
Headers show
Series Lockdown updates | expand

Commit Message

Seth Forshee June 19, 2020, 4:49 p.m. UTC
From: David Howells <dhowells@redhat.com>

BugLink: https://bugs.launchpad.net/bugs/1884159

When the kernel is running in secure boot mode, we lock down the kernel to
prevent userspace from modifying the running kernel image.  Whilst this
includes prohibiting access to things like /dev/mem, it must also prevent
access by means of configuring driver modules in such a way as to cause a
device to access or modify the kernel image.

To this end, annotate module_param* statements that refer to hardware
configuration and indicate for future reference what type of parameter they
specify.  The parameter parser in the core sees this information and can
skip such parameters with an error message if the kernel is locked down.
The module initialisation then runs as normal, but just sees whatever the
default values for those parameters is.

Note that we do still need to do the module initialisation because some
drivers have viable defaults set in case parameters aren't specified and
some drivers support automatic configuration (e.g. PNP or PCI) in addition
to manually coded parameters.

This patch annotates drivers in drivers/clocksource/.

[Note: With regard to cs5535-clockevt.c, Thomas Gleixner asked whether the
 timer_irq parameter is required for the driver to work on anything other than
 arbitrary hardware which has it mapped to 0.  Jens Rottmann replied that the
 parameter defaults to 0, which means:

	1. autodetect (=keep IRQ BIOS has set up)
	2. if that fails use CONFIG_CS5535_MFGPT_DEFAULT_IRQ
	   (see drivers/misc/cs5535-mfgpt.c: cs5535_mfgpt_set_irq())

 Jens further noted that there may not be any systems that have CS5535/36
 devices that support EFI and secure boot.]

Suggested-by: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Daniel Lezcano <daniel.lezcano@linaro.org>
cc: Thomas Gleixner <tglx@linutronix.de>
cc: Jens Rottmann <Jens.Rottmann@ADLINKtech.com>
cc: linux-kernel@vger.kernel.org
(cherry picked from commit cc9c617557cd0442294138188ac8611659768a10)
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
 drivers/clocksource/cs5535-clockevt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series


diff --git a/drivers/clocksource/cs5535-clockevt.c b/drivers/clocksource/cs5535-clockevt.c
index e1d7373e63e0..1de8cac99a0e 100644
--- a/drivers/clocksource/cs5535-clockevt.c
+++ b/drivers/clocksource/cs5535-clockevt.c
@@ -22,7 +22,7 @@ 
 #define DRV_NAME "cs5535-clockevt"
 static int timer_irq;
-module_param_named(irq, timer_irq, int, 0644);
+module_param_hw_named(irq, timer_irq, int, irq, 0644);
 MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks.");