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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 3/3] powerpc64/ftrace: workaround clang recording GEP in __patchable_function_entries Date: Sun, 9 Nov 2025 02:34:05 +0530 Message-ID: <20251108210405.2375472-4-hbathini@linux.ibm.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251108210405.2375472-1-hbathini@linux.ibm.com> References: <20251108210405.2375472-1-hbathini@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTA4MDAyMiBTYWx0ZWRfX4r5TgbFscT+s AhQPdF0ER1WQcySkAABHIDfD/bfdCqRuX0/IlfsgvljSo51LjqxYhi2U8/TW11rMTTwjDR+sxp1 dgIqKARBZWNGcwt9bUKPpksYCKabQyBb8d34cdLQ79lN7/sLowzdkjFu2Dk6RZat46ivbpZmmBP SUWIdYwrSuu31UzyefMNk23xOjzKrwlbyMwktTUllwDgUzd6v38eovIYIOUqhrCtu/gDewXf3so a+10mci9ez7KQlK5mdIbU6oZdVmiVSZdSlrR5kJ/fQn8lVPZZ5udAnMSJy+dUwIiGkxLGCE+EgD td5F8Tq4iZfvVAvwlA25ia6zwvqk4IkFvLZaSw5/Zfkxy8t1qtzwjvlKbstlSeDw6pStem+xOji wvqv20BEdyBKXJ3HNpLRUo4e7LMTEA== X-Authority-Analysis: v=2.4 cv=ZK3aWH7b c=1 sm=1 tr=0 ts=690fb056 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=NEAV23lmAAAA:8 a=VnNF1IyMAAAA:8 a=uKwTeKIhWMlc50DrV6sA:9 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-ORIG-GUID: C-Gva_oMsG4iLO6A8gtCmy71qa3B5KjZ X-Proofpoint-GUID: C-Gva_oMsG4iLO6A8gtCmy71qa3B5KjZ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-08_06,2025-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 phishscore=0 impostorscore=0 spamscore=0 bulkscore=0 adultscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511080022 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 --- 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; -- 2.51.1