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Tue, 9 Sep 2025 04:56:23 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2E36920043; Tue, 9 Sep 2025 04:56:23 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 54EA320040; Tue, 9 Sep 2025 04:56:20 +0000 (GMT) Received: from localhost.localdomain (unknown [9.109.199.159]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 9 Sep 2025 04:56:20 +0000 (GMT) From: Aditya Bodkhe To: linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, rostedt@goodmis.org, mhiramat@kernel.org, mark.rutland@arm.com, Aditya Bodkhe , Venkat Rao Bagalkote Subject: [PATCH v3 1/2] powerpc/ftrace: support CONFIG_FUNCTION_GRAPH_RETVAL Date: Tue, 9 Sep 2025 10:26:14 +0530 Message-ID: <20250909045615.50251-1-adityab1@linux.ibm.com> X-Mailer: git-send-email 2.50.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA2MDE5NSBTYWx0ZWRfX93tzDl9Pzve8 bxnJW8i7jTlwnuqk/O08g+lcuafogu0UCvf4xHINV4zO4prd2IghtkFyOMk1Hmnm4mEEROIDfFD kxM3whABviUsSlCXoJ/yPP6hplT0cY50Sq1bYUAbTi/T6hrJN5e+egB7aPL4OHPvfijYHZrvE1r UCUbqn7B5jvKW6ZDN7obSz5rtmRFHfqjrv5dqkrtTMZYjqhqNcO9vCT8kEji9K+ByQbx0x5WH8s UZSSYfJxoOf4vYZy+uT6DkQPakPNvAgox4l2i+ylZJqH2lVg9ucMowRqqpRwKLTxajQekBtLM4M DaqeY36heu6t4wxd5G7sHkCUgLxGdmeveuhaijFPdHIyAiobs3Q/9gq5PdYmax5pAwQhU1JMQFY nbPssjIt X-Proofpoint-ORIG-GUID: H3uRPYvDRMYUxZqCJCyovK7UBrvoMMLz X-Proofpoint-GUID: LmQuJcJQL1vpTCKNXmkETHON3xB_lgXM X-Authority-Analysis: v=2.4 cv=StCQ6OO0 c=1 sm=1 tr=0 ts=68bfb37c cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=yJojWOMRYYMA:10 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=1UX6Do5GAAAA:8 a=qcD_9p-UOgwsSRV2Pq8A:9 a=Et2XPkok5AAZYJIKzHr1:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-08_06,2025-09-08_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 malwarescore=0 bulkscore=0 clxscore=1015 adultscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509060195 commit a1be9ccc57f0 ("function_graph: Support recording and printing the return value of function") introduced support for function graph return value tracing. Additionally, commit a3ed4157b7d8 ("fgraph: Replace fgraph_ret_regs with ftrace_regs") further refactored and optimized the implementation, making `struct fgraph_ret_regs` unnecessary. This patch enables the above modifications for powerpc all, ensuring that function graph return value tracing is available on this architecture. In this patch we have redefined two functions: - 'ftrace_regs_get_return_value()' - the existing implementation on ppc returns -ve of return value based on some conditions not relevant to our patch. - 'ftrace_regs_get_frame_pointer()' - always returns 0 in current code . We also allocate stack space to equivalent of 'SWITCH_FRAME_SIZE', allowing us to directly use predefined offsets like 'GPR3' and 'GPR4' this keeps code clean and consistent with already defined offsets . After this patch, v6.14+ kernel can also be built with FPROBE on powerpc but there are a few other build and runtime dependencies for FPROBE to work properly. The next patch addresses them. Tested-by: Venkat Rao Bagalkote Reviewed-by: Christophe Leroy Signed-off-by: Aditya Bodkhe --- Changelog: v2 -> v3: - Rebase on Linux 6.17-rc4 v2:https://lore.kernel.org/all/20250722085648.1640-1-adityab1@linux.ibm.com/ v1 -> v2: - Added explanation for redefining ftrace_regs_get_return_value() and