linux-kernel - Re: Checking for support of ptrace(PTRACE

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Message-ID: <88991b38-26f5-e060-3a29-5f17c5fc85df@gmail.com>
Date:   Mon, 17 Apr 2023 20:46:51 +0200
From:   Alejandro Colomar <alx.manpages@...il.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Sergei Zhirikov <sfzhi@...oo.com>, linux-man@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Checking for support of ptrace(PTRACE_SEIZE,...) on older kernels

Hi Oleg,

On 4/17/23 13:50, Oleg Nesterov wrote:
> Well, from https://man7.org/linux/man-pages/man2/ptrace.2.html
> 
>        ESRCH  The specified process does not exist, or is not currently
>               being traced by the caller, or is not stopped (for
>               requests that require a stopped tracee).
> 
> so if the kernel doesn't support PTRACE_SEIZE then ptrace(PTRACE_SEIZE)
> should fail with -ESRCH as documented.
> 
> Perhaps this part
> 
>        EIO    request is invalid, or ...
> 
> can be improvef a bit to explain that this happens if the target is already
> traced by us and stopped.

I'm not sure if it's necessary.  When several errors happen at the same time,
there's usually no documentation about which takes precedence, with few
exceptions.  Knowing it's intentional, I'm content.

Thanks,

Alex

-- 
<http://www.alejandro-colomar.es/>
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