[PATCH v13 3/5] modules: Allow extended modversions without basic MODVERSIONS

Matthew Maurer
2025-01-03T17:37:10Z

If you know that your kernel modules will only ever be loaded by a newer
kernel, you can disable BASIC_MODVERSIONS to save space. This also
allows easy creation of test modules to see how tooling will respond to
modules that only have the new format.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
---
kernel/module/Kconfig | 15 +++++++++++++++
scripts/Makefile.modpost | 1 +
scripts/mod/modpost.c | 9 +++++++--
3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 9568b629a03ce8289d3f3597eefc66fc96445720..4538f3af63e1ca531d0f74ef45a6f5268e505aec 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -217,6 +217,21 @@ config EXTENDED_MODVERSIONS
The most likely reason you would enable this is to enable Rust
support. If unsure, say N.

+config BASIC_MODVERSIONS
+ bool "Basic Module Versioning Support"
+ depends on MODVERSIONS
+ default y
+ help
+ This enables basic MODVERSIONS support, allowing older tools or
+ kernels to potentially load modules.
+
+ Disabling this may cause older `modprobe` or `kmod` to be unable
+ to read MODVERSIONS information from built modules. With this
+ disabled, older kernels may treat this module as unversioned.
+
+ This is enabled by default when MODVERSIONS are enabled.
+ If unsure, say Y.
+
config MODULE_SRCVERSION_ALL
bool "Source checksum for all modules"
help
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 40426fc6350985780c0092beb49c6cc29b9eff62..d7d45067d08b94a82451d66a64eae29b6826e139 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -43,6 +43,7 @@ MODPOST = $(objtree)/scripts/mod/modpost
modpost-args = \
$(if $(CONFIG_MODULES),-M) \
$(if $(CONFIG_MODVERSIONS),-m) \
+ $(if $(CONFIG_BASIC_MODVERSIONS),-b) \
$(if $(CONFIG_EXTENDED_MODVERSIONS),-x) \
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 6324b30f6b97ac24dc517b9229f227c6c369f7d5..3784f1e08104dc2ca1da10d45ed92bb8adf4826a 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -33,6 +33,8 @@ static bool module_enabled;
static bool modversions;
/* Is CONFIG_MODULE_SRCVERSION_ALL set? */
static bool all_versions;
+/* Is CONFIG_BASIC_MODVERSIONS set? */
+static bool basic_modversions;
/* Is CONFIG_EXTENDED_MODVERSIONS set? */
static bool extended_modversions;
/* If we are modposting external module set to 1 */
@@ -1856,7 +1858,7 @@ static void add_versions(struct buffer *b, struct module *mod)
{
struct symbol *s;

- if (!modversions)
+ if (!basic_modversions)
return;

buf_printf(b, "\n");
@@ -2176,7 +2178,7 @@ int main(int argc, char **argv)
LIST_HEAD(dump_lists);
struct dump_list *dl, *dl2;

- while ((opt = getopt(argc, argv, "ei:MmnT:to:au:WwENd:x")) != -1) {
+ while ((opt = getopt(argc, argv, "ei:MmnT:to:au:WwENd:xb")) != -1) {
switch (opt) {
case 'e':
external_module = true;
@@ -2225,6 +2227,9 @@ int main(int argc, char **argv)
case 'd':
missing_namespace_deps = optarg;
break;
+ case 'b':
+ basic_modversions = true;
+ break;
case 'x':
extended_modversions = true;
break;

--
2.47.1.613.gc27f4b7a9f-goog