linux-kernel - [PATCH v6 21/39] kmsan: Accept ranges starting with 0 on s390

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Date: Fri, 21 Jun 2024 02:24:55 +0200
From: Ilya Leoshkevich <iii@...ux.ibm.com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>, Vlastimil Babka <vbabka@...e.cz>
Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH v6 21/39] kmsan: Accept ranges starting with 0 on s390

On s390 the virtual address 0 is valid (current CPU's lowcore is mapped
there), therefore KMSAN should not complain about it.

Disable the respective check on s390. There doesn't seem to be a
Kconfig option to describe this situation, so explicitly check for
s390.

Reviewed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 mm/kmsan/init.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/kmsan/init.c b/mm/kmsan/init.c
index 9de76ac7062c..3f8b1bbb9060 100644
--- a/mm/kmsan/init.c
+++ b/mm/kmsan/init.c
@@ -33,7 +33,10 @@ static void __init kmsan_record_future_shadow_range(void *start, void *end)
 	bool merged = false;
 
 	KMSAN_WARN_ON(future_index == NUM_FUTURE_RANGES);
-	KMSAN_WARN_ON((nstart >= nend) || !nstart || !nend);
+	KMSAN_WARN_ON((nstart >= nend) ||
+		      /* Virtual address 0 is valid on s390. */
+		      (!IS_ENABLED(CONFIG_S390) && !nstart) ||
+		      !nend);
 	nstart = ALIGN_DOWN(nstart, PAGE_SIZE);
 	nend = ALIGN(nend, PAGE_SIZE);
 
-- 
2.45.1