From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8428518DF6B; Tue, 22 Oct 2024 22:55:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729637717; cv=none; b=lcVUASxtu7d6lMO2h2Zk2xG1qlCdk5QnLsCzbRBvsPn3jmX6f8iBvZX8UsL+t2DHnLToCtwLNVbFsCj7Nw+n2QHpN4NqLj69myTPmZt4CiiMWXHRVIwi5XYdabRyG34TYZ/Ok+sFdnhWUm131eTkMfLEnzz7ar6F9Wip3cjJKec= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729637717; c=relaxed/simple; bh=mmB0h7GP5OEtq5xYgYIchtjpiU0bUWfBh3QydfmbdMc=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=hF9w3dMAPahlhNWbIOMYpRLVPifsbLSXMz2uHsi/Di204S8cSqEhruZeOO4Z74Qu20sF8yMBhZ2zguC09X8we4N51m3euF5HTsxiMPUXdX3dj4bnss3mkIpaTY3+wKPUWAOWSjorJO9lSCFGau8ZW81j64S1b9EjqqTKggcEeBk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ASu6p/OD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ASu6p/OD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93C8CC4CEC3; Tue, 22 Oct 2024 22:55:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729637717; bh=mmB0h7GP5OEtq5xYgYIchtjpiU0bUWfBh3QydfmbdMc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ASu6p/OD42ChIQmHFxFr9v3Uut7yuCh45MCO2hw++Lkjld6Jr/OQx9lqwZ+ZPNM10 oJq97rdJrwZ9XNlxjth4RPMSbnbpXgWWvWIRseRkBJEbPGoiLwYx6xyx2JAiKXZgZl GH8dMoAlfClEytaexMXLu2QkP+8gHyHWzhuWLOxtOtxjlZjaX6WRvv4N2yfkwAM9Ja Wfs0rJif2mmYcrLm+a3pHWwupTHdyiqFHPC+TiqNsWeyVwTGYJcO+bOjEHBlgaEh7b CQSFWKNhj8tkhBXOE8CkoX+57ZsDAs699JxntIAfOvvpKcWSzFaXM+g7YvGyvyLPtd 8F3OmoK82QV+A== Date: Wed, 23 Oct 2024 07:55:07 +0900 From: Masami Hiramatsu (Google) To: Will Deacon Cc: Alexei Starovoitov , Steven Rostedt , Florent Revest , linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Alexei Starovoitov , Jiri Olsa , Alan Maguire , Mark Rutland , linux-arch@vger.kernel.org, Catalin Marinas , Huacai Chen , WANG Xuerui , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Mathieu Desnoyers Subject: Re: [PATCH v17 01/16] function_graph: Pass ftrace_regs to entryfunc Message-Id: <20241023075507.ebeadc70579fc8a642213a55@kernel.org> In-Reply-To: <20241021170340.GB26122@willie-the-truck> References: <172904026427.36809.516716204730117800.stgit@devnote2> <172904027515.36809.1961937054923520469.stgit@devnote2> <20241021170340.GB26122@willie-the-truck> X-Mailer: Sylpheed 3.8.0beta1 (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 On Mon, 21 Oct 2024 18:03:40 +0100 Will Deacon wrote: > On Wed, Oct 16, 2024 at 09:57:55AM +0900, Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) > > > > Pass ftrace_regs to the fgraph_ops::entryfunc(). If ftrace_regs is not > > available, it passes a NULL instead. User callback function can access > > some registers (including return address) via this ftrace_regs. > > > > Note that the ftrace_regs can be NULL when the arch does NOT define: > > HAVE_DYNAMIC_FTRACE_WITH_ARGS or HAVE_DYNAMIC_FTRACE_WITH_REGS. > > More specifically, if HAVE_DYNAMIC_FTRACE_WITH_REGS is defined but > > not the HAVE_DYNAMIC_FTRACE_WITH_ARGS, and the ftrace ops used to > > register the function callback does not set FTRACE_OPS_FL_SAVE_REGS. > > In this case, ftrace_regs can be NULL in user callback. > > > > Signed-off-by: Masami Hiramatsu (Google) > > Cc: Steven Rostedt > > Cc: Mark Rutland > > Cc: Catalin Marinas > > Cc: Will Deacon > > Cc: Huacai Chen > > Cc: WANG Xuerui > > Cc: Michael Ellerman > > Cc: Nicholas Piggin > > Cc: Christophe Leroy > > Cc: Naveen N Rao > > Cc: Madhavan Srinivasan > > Cc: Paul Walmsley > > Cc: Palmer Dabbelt > > Cc: Albert Ou > > Cc: Thomas Gleixner > > Cc: Ingo Molnar > > Cc: Borislav Petkov > > Cc: Dave Hansen > > Cc: x86@kernel.org > > Cc: "H. Peter Anvin" > > Cc: Mathieu Desnoyers > > > > --- > > Changes in v16: > > - Add a note when the ftrace_regs can be NULL. > > - Update against for the latest kernel. > > Changes in v11: > > - Update for the latest for-next branch. > > Changes in v8: > > - Just pass ftrace_regs to the handler instead of adding a new > > entryregfunc. > > - Update riscv ftrace_graph_func(). > > Changes in v3: > > - Update for new multiple fgraph. > > --- > > arch/arm64/kernel/ftrace.c | 20 +++++++++++- > > arch/loongarch/kernel/ftrace_dyn.c | 10 +++++- > > arch/powerpc/kernel/trace/ftrace.c | 2 + > > arch/powerpc/kernel/trace/ftrace_64_pg.c | 10 ++++-- > > arch/riscv/kernel/ftrace.c | 17 ++++++++++ > > arch/x86/kernel/ftrace.c | 50 +++++++++++++++++++++--------- > > include/linux/ftrace.h | 17 ++++++++-- > > kernel/trace/fgraph.c | 25 +++++++++------ > > kernel/trace/ftrace.c | 3 +- > > kernel/trace/trace.h | 3 +- > > kernel/trace/trace_functions_graph.c | 3 +- > > kernel/trace/trace_irqsoff.c | 3 +- > > kernel/trace/trace_sched_wakeup.c | 3 +- > > kernel/trace/trace_selftest.c | 8 +++-- > > 14 files changed, 129 insertions(+), 45 deletions(-) > > > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > > index b2d947175cbe..a5a285f8a7ef 100644 > > --- a/arch/arm64/kernel/ftrace.c > > +++ b/arch/arm64/kernel/ftrace.c > > @@ -481,7 +481,25 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, > > void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > > struct ftrace_ops *op, struct ftrace_regs *fregs) > > { > > - prepare_ftrace_return(ip, &arch_ftrace_regs(fregs)->lr, arch_ftrace_regs(fregs)->fp); > > + unsigned long return_hooker = (unsigned long)&return_to_handler; > > + unsigned long frame_pointer = arch_ftrace_regs(fregs)->fp; > > + unsigned long *parent = &arch_ftrace_regs(fregs)->lr; > > + unsigned long old; > > + > > + if (unlikely(atomic_read(¤t->tracing_graph_pause))) > > + return; > > + > > + /* > > + * Note: > > + * No protection against faulting at *parent, which may be seen > > + * on other archs. It's unlikely on AArch64. > > + */ > > + old = *parent; > > Sorry to pick on this line again, but the comment is very non-committal] > and I think this is something on which we need to be definitive. Agreed. I think this does not happen because it is a part of __arch_ftrace_regs, which is stored on kernel stack. I copied it from prepare_ftrace_return(), so that also need to be changed too. Let me remove this comment. Thank you, > > Either the access can fault, and we should handle it, or it will never > fault and we don't need to handle it. Saying it's unlikely means we > need to handle it :) > > Will > -- Masami Hiramatsu (Google)