ftrace_regs_get_frame_pointer() - Explained why stack space equivalent to 'SWITCH_FRAME_SIZE' is allocated. v1:https://lore.kernel.org/all/20250528134820.74121-1-adityab1@linux.ibm.com/ --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/ftrace.h | 15 +++++++++ arch/powerpc/kernel/trace/ftrace_entry.S | 42 ++++++++++++++---------- 3 files changed, 41 insertions(+), 17 deletions(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 93402a1d9c9f..451d0e140051 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -246,6 +246,7 @@ config PPC select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_FUNCTION_DESCRIPTORS if PPC64_ELF_ABI_V1 select HAVE_FUNCTION_ERROR_INJECTION + select HAVE_FUNCTION_GRAPH_FREGS select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !COMPILE_TEST && (PPC64 || (PPC32 && CC_IS_GCC)) select HAVE_GCC_PLUGINS if GCC_VERSION >= 50200 # plugin support on gcc <= 5.1 is buggy on PPC diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h index 82da7c7a1d12..6ffc9c9cf4e3 100644 --- a/arch/powerpc/include/asm/ftrace.h +++ b/arch/powerpc/include/asm/ftrace.h @@ -50,6 +50,21 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs * asm volatile("mfmsr %0" : "=r" ((_regs)->msr)); \ } while (0) +#undef ftrace_regs_get_return_value +static __always_inline unsigned long +ftrace_regs_get_return_value(const struct ftrace_regs *fregs) +{ + return arch_ftrace_regs(fregs)->regs.gpr[3]; +} +#define ftrace_regs_get_return_value ftrace_regs_get_return_value + +#undef ftrace_regs_get_frame_pointer +static __always_inline unsigned long +ftrace_regs_get_frame_pointer(const struct ftrace_regs *fregs) +{ + return arch_ftrace_regs(fregs)->regs.gpr[1]; +} + static __always_inline void ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, unsigned long ip) diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S index 3565c67fc638..6599fe3c6234 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -409,23 +409,31 @@ EXPORT_SYMBOL(_mcount) _GLOBAL(return_to_handler) /* need to save return values */ #ifdef CONFIG_PPC64 - std r4, -32(r1) - std r3, -24(r1) + stdu r1, -SWITCH_FRAME_SIZE(r1) + std r4, GPR4(r1) + std r3, GPR3(r1) + /* Save previous stack pointer (r1) */ + addi r3, r1, SWITCH_FRAME_SIZE + std r3, GPR1(r1) /* save TOC */ - std r2, -16(r1) - std r31, -8(r1) + std r2, 24(r1) + std r31, 32(r1) mr r31, r1 - stdu r1, -112(r1) - + /* pass ftrace_regs/pt_regs to ftrace_return_to_handler */ + addi r3, r1, STACK_INT_FRAME_REGS /* * We might be called from a module. * Switch to our TOC to run inside the core kernel. */ LOAD_PACA_TOC() #else - stwu r1, -16(r1) - stw r3, 8(r1) - stw r4, 12(r1) + stwu r1, -SWITCH_FRAME_SIZE(r1) + stw r4, GPR4(r1) + stw r3, GPR3(r1) + addi r3, r1, SWITCH_FRAME_SIZE + stw r3, GPR1(r1) + /* pass ftrace_regs/pt_regs to ftrace_return_to_handler */ + addi r3, r1, STACK_INT_FRAME_REGS #endif bl ftrace_return_to_handler @@ -435,15 +443,15 @@ _GLOBAL(return_to_handler) mtlr r3 #ifdef CONFIG_PPC64 - ld r1, 0(r1) - ld r4, -32(r1) - ld r3, -24(r1) - ld r2, -16(r1) - ld r31, -8(r1) + ld r4, GPR4(r1) + ld r3, GPR3(r1) + ld r2, 24(r1) + ld r31, 32(r1) + ld r1, 0(r1) #else - lwz r3, 8(r1) - lwz r4, 12(r1) - addi r1, r1, 16 + lwz r3, GPR3(r1) + lwz r4, GPR4(r1) + addi r1, r1, SWITCH_FRAME_SIZE #endif /* Jump back to real return address */ -- 2.51.0