The patch titled
Subject: kmsan: fix memcpy tests
has been added to the -mm mm-unstable branch. Its filename is
kmsan-fix-memcpy-tests.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kmsan-fix-memcpy-tests.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: kmsan: fix memcpy tests
Date: Mon, 5 Dec 2022 15:57:40 +0100
Recent Clang changes may cause it to delete calls of memcpy(), if the
source is an uninitialized volatile local. This happens because passing a
pointer to a volatile local into memcpy() discards the volatile qualifier,
giving the compiler a free hand to optimize the memcpy() call away.
Use OPTIMIZER_HIDE_VAR() to hide the uninitialized var from the too-smart
compiler.
Link: https://lkml.kernel.org/r/20221205145740.694038-1-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Suggested-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kmsan/kmsan_test.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/kmsan/kmsan_test.c~kmsan-fix-memcpy-tests
+++ a/mm/kmsan/kmsan_test.c
@@ -419,6 +419,7 @@ static void test_memcpy_aligned_to_align
kunit_info(
test,
"memcpy()ing aligned uninit src to aligned dst (UMR report)\n");
+ OPTIMIZER_HIDE_VAR(uninit_src);
memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
@@ -441,6 +442,7 @@ static void test_memcpy_aligned_to_unali
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst (UMR report)\n");
+ OPTIMIZER_HIDE_VAR(uninit_src);
memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)dst, 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
@@ -464,6 +466,7 @@ static void test_memcpy_aligned_to_unali
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst - part 2 (UMR report)\n");
+ OPTIMIZER_HIDE_VAR(uninit_src);
memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst[4], sizeof(uninit_src));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
lockdep-allow-instrumenting-lockdepc-with-kmsan.patch
kmsan-allow-using-__msan_instrument_asm_store-inside-runtime.patch
kmsan-fix-memcpy-tests.patch
