Re: [Xen-devel] [PATCH v2 1/2] cmdline_parse: Convert no- prefix into =no for OPT_CUSTOM

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.07.14 at 21:57, <dslutz@xxxxxxxxxxx> wrote:
> This allows converting OPT_BOOL into OPT_CUSTOM and still do what is
> expected.
> 
> Note: if both no- and = provided, pass provided = if not a zero
> length string.  Also log a warning about this.
> 
> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> ---
>  xen/common/kernel.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/common/kernel.c b/xen/common/kernel.c
> index 7e83353..9857159 100644
> --- a/xen/common/kernel.c
> +++ b/xen/common/kernel.c
> @@ -135,7 +135,20 @@ void __init cmdline_parse(const char *cmdline)
>                      parse_size_and_unit(optval, NULL));
>                  break;
>              case OPT_CUSTOM:
> -                ((void (*)(const char *))param->var)(optval);
> +                if ( !bool_assert )
> +                {
> +                    if ( *optval )
> +                    {
> +                        printk(XENLOG_WARNING
> +                               "Warning: ignored no- prefix for %s=%s\n",
> +                               param->name, optval);

Log messages printed before the consoles get initialized are of limited
value (they would only show up in "xl dmesg" or equivalent output).
Therefore I'm not really certain this is worthwhile.

> +                        ((void (*)(const char *))param->var)(optval);
> +                    }
> +                    else
> +                        ((void (*)(const char *))param->var)("no");
> +                }
> +                else
> +                    ((void (*)(const char *))param->var)(optval);

Considering this repeated cast I'd prefer coding this quite
differently, not the least because you also can't pass a literal
"no" to the parsing functions (as they're permitted to alter the
string), and at once also ignoring bogus "no-<name>=<value>"
options instead of trying to assign a (perhaps unexpected)
meaning:

convert "no-" command line option prefix into "=no" for OPT_CUSTOM

... to allow restoring/retaining previous behavior for options getting
converted from boolean to custom.

Reported-by: Don Slutz <dslutz@xxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -135,6 +135,13 @@ void __init cmdline_parse(const char *cm
                     parse_size_and_unit(optval, NULL));
                 break;
             case OPT_CUSTOM:
+                if ( !bool_assert )
+                {
+                    if ( *optval )
+                        break;
+                    safe_strcpy(opt, "no");
+                    optval = opt;
+                }
                 ((void (*)(const char *))param->var)(optval);
                 break;
             default:

Attachment: cmdline-with-no-prefix.patch
Description: Text document

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