linux-kernel - [PATCH v2 10/33] kmsan: Expose kmsan_get

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Message-ID: <20231121220155.1217090-11-iii@linux.ibm.com>
Date:   Tue, 21 Nov 2023 23:01:04 +0100
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 v2 10/33] kmsan: Expose kmsan_get_metadata()

Each s390 CPU has lowcore pages associated with it. Each CPU sees its
own lowcore at virtual address 0 through a hardware mechanism called
prefixing. Additionally, all lowcores are mapped to non-0 virtual
addresses stored in the lowcore_ptr[] array.

When lowcore is accessed through virtual address 0, one needs to
resolve metadata for lowcore_ptr[raw_smp_processor_id()].

Expose kmsan_get_metadata() to make it possible to do this from the
arch code.

Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 include/linux/kmsan.h      | 14 ++++++++++++++
 mm/kmsan/instrumentation.c |  1 +
 mm/kmsan/kmsan.h           |  1 -
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index e0c23a32cdf0..ff8fd95733fa 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -230,6 +230,15 @@ void kmsan_handle_urb(const struct urb *urb, bool is_out);
  */
 void kmsan_unpoison_entry_regs(const struct pt_regs *regs);
 
+/**
+ * kmsan_get_metadata() - Return a pointer to KMSAN shadow or origins.
+ * @addr:      kernel address.
+ * @is_origin: whether to return origins or shadow.
+ *
+ * Return NULL if metadata cannot be found.
+ */
+void *kmsan_get_metadata(void *addr, bool is_origin);
+
 #else
 
 static inline void kmsan_init_shadow(void)
@@ -329,6 +338,11 @@ static inline void kmsan_unpoison_entry_regs(const struct pt_regs *regs)
 {
 }
 
+static inline void *kmsan_get_metadata(void *addr, bool is_origin)
+{
+	return NULL;
+}
+
 #endif
 
 #endif /* _LINUX_KMSAN_H */
diff --git a/mm/kmsan/instrumentation.c b/mm/kmsan/instrumentation.c
index 8a1bbbc723ab..94b49fac9d8b 100644
--- a/mm/kmsan/instrumentation.c
+++ b/mm/kmsan/instrumentation.c
@@ -14,6 +14,7 @@
 
 #include "kmsan.h"
 #include <linux/gfp.h>
+#include <linux/kmsan.h>
 #include <linux/kmsan_string.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
diff --git a/mm/kmsan/kmsan.h b/mm/kmsan/kmsan.h
index adf443bcffe8..34b83c301d57 100644
--- a/mm/kmsan/kmsan.h
+++ b/mm/kmsan/kmsan.h
@@ -66,7 +66,6 @@ struct shadow_origin_ptr {
 
 struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size,
 						     bool store);
-void *kmsan_get_metadata(void *addr, bool is_origin);
 void __init kmsan_init_alloc_meta_for_range(void *start, void *end);
 
 enum kmsan_bug_reason {
-- 
2.41.0