| Message ID | 20210423142440.582188-1-thuth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer | expand |
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>
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 >
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
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(-)