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Rao" , Michael Ellerman , linux-trace-kernel@vger.kernel.org, Mark Rutland , Steven Rostedt , Masami Hiramatsu , llvm@lists.linux.dev, Maryam Moghadas Subject: [PATCH v2 3/3] powerpc64/ftrace: workaround clang recording GEP in __patchable_function_entries Date: Tue, 27 Jan 2026 14:19:26 +0530 Message-ID: <20260127084926.34497-4-hbathini@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260127084926.34497-1-hbathini@linux.ibm.com> References: <20260127084926.34497-1-hbathini@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Z4vh3XRA c=1 sm=1 tr=0 ts=69787c26 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=NEAV23lmAAAA:8 a=VnNF1IyMAAAA:8 a=uKwTeKIhWMlc50DrV6sA:9 X-Proofpoint-GUID: XjJsHACuOfQ2kOJ4PdFC9o8rVXYy91vQ X-Proofpoint-ORIG-GUID: XjJsHACuOfQ2kOJ4PdFC9o8rVXYy91vQ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTI3MDA3MSBTYWx0ZWRfXzmDc5a26G4Mc 47oy6Yrwkn8GtWf0J+FveLWe0ocrIFNm7DbFmSTvbbJzwh9npFskr+3EXi5KBuRfKJJfNEqzC6N 45wDN9mjibC+AGPsLauvdRkjaZlOzP+IGUVQPJPFpkt5xZ8WVjQCYV/B63LRO+5kQhetEtf5l80 mtE3PrsJGTfjSn98tQektnzePdRUp3YEjH750p1tL66vNTF+xHcyRHiQgzmRHh4IuAdjO0ZgW7B +Cu8ORwxShXW85NDyq2vKmtZ+tEAKOCFTotJx8EPbrcihA/0WAn9wJsMT1D1yFxVofpRLoD3RQQ P52FQ8yt+4OYYqbkgV5tDuVhyspSxNucSc4yUHwGvq6jwYt92bazzSmRDLMlh4CI/S8Sw+eBiTo 62MhSueie0BQrTVRQ5VIrAUq7l5B79iBh7+3LPkgni/I2xU8xFvbR5/kvejKZefyw79gzB316x/ Sd6cuWzwrbaOwCuegKQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.20,FMLib:17.12.100.49 definitions=2026-01-27_01,2026-01-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 phishscore=0 priorityscore=1501 bulkscore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601270071 Support for -fpatchable-function-entry on ppc64le was added in Clang with [1]. However, when no prefix NOPs are specified - as is the case with CONFIG_PPC_FTRACE_OUT_OF_LINE - the first NOP is emitted at LEP, but Clang records the Global Entry Point (GEP) unlike GCC which does record the Local Entry Point (LEP). Issue [2] has been raised to align Clang's behavior with GCC. As a temporary workaround to ensure ftrace initialization works as expected with Clang, derive the LEP using ppc_function_entry() for kernel symbols and by looking for the below module GEP sequence for module addresses, until [2] is resolved: ld r2, -8(r12) add r2, r2, r12 [1] https://github.com/llvm/llvm-project/pull/151569 [2] https://github.com/llvm/llvm-project/issues/163706 Cc: Maryam Moghadas Signed-off-by: Hari Bathini --- * No changes since v1. arch/powerpc/kernel/trace/ftrace.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 841d077e2825..1b2f293e7dcb 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -37,11 +37,29 @@ unsigned long ftrace_call_adjust(unsigned long addr) if (addr >= (unsigned long)__exittext_begin && addr < (unsigned long)__exittext_end) return 0; - if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) && - !IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) { - addr += MCOUNT_INSN_SIZE; - if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS)) + if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) { + if (!IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) { addr += MCOUNT_INSN_SIZE; + if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS)) + addr += MCOUNT_INSN_SIZE; + } else if (IS_ENABLED(CONFIG_CC_IS_CLANG) && IS_ENABLED(CONFIG_PPC64)) { + /* + * addr points to global entry point though the NOP was emitted at local + * entry point due to https://github.com/llvm/llvm-project/issues/163706 + * Handle that here with ppc_function_entry() for kernel symbols while + * adjusting module addresses in the else case, by looking for the below + * module global entry point sequence: + * ld r2, -8(r12) + * add r2, r2, r12 + */ + if (is_kernel_text(addr) || is_kernel_inittext(addr)) + addr = ppc_function_entry((void *)addr); + else if ((ppc_inst_val(ppc_inst_read((u32 *)addr)) == + PPC_RAW_LD(_R2, _R12, -8)) && + (ppc_inst_val(ppc_inst_read((u32 *)(addr+4))) == + PPC_RAW_ADD(_R2, _R2, _R12))) + addr += 8; + } } return addr; -- 2.52.0