On Tue, Jun 03, 2025 at 04:00:30AM +0900, Masahiro Yamada wrote:
On Mon, Jun 2, 2025 at 10:06 PM Masahiro Yamada <masahi...@kernel.org> wrote:
In the old days, KBUILD_MODNAME was passed to C without double quotes,
and then handled by __stringify() on the C side. This was the reason
why KBUILD_MODNAME was mangled: characters such as commas (,) and
hyphens (-) are not allowed in C identifiers, so they were replaced
with underscores (_) in Kbuild.
Since commit f83b5e323f57 ("kbuild: set correct KBUILD_MODNAME when
using well known kernel symbols as module names"), KBUILD_MODNAME has
been passed to C as a string literal, which allows any characters.
Aside from this historical behavior in the build system, there is no
longer a reason for mangling. In fact, it is rather annoying, as we
now need to convert between hyphens and underscores in some places,
but not in others. See commit 0267cbf297bf ("module: Account for the
build time module name mangling").
This commit eliminates that oddity, so the module name will now match
the filename. For example, the module name of "foo-bar.ko" will be
"foo-bar", not "foo_bar".
However, this oddity persisted for so long and also affected the
userspace. To adapt to this behavior, when a user runs "rmmod foo-bar",
kmod converts hyphens to underscores, and passes "foo_bar" to the
delete_module syscall.
Hmm. That was modprobe/rmmod from busybox.
kmod tries to open /sys/module/*, and
hyphen/underscore conversion happens everywhere.
libkmod: ERROR ../libkmod/libkmod-module.c:2039
kmod_module_get_holders: could not open '/sys/module/fo_o/holders': No
such file or directory
the dash to underscore is done everywhere in kmod (and previously in
module-init-tools), otherwise we couldn't reliably compare modules by
name, open the right sysfs file, etc.
$ git grep underscore
libkmod/libkmod-config.c: if (underscores(modname) < 0) {
libkmod/libkmod-config.c: if (underscores(alias) < 0 ||
underscores(modname) < 0)
libkmod/libkmod-config.c: if (underscores(modname) < 0)
libkmod/libkmod-config.c: if (underscores(modname) < 0 ||
options == NULL)
libkmod/libkmod-config.c: if (underscores(modname) < 0 ||
installcmd == NULL)
libkmod/libkmod-config.c: if (underscores(modname) < 0 ||
removecmd == NULL)
libkmod/libkmod-config.c: if (underscores(modname) < 0 ||
softdeps == NULL)
libkmod/libkmod-config.c: if (underscores(modname) < 0 ||
weakdeps == NULL)
libkmod/libkmod.h: * it's always normalized (dashes are replaced with
underscores).
man/modprobe.8.scd:(automatic underscore conversion is performed). *modprobe*
looks in the module
man/modprobe.d.5.scd:them: both are interchangeable throughout all the module
commands as underscore
shared/util.c: * Replace dashes with underscores.
shared/util.c:int underscores(char *s)
shared/util.h:_must_check_ int underscores(char *s);
testsuite/test-util.c:static int test_underscores(const struct test *t)
testsuite/test-util.c: assert_return(!underscores(val), EXIT_FAILURE);
testsuite/test-util.c:DEFINE_TEST(test_underscores, .description = "check
implementation of underscores()");
I think it's reasonable to apply
https://lore.kernel.org/linux-modules/vqeq3ioklrgrf227zgdfho4virh74qrt5reoyptmzgktyronbr@c2mw32pqikft/
otherwise there's also an implicit conversion needed for '/', probably
moving string_is_vfs_ready() to kernel/module/
Lucas De Marchi
So, we may need to carry this forever...
Therefore, the mod_strncmp() needs to remain in find_module_all(),
otherwise, we cannot unload modules.
Signed-off-by: Masahiro Yamada <masahi...@kernel.org>
---
kernel/module/main.c | 8 ++++++--
scripts/Makefile.lib | 4 ++--
2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/kernel/module/main.c b/kernel/module/main.c
index b8440b0887e3..1fa90a95e0c5 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -410,7 +410,11 @@ struct module *find_module_all(const char *name, size_t
len,
lockdep_is_held(&module_mutex)) {
if (!even_unformed && mod->state == MODULE_STATE_UNFORMED)
continue;
- if (strlen(mod->name) == len && !memcmp(mod->name, name, len))
+ /*
+ * For historical reasons, kmod passes a module name with
+ * a hyphen replaced with an underscore.
+ */
+ if (!mod_strncmp(mod->name, name, len))
return mod;
}
return NULL;
@@ -1135,7 +1139,7 @@ static bool module_match(const char *modname, const char
*patterns)
if (*sep)
sep++;
- if (mod_strncmp(patterns, modname, len) == 0 && (glob || len ==
modlen))
+ if (strncmp(patterns, modname, len) == 0 && (glob || len ==
modlen))
return true;
}
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 336fb0d763c7..e37e2db5f528 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -18,8 +18,8 @@ target-stem = $(basename $(patsubst $(obj)/%,%,$@))
# end up in (or would, if it gets compiled in)
name-fix-token = $(subst $(comma),_,$(subst -,_,$1))
name-fix = $(call stringify,$(call name-fix-token,$1))
-basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
-modname_flags = -DKBUILD_MODNAME=$(call name-fix,$(modname)) \
+basename_flags = -DKBUILD_BASENAME=$(call stringify,$(basetarget))
+modname_flags = -DKBUILD_MODNAME=$(call stringify,$(modname)) \
-D__KBUILD_MODNAME=kmod_$(call name-fix-token,$(modname))
modfile_flags = -DKBUILD_MODFILE=$(call stringify,$(modfile))
--
2.43.0
--
Best Regards
Masahiro Yamada
