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Subject: Re: [PATCH 1/1] process_madvise.2: Add process_madvise man page
To:     Suren Baghdasaryan <surenb@google.com>
References: <20210120202337.1481402-1-surenb@google.com>
 <CAKgNAkgsQWL3QAyF6CQU=yifzA1tfp_E5kBBNKuAq_+sB4Amyw@mail.gmail.com>
 <CAJuCfpEfMgA6z5S5gmHwJB_3KWwmKKp434GeHheUGF3yC7r01w@mail.gmail.com>
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Message-ID: <6cd84701-fb65-7aa0-38db-b69fe5748754@gmail.com>
Date:   Thu, 28 Jan 2021 21:31:19 +0100
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Hello Suren,

On 1/28/21 7:40 PM, Suren Baghdasaryan wrote:
> On Thu, Jan 28, 2021 at 4:24 AM Michael Kerrisk (man-pages)
> <mtk.manpages@gmail.com> wrote:
>>
>> Hello Suren,
>>
>> Thank you for writing this page! Some comments below.
> 
> Thanks for the review!
> Couple questions below and I'll respin the new version once they are clarified.

Okay. See below.

>> On Wed, 20 Jan 2021 at 21:36, Suren Baghdasaryan <surenb@google.com> wrote:
>>>

[...]

Thanks for all the acks. That let's me know that you saw what I said.

>>> RETURN VALUE
>>>     On success, process_madvise() returns the number of bytes advised. This
>>>     return value may be less than the total number of requested bytes, if an
>>>     error occurred. The caller should check return value to determine whether
>>>     a partial advice occurred.
>>
>> So there are three return values possible,
> 
> Ok, I think I see your point. How about this instead:

Well, I'm glad you saw it, because I forgot to finish it. But yes,
you understood what I forgot to say.

> RETURN VALUE
>      On success, process_madvise() returns the number of bytes advised. This
>      return value may be less than the total number of requested bytes, if an
>      error occurred after some iovec elements were already processed. The caller
>      should check the return value to determine whether a partial
> advice occurred.
> 
>     On error, -1 is returned and errno is set appropriately.

We recently standardized some wording here:
s/appropriately/to indicate the error/.


>>> +.PP
>>> +The pointer
>>> +.I iovec
>>> +points to an array of iovec structures, defined in
>>
>> "iovec" should be formatted as
>>
>> .I iovec
> 
> I think it is formatted that way above. What am I missing?

But also in "an array of iovec structures"...

> BTW, where should I be using .I vs .IR? I was looking for an answer
> but could not find it.

.B / .I == bold/italic this line
.BR / .IR == alternate bold/italic with normal (Roman) font.

So:
.I iovec
.I iovec ,       # so that comma is not italic
.BR process_madvise ()
etc.

[...]

>>> +.I iovec
>>> +if one of its elements points to an invalid memory
>>> +region in the remote process. No further elements will be
>>> +processed beyond that point.
>>> +.PP
>>> +Permission to provide a hint to external process is governed by a
>>> +ptrace access mode
>>> +.B PTRACE_MODE_READ_REALCREDS
>>> +check; see
>>> +.BR ptrace (2)
>>> +and
>>> +.B CAP_SYS_ADMIN
>>> +capability that caller should have in order to affect performance
>>> +of an external process.
>>
>> The preceding sentence is garbled. Missing words?
> 
> Maybe I worded it incorrectly. What I need to say here is that the
> caller should have both PTRACE_MODE_READ_REALCREDS credentials and
> CAP_SYS_ADMIN capability. The first part I shamelessly copy/pasted
> from https://man7.org/linux/man-pages/man2/process_vm_readv.2.html and
> tried adding the second one to it, obviously unsuccessfully. Any
> advice on how to fix that?

I think you already got pretty close. How about:

[[
Permission to provide a hint to another process is governed by a
ptrace access mode
.B PTRACE_MODE_READ_REALCREDS
check (see
BR ptrace (2));
in addition, the caller must have the
.B CAP_SYS_ADMIN
capability.
]]

[...]

>>> +.TP
>>> +.B ESRCH
>>> +No process with ID
>>> +.I pidfd
>>> +exists.
>>
>> Should this maybe be:
>> [[
>> The target process does not exist (i.e., it has terminated and
>> been waited on).
>> ]]
>>
>> See pidfd_send_signal(2).
> 
> I "borrowed" mine from
> https://man7.org/linux/man-pages/man2/process_vm_readv.2.html but
> either one sounds good to me. Maybe for pidfd_send_signal the wording
> about termination is more important. Anyway, it's up to you. Just let
> me know which one to use.

I think the pidfd_send_signal(2) wording fits better.

[...]

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/