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[37.188.197.68]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b2864cd8376sm218759666b.80.2025.09.20.15.17.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 20 Sep 2025 15:17:48 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Sun, 21 Sep 2025 00:17:42 +0200 To: Alexei Starovoitov , Will Deacon Cc: Feng Yang , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , bpf , LKML , linux-trace-kernel , Masami Hiramatsu Subject: Re: [BUG] Failed to obtain stack trace via bpf_get_stackid on ARM64 architecture Message-ID: References: <20250919071902.554223-1-yangfeng59949@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Sep 19, 2025 at 07:56:20PM -0700, Alexei Starovoitov wrote: > On Fri, Sep 19, 2025 at 12:19 AM Feng Yang wrote: > > > > When I use bpf_program__attach_kprobe_multi_opts to hook a BPF program that contains the bpf_get_stackid function on the arm64 architecture, > > I find that the stack trace cannot be obtained. The trace->nr in __bpf_get_stackid is 0, and the function returns -EFAULT. > > > > For example: > > diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi.c b/tools/testing/selftests/bpf/progs/kprobe_multi.c > > index 9e1ca8e34913..844fa88cdc4c 100644 > > --- a/tools/testing/selftests/bpf/progs/kprobe_multi.c > > +++ b/tools/testing/selftests/bpf/progs/kprobe_multi.c > > @@ -36,6 +36,15 @@ __u64 kretprobe_test6_result = 0; > > __u64 kretprobe_test7_result = 0; > > __u64 kretprobe_test8_result = 0; > > > > +typedef __u64 stack_trace_t[2]; > > + > > +struct { > > + __uint(type, BPF_MAP_TYPE_STACK_TRACE); > > + __uint(max_entries, 1024); > > + __type(key, __u32); > > + __type(value, stack_trace_t); > > +} stacks SEC(".maps"); > > + > > static void kprobe_multi_check(void *ctx, bool is_return) > > { > > if (bpf_get_current_pid_tgid() >> 32 != pid) > > @@ -100,7 +109,9 @@ int test_kretprobe(struct pt_regs *ctx) > > SEC("kprobe.multi") > > int test_kprobe_manual(struct pt_regs *ctx) > > { > > + int id = bpf_get_stackid(ctx, &stacks, 0); > > ftrace_partial_regs() supposed to work on x86 and arm64, > but since multi-kprobe is the only user... > I suspect the arm64 implementation wasn't really tested. > Or maybe there is some other issue. > > Masami, Jiri, > thoughts? hi, I did quick test for kprobe multi and I can reproduce the issue on arm64 with ci: https://github.com/kernel-patches/bpf/pull/9809 but can't really tell what's missing on arm side.. cc-ing Will thanks, jirka