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Thu, 03 Feb 2022 08:11:41 -0800 (PST) X-Gm-Message-State: AOAM532laLb6xdoi3WaK5BWjfTralPutEks9MGYxKNEEJdrV50bnIpOq BBXO8DE1PjAKK8+pnahcwQo8e95zflJB6BAKZVU= X-Google-Smtp-Source: ABdhPJzmd2eYQdqcuncOoRY58v/fFL3ryQLEF8m7HFha4wkg/OyyX2ullaVirt+vEgoTKi8aASPOyvKRJhsQckkH780= X-Received: by 2002:a05:6000:1c9:: with SMTP id t9mr30432251wrx.550.1643904699727; Thu, 03 Feb 2022 08:11:39 -0800 (PST) MIME-Version: 1.0 References: <20220203082204.1176734-1-ardb@kernel.org> <20220203082204.1176734-9-ardb@kernel.org> In-Reply-To: From: Ard Biesheuvel Date: Thu, 3 Feb 2022 17:11:28 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 08/13] ARM: ftrace: enable the graph tracer with the EABI unwinder To: Nathan Chancellor Cc: Arnd Bergmann , Russell King - ARM Linux , Linux ARM , Steven Rostedt , Sudeep Holla , Cristian Marussi , Nick Desaulniers , Linus Walleij , Masami Hiramatsu X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220203_081145_856602_0B987ED4 X-CRM114-Status: GOOD ( 30.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 3 Feb 2022 at 17:09, Nathan Chancellor wrote: > > On Thu, Feb 03, 2022 at 10:16:57AM +0100, Arnd Bergmann wrote: > > On Thu, Feb 3, 2022 at 9:21 AM Ard Biesheuvel wrote: > > > > > > Enable the function graph tracer in combination with the EABI unwinder, > > > so that Thumb2 builds or Clang ARM builds can make use of it. > > > > > > This involves using the unwinder to locate the return address of an > > > instrumented function on the stack, so that it can be overridden and > > > made to refer to the ftrace handling routines that need to be called at > > > function return. > > > > > > Given that for these builds, it is not guaranteed that the value of the > > > link register is stored on the stack, fall back to the stack slot that > > > will be used by the ftrace exit code to restore LR in the instrumented > > > function's execution context. > > > > > > Signed-off-by: Ard Biesheuvel > > > Reviewed-by: Steven Rostedt (Google) > > > > > diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug > > > index 07055a503022..cc7523f44be4 100644 > > > --- a/arch/arm/Kconfig.debug > > > +++ b/arch/arm/Kconfig.debug > > > @@ -65,7 +65,7 @@ config UNWINDER_FRAME_POINTER > > > > > > config UNWINDER_ARM > > > bool "ARM EABI stack unwinder" > > > - depends on AEABI && !FUNCTION_GRAPH_TRACER > > > + depends on AEABI > > > # https://github.com/ClangBuiltLinux/linux/issues/732 > > > depends on !LD_IS_LLD || LLD_VERSION >= 110000 > > > select ARM_UNWIND > > > > What are the remaining tradeoffs between the two unwinders > > on EABI kernels? Since we require llvm-11 as the minimum > > toolchain now, we can probably drop the LLD_VERSION > > check here as well, so UNWINDER_ARM should finally work > > for any EABI kernel. > > For what it's worth, that check was eliminated in the same series as > bumping the minimum version: e1ab4182ca11 ("Revert "ARM: 9070/1: Make > UNWINDER_ARM depend on ld.bfd or ld.lld 11.0.0+"") > OK. This series is currently based on Russell's tree which does not include v5.17-rc1 yet. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel