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Date: Mon, 7 Oct 2019 07:46:31 +0100 From: Matthias Maennich <maennich@...gle.com> To: Masahiro Yamada <yamada.masahiro@...ionext.com> Cc: Lucas De Marchi <lucas.de.marchi@...il.com>, lkml <linux-kernel@...r.kernel.org>, "Cc: Android Kernel" <kernel-team@...roid.com>, Stefan Wahren <stefan.wahren@...e.com>, Jessica Yu <jeyu@...nel.org>, Martijn Coenen <maco@...roid.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-modules <linux-modules@...r.kernel.org> Subject: Re: [PATCH] depmod: create and use System.map.no_namespaces 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 ><lucas.de.marchi@...il.com> wrote: >> >> On Fri, Oct 4, 2019 at 2:57 AM Matthias Maennich <maennich@...gle.com> wrote: >> > >> > 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/ >> > >> > Reported-by: Stefan Wahren <stefan.wahren@...e.com> >> > Fixes: 8651ec01daed ("module: add support for symbol namespaces.") >> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com> >> > Cc: Lucas De Marchi <lucas.de.marchi@...il.com> >> > Cc: Jessica Yu <jeyu@...nel.org> >> > Cc: Martijn Coenen <maco@...roid.com> >> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> >> > Cc: linux-modules@...r.kernel.org >> > Signed-off-by: Matthias Maennich <maennich@...gle.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/ >> >> I don't really agree with that thought, more below. >> >> > >> > 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/), 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 > > > > >> Lucas De Marchi >> >> > + >> > +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
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