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([202.212.79.55]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23acb2f069csm145433795ad.59.2025.07.03.01.48.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jul 2025 01:48:24 -0700 (PDT) From: ChenMiao To: Linux RISCV Cc: chenmiao , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , linux-kernel@vger.kernel.org Subject: [PATCH] riscv: ftrace: Fix the logic issue in DYNAMIC_FTRACE selection Date: Thu, 3 Jul 2025 08:48:18 +0000 Message-ID: <20250703084818.394491-1-chenmiao.ku@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: chenmiao When I was reading the source code of ftrace, I learned that ftrace has two types: static and dynamic. Initially, I planned to prioritize reading the static source code, so I disabled the enable dynamic option in RISCV. [*] Kernel Function Tracer [ ] Kernel Function Graph Tracer [ ] enable/disable function tracing dynamically (NEW) However, when I tried to compile it, the build failed. ./include/linux/ftrace.h:190:16: error: implicit declaration of function =E2=80=98arch_ftrace_get_regs=E2=80=99; did you mean =E2=80=98arch= _ftrace_regs=E2=80=99? [-Wimplicit-function-declaration] 190 | return arch_ftrace_get_regs(fregs); | ^~~~~~~~~~~~~~~~~~~~ | arch_ftrace_regs After comparing it with the ARM64 architecture, I found that ARM64 automatically enables DYNAMIC_FTRACE by default once FUNCTION_TRACER is turned on, and this cannot be set to "no". Therefore, I believe the optional DYNAMIC_FTRACE setting in RISC-V has a logic flaw=E2=80=94if FUNCTION_TRACER is enabled, DYNAMIC_FTRACE should also be enabled, and vice versa. Moreover, it's clear that RISC-V lacks the necessary support to successfully compile the kernel when DYNAMIC_FTRACE is disabled. [*] Kernel Function Tracer [ ] Kernel Function Graph Tracer -*- enable/disable function tracing dynamically Signed-off-by: chenmiao --- arch/riscv/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 36061f473..f7fc8b460 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -97,6 +97,7 @@ config RISCV select CLONE_BACKWARDS select COMMON_CLK select CPU_PM if CPU_IDLE || HIBERNATION || SUSPEND + select DYNAMIC_FTRACE if FUNCTION_TRACER select EDAC_SUPPORT select FRAME_POINTER if PERF_EVENTS || (FUNCTION_TRACER && !DYNAMIC_FTRAC= E) select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if DYNAMIC_FTRACE --=20 2.45.2