From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17161233710; Mon, 4 Aug 2025 07:10:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.156.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754291444; cv=none; b=eRpikBOwnyWzwyg1A+rpTvBSnstq/UY6MggHo5CtXMarN985ugk2gJhAx4J0oJRMYO5OtDreyolWh5oXI3nMKeyX7cCexv4i/SIwcm8SMUxpR0Rt0RwFDtfZV1rNrAkvVIOX9B45t2kTK4dObhkTk1/PfNqeTWpSl/J4WBqPyEM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754291444; c=relaxed/simple; bh=HrsOW22baBZHUqSVf1topf9Fih/6rEOGbnxwilBnzAU=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=LIoisLcXaIIbIr2aeYJh3WGvAEzLuzhS5GPXzce4hI5TvF838156z/GjBVcxeQ7tI/qNEJFmA6th2c46DEDf57RVDoAG/gHNgYGioqlQanAis/oTsrtCqieQpoG/xP6RfrkAXrsP24ZSHM2BnaNCtQVgtx9aDPsalEliBF+2Xa8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=Nr7dHrb3; arc=none smtp.client-ip=148.163.156.1 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="Nr7dHrb3" Received: from pps.filterd (m0356517.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 573LxwWM022899; Mon, 4 Aug 2025 07:10:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=ramS1p jeVqGHWF62ogc3ChKuur9gxv5FESmY3rJXJ3k=; b=Nr7dHrb3gQre9O1N3YGGHV zc4A9ZYxxm1Y+FreEygz/5Ey97+A9fxsffKBn9xzPLs/WeeQcKwCpk98gO7WgXCI BaS6Z0qGvQuzmQHqylVJE8qDLk+jUo9L9NmLTFDIlSHzMv6h0fdzWTGD2X48Cfd/ p1vByYhP1Bi/d6uhpNY78vjef/n0IoNrGjP4O5TOgHVHyXb4imXVpAAzYuDdnXDH 1NFnreUg47YFxS+thvHXu95rpFoULeuHE6gihQhy/grxwRo7yU25Z2AlJrx4TTTM mlKf5d7S029jfDqItIv4gffH9/cZlLmPC6Y5MOChEpquOK5VnbKKk+I5jhzw9KFw == Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 48a4a9ud6f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 04 Aug 2025 07:10:23 +0000 (GMT) Received: from m0356517.ppops.net (m0356517.ppops.net [127.0.0.1]) by pps.reinject (8.18.1.12/8.18.0.8) with ESMTP id 5747AMxE016695; Mon, 4 Aug 2025 07:10:22 GMT Received: from ppma21.wdc07v.mail.ibm.com (5b.69.3da9.ip4.static.sl-reverse.com [169.61.105.91]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 48a4a9ud66-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 04 Aug 2025 07:10:22 +0000 (GMT) Received: from pps.filterd (ppma21.wdc07v.mail.ibm.com [127.0.0.1]) by ppma21.wdc07v.mail.ibm.com (8.18.1.2/8.18.1.2) with ESMTP id 5746JtsP009594; Mon, 4 Aug 2025 07:10:21 GMT Received: from smtprelay05.wdc07v.mail.ibm.com ([172.16.1.72]) by ppma21.wdc07v.mail.ibm.com (PPS) with ESMTPS id 489x0nvj0e-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 04 Aug 2025 07:10:21 +0000 Received: from smtpav05.dal12v.mail.ibm.com (smtpav05.dal12v.mail.ibm.com [10.241.53.104]) by smtprelay05.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 5747AJMp10420968 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 4 Aug 2025 07:10:20 GMT Received: from smtpav05.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B433758068; Mon, 4 Aug 2025 07:10:19 +0000 (GMT) Received: from smtpav05.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4282F5806A; Mon, 4 Aug 2025 07:10:16 +0000 (GMT) Received: from smtpclient.apple (unknown [9.61.249.29]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTPS; Mon, 4 Aug 2025 07:10:15 +0000 (GMT) Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3774.600.62\)) Subject: Re: [PATCH v2 1/2] powerpc/ftrace: support CONFIG_FUNCTION_GRAPH_RETVAL From: Venkat In-Reply-To: <20250722085648.1640-1-adityab1@linux.ibm.com> Date: Mon, 4 Aug 2025 12:40:03 +0530 Cc: linuxppc-dev@lists.ozlabs.org, LKML , linux-trace-kernel@vger.kernel.org, maddy@linux.ibm.com, Michael Ellerman , npiggin@gmail.com, christophe.leroy@csgroup.eu, rostedt@goodmis.org, mhiramat@kernel.org, mark.rutland@arm.com