Messages in this thread | | | Date | Mon, 7 Nov 2022 15:19:30 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v2] mte: Initialize tag storage to KASAN_TAG_INVALID |
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On Wed, Sep 07, 2022 at 12:00:15PM +0100, Vincenzo Frascino wrote: > When the kernel is entered on aarch64, the MTE allocation tags are in an > UNKNOWN state. > > With MTE enabled, the tags are initialized: > - When a page is allocated and the user maps it with PROT_MTE. > - On allocation, with in-kernel MTE enabled (HW_TAGS KASAN). > > If the tag pool is zeroed by the hardware at reset, it makes it > difficult to track potential places where the initialization of the > tags was missed. > > This can be observed under QEMU for aarch64, which initializes the MTE > allocation tags to zero. > > Initialize to tag storage to KASAN_TAG_INVALID to catch potential > places where the initialization of the tags was missed. > > This is done introducing a new kernel command line parameter > "mte.tags_init" that enables the debug option. > > Note: The proposed solution should be considered a debug option because > it might have performance impact on large machines at boot. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > --- > arch/arm64/kernel/mte.c | 47 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 47 insertions(+)
I don't really see the point in this change -- who is going to use this option?
Will
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