processor flags

processor flags

[Cyrill Gorcunov]

Hi Peter, Ingo

could you spend a few minutes on me? ;)

You know, I'm almost complete changing the vm86 flags
with X86_EFLAGS_... but there is a hidden problem lays.
Look, in vm86.h we have the definition

#ifdef CONFIG_VM86
#define VM_MASK		0x00020000
#else
#define VM_MASK		0 /* ignored */
#endif

which has an indirect conditional compilation effect.
For example, if we take a look on include/asm-x86/ptrace.h

	static inline int v8086_mode(struct pt_regs *regs)
	{
	#ifdef CONFIG_X86_32
		return (regs->flags & VM_MASK);
	#else
		return 0;	/* No V86 mode support in long mode */
	#endif
	}

so if we don't have CONFIG_VM86 defined this function *always*
returning 0 so there I can't just change VM_MASK to X86_EFLAGS_VM.

Another piece of code from traps_32.c:do_general_protection

	if (regs->flags & VM_MASK)
		goto gp_in_vm86;

so if we didn't set CONFIG_VM86 i think this part is just thrown out
by gcc. So as we see, this VM_MASK original flag is not *just* a flag
but also says gcc which part of code to compile.

And now I'm in confusion - the way of changing this code I see is the
following:

- or use additional #ifdef CONFIG_VM86 in code where VM_MASK is used
  (that would be ugly IMHO)
- rename VM_MASK to say X86_EFLAGS_VM86 with that #ifdef remained
- rest VM_MASK as it is

How do you think?

		- Cyrill -

Re: processor flags

[H. Peter Anvin]

Cyrill Gorcunov wrote:
> 
> And now I'm in confusion - the way of changing this code I see is the
> following:
> 
> - or use additional #ifdef CONFIG_VM86 in code where VM_MASK is used
>   (that would be ugly IMHO)
> - rename VM_MASK to say X86_EFLAGS_VM86 with that #ifdef remained
> - rest VM_MASK as it is
> 
> How do you think?
> 

I think what we should do is:

- Rename VM_MASK to X86_VM_MASK (it's x86-specific after all)
- Have:

#if CONFIG_VM86
# define X86_VM_MASK X86_EFLAGS_VM
#else
# define X86_VM_MASK 0		/* No V86 support */
#endif

	-hpa

Re: processor flags

[Cyrill Gorcunov]

[H. Peter Anvin - Thu, Mar 27, 2008 at 12:55:42PM -0700]
> Cyrill Gorcunov wrote:
>> And now I'm in confusion - the way of changing this code I see is the
>> following:
>> - or use additional #ifdef CONFIG_VM86 in code where VM_MASK is used
>>   (that would be ugly IMHO)
>> - rename VM_MASK to say X86_EFLAGS_VM86 with that #ifdef remained
>> - rest VM_MASK as it is
>> How do you think?
>
> I think what we should do is:
>
> - Rename VM_MASK to X86_VM_MASK (it's x86-specific after all)
> - Have:
>
> #if CONFIG_VM86
> # define X86_VM_MASK X86_EFLAGS_VM
> #else
> # define X86_VM_MASK 0		/* No V86 support */
> #endif
>
> 	-hpa
>

Thanks a lot, Peter

		- Cyrill -