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Message-ID: <718f8021-f423-2fc8-da70-300b19942ea8@linux.microsoft.com> Date: Fri, 22 Jan 2021 15:16:28 -0600 From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com> To: Mark Brown <broonie@...nel.org>, Josh Poimboeuf <jpoimboe@...hat.com> Cc: Mark Rutland <mark.rutland@....com>, Michal Marek <michal.lkml@...kovi.net>, Julien Thierry <jthierry@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Catalin Marinas <catalin.marinas@....com>, Masahiro Yamada <masahiroy@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-efi <linux-efi@...r.kernel.org>, linux-hardening@...r.kernel.org, live-patching@...r.kernel.org, Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Kees Cook <keescook@...omium.org> Subject: Re: [RFC PATCH 00/17] objtool: add base support for arm64 On 1/22/21 11:43 AM, Mark Brown wrote: > On Thu, Jan 21, 2021 at 12:54:52PM -0600, Josh Poimboeuf wrote: > >> 2) The shadow stack idea sounds promising -- how hard would it be to >> make a prototype reliable unwinder? > > In theory it doesn't look too hard and I can't see a particular reason > not to try doing this - there's going to be edge cases but hopefully for > reliable stack trace they're all in areas where we would be happy to > just decide the stack isn't reliable anyway, things like nesting which > allocates separate shadow stacks for each nested level for example. > I'll take a look. > I am a new comer to this discussion and I am learning. Just have some questions. Pardon me if they are obvious or if they have already been asked and answered. Doesn't Clang already have support for a shadow stack implementation for ARM64? We could take a look at how Clang does it. Will there not be a significant performance hit? May be, some of it can be mitigated by using a parallel shadow stack rather than a compact one. Are there any longjmp style situations in the kernel where the stack is unwound by several frames? In these cases, the shadow stack must be unwound accordingly. Madhavan > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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