linux-kernel - Re: [PATCH bpf-next] uprobes: Fix the xol slots reserved for uretprobe trampoline

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Date: Thu, 20 Jun 2024 12:52:03 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: "Liao, Chang" <liaochang1@...wei.com>
Cc: jolsa@...nel.org, rostedt@...dmis.org, mhiramat@...nel.org,
	ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
	nathan@...nel.org, peterz@...radead.org, mingo@...hat.com,
	mark.rutland@....com, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] uprobes: Fix the xol slots reserved for
 uretprobe trampoline

On 06/20, Liao, Chang wrote:
>
> 在 2024/6/20 16:36, Oleg Nesterov 写道:
> > On 06/20, Liao, Chang wrote:
> >>
> >> However, when i asm porting uretprobe trampoline to arm64
> >> to explore its benefits on that architecture, i discovered the problem that
> >> single slot is not large enought for trampoline code.
> >
> > Ah, but then I'd suggest to make the changelog more clear. It looks as
> > if the problem was introduced by the patch from Jiri. Note that we was
> > confused as well ;)
>
> Perhaps i should use 'RFC' in the subject line, instead of 'PATCH'?

Well. IMO the changelog should explain that the current code is correct,
but you are going to change arm64 and arch_uprobe_trampoline(psize) on
arm64 can return with *psize > UPROBE_XOL_SLOT_BYTES.

Oleg.