Re: [PATCH] ptrace.2: Add details about usage of PTRACE_GET_SYSCALL_INFO

["Φώτης Βαλασιάδης" <fvalasiad@gmail.com>]

Ah yes sorry for the confusion.

First name is Φώτιος, surname Βαλασιάδης,
just call me Fotis!

we use both formats in Greece, confusing i know . :D

It's fine by me, you know best! But if I have to point something it's 
that Dmitry didn't like the word "Fixed" and we in fact agreed to replace:

Fixed incomplete doc.  PTRACE_GET_SYSCALL_INFO's description wouldn't
     inform the user that they need to enable PTRACE_O_TRACESYSGOOD to get
     detailed information from said operation.

with:

Document the role of PTRACE_O_TRACESYSGOOD option in connection with
     PTRACE_GET_SYSCALL_INFO.

So perhaps you'd want to look into that? Can probably communicate on 
this with Dmitry so we can all agree to something.

I repeat though, from me it's all good, you know best!

Cheers!

-- fvalasiad --

On 27/2/23 02:19, Alejandro Colomar wrote:
> Hi Βαλασιάδης Φώτιος,
>
> (did I write your name correctly?
> I've seen it previously in the reverse order)
>
> On 2/27/23 00:22, Fotios Valasiadis wrote:
>> Document the role of PTRACE_O_TRACESYSGOOD option in connection with PTRACE_GET_SYSCALL_INFO.
>>
>> Signed-off-by: Fotios Valasiadis <fvalasiad@gmail.com>
>> Cowritten-by: Dmitry V. Levin <ldv@strace.io>
>> Complements: fc91449cb "ptrace.2: Document PTRACE_GET_SYSCALL_INFO"
> Patch applied.  Thanks!
>
> I tweaked the commit message to include the original one,
> which was great.  I forgot to mention this, but please
> keep the commit message for revisions of patches; it's
> always easier to discard some information later if it's
> unnecessary, but usually it's best to keep as much as
> possible in the commit message.
>
>> ---
>>   man2/ptrace.2 | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/man2/ptrace.2 b/man2/ptrace.2
>> index 55d9fd36d..9737b3825 100644
>> --- a/man2/ptrace.2
>> +++ b/man2/ptrace.2
>> @@ -1111,6 +1111,15 @@ stop.
>>   .B PTRACE_SYSCALL_INFO_NONE
>>   No component of the union contains relevant information.
>>   .RE
>> +.IP
>> +In case of system call entry or exit stops,
>> +the data returned by
>> +.B PTRACE_GET_SYSCALL_INFO
>> +is limited to type
>> +.B PTRACE_SYSCALL_INFO_NONE
>> +unless
>> +.B PTRACE_O_TRACESYSGOOD
>> +option is set before the corresponding system call stop has occurred.
>>   .\"
>>   .SS Death under ptrace
>>   When a (possibly multithreaded) process receives a killing signal
> On 2/27/23 00:30, Φώτης Βαλασιάδης wrote:
>> Tried my best, hope I did it right!
>>
>> Thanks for the assist!
>>
>> And yes, it's Greek!
> :-)
>
>> Signing off with my github username most of the time.
> Okay.
>
>> Thanks again, here you go!
>>
>> Βαλασιάδης Φώτιος
> The applied patch is below:
>
> $ git show
> commit f04064d73b9f60f189c490e7ef5c3b9fa5498920 (HEAD -> master)
> Author: Fotios Valasiadis <fvalasiad@gmail.com>
> Date:   Mon Feb 27 01:22:01 2023 +0200
>
>      ptrace.2: Add details about usage of PTRACE_GET_SYSCALL_INFO
>      
>      Document the role of PTRACE_O_TRACESYSGOOD option in connection with
>      PTRACE_GET_SYSCALL_INFO.
>      
>      Fixed incomplete doc.  PTRACE_GET_SYSCALL_INFO's description wouldn't
>      inform the user that they need to enable PTRACE_O_TRACESYSGOOD to get
>      detailed information from said operation.
>      
>      Came upon this bug after writing a test program using
>      PTRACE_O_TRACESYSGOOD.  After failing to find what's wrong I posted a
>      stackoverflow question which you can find right here:
>      <https://stackoverflow.com/questions/72410182/ptrace-get-syscall-info-always-returns-info-op-as-ptrace-syscall-info-none>
>      
>      Nate Eldredge found out what's wrong by looking into the kernel's source
>      code, here is a link to the relevant part
>      <https://github.com/torvalds/linux/blob/8291eaafed36f575f23951f3ce18407f480e9ecf/kernel/ptrace.c#L1018>
>      
>      In the code it can be seen that the union is filled if and only if the
>      signal matches "SIGTRAP | 0x80", a signal which is only sent if the
>      PTRACE_O_TRACESYSGOOD option is set.  You can read about that in the
>      PTRACE_O_TRACESYSGOOD section of ptrace(2)'s manual.
>      
>      Complements: fc91449cb "ptrace.2: Document PTRACE_GET_SYSCALL_INFO"
>      Cowritten-by: Dmitry V. Levin <ldv@strace.io>
>      Signed-off-by: Dmitry V. Levin <ldv@strace.io>
>      Signed-off-by: Fotios Valasiadis <fvalasiad@gmail.com>
>      Acked-by: Nate Eldredge <nate@thatsmathematics.com>
>      Cc: Elvira Khabirova <lineprinter0@gmail.com>
>      Signed-off-by: Alejandro Colomar <alx@kernel.org>
>
> diff --git a/man2/ptrace.2 b/man2/ptrace.2
> index 55d9fd36d..9737b3825 100644
> --- a/man2/ptrace.2
> +++ b/man2/ptrace.2
> @@ -1111,6 +1111,15 @@ .SH DESCRIPTION
>   .B PTRACE_SYSCALL_INFO_NONE
>   No component of the union contains relevant information.
>   .RE
> +.IP
> +In case of system call entry or exit stops,
> +the data returned by
> +.B PTRACE_GET_SYSCALL_INFO
> +is limited to type
> +.B PTRACE_SYSCALL_INFO_NONE
> +unless
> +.B PTRACE_O_TRACESYSGOOD
> +option is set before the corresponding system call stop has occurred.
>   .\"
>   .SS Death under ptrace
>   When a (possibly multithreaded) process receives a killing signal
>
>
>
> Please confirm if you want me to push it like that, or if there's anything
> you'd like to tweak.
>
> Cheers,
>
> Alex
>