[PATCH v2 11/26] modpost: make multiple export error

Masahiro Yamada
2022-05-01T08:42:52Z

This is currently a warning, but I think modpost should stop building
in this case.

If the same symbol is exported multiple times and we let it keep going,
the sanity check becomes difficult.

Only the legitimate case is that an external module overrides the
corresponding in-tree module to provide a different implementation
with the same interface.

Also, there exists an upstream example that exploits this feature.

$ make M=tools/testing/nvdimm

... builds tools/testing/nvdimm/libnvdimm.ko. This is a mocked module
that overrides the symbols from drivers/nvdimm/libnvdimm.ko.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---

Changes in v2:
- Add more commit description

scripts/mod/modpost.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 4ce8d164b8e0..1f01fc942f94 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -417,9 +417,9 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,
list_add_tail(&s->list, &mod->exported_symbols);
} else if (!external_module || s->module->is_vmlinux ||
s->module == mod) {
- warn("%s: '%s' exported twice. Previous export was in %s%s\n",
- mod->name, name, s->module->name,
- s->module->is_vmlinux ? "" : ".ko");
+ error("%s: '%s' exported twice. Previous export was in %s%s\n",
+ mod->name, name, s->module->name,
+ s->module->is_vmlinux ? "" : ".ko");
return s;
}

--
2.32.0