pc-bios/s390-ccw/jump2ipl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
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 <philmd@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
v2: Extend comment as suggested by Cornelia
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
--
2.27.0
On 4/23/21 4:24 PM, Thomas Huth 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. LGTM, I'm just wondering why I didn't clean that up when I last changed the file. Reviewed-by: Janosch Frank <frankja@linux.ibm.com> > > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > v2: Extend comment as suggested by Cornelia > > 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 >
On Fri, 23 Apr 2021 16:24:40 +0200 Thomas Huth <thuth@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 <philmd@redhat.com> > Signed-off-by: Thomas Huth <thuth@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 <cohuck@redhat.com>
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