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Date: Fri, 16 Feb 2024 09:24:39 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>, Florent Revest
 <revest@chromium.org>, linux-trace-kernel@vger.kernel.org, LKML
 <linux-kernel@vger.kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>,
 bpf <bpf@vger.kernel.org>, Sven Schnelle <svens@linux.ibm.com>, Alexei
 Starovoitov <ast@kernel.org>, Jiri Olsa <jolsa@kernel.org>, Arnaldo
 Carvalho de Melo <acme@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
 Alan Maguire <alan.maguire@oracle.com>, Mark Rutland
 <mark.rutland@arm.com>, Peter Zijlstra <peterz@infradead.org>, Thomas
 Gleixner <tglx@linutronix.de>, Guo Ren <guoren@kernel.org>
Subject: Re: [PATCH v7 28/36] tracing: Add ftrace_partial_regs() for
 converting ftrace_regs to pt_regs
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On Fri, 16 Feb 2024 22:09:02 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:

> On Thu, 15 Feb 2024 11:11:34 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > On Wed,  7 Feb 2024 00:12:40 +0900
> > "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> >   
> > > From: Masami Hiramatsu (Google) <mhiramat@kernel.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, that should go into the change log.

-- Steve