On Thu, Dec 14, 2023 at 12:24:45AM +0100, Ilya Leoshkevich wrote:
> Diagnose 224 stores 4k bytes, which cannot be deduced from the inline
> assembly constraints. This leads to KMSAN false positives.
>
> Unpoison the output buffer manually with kmsan_unpoison_memory().
>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> ---
> arch/s390/kernel/diag.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/kernel/diag.c b/arch/s390/kernel/diag.c
> index 92fdc35f028c..fb83a21014d0 100644
> --- a/arch/s390/kernel/diag.c
> +++ b/arch/s390/kernel/diag.c
> @@ -9,6 +9,7 @@
> #include <linux/export.h>
> #include <linux/init.h>
> #include <linux/cpu.h>
> +#include <linux/kmsan-checks.h>
> #include <linux/seq_file.h>
> #include <linux/debugfs.h>
> #include <linux/vmalloc.h>
> @@ -255,6 +256,7 @@ int diag224(void *ptr)
> "1:\n"
> EX_TABLE(0b,1b)
> : "+d" (rc) :"d" (0), "d" (addr) : "memory");
> + kmsan_unpoison_memory(ptr, PAGE_SIZE);
Wouldn't it be better to adjust the inline assembly instead?
Something like this:
diff --git a/arch/s390/kernel/diag.c b/arch/s390/kernel/diag.c
index 92fdc35f028c..b1b0acda50c6 100644
--- a/arch/s390/kernel/diag.c
+++ b/arch/s390/kernel/diag.c
@@ -247,14 +247,18 @@ int diag224(void *ptr)
{
unsigned long addr = __pa(ptr);
int rc = -EOPNOTSUPP;
+ struct _d {
+ char _d[4096];
+ };
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 _d *)ptr)
+ : [type] "d" (0), [addr] "d" (addr));
return rc;
}
EXPORT_SYMBOL(diag224);
