[PATCH v5 27/37] s390/diag: Unpoison diag224() output buffer

Ilya Leoshkevich
2024-06-19T15:46:17Z

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>
Reviewed-by: Alexander Potapenko <glider@google.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