+++ Matthias Maennich [07/10/19 07:46 +0100]:
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
<[email protected]> wrote:
On Fri, Oct 4, 2019 at 2:57 AM Matthias Maennich <[email protected]> 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/[email protected]/
Reported-by: Stefan Wahren <[email protected]>
Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
Cc: Masahiro Yamada <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Martijn Coenen <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: [email protected]
Signed-off-by: Matthias Maennich <[email protected]>
---
Please note this depends on the new ksymtab entry format proposed in
https://lore.kernel.org/lkml/[email protected]/
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_9zxeokq...@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.
That sounds like a good idea. Maybe one way of going about it is to
take the symbol value of __kstrtabns_##sym, subtract the section address
(the section referred to by the st_shndx) from it to obtain the offset
into __ksymtab_strings, and read in the namespace string from that
offset.
