ANDROID: modules: introduce the MODULE_SCMVERSION config
Config MODULE_SCMVERSION introduces a new module attribute --
`scmversion` -- which can be used to identify a given module's SCM
version. This is very useful for developers that update their kernel
independently from their kernel modules or vice-versa since the SCM
version provided by UTS_RELEASE (`uname -r`) will now differ from the
module's vermagic attribute.
For example, we have a CI setup that tests new kernel changes on the
hikey960 and db845c devices without updating their kernel modules. When
these tests fail, we need to be able to identify the exact device
configuration the test was using. By including MODULE_SCMVERSION, we can
identify the exact kernel and modules' SCM versions for debugging the
failures.
Additionally, by exposing the SCM version via the sysfs node
/sys/module/MODULENAME/scmversion, one can also verify the SCM versions
of the modules loaded from the initramfs. Currently, modinfo can only
retrieve module attributes from the module's ko on disk and not from the
actual module that is loaded in RAM.
You can retrieve the SCM version in two ways,
1) By using modinfo:
> modinfo -F scmversion MODULENAME
2) By module sysfs node:
> cat /sys/module/MODULENAME/scmversion
Bug: 180027765
Link: https://lkml.org/lkml/2021/1/21/1388
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: Ib7c72c72f95c4545adb7cd4e842729557039ce3a
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index f54b6ac..13ec3e9 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -66,6 +66,7 @@
input-symdump := vmlinux.symvers
output-symdump := Module.symvers
+module_srcpath := $(srctree)
else
@@ -82,9 +83,22 @@
input-symdump := Module.symvers $(KBUILD_EXTRA_SYMBOLS)
output-symdump := $(KBUILD_EXTMOD)/Module.symvers
+module_srcpath := $(KBUILD_EXTMOD)
endif
+ifeq ($(CONFIG_MODULE_SCMVERSION),y)
+# Get the SCM version of the module. Sed verifies setlocalversion returns
+# a proper revision based on the SCM type, e.g. git, mercurial, or svn.
+# Note: relative M= paths are not supported when building the kernel out of the
+# srctree since setlocalversion won't be able to find the module srctree.
+module_scmversion := $(shell $(srctree)/scripts/setlocalversion $(module_srcpath) | \
+ sed -n 's/.*-\(\(g\|hg\)[a-fA-F0-9]\+\(-dirty\)\?\|svn[0-9]\+\).*/\1/p')
+ifneq ($(module_scmversion),)
+MODPOST += -v $(module_scmversion)
+endif
+endif
+
# modpost options for modules (both in-kernel and external)
MODPOST += \
$(addprefix -i ,$(wildcard $(input-symdump))) \
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 1eb902b..a702ce3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -30,6 +30,8 @@ static int have_vmlinux = 0;
static int all_versions = 0;
/* If we are modposting external module set to 1 */
static int external_module = 0;
+#define MODULE_SCMVERSION_SIZE 64
+static char module_scmversion[MODULE_SCMVERSION_SIZE];
/* Only warn about unresolved symbols */
static int warn_unresolved = 0;
/* How a symbol is exported */
@@ -2263,6 +2265,20 @@ static void add_intree_flag(struct buffer *b, int is_intree)
buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
}
+/**
+ * add_scmversion() - Adds the MODULE_INFO macro for the scmversion.
+ * @b: Buffer to append to.
+ *
+ * This function fills in the module attribute `scmversion` for the kernel
+ * module. This is useful for determining a given module's SCM version on
+ * device via /sys/modules/<module>/scmversion and/or using the modinfo tool.
+ */
+static void add_scmversion(struct buffer *b)
+{
+ if (module_scmversion[0] != '\0')
+ buf_printf(b, "\nMODULE_INFO(scmversion, \"%s\");\n", module_scmversion);
+}
+
/* Cannot check for assembler */
static void add_retpoline(struct buffer *b)
{
@@ -2545,7 +2561,7 @@ int main(int argc, char **argv)
struct dump_list *dump_read_start = NULL;
struct dump_list **dump_read_iter = &dump_read_start;
- while ((opt = getopt(argc, argv, "ei:mnT:o:awENd:")) != -1) {
+ while ((opt = getopt(argc, argv, "ei:mnT:o:awENd:v:")) != -1) {
switch (opt) {
case 'e':
external_module = 1;
@@ -2583,6 +2599,9 @@ int main(int argc, char **argv)
case 'd':
missing_namespace_deps = optarg;
break;
+ case 'v':
+ strncpy(module_scmversion, optarg, sizeof(module_scmversion) - 1);
+ break;
default:
exit(1);
}
@@ -2629,6 +2648,7 @@ int main(int argc, char **argv)
add_depends(&buf, mod);
add_moddevtable(&buf, mod);
add_srcversion(&buf, mod);
+ add_scmversion(&buf);
sprintf(fname, "%s.mod.c", mod->name);
write_if_changed(&buf, fname);