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Fri, 16 Jan 2026 05:38:29 +0000 (GMT) Message-ID: <6581bdf8-9894-487d-8af9-6a2c1835f928@linux.ibm.com> Date: Fri, 16 Jan 2026 11:08:29 +0530 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/6] powerpc64/bpf: Add arch_bpf_stack_walk() for BPF JIT To: adubey , "Christophe Leroy (CS GROUP)" Cc: adubey@linux.ibm.com, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, 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, 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: <20260114114450.30405-1-adubey@linux.ibm.com> <20260114114450.30405-5-adubey@linux.ibm.com> <18dacad3-ec1d-4c91-adfb-2ee8d592de29@kernel.org> Content-Language: en-US From: Hari Bathini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=KvJAGGWN c=1 sm=1 tr=0 ts=6969cee2 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=lYxblflcVYe3kxWlPs0A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTE2MDA0MSBTYWx0ZWRfXyXZg9DW4MZUw xt9toPifdcKfFmlCwtHJtx+AwHz4RfGAX4trJbJ+BJeMm+uv8XE4BM/wouUG4wQMoTZLXS0YcEo a9bb8Ths3qxHcYRW17QtT/MR1xbhY9lYcAU47PO+7ViM96cL1kcPFyoD9gOoON0yOfysh7taTJ3 ONbN2XBx+MZcwvr5oZp71Qo1Q0VEr+5yuY85fOuBUgxn9mcYp2VBtv3kuRWmWYXOzAZBJrZMtmL 3rPvxBOouPBEaeS4TJAgvmFxbMP/jpFImxj8ix7i4u9+bBVIbYeocbgfpFH4Qzd3mwwhj1GdgO9 dEqcgC1nqfGBeBGuBbjgQmUpkF2b2IppGJYkWG4P7Hc4sQ3MRkI7m4vCuDiH8EKOGga6ZjOQHcp pRuBz+P8fH/jErkjmR7JvCYNUh2/BbrqAHvepRHO5PYGeVDhMagJNrM+yF8ABpUsVeSXuGLqDbv R9DB4zDMvNAjwQ8BPxA== X-Proofpoint-GUID: eIoYnUEObe_7qWne2iLAqzI3t2kKt8Xs X-Proofpoint-ORIG-GUID: Af97WJLKubpArLrWsKGXjjHPG2-iARZN 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=2026-01-16_01,2026-01-15_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 impostorscore=0 phishscore=0 adultscore=0 clxscore=1015 spamscore=0 bulkscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2512120000 definitions=main-2601160041 On 14/01/26 6:50 pm, adubey wrote: > On 2026-01-14 18:07, Christophe Leroy (CS GROUP) wrote: >> Le 14/01/2026 à 12:44, adubey@linux.ibm.com a écrit : >>> 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 cebf81fbd59f..ec58395f74f7 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]; >>> +    } >>> +} >>> + >> >> This fonction looks very close to arch_stack_walk(). Would it be >> possible to refactor and have a common part used by both functions, >> like ARM64 for instance ? > Yes, its inspired from arch_stack_walk(). consume_entry() have different > parameter count in both cases. > If merged, it need additional handling to identify which call_back to > invoke. > Also, we need to define arch-specific weak function > arch_bpf_stack_walk(), so renaming of arch_stack_walk is needed on merge. > Stack walker logic with "bpf" name might be confusing when used at other > places. Thoughts? Not sure what you mean by renaming of arch_stack_walk is needed on merge but refactoring does not have to change API signature or any common code for that matter.. - Hari