Date: Thu, 7 Nov 2019 08:26:30 -0800 From: Sami Tolvanen <samitolvanen@...gle.com> To: Ard Biesheuvel <ard.biesheuvel@...aro.org> Cc: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, Dave Martin <Dave.Martin@....com>, Kees Cook <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, Marc Zyngier <maz@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Jann Horn <jannh@...gle.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, clang-built-linux <clang-built-linux@...glegroups.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v5 11/14] arm64: efi: restore x18 if it was corrupted On Thu, Nov 7, 2019 at 2:51 AM Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote: > > On Wed, 6 Nov 2019 at 05:46, Miguel Ojeda > <miguel.ojeda.sandonis@...il.com> wrote: > > > > On Wed, Nov 6, 2019 at 12:56 AM Sami Tolvanen <samitolvanen@...gle.com> wrote: > > > > > > If we detect a corrupted x18 and SCS is enabled, restore the register > > > before jumping back to instrumented code. This is safe, because the > > > wrapper is called with preemption disabled and a separate shadow stack > > > is used for interrupt handling. > > > > In case you do v6: I think putting the explanation about why this is > > safe in the existing comment would be best given it is justifying a > > subtlety of the code rather than the change itself. Ard? > > > > Agreed, but only if you have to respin for other reasons. Sure, sounds good to me. I'll update the comment if other changes are needed. Sami
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