Re: [PATCH] arch: x86: kvm: x86.c: Cleaning up uninitialized variables

[Michael Tokarev <mjt@tls.msk.ru>]

03.06.2014 16:04, Paolo Bonzini wrote:
> Il 01/06/2014 01:05, Rickard Strandqvist ha scritto:
>> There is a risk that the variable will be used without being initialized.
>>
>> This was largely found by using a static code analysis program called cppcheck.
>>
>> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
> 
> No, there isn't.  The full context looks like this:
> 
>         longmode = is_long_mode(vcpu) && cs_l == 1;
>         if (!longmode) {
>                 param = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDX) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RAX) & 0xffffffff);
>                 ingpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RBX) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RCX) & 0xffffffff);
>                 outgpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDI) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RSI) & 0xffffffff);
>         }
> #ifdef CONFIG_X86_64
>         else {
>                 param = kvm_register_read(vcpu, VCPU_REGS_RCX);
>                 ingpa = kvm_register_read(vcpu, VCPU_REGS_RDX);
>                 outgpa = kvm_register_read(vcpu, VCPU_REGS_R8);
>         }
> #endif
> 
> and longmode must be zero if !CONFIG_X86_64:

This is not the first time this code is attempted to be changed.

Maybe adding an additional #ifdef..endif around the longmode
assignment and the "if" above will solve this for good?

Or maybe something like this:

 #ifdef CONFIG_X86_64
         if (!(is_long_mode(vcpu) && cs_l == 1)) {
 #else
         if (1) {
 #endif
                 param = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDX) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RAX) & 0xffffffff);
                 ingpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RBX) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RCX) & 0xffffffff);
                 outgpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDI) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RSI) & 0xffffffff);
         }
         else {
                 param = kvm_register_read(vcpu, VCPU_REGS_RCX);
                 ingpa = kvm_register_read(vcpu, VCPU_REGS_RDX);
                 outgpa = kvm_register_read(vcpu, VCPU_REGS_R8);
         }

, to make it all explicit and obvious?

Thanks,

/mjt