Re: [XEN PATCH 2/4] x86/hvm: address violations of MISRA C Rule 20.7

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2024-05-16 01:18, Stefano Stabellini wrote:
> On Wed, 15 May 2024, Nicola Vetrini wrote:
> > MISRA C Rule 20.7 states: "Expressions resulting from the expansion
> > of macro parameters shall be enclosed in parentheses". Therefore, some
> > macro definitions should gain additional parentheses to ensure that 
> > all
> > current and future users will be safe with respect to expansions that
> > can possibly alter the semantics of the passed-in macro parameter.
> >
> > No functional change.
> >
> > Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
>
> > ---
> >  xen/arch/x86/hvm/mtrr.c             | 2 +-
> >  xen/arch/x86/hvm/rtc.c              | 2 +-
> >  xen/arch/x86/include/asm/hvm/save.h | 2 +-
> >  3 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/xen/arch/x86/hvm/mtrr.c b/xen/arch/x86/hvm/mtrr.c
> > index 32f74c1db03b..1079851f70ed 100644
> > --- a/xen/arch/x86/hvm/mtrr.c
> > +++ b/xen/arch/x86/hvm/mtrr.c
> > @@ -16,7 +16,7 @@
> >  #include <public/hvm/e820.h>
> >
> >  /* Get page attribute fields (PAn) from PAT MSR. */
> > -#define pat_cr_2_paf(pat_cr,n)  ((((uint64_t)pat_cr) >> ((n)<<3)) & 
> > 0xff)
> > +#define pat_cr_2_paf(pat_cr, n)  ((((uint64_t)(pat_cr)) >> ((n) << 
> > 3)) & 0xff)
> just a cosmetic change
No. The point here is that pat_cr could in principle be something like 1 
+ 2, which without parentheses may not expand as intended (in this case 
because of the nearby cast). Then there's also the style fix on n
> >  /* Effective mm type lookup table, according to MTRR and PAT. */
> >  static const uint8_t mm_type_tbl[MTRR_NUM_TYPES][X86_NUM_MT] = {
> > diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c
> > index 4bb1c7505534..72c7bdbfcd02 100644
> > --- a/xen/arch/x86/hvm/rtc.c
> > +++ b/xen/arch/x86/hvm/rtc.c
> > @@ -45,7 +45,7 @@
> >  #define vrtc_domain(x) (container_of(x, struct pl_time, 
> > vrtc)->domain)
> >  #define vrtc_vcpu(x)   (pt_global_vcpu_target(vrtc_domain(x)))
> >  #define epoch_year     1900
> > -#define get_year(x)    (x + epoch_year)
> > +#define get_year(x)    ((x) + epoch_year)
> >
> >  enum rtc_mode {
> >     rtc_mode_no_ack,
> > diff --git a/xen/arch/x86/include/asm/hvm/save.h 
> > b/xen/arch/x86/include/asm/hvm/save.h
> > index 8149aa113cb4..ec8de029319d 100644
> > --- a/xen/arch/x86/include/asm/hvm/save.h
> > +++ b/xen/arch/x86/include/asm/hvm/save.h
> > @@ -50,7 +50,7 @@ int _hvm_check_entry(struct hvm_domain_context *h,
> >                            HVM_SAVE_LENGTH(x), true) == 0 )      \
> >      {                                                           \
> >          ptr = &(h)->data[(h)->cur];                             \
> > -        h->cur += HVM_SAVE_LENGTH(x);                           \
> > +        (h)->cur += HVM_SAVE_LENGTH(x);                         \
> >      }                                                           \
> >      ptr; })
> >
> > --
> > 2.34.1
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)