linux-kernel - Re: [PATCH 05/12] selftests/mm: fix invocation of tests that are run via shell scripts

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Message-ID: <e31f1411-1986-c25d-af74-05ad73a53c8d@nvidia.com>
Date:   Fri, 2 Jun 2023 12:19:17 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Peter Xu <peterx@...hat.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>, <linux-mm@...ck.org>,
        <linux-kselftest@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/12] selftests/mm: fix invocation of tests that are run
 via shell scripts

On 6/2/23 08:34, Peter Xu wrote:
> On Thu, Jun 01, 2023 at 06:33:51PM -0700, John Hubbard wrote:
>> We cannot depend upon git to reliably retain the executable bit on shell
>> scripts, or so I was told several years ago while working on this same
>> run_vmtests.sh script. And sure enough, things such as test_hmm.sh are
>> lately failing to run, due to lacking execute permissions.
>>
>> A nice clean way to fix this would have been to use TEST_PROGS instead
>> of TEST_FILES for the .sh scripts here. That tells the selftest
>> framework to run these (and emit a warning if the files are not
>> executable, but still run them anyway).
>>
>> Unfortunately, run_vmtests.sh has its own run_test() routine, which does
>> *not* do the right thing for shell scripts.
>>
>> Fix this by explicitly adding "bash" to each of the shell script
>> invocations. Leave fixing the overall approach to another day.
> 
> Is it possible someone just doesn't have "bash" at all?  I used to only use

Well, maybe [1]. But that someone won't be running these tests as-is, because
the tests explicitly require bash, even before this patch.

> "sh" without bash installed I think, but that was not on Linux, so I'm not
> sure how much that applies..

sh invocations are for when you want to express that this script should
avoid using bash-specific things, in order to ensure portability to
other environments.

But here, the run_vmtests.sh file requires bash already, as per the
first line:

     #!/bin/bash

...which is ultimately why I decided to use bash, rather than sh here.

> 
> Maybe use $(SHELL)?  I saw a bunch of usage in the tree too.
> 

That's more of a Makefile construct that you are seeing, and only in a
few odd Makefiles. Recall that in Make, $(SHELL) has the same effect
that ${SHELL} has in bash/sh, by the way: dereferencing a variable.

And Make's "$(shell ...)" command is what is normally used to *run* a
shell command, in the kernel's build system.

Having said all that, I will take a quick look at what it would take
to shift over to the selftest framework's run_test() instead, in
order to avoid this ugly "fix".

[1] https://www.bleepingcomputer.com/news/linux/kali-linux-20204-switches-the-default-shell-from-bash-to-zsh/

thanks,
-- 
John Hubbard
NVIDIA