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Wed, 24 Sep 2025 08:42:21 -0700 (PDT) Received: from krava ([2a02:8308:a00c:e200::31e0]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e2ab61eecsm36596225e9.20.2025.09.24.08.42.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Sep 2025 08:42:20 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Wed, 24 Sep 2025 17:42:18 +0200 To: Feng Yang Cc: mhiramat@kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, haoluo@google.com, john.fastabend@gmail.com, kpsingh@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, martin.lau@linux.dev, sdf@fomichev.me, song@kernel.org, yonghong.song@linux.dev Subject: Re: [BUG] Failed to obtain stack trace via bpf_get_stackid on ARM64 architecture Message-ID: References: <20250924003215.365db154e1fc79163d9d80fe@kernel.org> <20250924062536.471231-1-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=us-ascii Content-Disposition: inline In-Reply-To: <20250924062536.471231-1-yangfeng59949@163.com> On Wed, Sep 24, 2025 at 02:25:36PM +0800, Feng Yang wrote: SNIP > > Hmm, can you also dump the regs and insert pr_info() to find > > which function fails? > > > > Thanks, > > > > After testing, it was found that the stack could not be obtained because user_mode(regs) returned 1. > Referring to the arch_ftrace_fill_perf_regs function in your email > (https://lore.kernel.org/all/173518997908.391279.15910334347345106424.stgit@devnote2/), > I made the following modification: by setting the value of pstate, the stack can now be obtained successfully. > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 058a99aa44bd..f2814175e958 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -159,11 +159,13 @@ ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) > { > struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs); > > memcpy(regs->regs, afregs->regs, sizeof(afregs->regs)); > regs->sp = afregs->sp; > regs->pc = afregs->pc; > regs->regs[29] = afregs->fp; > regs->regs[30] = afregs->lr; > + regs->pstate = PSR_MODE_EL1h; > return regs; > } > However, I'm not sure if there will be any other impacts... nice, the test works for me with this change.. could you please send formal patch? I can polish and send out the test [1] thanks, jirka [1] https://github.com/kernel-patches/bpf/pull/9845/commits/11b31cd465a83b8719cb06331c8e81794cca40fa