On Oct 24, 2006, at 3:41 AM, Havard Eidnes wrote:

> Hi,
>
> the new gcc propagates const-ness from structs to struct members.
> This exposes a build problem, in that an assignment in
> sig_machdep.c's cpu_setmcontext() loses a qualification, and that
> gets turned into an error with -Werror.
>
> Nick Hudson suggested that the passed mcontext should probably
> not be modified, only the trap frame should get the result of the
> "masked MSR" register value.
>
> Since I'm not intimate with the powerpc code, I have to ask if
> this looks reasonable:

This patch looks OK to me.

>
>
> Index: sig_machdep.c
> ===================================================================
> RCS file: /u/nb/src/sys/arch/powerpc/powerpc/sig_machdep.c,v
> retrieving revision 1.25
> diff -u -r1.25 sig_machdep.c
> --- sig_machdep.c       26 Mar 2006 16:15:57 -0000      1.25
> +++ sig_machdep.c       24 Oct 2006 10:33:38 -0000
> @@ -216,20 +216,13 @@
>  cpu_setmcontext(struct lwp *l, const mcontext_t *mcp, unsigned int  
> flags)
>  {
>         struct trapframe *tf = trapframe(l);
> -       __greg_t *gr = mcp->__gregs;
> +       const __greg_t *gr = mcp->__gregs;
>  #ifdef PPC_HAVE_FPU
>         struct pcb *pcb = &l->l_addr->u_pcb;
>  #endif
>
>         /* Restore GPR context, if any. */
>         if (flags & _UC_CPU) {
> -               /*
> -                * Accept all user-settable bits without complaint;
> -                * userland should not need to know the machine- 
> specific
> -                * MSR value.
> -                */
> -               gr[_REG_MSR] = (gr[_REG_MSR] & PSL_USERMOD) |  
> PSL_USERSET;
> -
>  #ifdef PPC_HAVE_FPU
>                 /*
>                  * Always save the FP exception mode in the PCB.
> @@ -242,7 +235,12 @@
>                 tf->cr   = gr[_REG_CR];
>                 tf->lr   = gr[_REG_LR];
>                 tf->srr0 = gr[_REG_PC];
> -               tf->srr1 = gr[_REG_MSR];
> +               /*
> +                * Accept all user-settable bits without complaint;
> +                * userland should not need to know the machine- 
> specific
> +                * MSR value.
> +                */
> +               tf->srr1 = (gr[_REG_MSR] & PSL_USERMOD) | PSL_USERSET;
>                 tf->ctr  = gr[_REG_CTR];
>                 tf->xer  = gr[_REG_XER];
>  #ifdef PPC_OEA
>
>
> Regards,
>
> - Havard

-- thorpej