Re: [PATCH] modpost: return error if module is missing ns imports and MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n

[Jessica Yu]

+++ Masahiro Yamada [19/02/20 04:27 +0900]:
> On Wed, Feb 19, 2020 at 1:06 AM Jessica Yu <jeyu@xxxxxxxxxx> wrote:
> > +++ Matthias Maennich [17/02/20 14:56 +0000]:
> > >Hi Jessica!
> > >
> > >On Fri, Feb 14, 2020 at 03:37:09PM +0100, Jessica Yu wrote:
> > >>Currently when CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n, modpost only warns
> > >>when a module is missing namespace imports. Under this configuration, such a module
> > >>cannot be loaded into the kernel anyway, as the module loader would reject it.
> > >>We might as well return a build error when a module is missing namespace imports
> > >>under CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n, so that the build
> > >>warning does not go ignored/unnoticed.
> > >
> > >I generally agree with the idea of the patch. Thanks for working on
> > >this! I also can't remember any reason why I did not write it like this
> > >initially. Probably just because I introduced this configuration option
> > >quite late in the development process of the initial patches.
> > >
> > >>
> > >>Signed-off-by: Jessica Yu <jeyu@xxxxxxxxxx>
> > >>---
> > >>scripts/Makefile.modpost |  1 +
> > >>scripts/mod/modpost.c    | 19 +++++++++++++++----
> > >>2 files changed, 16 insertions(+), 4 deletions(-)
> > >>
> > >>diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> > >>index b4d3f2d122ac..a53660f910a9 100644
> > >>--- a/scripts/Makefile.modpost
> > >>+++ b/scripts/Makefile.modpost
> > >>@@ -53,6 +53,7 @@ MODPOST = scripts/mod/modpost                                               \
> > >>      $(if $(KBUILD_EXTMOD),$(addprefix -e ,$(KBUILD_EXTRA_SYMBOLS))) \
> > >>      $(if $(KBUILD_EXTMOD),-o $(modulesymfile))                      \
> > >>      $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)                  \
> > >>+     $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS),,-N)      \
> > >>      $(if $(KBUILD_MODPOST_WARN),-w)
> > >>
> > >>ifdef MODPOST_VMLINUX
> > >>diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > >>index 7edfdb2f4497..53e966f7d557 100644
> > >>--- a/scripts/mod/modpost.c
> > >>+++ b/scripts/mod/modpost.c
> > >>@@ -39,6 +39,8 @@ static int sec_mismatch_count = 0;
> > >>static int sec_mismatch_fatal = 0;
> > >>/* ignore missing files */
> > >>static int ignore_missing_files;
> > >>+/* Return an error when there are missing namespace imports */
> > >>+static int missing_ns_import_error = 0;
> > >
> > >A more suitable name is maybe missing_ns_import_is_error or follow the
> > >naming of the config option: allow_missing_ns_imports (with default = 1).
> > >
> > >>
> > >>enum export {
> > >>      export_plain,      export_unused,     export_gpl,
> > >>@@ -2216,9 +2218,15 @@ static int check_exports(struct module *mod)
> > >>
> > >>              if (exp->namespace &&
> > >>                  !module_imports_namespace(mod, exp->namespace)) {
> > >>-                     warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
> > >>-                          basename, exp->name, exp->namespace);
> > >>-                     add_namespace(&mod->missing_namespaces, exp->namespace);
> > >>+                     if (missing_ns_import_error) {
> > >>+                             merror("module %s uses symbol %s from namespace %s, but does not import it.\n",
> > >>+                                     basename, exp->name, exp->namespace);
> > >
> > >I would like to avoid the code duplication here. The string literal is
> > >identical for both cases.
> >
> > Hm, but one is a call to merror() and the other to warn(). The
> > previous if (warn_unresolved) block does the same thing. I am not sure
> > how to simplify it to one call without introducing macro magic or
> > overcomplicating things. Or were you thinking of something else?
>
>
> I would not say this is a horrible duplication,
> but if you avoid repeating the same string,
> maybe you could do like this:
>
> PRINTF log(enum loglevel loglevel, const char *fmt, ...)
>
>
>
> BTW, you accidentally changed the indentation of
> add_namespace(&mod->missing_namespaces, exp->namespace);
>
>
>
> > >>+                             err = 1;
> > >
> > >Also, if we fail here, we might as well help the user to fix it by
> > >suggesting to run `make nsdeps` (once per failed modpost run). Speaking
> > >of which, `make nsdeps` is currently broken by this patch as it relies
> > >on a successful (yet warning-full) build of the modules. So, in case of
> > >`make nsdeps`, we probably have to omit the -N flag again when invoking
> > >modpost.
> >
> > Good catch! Since KBUILD_NSDEPS is set when running `make nsdeps`,
> > maybe we can do something like:
> >
> > diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> > index a53660f910a9..145703ef8d3a 100644
> > --- a/scripts/Makefile.modpost
> > +++ b/scripts/Makefile.modpost
> > @@ -53,7 +53,7 @@ MODPOST = scripts/mod/modpost                                         \
> >         $(if $(KBUILD_EXTMOD),$(addprefix -e ,$(KBUILD_EXTRA_SYMBOLS))) \
> >         $(if $(KBUILD_EXTMOD),-o $(modulesymfile))                      \
> >         $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)                  \
> > -       $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS),,-N)      \
> > +       $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS),,$(if $(KBUILD_NSDEPS),,-N))      \
>
>
> If you follow Matthias' suggestion
> "follow the naming of the config option: allow_missing_ns_imports
> (with default = 1)."
> the option is inverted, and you can write it more simply:
>
>
>      $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-n)
>     \

Yeah, that looks much better. Thanks!

Jessica