Content-Transfer-Encoding: quoted-printable Message-Id: <401DC39A-0A74-467F-AE01-68B164BEDCF6@linux.ibm.com> References: <20250722085648.1640-1-adityab1@linux.ibm.com> To: Aditya Bodkhe X-Mailer: Apple Mail (2.3774.600.62) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: vmIqo5qkpwOUPwTHBdryw-kouyk2yfb0 X-Authority-Analysis: v=2.4 cv=dNummPZb c=1 sm=1 tr=0 ts=68905cdf cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=VnNF1IyMAAAA:8 a=dNnesIPfpvp5sUh9fRYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: rY8OKm7Bh0NIlp7qqJINZ-QryM85_CqE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODA0MDAzNSBTYWx0ZWRfXzixPKAmFRwjV gpwzjRTIinCjcYAi4Gh6f/tcBFbuKoL9/DKL1WntrFLh23MVdBFEFuHIw56qvaHKjkLwqdH2aaE NpZ/jvAV3htbnY/a1iaiFkSdof4jWzy2hnEPJ0w6lmrLOolV4rNVGEkJhearoiO/k81HDZFXFrx RuXpkTiEX3EItA+i4oPRH4bAa4pHO3hvUN7r4U+AyHbHXxZsM1eDrCB+LaeRiq8tvPMHGR6rEUS +4RhTE3x09j0pYpQJZcC4G5EMfqYttuiR9/C928XQAa6X8L0JEVlvGOAIREb13+i9QTYQyALyqu yd/hwZYm2k4aelHt6vSOM8IIpm/4TA+gYfY/+fEc1iP1HZI0/avDQXTHtEulhwmYs1kKpvvcJ1M TFuVpQhLiFDSyHjmZkI7xmlMIs9DiTidDaq7/20CU7VS+4zB+I/q/BgdHrwdQoxv3DsBT105 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-04_03,2025-08-04_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 mlxscore=0 clxscore=1015 mlxlogscore=999 malwarescore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 spamscore=0 suspectscore=0 impostorscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2508040035 > On 22 Jul 2025, at 2:26=E2=80=AFPM, Aditya Bodkhe = wrote: >=20 > commit a1be9ccc57f0 ("function_graph: Support recording and printing = the > return value of function") introduced support for function graph = return > value tracing. >=20 > Additionally, commit a3ed4157b7d8 ("fgraph: Replace fgraph_ret_regs = with > ftrace_regs") further refactored and optimized the implementation, > making `struct fgraph_ret_regs` unnecessary. >=20 > This patch enables the above modifications for powerpc all, ensuring = that > function graph return value tracing is available on this architecture. >=20 > 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 = . >=20 > 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 . >=20 > 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. >=20 > Signed-off-by: Aditya Bodkhe > --- >=20 > Changelog: > v1 -> v2: > - Added explanation for redefining ftrace_regs_get_return_value()=20 > and ftrace_regs_get_frame_pointer() > - Explained why stack space equivalent to 'SWITCH_FRAME_SIZE' is = allocated. >=20 > 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(-) >=20 > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index c3e0cc83f120..9163521bc4b9 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -250,6 +250,7 @@ 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 >=3D 50200 # plugin support = on gcc <=3D 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" : "=3Dr" ((_regs)->msr)); \ > } while (0) >=20 > +#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..3da14d8271d9 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 >=20 >=20 > bl ftrace_return_to_handler > @@ -435,15 +443,15 @@ _GLOBAL(return_to_handler) > mtlr r3 >=20 > #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 >=20 > /* Jump back to real return address */ > --=20 > 2.50.0 >=20 Tested this patch by applying on top of mainline. Build and boot is = successful. Also ran ftrace selftest, intended test passed and no new = failures/errors introduced with this patch. Hence, Tested-by: Venkat Rao Bagalkote Regards, Venkat.