Re: [PATCH] Make sure GDB uses a valid shell when starting the inferior and to perform the "shell" command

Simon Marchi
2015-07-24T19:54:34Z

On 15-07-24 03:10 PM, Sergio Durigan Junior wrote:
> On Friday, July 24 2015, Simon Marchi wrote:
>
>> On 15-07-24 02:19 PM, Sergio Durigan Junior wrote:
>>> It is known that GDB needs a valid shell to start the inferior and to
>>> offer the "shell" command to the user. This has recently been the
>>> cause of a problem on the MIPS buildslave, because $SHELL was set to
>>> /sbin/nologin and several tests were failing. The thread is here:
>>>
>>> <https://sourceware.org/ml/gdb-patches/2015-07/msg00535.html>
>>>
>>> However, I think we can do better than that. If 'startup-with-shell'
>>> is on, which is the default, we blindly trust that the user will
>>> provide a valid shell for us, and this may not be true all the time.
>>> So I am proposing a patch to increment the tests made by GDB before
>>> running the inferior to decide whether it will use $SHELL or not.
>>> Particularly, I created a new function, called "valid_shell", which
>>> defines the concept of a valid shell for GDB:
>>>
>>> - A file that exists and is executable by the user
>>>
>>> - A file that is not /sbin/nologin
>>
>> Note that on my Ubuntu 14.04:
>>
>> $ which nologin
>> /usr/sbin/nologin
>
> /sbin/nologin is probably a symlink to this file, isn't it? But yeah,
> the check could include /usr/sbin/nologin as well.

No it isn't:

$ ls -l /sbin/nologin
ls: cannot access /sbin/nologin: No such file or directory