linux-kernel - Re: [PATCH v7 28/36] tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt

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Date: Fri, 16 Feb 2024 22:09:02 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Florent Revest
 <revest@...omium.org>, linux-trace-kernel@...r.kernel.org, LKML
 <linux-kernel@...r.kernel.org>, Martin KaFai Lau <martin.lau@...ux.dev>,
 bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>, Alexei
 Starovoitov <ast@...nel.org>, Jiri Olsa <jolsa@...nel.org>, Arnaldo
 Carvalho de Melo <acme@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Alan Maguire <alan.maguire@...cle.com>, Mark Rutland
 <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>, Thomas
 Gleixner <tglx@...utronix.de>, Guo Ren <guoren@...nel.org>
Subject: Re: [PATCH v7 28/36] tracing: Add ftrace_partial_regs() for
 converting ftrace_regs to pt_regs

On Thu, 15 Feb 2024 11:11:34 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed,  7 Feb 2024 00:12:40 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Add ftrace_partial_regs() which converts the ftrace_regs to pt_regs.
> > If the architecture defines its own ftrace_regs, this copies partial
> > registers to pt_regs and returns it. If not, ftrace_regs is the same as
> > pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.
> 
> This says what this patch is doing and not why it is doing it.

Hmm, OK. The reason is the eBPF needs this to keep the same pt_regs
interface to access registers.
Thus when replacing the pt_regs with ftrace_regs in fprobes (which is
used by kprobe_multi eBPF event), this will be required.
I'll add this to next version.

Thanks,

> 
> -- Steve
> 
> > 
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > Acked-by: Florent Revest <revest@...omium.org>
> > ---
> >  Changes from previous series: NOTHING, just forward ported.
> > ---


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>