Re: [PATCH] libkmod-module: convert return value from system() to errno

[Topi Miettinen <toiwoton@gmail.com>]

On 29.12.2019 0.59, Lucas De Marchi wrote:
> On Tue, Dec 24, 2019 at 11:54:58AM +0200, Topi Miettinen wrote:
>> On 24.12.2019 4.54, Lucas De Marchi wrote:
>>> On Mon, Dec 23, 2019 at 9:07 AM Topi Miettinen <toiwoton@gmail.com> 
>>> wrote:
>>>>
>>>> Don't use exit status of a command directly as errno code, callers
>>>> will be confused.
>>>>
>>>> Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
>>>> ---
>>>>   libkmod/libkmod-module.c | 8 +++++---
>>>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
>>>> index 8044a8f..6031d80 100644
>>>> --- a/libkmod/libkmod-module.c
>>>> +++ b/libkmod/libkmod-module.c
>>>> @@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod,
>>>> const char *type,
>>>>          if (err == -1 || WEXITSTATUS(err)) {
>>>>                  ERR(mod->ctx, "Error running %s command for %s\n",
>>>>                                                                  type,
>>>> modname);
>>>> -               if (err != -1)
>>>> -                       err = -WEXITSTATUS(err);
>>>
>>> I don't think we actually care about differentiating them. So just a 
>>> plain
>>> return -EINVAL;  here would suffice, makes sense?
>>
>> I think it would lose potentially valuable information. For example 
>> EPERM could tell the system administrator of a problem with MAC 
>> configuration preventing execution of the shell, ENOENT could show 
>> that the shell or shared libraries are missing and so forth.
> 
> makes sense, but we take decisions on the callers depending on the
> return value. I don't want to mix that with return values from the
> commands executed. E.g. if the command returned EEXIST the caller would
> treat a fail differently.
> 
> I think it would be good here to give different error messages and
> always return -EINVAL. I'm thinking on squashing the following diff,
> what do you think?

OK, maybe that's better.

-Topi

> 
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 6031d80..714ee21 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -980,13 +980,16 @@ static int command_do(struct kmod_module *mod, 
> const char *type,
>       err = system(cmd);
>       unsetenv("MODPROBE_MODULE");
> 
> -    if (err == -1 || WEXITSTATUS(err)) {
> -        ERR(mod->ctx, "Error running %s command for %s\n",
> -                                type, modname);
> -        if (err != -1) /* nonzero exit status: something bad happened */
> -            return -EINVAL;
> -        else /* child process could not be created */
> -            return -errno;
> +    if (err == -1) {
> +        ERR(mod->ctx, "Could not run %s command '%s' for module %s: %m\n",
> +            type, cmd, modname);
> +        return -EINVAL;
> +    }
> +
> +    if (WEXITSTATUS(err)) {
> +        ERR(mod->ctx, "Error running %s command '%s' for module %s: 
> retcode %d\n",
> +            type, cmd, modname, WEXITSTATUS(err));
> +        return -EINVAL;
>       }
> 
>       return 0;
> 
> 
> thanks
> Lucas De Marchi