On Fri, 23 Apr 2021 16:24:40 +0200
Thomas Huth <th...@redhat.com> wrote:
> When compiling the s390-ccw bios with clang, it emits a warning like this:
>
> pc-bios/s390-ccw/jump2ipl.c:86:9: warning: indirection of non-volatile null
> pointer will be deleted, not trap [-Wnull-dereference]
> if (*((uint64_t *)0) & RESET_PSW_MASK) {
> ^~~~~~~~~~~~~~~~
> pc-bios/s390-ccw/jump2ipl.c:86:9: note: consider using __builtin_trap() or
> qualifying pointer with 'volatile'
>
> We could add a "volatile" here to shut it up, but on the other hand,
> we also have a pointer variable called "reset_psw" in this file already
> that points to the PSW at address 0, so we can simply use that pointer
> variable instead.
>
> Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
> Signed-off-by: Thomas Huth <th...@redhat.com>
> ---
> v2: Extend comment as suggested by Cornelia
Thanks for helping my poor brain :)
>
> pc-bios/s390-ccw/jump2ipl.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
> index b9c70d64a5..73e4367e09 100644
> --- a/pc-bios/s390-ccw/jump2ipl.c
> +++ b/pc-bios/s390-ccw/jump2ipl.c
> @@ -82,8 +82,8 @@ void jump_to_low_kernel(void)
> jump_to_IPL_code(KERN_IMAGE_START);
> }
>
> - /* Trying to get PSW at zero address */
> - if (*((uint64_t *)0) & RESET_PSW_MASK) {
> + /* Trying to get PSW at zero address (pointed to by reset_psw) */
> + if (*reset_psw & RESET_PSW_MASK) {
> /*
> * Surely nobody will try running directly from lowcore, so
> * let's use 0 as an indication that we want to load the reset
Reviewed-by: Cornelia Huck <coh...@redhat.com>
