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  • David Howells's avatar
    Annotate hardware config module parameters in drivers/clocksource/ · cc9c6175
    David Howells authored
    
    
    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: default avatarAlan Cox <gnomes@lxorguk.ukuu.org.uk>
    Signed-off-by: default avatarDavid 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
    cc9c6175