Re: [PATCH v21 2/2] arm64: expose FAR_EL1 tag bits in siginfo
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From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-01-13 15:47:48
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On Wed, Jan 13, 2021 at 03:51:42PM +0100, Andrey Konovalov wrote:
On Fri, Nov 20, 2020 at 9:34 PM Peter Collingbourne [off-list ref] wrote:quoted
The kernel currently clears the tag bits (i.e. bits 56-63) in the fault address exposed via siginfo.si_addr and sigcontext.fault_address. However, the tag bits may be needed by tools in order to accurately diagnose memory errors, such as HWASan [1] or future tools based on the Memory Tagging Extension (MTE). Expose these bits via the arch_untagged_si_addr mechanism, so that they are only exposed to signal handlers with the SA_EXPOSE_TAGBITS flag set. [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html Signed-off-by: Peter Collingbourne <redacted> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446
[...]
Not sure if it's expected, but this patch changes the way in-kernel MTE faults are reported. The address of any in-kernel fault now gets its top byte zeroed out, even though it was set to 0xf. However I guess it's related to the fact that MTE always uses pointer tags in 0x0_ format.
Is this for _any_ faults or just MTE tag check faults? I tried the former and seems fine. Do you have a concrete example to make sure I understand the issue? -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel