| Message ID | 20210423083604.526367-1-thuth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | pc-bios/s390-ccw: Use reset_psw pointer instead of hard-coded null pointer | expand |
On 4/23/21 10:36 AM, 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. > > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > pc-bios/s390-ccw/jump2ipl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
On Fri, 23 Apr 2021 10:36:04 +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. > > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > pc-bios/s390-ccw/jump2ipl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c > index b9c70d64a5..de1541ea5d 100644 > --- a/pc-bios/s390-ccw/jump2ipl.c > +++ b/pc-bios/s390-ccw/jump2ipl.c > @@ -83,7 +83,7 @@ void jump_to_low_kernel(void) > } > > /* Trying to get PSW at zero address */ Maybe make this /* Trying to get PSW at zero address (pointed to by reset_psw) */ I'm always getting a headache when I'm reading this file, so let's make it easy :) > - if (*((uint64_t *)0) & RESET_PSW_MASK) { > + 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..de1541ea5d 100644 --- a/pc-bios/s390-ccw/jump2ipl.c +++ b/pc-bios/s390-ccw/jump2ipl.c @@ -83,7 +83,7 @@ void jump_to_low_kernel(void) } /* Trying to get PSW at zero address */ - if (*((uint64_t *)0) & RESET_PSW_MASK) { + 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. Signed-off-by: Thomas Huth <thuth@redhat.com> --- pc-bios/s390-ccw/jump2ipl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)