diff mbox series

[v2,32/33] s390: Implement the architecture-specific kmsan functions

Message ID 20231121220155.1217090-33-iii@linux.ibm.com
State New
Headers
Series kmsan: Enable on s390 |

Commit Message

Ilya Leoshkevich Nov. 21, 2023, 10:01 p.m. UTC 
  arch_kmsan_get_meta_or_null() finds the lowcore shadow by querying the
prefix and calling kmsan_get_metadata() again.

kmsan_virt_addr_valid() delegates to virt_addr_valid().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/include/asm/kmsan.h | 36 +++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 arch/s390/include/asm/kmsan.h

Comments

Alexander Potapenko Dec. 11, 2023, 10:26 a.m. UTC | #1 
> +static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin)
> +{
> +       if (addr >= (void *)&S390_lowcore &&
> +           addr < (void *)(&S390_lowcore + 1)) {
> +               /*
> +                * Different lowcores accessed via S390_lowcore are described
> +                * by the same struct page. Resolve the prefix manually in
> +                * order to get a distinct struct page.
> +                */
> +               addr += (void *)lowcore_ptr[raw_smp_processor_id()] -
> +                       (void *)&S390_lowcore;
> +               return kmsan_get_metadata(addr, is_origin);
> +       }
> +       return NULL;
> +}

Is there a possibility for infinite recursion here? E.g. can
`lowcore_ptr[raw_smp_processor_id()]` point somewhere in between
`(void *)&S390_lowcore` and `(void *)(&S390_lowcore + 1))`?
Ilya Leoshkevich Dec. 11, 2023, 10:39 a.m. UTC | #2 
On Mon, 2023-12-11 at 11:26 +0100, Alexander Potapenko wrote:
> > +static inline void *arch_kmsan_get_meta_or_null(void *addr, bool
> > is_origin)
> > +{
> > +       if (addr >= (void *)&S390_lowcore &&
> > +           addr < (void *)(&S390_lowcore + 1)) {
> > +               /*
> > +                * Different lowcores accessed via S390_lowcore are
> > described
> > +                * by the same struct page. Resolve the prefix
> > manually in
> > +                * order to get a distinct struct page.
> > +                */
> > +               addr += (void *)lowcore_ptr[raw_smp_processor_id()]
> > -
> > +                       (void *)&S390_lowcore;
> > +               return kmsan_get_metadata(addr, is_origin);
> > +       }
> > +       return NULL;
> > +}
> 
> Is there a possibility for infinite recursion here? E.g. can
> `lowcore_ptr[raw_smp_processor_id()]` point somewhere in between
> `(void *)&S390_lowcore` and `(void *)(&S390_lowcore + 1))`?

No, it's allocated with __get_free_pages() or memblock_alloc_low().
But since this question came up, I should probably add a check and
a WARN_ON_ONCE() here.
Alexander Potapenko Dec. 11, 2023, 10:45 a.m. UTC | #3 
> > Is there a possibility for infinite recursion here? E.g. can
> > `lowcore_ptr[raw_smp_processor_id()]` point somewhere in between
> > `(void *)&S390_lowcore` and `(void *)(&S390_lowcore + 1))`?
>
> No, it's allocated with __get_free_pages() or memblock_alloc_low().
> But since this question came up, I should probably add a check and
> a WARN_ON_ONCE() here.

Yes, please.
diff mbox series

Patch

diff --git a/arch/s390/include/asm/kmsan.h b/arch/s390/include/asm/kmsan.h
new file mode 100644
index 000000000000..afec71e9e9ac
--- /dev/null
+++ b/arch/s390/include/asm/kmsan.h
@@ -0,0 +1,36 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_KMSAN_H
+#define _ASM_S390_KMSAN_H
+
+#include <asm/lowcore.h>
+#include <asm/page.h>
+#include <linux/kmsan.h>
+#include <linux/mmzone.h>
+#include <linux/stddef.h>
+
+#ifndef MODULE
+
+static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin)
+{
+	if (addr >= (void *)&S390_lowcore &&
+	    addr < (void *)(&S390_lowcore + 1)) {
+		/*
+		 * Different lowcores accessed via S390_lowcore are described
+		 * by the same struct page. Resolve the prefix manually in
+		 * order to get a distinct struct page.
+		 */
+		addr += (void *)lowcore_ptr[raw_smp_processor_id()] -
+			(void *)&S390_lowcore;
+		return kmsan_get_metadata(addr, is_origin);
+	}
+	return NULL;
+}
+
+static inline bool kmsan_virt_addr_valid(void *addr)
+{
+	return virt_addr_valid(addr);
+}
+
+#endif /* !MODULE */
+
+#endif /* _ASM_S390_KMSAN_H */