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Date: Tue, 8 Aug 2017 19:57:08 +0200
From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Florian Fainelli <f.fainelli@gmail.com>,
        Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org,
        labbott@redhat.com, Andrew Morton <akpm@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Kees Cook <keescook@chromium.org>, Ingo Molnar <mingo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Nicholas Piggin <npiggin@gmail.com>, Olof Johansson <olof@lixom.net>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Thomas Gleixner <tglx@linutronix.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Bart Van Assche <bart.vanassche@sandisk.com>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Jiri Pirko <jiri@mellanox.com>,
        Jeff Layton <jlayton@redhat.com>
Subject: Re: [PATCH] lib: Add test module for CONFIG_DEBUG_VIRTUAL
Message-ID: <20170808175708.GR27873@wotan.suse.de>
References: <20170808164035.26725-1-f.fainelli@gmail.com>
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On Tue, Aug 08, 2017 at 09:40:26AM -0700, Florian Fainelli wrote:
> Add a test module that allows testing that CONFIG_DEBUG_VIRTUAL works
> correctly, at least that it can catch invalid calls to virt_to_phys()
> against the non-linear kernel virtual address map.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  lib/Kconfig.debug        | 11 +++++++++++
>  lib/Makefile             |  1 +
>  lib/test_debug_virtual.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 61 insertions(+)
>  create mode 100644 lib/test_debug_virtual.c
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 98fe715522e8..d16bbc12429f 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1902,6 +1902,17 @@ config TEST_KMOD
>  
>  	  If unsure, say N.
>  
> +config TEST_DEBUG_VIRTUAL
> +	tristate "Test CONFIG_DEBUG_VIRTUAL feature"
> +	depends on DEBUG_VIRTUAL
> +	help
> +	  Test the kernel's ability to detect incorrect calls to
> +	  virt_to_phys() done against the non-linear part of the
> +	  kernel's virtual address map.
> +
> +	  If unsure, say N.
> +
> +
>  source "samples/Kconfig"
>  
>  source "lib/Kconfig.kgdb"
> diff --git a/lib/Makefile b/lib/Makefile
> index 40c18372b301..469ce5e24e4f 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -62,6 +62,7 @@ obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
>  obj-$(CONFIG_TEST_UUID) += test_uuid.o
>  obj-$(CONFIG_TEST_PARMAN) += test_parman.o
>  obj-$(CONFIG_TEST_KMOD) += test_kmod.o
> +obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
>  
>  ifeq ($(CONFIG_DEBUG_KOBJECT),y)
>  CFLAGS_kobject.o += -DDEBUG
> diff --git a/lib/test_debug_virtual.c b/lib/test_debug_virtual.c
> new file mode 100644
> index 000000000000..b9cdeecc19dc
> --- /dev/null
> +++ b/lib/test_debug_virtual.c
> @@ -0,0 +1,49 @@
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/export.h>
> +#include <linux/mm.h>
> +#include <linux/vmalloc.h>
> +#include <linux/slab.h>
> +#include <linux/sizes.h>
> +
> +#include <asm/page.h>
> +#ifdef CONFIG_MIPS
> +#include <asm/bootinfo.h>
> +#endif
> +
> +struct foo {
> +	unsigned int bar;
> +};
> +
> +struct foo *foo;
> +
> +static int __init test_debug_virtual_init(void)
> +{
> +	phys_addr_t pa;
> +	void *va;
> +
> +	va = (void *)VMALLOC_START;
> +	pa = virt_to_phys(va);
> +
> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);
> +
> +	foo = kzalloc(sizeof(*foo), GFP_KERNEL);
> +	if (!foo)
> +		return -ENOMEM;
> +
> +	pa = virt_to_phys(foo);
> +	va = foo;
> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);

Should there be a tests here of some sort? When should this fail, why?
There is no docs on this self test, could one be added?

  Luis

> +
> +	return 0;
> +}
> +module_init(test_debug_virtual_init);
> +
> +static void __exit test_debug_virtual_exit(void)
> +{
> +	kfree(foo);
> +}
> +module_exit(test_debug_virtual_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Test module for CONFIG_DEBUG_VIRTUAL");
> -- 
> 2.9.3
> 
> 

-- 
Luis Rodriguez, SUSE LINUX GmbH
Maxfeldstrasse 5; D-90409 Nuernberg