[PATCH v4 26/35] s390/diag: Unpoison diag224() output buffer

[Ilya Leoshkevich <iii@linux.ibm.com>]

Diagnose 224 stores 4k bytes, which currently cannot be deduced from
the inline assembly constraints. This leads to KMSAN false positives.

Fix the constraints by using a 4k-sized struct instead of a raw
pointer. While at it, prettify them too.

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/kernel/diag.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/diag.c b/arch/s390/kernel/diag.c
index 8dee9aa0ec95..8a7009618ba7 100644
--- a/arch/s390/kernel/diag.c
+++ b/arch/s390/kernel/diag.c
@@ -278,12 +278,14 @@ int diag224(void *ptr)
 	int rc = -EOPNOTSUPP;
 
 	diag_stat_inc(DIAG_STAT_X224);
-	asm volatile(
-		"	diag	%1,%2,0x224\n"
-		"0:	lhi	%0,0x0\n"
+	asm volatile("\n"
+		"	diag	%[type],%[addr],0x224\n"
+		"0:	lhi	%[rc],0\n"
 		"1:\n"
 		EX_TABLE(0b,1b)
-		: "+d" (rc) :"d" (0), "d" (addr) : "memory");
+		: [rc] "+d" (rc)
+		, "=m" (*(struct { char buf[PAGE_SIZE]; } *)ptr)
+		: [type] "d" (0), [addr] "d" (addr));
 	return rc;
 }
 EXPORT_SYMBOL(diag224);
-- 
2.45.1