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Subject: Re: [PATCH v2 2/3] kconfig: Ask user if string needs to be changed
 when dependency changed
To:     Masahiro Yamada <masahiroy@kernel.org>,
        Casey Schaufler <casey@schaufler-ca.com>
Cc:     James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Nicolas Iooss <nicolas.iooss@m4x.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= <mic@linux.microsoft.com>
References: <20210215181511.2840674-1-mic@digikod.net>
 <20210215181511.2840674-3-mic@digikod.net>
 <CAK7LNAS54Zw7d8Lp5BNs1JVktSLTFx0dNbLMA7W0U_sH2712_A@mail.gmail.com>
From:   =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= <mic@digikod.net>
Message-ID: <b3ea85ca-5c49-61ab-4769-f2e4557df3c7@digikod.net>
Date:   Sun, 21 Feb 2021 12:10:14 +0100
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On 21/02/2021 09:47, Masahiro Yamada wrote:
> On Tue, Feb 16, 2021 at 3:14 AM Mickaël Salaün <mic@digikod.net> wrote:
>>
>> From: Mickaël Salaün <mic@linux.microsoft.com>
>>
>> Content of string configuration may depend on related kernel
>> configurations.  Modify oldconfig and syncconfig to inform users about
>> possible required configuration update and give them the opportunity to
>> update it:
>> * if dependencies of this string has changed (e.g. enabled or disabled),
>> * and if the current value of this string is different than the (new)
>>   default one.
>>
>> This is particularly relevant for CONFIG_LSM which contains a list of
>> LSMs enabled at boot, but users will not have a chance to update this
>> list with a make oldconfig.
> 
> If CONFIG_LSM already exists in the .config,
> oldconfig does not show a prompt.
> This is the expected behavior.

It is not the behavior wished for LSM stacking.

> 
> You are trying to fix your problem in a wrong way.
> NACK.

What do you suggest to ensure that users will be asked to update the
CONFIG_LSM string if they add or remove an LSM?


> 
> 
> 
>>
>> Cc: Casey Schaufler <casey@schaufler-ca.com>
>> Cc: James Morris <jmorris@namei.org>
>> Cc: Masahiro Yamada <masahiroy@kernel.org>
>> Cc: Serge E. Hallyn <serge@hallyn.com>
>> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
>> Link: https://lore.kernel.org/r/20210215181511.2840674-3-mic@digikod.net
>> ---
>>  scripts/kconfig/conf.c | 37 ++++++++++++++++++++++++++++++++++---
>>  1 file changed, 34 insertions(+), 3 deletions(-)
>>
>> diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
>> index 18a233d27a8d..8633dacd39a9 100644
>> --- a/scripts/kconfig/conf.c
>> +++ b/scripts/kconfig/conf.c
>> @@ -82,6 +82,26 @@ static void xfgets(char *str, int size, FILE *in)
>>                 printf("%s", str);
>>  }
>>
>> +static bool may_need_string_update(struct symbol *sym, const char *def)
>> +{
>> +       const struct symbol *dep_sym;
>> +       const struct expr *e;
>> +
>> +       if (sym->type != S_STRING)
>> +               return false;
>> +       if (strcmp(def, sym_get_string_default(sym)) == 0)
>> +               return false;
>> +       /*
>> +        * The user may want to synchronize the content of a string related to
>> +        * changed dependencies (e.g. CONFIG_LSM).
>> +        */
>> +       expr_list_for_each_sym(sym->dir_dep.expr, e, dep_sym) {
>> +               if (dep_sym->flags & SYMBOL_CHANGED)
>> +                       return true;
>> +       }
>> +       return false;
>> +}
>> +
>>  static int conf_askvalue(struct symbol *sym, const char *def)
>>  {
>>         enum symbol_type type = sym_get_type(sym);
>> @@ -102,7 +122,7 @@ static int conf_askvalue(struct symbol *sym, const char *def)
>>         switch (input_mode) {
>>         case oldconfig:
>>         case syncconfig:
>> -               if (sym_has_value(sym)) {
>> +               if (sym_has_value(sym) && !may_need_string_update(sym, def)) {
>>                         printf("%s\n", def);
>>                         return 0;
>>                 }
>> @@ -137,8 +157,19 @@ static int conf_string(struct menu *menu)
>>                 printf("%*s%s ", indent - 1, "", menu->prompt->text);
>>                 printf("(%s) ", sym->name);
>>                 def = sym_get_string_value(sym);
>> -               if (def)
>> -                       printf("[%s] ", def);
>> +               if (def) {
>> +                       if (may_need_string_update(sym, def)) {
>> +                               indent += 2;
>> +                               printf("\n%*sDefault value is [%s]\n",
>> +                                               indent - 1, "",
>> +                                               sym_get_string_default(sym));
>> +                               printf("%*sCurrent value is [%s] ",
>> +                                               indent - 1, "", def);
>> +                               indent -= 2;
>> +                       } else {
>> +                               printf("[%s] ", def);
>> +                       }
>> +               }
>>                 if (!conf_askvalue(sym, def))
>>                         return 0;
>>                 switch (line[0]) {
>> --
>> 2.30.0
>>
> 
>