Hi Nathan And Nicolas ,
Thanks for the feedback.
I took another look at this and experimented with a different approach for
external modules:
diff --git a/scripts/Makefile.kstack_erase b/scripts/Makefile.kstack_erase
index ee7e4ef7b892..xxxxxxxxxxxx 100644
--- a/scripts/Makefile.kstack_erase
+++ b/scripts/Makefile.kstack_erase
@@ -5,6 +5,10 @@ kstack-erase-cflags-y +=
-fplugin=$(objtree)/scripts/gcc-plugins/stackleak_plugin.so
kstack-erase-cflags-y +=
-fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_KSTACK_ERASE_TRACK_MIN_SIZE)
kstack-erase-cflags-y += -fplugin-arg-stackleak_plugin-arch=$(SRCARCH)
kstack-erase-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) +=
-fplugin-arg-stackleak_plugin-verbose
+ifneq ($(KBUILD_EXTMOD),)
+# Avoid embedding absolute -fplugin paths into external module DWARF metadata.
+kstack-erase-cflags-y += -gno-record-gcc-switches
+endif
DISABLE_KSTACK_ERASE := -fplugin-arg-stackleak_plugin-disable
endif
In my testing, this prevents the absolute stackleak plugin path specified via
-fplugin=$(objtree)/scripts/gcc-plugins/stackleak_plugin.so
from being recorded in the DWARF information of out-of-tree modules, while
avoiding the use of platform-specific utilities such as realpath/readlink
--relative-to.
I agree this does not solve the broader issue for all GCC plugins, but it
appears to address the specific KSTACK_ERASE case that originally motivated the
discussion.
Would this direction be more acceptable than the previous relative-path
approach, or would suppressing GCC switch recording for external modules be
considered undesirable from a debugging-information perspective?
Thanks,
Jaihind
-----Original Message-----
From: Nathan Chancellor <[email protected]>
Sent: Monday, August 3, 2026 11:42 PM
To: Nicolas Schier <[email protected]>
Cc: Jaihind Yadav <[email protected]>; [email protected];
[email protected]; [email protected];
[email protected]; [email protected]
Subject: Re: [PATCH 1/1] scripts: kstack_erase: use relative stackleak plugin
path
WARNING: This email originated from outside of Qualcomm. Please be wary of any
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On Fri, Jul 24, 2026 at 10:18:57PM +0200, Nicolas Schier wrote:
> On Wed, Jul 22, 2026 at 07:00:43PM +0000, Jaihind Yadav wrote:
> >
> > Hi Nicolas Schier,
> >
> > Thanks for the suggestion. I tested the proposed change:
> >
> > -kstack-erase-cflags-y +=
> > -fplugin=$(objtree)/scripts/gcc-plugins/stackleak_plugin.so
> > +kstack-erase-cflags-y +=
> > +-fplugin=scripts/gcc-plugins/stackleak_plugin.so
> >
> >
> > Unfortunately, it does not work for the out-of-tree module builds in
> > my environment.
>
> Thanks for checking; and yes I forgot out-of-tree modules. When
> building them, Kbuild changes to their respective output directory so
> my suggestion had to fail for oot kmods.
Technically, this is only a problem for out of tree kernel modules, right? When
building in-tree kernel modules, objtree is always '.', so we will never have
the output directory path in the debug information (at least based on my brief
testing).
> > Given that the proposed relative path breaks out-of-tree module
> > builds, could you please take a look at the patch I posted? If the
> > approach looks reasonable, I would appreciate your review and
> > consideration for merging it.
>
> I am not sure, if we can take your path, as 'readlink --relative-to'
> is only available in coreutils/Linux but coreutils are not a
> documented requirement for Linux builds (cp.
> Documentation/process/changes.rst),
> thus this would probably kill Linux builds on BSDs and Darwin/MacOS.
>
> But let me think about that a few days; and perhaps someone else
> comes up with an idea.
Yeah, I don't really like 'realpath --relative-to' either, it feels a bit like
a hack since it will only avoid including a full path if the module output
directory includes part of the build directory. For
example:
O=/mnt/build/kernel
MO=/mnt/build/extmod
$ realpath -m --relative-to /mnt/build/extmod /mnt/build/kernel ../kernel
vs.
O=/home/nathan/build/kernel
MO=/mnt/build/extmod
$ realpath -m --relative-to /mnt/build/extmod /home/nathan/build/kernel
../../../home/nathan/build/kernel
Furthermore, this patch only fixes KSTACK_ERASE but we have other GCC plugins
that presumably have the same problem.
I do not have a good solution for this either but since it only affects
external kernel modules, I am not particularly inclined to think too hard about
it.
--
Cheers,
Nathan
