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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Markus Ongyerth <bpf@ongy.net>
Cc: bpf <bpf@vger.kernel.org>
Subject: Re: HELP: bpf_probe_user_write for registers
Date: Sun, 29 Nov 2020 14:22:06 -0800	[thread overview]
Message-ID: <CAADnVQ+2DiSH42cSjQ2fNEEc217c6C+SPEqSEzBJb22aZdm3kA@mail.gmail.com> (raw)
In-Reply-To: <eea9673f-5ee4-4adc-bc64-fcc88f715cc8@www.fastmail.com>

On Sun, Nov 29, 2020 at 10:38 AM Markus Ongyerth <bpf@ongy.net> wrote:
>
> Hi,
>
> I've been looking into introspecting and possibly convincing an application to behave slightly different with bpf measures.
>
> I found `bpf_probe_user_write` but as far as I can tell, that only works for memory areas.
> Is there an alternative that can be used on registers as well?

fyi bpf_probe_write_user() warns in dmesg.
That was done on purpose to avoid usage of this helper in production code.
A new helper can be added to adjust user regs, but it will have similar warning.
It's better to discuss the use case first.
Do you envision user regs to be changed after uprobe in an arbitrary location
or in some fixed place and only particular regs?

  reply	other threads:[~2020-11-29 22:22 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-29 18:34 HELP: bpf_probe_user_write for registers Markus Ongyerth
2020-11-29 22:22 ` Alexei Starovoitov [this message]
2020-11-30  4:33   ` Markus Ongyerth
2020-12-01  2:27     ` Alexei Starovoitov

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