From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) (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 9AB91399A54; Wed, 7 Jan 2026 15:52:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767801198; cv=none; b=CI+D9Ba3r+x34eKskEKDcGZd8fqsHSGD1+uA+Va5hVVUqVlo52roWQH3scIJjcRs0yaY0M8n9jbo4OoG7e/URC9BMddY/eMP4fxNT3VxUzYIpAwXALdMZSGSYFEs7/LEJZQC9htItatYZJRaiN2Kqv0UI0QfdNdpYP92/62Hm20= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767801198; c=relaxed/simple; bh=Tt2AtrMSewMzULqLE1VhdgEpismAuO+TcOXUIcITff0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=qfeT2CtMNjEoZM/Wkw3WUTkqP8JLxGrUNnotgKo+gzsLSWhr7NdT+/9dgWa/f3eEnFytUhh6SMAFD2LGtBHlLLET5plt3xMb+q1xy7RJfV7/I/7SNAmymi83M3MiyeAePA9JgTB2PXD/dV0lwwce3MkJ8hhv9tszQCAuRKThu+w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 5F3D8140441; Wed, 7 Jan 2026 15:52:52 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf05.hostedemail.com (Postfix) with ESMTPA id A363F20019; Wed, 7 Jan 2026 15:52:49 +0000 (UTC) Date: Wed, 7 Jan 2026 10:53:16 -0500 From: Steven Rostedt To: Jiri Olsa Cc: "Masami Hiramatsu (Google)" , Will Deacon , Peter Zijlstra , bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, Yonghong Song , Song Liu , Andrii Nakryiko , Mark Rutland , Mahe Tardy Subject: Re: [BUG/RFC 1/2] arm64/ftrace,bpf: Fix partial regs after bpf_prog_run Message-ID: <20260107105316.2b70a308@gandalf.local.home> In-Reply-To: References: <20251105125924.365205-1-jolsa@kernel.org> <20260104223415.0a31f423c861c0b651de966b@kernel.org> <20260105162220.6ba5129a@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: d78ujc6wjwrs4np7zp9k9df8wcrg8spq X-Rspamd-Server: rspamout02 X-Rspamd-Queue-Id: A363F20019 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19y53fBfBOjUg/Mlrbjm27/1NrjOMyHETA= X-HE-Tag: 1767801169-452600 X-HE-Meta: U2FsdGVkX1+hldrlx96Y7+EcduT/AqiVoSH8QmMOWvVLBMrUv1IVv6IO41fhZ4RVAeaEuFfgunBNpxHvG1O1TGLPQ3JiX1a9nfHStvtPjZ+qC6M8Sj4BCMDlqjH//NEprQR2dFXHSO2Q85qKa8ZWd1JmEn8jCjbgD2LzKFFzpxSkbyws8Nw8h5fNGqR9CTdBpatoTRQgXUAqlhWk4gttSADniPTDpYyuvv2n2RwYFSFCyOQdUT8abxn44s6dkRK5JKxdWq5ttP5G1uGsINNp7MeadAIwBGYnyflqKunhECWqX14W7J8qUJy2BT5whAKLzhYH1LrALs1vk1R4DAhVELV+ikzLGxZWFRGjXFouFsoppxNwQBvckPM+gbwdLbSg On Wed, 7 Jan 2026 09:23:01 +0100 Jiri Olsa wrote: > --- > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 1621c84f44b3..177c7bbf3b84 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -157,6 +157,30 @@ ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) > return regs; > } > > +/* > + * ftrace_partial_regs_update - update the original ftrace_regs from regs > + * @fregs: The ftrace_regs to update from @regs > + * @regs: The partial regs from ftrace_partial_regs() that was updated > + * > + * Some architectures have the partial regs living in the ftrace_regs > + * structure, whereas other architectures need to make a different copy > + * of the @regs. If a partial @regs is retrieved by ftrace_partial_regs() and > + * if the code using @regs updates a field (like the instruction pointer or > + * stack pointer) it may need to propagate that change to the original @fregs > + * it retrieved the partial @regs from. Use this function to guarantee that > + * update happens. > + */ I think the kernel doc should go into the generic function, and this just say: /* See description of this function in the generic header */ or something similar. Also, should probably have the description in the general function say: * * For architectures that need to update @fregs from @regs, this function needs to be * defined. Or something similar. -- Steve > +static __always_inline void > +ftrace_partial_regs_update(const struct ftrace_regs *fregs, struct pt_regs *regs) > +{ > + struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs); > + > + if (afregs->pc != regs->pc) { > + afregs->pc = regs->pc; > + afregs->regs[0] = regs->regs[0]; > + } > +} > + > #define arch_ftrace_fill_perf_regs(fregs, _regs) do { \ > (_regs)->pc = arch_ftrace_regs(fregs)->pc; \ > (_regs)->regs[29] = arch_ftrace_regs(fregs)->fp; \ > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 770f0dc993cc..ae22559b4099 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -213,6 +213,9 @@ ftrace_partial_regs(struct ftrace_regs *fregs, struct pt_regs *regs) > return regs; > } > > +static __always_inline void > +ftrace_partial_regs_update(struct ftrace_regs *fregs, struct pt_regs *regs) { } > + > #endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS */ > > #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index 6e076485bf70..3a17f79b20c2 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -2564,6 +2564,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, > old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx); > err = bpf_prog_run(link->link.prog, regs); > bpf_reset_run_ctx(old_run_ctx); > + ftrace_partial_regs_update(fregs, bpf_kprobe_multi_pt_regs_ptr()); > rcu_read_unlock(); > > out: > --