Re: [PATCH 3/4] x86/kvm: Resolve shadow warnings in macro expansion

Rustad, Mark D
2014-07-25T17:19:11Z

On Jul 25, 2014, at 7:06 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 25/07/2014 15:27, Jeff Kirsher ha scritto:
>> From: Mark Rustad <mark.d.rustad@intel.com>
>>
>> Resolve shadow warnings that appear in W=2 builds. In this case,
>> a macro declared an inner local variable with the same name as an
>> outer one. This can be a serious hazard in the event that the outer
>> variable is ever passed as a parameter, as the inner variable will
>> be referenced instead of what was intended. This macro doesn't have
>> any parameters - at this time - but prepend an _ to all of the
>> macro-declared variables as is the custom, to resolve the warnings
>> and eliminate any future hazard.
>>
>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
>> ---
>> arch/x86/kvm/mmutrace.h | 24 ++++++++++++------------
>> 1 file changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/x86/kvm/mmutrace.h b/arch/x86/kvm/mmutrace.h
>> index 9d2e0ff..2d8d00c 100644
>> --- a/arch/x86/kvm/mmutrace.h
>> +++ b/arch/x86/kvm/mmutrace.h
>> @@ -22,26 +22,26 @@
>> __entry->unsync = sp->unsync;
>>
>> #define KVM_MMU_PAGE_PRINTK() ({ \
>> - const char *ret = p->buffer + p->len; \
>> - static const char *access_str[] = { \
>> + const char *_ret = p->buffer + p->len; \
>> + static const char *_access_str[] = { \
>> "---", "--x", "w--", "w-x", "-u-", "-ux", "wu-", "wux" \
>> }; \
>> - union kvm_mmu_page_role role; \
>> + union kvm_mmu_page_role _role; \
>> \
>> - role.word = __entry->role; \
>> + _role.word = __entry->role; \
>> \
>> trace_seq_printf(p, "sp gen %lx gfn %llx %u%s q%u%s %s%s" \
>> " %snxe root %u %s%c", __entry->mmu_valid_gen, \
>> - __entry->gfn, role.level, \
>> - role.cr4_pae ? " pae" : "", \
>> - role.quadrant, \
>> - role.direct ? " direct" : "", \
>> - access_str[role.access], \
>> - role.invalid ? " invalid" : "", \
>> - role.nxe ? "" : "!", \
>> + __entry->gfn, _role.level, \
>> + _role.cr4_pae ? " pae" : "", \
>> + _role.quadrant, \
>> + _role.direct ? " direct" : "", \
>> + _access_str[_role.access], \
>> + _role.invalid ? " invalid" : "", \
>> + _role.nxe ? "" : "!", \
>> __entry->root_count, \
>> __entry->unsync ? "unsync" : "sync", 0); \
>> - ret; \
>> + _ret; \
>> })
>>
>> #define kvm_mmu_trace_pferr_flags \
>>
>
> I think this unnecessarily uglifies the code, so I am not applying it.
> Gleb, what do you think?

Would you consider a version that only changes ret to _ret? That would be enough to resolve the warning. I only did the other variables because it seemed to be a best practice for these inner block declarations.

Hmmm. It seems like p should really be a parameter to this macro.

--
Mark Rustad, Networking Division, Intel Corporation