The patch titled
Subject: lib/stackdepot.c: build with -fno-builtin
has been added to the -mm tree. Its filename is
stackdepot-build-with-fno-builtin.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/stackdepot-build-with-fno-builtin.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/stackdepot-build-with-fno-builtin.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: lib/stackdepot.c: build with -fno-builtin
Clang may replace stackdepot_memcmp() with a call to instrumented bcmp(),
which is exactly what we wanted to avoid creating stackdepot_memcmp().
Building the file with -fno-builtin prevents such optimizations.
This patch has been previously mailed as part of KMSAN RFC patch series.
Link: http://lkml.kernel.org/r/20200220141916.55455-2-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/Makefile | 4 ++++
1 file changed, 4 insertions(+)
--- a/lib/Makefile~stackdepot-build-with-fno-builtin
+++ a/lib/Makefile
@@ -222,6 +222,10 @@ obj-$(CONFIG_MEMREGION) += memregion.o
obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
obj-$(CONFIG_IRQ_POLL) += irq_poll.o
+# stackdepot.c should not be instrumented or call instrumented functions.
+# Prevent the compiler from calling builtins like memcmp() or bcmp() from this
+# file.
+CFLAGS_stackdepot.o += -fno-builtin
obj-$(CONFIG_STACKDEPOT) += stackdepot.o
KASAN_SANITIZE_stackdepot.o := n
KCOV_INSTRUMENT_stackdepot.o := n
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
lib-stackdepot-fix-global-out-of-bounds-in-stack_slabs.patch
stackdepot-check-depot_index-before-accessing-the-stack-slab.patch
stackdepot-build-with-fno-builtin.patch
kasan-stackdepot-move-filter_irq_stacks-to-stackdepotc.patch
