Date: Tue, 29 Oct 2019 10:45:22 -0700 From: Sami Tolvanen <samitolvanen@...gle.com> To: Mark Rutland <mark.rutland@....com>, Nick Desaulniers <ndesaulniers@...gle.com> Cc: Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Dave Martin <Dave.Martin@....com>, Kees Cook <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Jann Horn <jannh@...gle.com>, Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, clang-built-linux <clang-built-linux@...glegroups.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 09/17] arm64: disable function graph tracing with SCS On Fri, Oct 25, 2019 at 4:03 AM Mark Rutland <mark.rutland@....com> wrote: > I'm guessing it's difficult to always figure out the SCS slot for an > instrumented callsite unless we pass this explicitly from the ftrace > entry code, so we'd probably have to change some common infrastructure > for that. > > We have a similar issue with pointer authentication, and we're solving > that with -fpatchable-function-entry, which allows us to hook the > callsite before it does anything with the return address. IIUC we could > use the same mechanism here (and avoid introducing a third). > > Are there plans to implement -fpatchable-function-entry on the clang > side? I'm not sure if there are plans at the moment, but if this feature is needed for PAC, adding it to clang shouldn't be a problem. Nick, did you have any thoughts on this? Sami
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