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

[Lucas De Marchi <lucas.demarchi@intel.com>]

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?


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