Hi!

On Sat, Oct 05, 2019 at 04:53:56PM +0900, Masahiro Yamada wrote:

On Sat, Oct 5, 2019 at 3:25 AM Lucas De Marchi
[off-list ref] wrote:

quoted

On Fri, Oct 4, 2019 at 2:57 AM Matthias Maennich [off-list ref] wrote:

quoted

depmod in its current version is not aware of symbol namespace in
ksymtab entries introduced with 8651ec01daed ("module: add support for
symbol namespaces."). They have the form

  __ksymtab_NAMESPACE.symbol_name

A fix for kmod's depmod has been proposed [1]. In order to support older
versions of depmod as well, create a System.map.no_namespaces during
scripts/depmod.sh that has the pre-namespaces format. That way users do
not immediately upgrade the userspace tool.

[1] https://lore.kernel.org/linux-modules/20191004094136.166621-1-maennich@google.com/ (local)

Reported-by: Stefan Wahren <redacted>
Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
Cc: Masahiro Yamada <redacted>
Cc: Lucas De Marchi <redacted>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Martijn Coenen <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-modules@vger.kernel.org
Signed-off-by: Matthias Maennich <maennich@google.com>
---

Please note this depends on the new ksymtab entry format proposed in
https://lore.kernel.org/lkml/20191003075826.7478-2-yamada.masahiro@socionext.com/ (local)

I don't really agree with that thought, more below.

quoted

That is likely to be merged soon as well as it fixes problems in 5.4-rc*, hence
this patch depends on it.

Cheers,
Matthias

 .gitignore        | 1 +
 scripts/depmod.sh | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 70580bdd352c..5ed58a7cb433 100644
--- a/.gitignore
+++ b/.gitignore

@@ -59,6 +59,7 @@ modules.order
 /vmlinux-gdb.py
 /vmlinuz
 /System.map
+/System.map.no_namespaces
 /Module.markers
 /modules.builtin.modinfo

diff --git a/scripts/depmod.sh b/scripts/depmod.sh
index e083bcae343f..602e1af072c7 100755
--- a/scripts/depmod.sh
+++ b/scripts/depmod.sh

@@ -39,7 +39,13 @@ if $depmod_hack_needed; then
        KERNELRELEASE=99.98.$KERNELRELEASE
 fi

-set -- -ae -F System.map
+# Older versions of depmod do not support symbol namespaces in ksymtab entries,
+# hence create an alternative System.map with namespace patched out to use for
+# depmod. I.e. transform entries as follows:
+#    __ksymtab_NAMESPACE.symbol_name -> __ksymtab_symbol_name
+sed 's/__ksymtab_.*\./__ksymtab_/' System.map > System.map.no_namespaces

So people with old kmod will have to know they need to pass
System.map.no_namespaces rather than the usual
System.map. Also, distros will need to be update to also copy the new
file to the kernel package (or upgrade/patch kmod).

I'd rather maintain the current format and fix the bug that patch is
fixing. The namespace
in the end IMO is just a small annoyance with a reason to  exist.

I agree, this fix is bad.
We should not bother kmod or any tools.
And System.map.no_namespaces is a cheesy workaround.

Thanks for the feedback!

Based on the discussion from last year about changing kmod/depmod for
this change to the ksymtab entries,
(https://lore.kernel.org/lkml/CAKi4VA+wvVxPxVSP6ruSR++TYvavKPNAQ5XhREF_9ZxeOKQirg@mail.gmail.com/ (local)),
I assumed this approach would be acceptable. The workaround (yeah, it is
a hack) is a way to mitigate the issue for people that can't update
depmod so easily. System.map.no_namespaces was not intended to be part
of any distribution, but rather used locally in depmod.sh. I could have
made this more clear.

BTW, I expressed my negative opinion in the review process
for the patch set. I am still not convinced with the
namespace feature, but anyway it was merged
(with poor review and test).



Get back on track, probably the right fix would be to
stop using __ksymtab_<namespace>.<symbol>.

It is not used for any purposes but passing
<namespace> / <symbol> pairs to modpost.


For example, __kstrtabns_##sym points to
the namespace string, so it would be possible
to parse it from modpost?

Then, asm("__ksymtab_" #ns NS_SEPARATOR #sym)
will go away.

I will give this a try.

Cheers,
Matthias

Masahiro

quoted

Lucas De Marchi

quoted

+
+set -- -ae -F System.map.no_namespaces
 if test -n "$INSTALL_MOD_PATH"; then
        set -- "$@" -b "$INSTALL_MOD_PATH"
 fi
--
2.23.0.581.g78d2f28ef7-goog

--
Lucas De Marchi

-- 
Best Regards
Masahiro Yamada