Re: Make LdrAccessResource Call an Internal Function to Satisfy Shrinker

[Robert Shearman]

Dmitry Timoshkov wrote:
> "Robert Shearman"  wrote:
> > -/**********************************************************************
> > -
> > - LdrAccessResource  (NTDLL.@)
> > - */
> >
> > -NTSTATUS WINAPI LdrAccessResource( HMODULE hmod, const IMAGE_RESOURCE_DATA_ENTRY *entry,
> > -
> >                               void **ptr, ULONG *size )
> >
> > +/* don't penalize other platforms stuff needed on i386 for compatibility */
> > +#ifdef __i386__
> > +NTSTATUS WINAPI access_resource( HMODULE hmod, const IMAGE_RESOURCE_DATA_ENTRY *entry,
> > -
> >                             void **ptr, ULONG *size )
> >
> > +#else
> > +static inline NTSTATUS access_resource( HMODULE hmod, const IMAGE_RESOURCE_DATA_ENTRY *entry,
> > -
> >                                    void **ptr, ULONG *size )
> >
> > +#endif
> > {
> >     NTSTATUS status;
> >
> > @@ -355,6 +358,30 @@ NTSTATUS WINAPI LdrAccessResource( HMODU
> >     return status;
> > }
> >
> > +/**********************************************************************
> > -
> > - LdrAccessResource  (NTDLL.@)
> > - */
> >
> > +#ifdef __i386__
> > +/* Shrinker depends on the "call access_resource" instruction being there */
> > +__ASM_GLOBAL_FUNC( LdrAccessResource,
> > - "pushl %ebp\n"
> > - "movl %esp, %ebp\n"
> > - "pushl 24(%ebp)\n"
> > - "pushl 20(%ebp)\n"
> > - "pushl 16(%ebp)\n"
> > - "pushl 12(%ebp)\n"
> > - "pushl 8(%ebp)\n"
> > - "call access_resource\n"
> > - "leave\n"
> > - "ret\n"
> >
> > +);
> > +#else
> > +NTSTATUS WINAPI LdrAccessResource( HMODULE hmod, const IMAGE_RESOURCE_DATA_ENTRY *entry,
> > -
> >                               void **ptr, ULONG *size )
> >
> > +{
> > - return access_resource( hmod, entry, ptr, size );
> >
> > +}
> > +#endif
>
> Shouldn't be enough for the __i386__ case just omitting 'inline' in access_resource
> definition?

No. Marcus already discovered with the previous version of 
EXC_CallHandler using the "-funit-at-a-time" option that the compiler 
can re-order the arguments and generally do whatever it wants if we hint 
that it won't be used outside of the module. The compiler is also free 
to generate LdrAccessResource as a simple jump to access_resource, or 
even to just make access_resource point to the same address as 
LdrAccessResource. In short, the only sure way of generating code that 
Shrinker needs is to do it explicitly.