[PATCH 04/27] modpost: add a separate error for exported symbols without definition

From: Masahiro Yamada
Date: Sun Apr 24 2022 - 15:11:11 EST

It took me a while to understand the intent of "exp->module == mod".

This code goes back to 2003 (pre-git era).

The commit is not in this git repository, and might be worth a little

You can add EXPORT_SYMBOL() with no definition in the same file (but you
need to put a declaration).

int foo(void);

This is typical when EXPORT_SYMBOL() is defined in a C file, but the
actual implementation is in a separate assembly file. In old days,
EXPORT_SYMBOL() were only available in C files (but this limitation
does not exist any more).

Add a separate, clearer message if an exported symbol has no definition.
It should be an error even if KBUILD_MODPOST_WARN is given.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=2763b6bcb96e6a38a2fe31108fe5759ec5bcc80a

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>

scripts/mod/modpost.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index c7cfeeb088f7..969a081dba62 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2147,13 +2147,18 @@ static void check_exports(struct module *mod)
for (s = mod->unres; s; s = s->next) {
const char *basename;
exp = find_symbol(s->name);
- if (!exp || exp->module == mod) {
+ if (!exp) {
if (!s->weak && nr_unresolved++ < MAX_UNRESOLVED_REPORTS)
modpost_log(warn_unresolved ? LOG_WARN : LOG_ERROR,
"\"%s\" [%s.ko] undefined!\n",
s->name, mod->name);
+ if (exp->module == mod) {
+ error("\"%s\" [%s.ko] was exported without definition\n",
+ s->name, mod->name);
+ continue;
+ }
basename = strrchr(mod->name, '/');
if (basename)