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Fri, 23 Jan 2026 12:51:52 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 620CE20043; Fri, 23 Jan 2026 12:51:52 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3677E20040; Fri, 23 Jan 2026 12:51:47 +0000 (GMT) Received: from [9.78.106.105] (unknown [9.78.106.105]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 23 Jan 2026 12:51:47 +0000 (GMT) Message-ID: <7a5c0997-a5d1-4a2d-8d6a-f2697f575b65@linux.ibm.com> Date: Fri, 23 Jan 2026 18:21:46 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/6] powerpc64/bpf: Add arch_bpf_stack_walk() for BPF JIT To: adubey@linux.ibm.com, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: sachinpb@linux.ibm.com, venkat88@linux.ibm.com, andrii@kernel.org, eddyz87@gmail.com, mykolal@fb.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, christophe.leroy@csgroup.eu, naveen@kernel.org, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, memxor@gmail.com, iii@linux.ibm.com, shuah@kernel.org References: <20260122211854.5508-1-adubey@linux.ibm.com> <20260122211854.5508-5-adubey@linux.ibm.com> Content-Language: en-US From: Hari Bathini In-Reply-To: <20260122211854.5508-5-adubey@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTIzMDEwNSBTYWx0ZWRfX60X9yPmpZv+o D6AbgOMbFXnlqHhvVml2SVJY1AhRdIbp5U6y55CtLM5svVigjFEdWA/7FSvgJEZDRJjhemsQXbc vFsfs4IM40rHkhT9spuT1QyhqnmRdu3SHA4fud4obttvgrwHayLQISLwtHHzxKzrmVmGXHV/oPz 0n/MpNq4ynrP/3WEE/VYZRh6rfXoORCWt99nhZNDc+lL9ojxKLEjP8qzg1ukKhOuKLd3NVMaKVS vRsJf4cjh54tT40orB9zDLKOOgZwxIy0zFlw40Fohrewg9sD4Ka8aojWBS5GpR7zDKRBWRCg+13 H1Jv0DKNa8rW6bFeU5YdacBfVbhLK/f8nOOXBLJc16s/dhBiG6U6GUjAdy+T1tIfyvsLDsfs5IZ kQifRURL37YLzyHpUkZIW0t9mhYNk/bAWktqWccQ/bZmYbERnHEvCZV7sgdQYq0XeXmpH60+vqo PV4OQFcRE1kZjUtCQmw== X-Authority-Analysis: v=2.4 cv=BpSQAIX5 c=1 sm=1 tr=0 ts=69736eee cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=DG0_Qwyj5ITTcQcW4q8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: eGZ4HzSdcozE9GHkEshG_CPU23K_dgTB X-Proofpoint-ORIG-GUID: YWWtRqAs31Iq652K2nCfH24MOxC874Mn 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=2026-01-23_02,2026-01-22_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 clxscore=1015 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 suspectscore=0 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601230105 On 23/01/26 2:48 am, adubey@linux.ibm.com wrote: > From: Abhishek Dubey > > This function is used by bpf_throw() to unwind the stack > until frame of exception-boundary during BPF exception > handling. > > This function is necessary to support BPF exceptions on > PowerPC. > > Signed-off-by: Abhishek Dubey > --- > arch/powerpc/net/bpf_jit_comp64.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c > index 18da5a866447..c25ba1ad587a 100644 > --- a/arch/powerpc/net/bpf_jit_comp64.c > +++ b/arch/powerpc/net/bpf_jit_comp64.c > @@ -247,6 +247,34 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) > bpf_jit_build_fentry_stubs(image, ctx); > } > > +void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie) > +{ > + // callback processing always in current context > + unsigned long fp = current_stack_frame(); > + > + for (;;) { > + unsigned long *frame = (unsigned long *) fp; > + unsigned long ip; > + > + if (!validate_sp(fp, current)) > + return; > + > + ip = frame[STACK_FRAME_LR_SAVE]; > + if (!ip) > + break; > + > + /* > + * consume_fn common code expects stack pointer(sp) in third > + * argument. There is no sp in ppc64, rather pass frame > + * pointer. > + */ > + if (ip && !consume_fn(cookie, ip, fp, fp)) > + break; > + > + fp = frame[0]; > + } > +} > + > int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func) > { > unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0; Ok. Refactoring of arch_stack_walk() & arch_bpf_stack_walk() can be done as a follow-up, but keep the code as identical as possible. Use 'sp' instead of 'fp' and 'stack' instead of 'frame' to make it easy to spot the similarities. Also, a "TODO:" comment on refactoring would be good.. - Hari