Re: [Xen-devel] [PATCH] x86/Viridian: don't depend on undefined register state

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 14 October 2016 05:38
> To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Subject: [PATCH] x86/Viridian: don't depend on undefined register state
> 
> The high halves of all GPRs are undefined in 32-bit and compat modes,
> and the dependency is being obfuscated by our structure field names not
> matching architectural register names (it was actually while putting
> together a patch to correct this when I noticed the issue here).
> 
> For consistency also use the architecturally correct names on the
> output side.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> 
> --- a/xen/arch/x86/hvm/viridian.c
> +++ b/xen/arch/x86/hvm/viridian.c
> @@ -667,9 +667,9 @@ int viridian_hypercall(struct cpu_user_r
>          output_params_gpa = regs->r8;
>          break;
>      case 4:
> -        input.raw = ((uint64_t)regs->edx << 32) | regs->eax;
> -        input_params_gpa = ((uint64_t)regs->ebx << 32) | regs->ecx;
> -        output_params_gpa = ((uint64_t)regs->edi << 32) | regs->esi;
> +        input.raw = (regs->rdx << 32) | regs->_eax;
> +        input_params_gpa = (regs->rbx << 32) | regs->_ecx;
> +        output_params_gpa = (regs->rdi << 32) | regs->_esi;
>          break;
>      default:
>          goto out;
> @@ -770,8 +770,8 @@ out:
>          regs->rax = output.raw;
>          break;
>      default:
> -        regs->edx = output.raw >> 32;
> -        regs->eax = output.raw;
> +        regs->rdx = output.raw >> 32;
> +        regs->rax = (uint32_t)output.raw;
>          break;
>      }
> 
> 
> 

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