[v2,2/2] s390x: Use strpadcpy for copying vm name

When using strncpy with lenght equal to size of target array,
GCC 11 produce following warning:

   warning: '__builtin_strncpy' specified bound 256 equals destination size [-Wstringop-truncation]

To prevent this warning, use strpadcpy function that will enusure that
provide functionality similar to strncpy but allow copy strings with
length equal size of target array (and discarding endint zero) and
ensure array is zeroed after copied string.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 target/s390x/kvm.c         | 12 +++++-------
 target/s390x/misc_helper.c |  7 +++++--
 2 files changed, 10 insertions(+), 9 deletions(-)

On 1/11/21 6:09 PM, Miroslav Rezanina wrote:
> When using strncpy with lenght equal to size of target array,

Typo "length".

> GCC 11 produce following warning:
> 
>    warning: '__builtin_strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
> 
> To prevent this warning, use strpadcpy function that will enusure that
> provide functionality similar to strncpy but allow copy strings with
> length equal size of target array (and discarding endint zero) and
> ensure array is zeroed after copied string.

Hard to understand... Look like incorrect copy/paste in the middle?

> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> ---
>  target/s390x/kvm.c         | 12 +++++-------
>  target/s390x/misc_helper.c |  7 +++++--
>  2 files changed, 10 insertions(+), 9 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

On 11/01/2021 18.09, Miroslav Rezanina wrote:
> When using strncpy with lenght equal to size of target array,

s/lenght/length/

> GCC 11 produce following warning:
> 
>     warning: '__builtin_strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
> 
> To prevent this warning, use strpadcpy function that will enusure that
> provide functionality similar to strncpy but allow copy strings with
> length equal size of target array (and discarding endint zero) and

s/endint/ending/

> ensure array is zeroed after copied string.
> 
> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> ---
>   target/s390x/kvm.c         | 12 +++++-------
>   target/s390x/misc_helper.c |  7 +++++--
>   2 files changed, 10 insertions(+), 9 deletions(-)

With the two typos fixed:

Reviewed-by: Thomas Huth <thuth@redhat.com>

> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index b8385e6b95..dc27fa36c9 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -29,6 +29,7 @@
>   #include "internal.h"
>   #include "kvm_s390x.h"
>   #include "sysemu/kvm_int.h"
> +#include "qemu/cutils.h"
>   #include "qapi/error.h"
>   #include "qemu/error-report.h"
>   #include "qemu/timer.h"
> @@ -1910,18 +1911,15 @@ static void insert_stsi_3_2_2(S390CPU *cpu, __u64 addr, uint8_t ar)
>                                                       strlen(qemu_name)));
>       }
>       sysib.vm[0].ext_name_encoding = 2; /* 2 = UTF-8 */
> -    memset(sysib.ext_names[0], 0, sizeof(sysib.ext_names[0]));
>       /* If hypervisor specifies zero Extended Name in STSI322 SYSIB, it's
>        * considered by s390 as not capable of providing any Extended Name.
>        * Therefore if no name was specified on qemu invocation, we go with the
>        * same "KVMguest" default, which KVM has filled into short name field.
>        */
> -    if (qemu_name) {
> -        strncpy((char *)sysib.ext_names[0], qemu_name,
> -                sizeof(sysib.ext_names[0]));
> -    } else {
> -        strcpy((char *)sysib.ext_names[0], "KVMguest");
> -    }
> +    strpadcpy((char *)sysib.ext_names[0],
> +              sizeof(sysib.ext_names[0]),
> +              qemu_name ?: "KVMguest", '\0');
> +
>       /* Insert UUID */
>       memcpy(sysib.vm[0].uuid, &qemu_uuid, sizeof(sysib.vm[0].uuid));
>   
> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
> index 58dbc023eb..7ea90d414a 100644
> --- a/target/s390x/misc_helper.c
> +++ b/target/s390x/misc_helper.c
> @@ -19,6 +19,7 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#include "qemu/cutils.h"
>   #include "qemu/main-loop.h"
>   #include "cpu.h"
>   #include "internal.h"
> @@ -369,8 +370,10 @@ uint32_t HELPER(stsi)(CPUS390XState *env, uint64_t a0, uint64_t r0, uint64_t r1)
>                   ebcdic_put(sysib.sysib_322.vm[0].name, qemu_name,
>                              MIN(sizeof(sysib.sysib_322.vm[0].name),
>                                  strlen(qemu_name)));
> -                strncpy((char *)sysib.sysib_322.ext_names[0], qemu_name,
> -                        sizeof(sysib.sysib_322.ext_names[0]));
> +                strpadcpy((char *)sysib.sysib_322.ext_names[0],
> +                          sizeof(sysib.sysib_322.ext_names[0]),
> +                          qemu_name, '\0');
> +
>               } else {
>                   ebcdic_put(sysib.sysib_322.vm[0].name, "TCGguest", 8);
>                   strcpy((char *)sysib.sysib_322.ext_names[0], "TCGguest");
>