Re: [PATCH] powerpc/booke: Avoid link stack corruption in several places

Segher Boessenkool
2021-08-23T20:18:08Z

On Mon, Aug 23, 2021 at 07:05:38PM +0200, Christophe Leroy wrote:
> Le 23/08/2021 à 17:58, Segher Boessenkool a écrit :
> >On Mon, Aug 23, 2021 at 07:53:01AM +0000, Christophe Leroy wrote:
> >> /* Be careful, this will clobber the lr register. */
> >> #define LOAD_REG_ADDR_PIC(reg, name) \
> >>- bl 0f; \
> >>+ bcl 20,31,0f \
> >> 0: mflr reg; \
> >> addis reg,reg,(name - 0b)@ha; \
> >> addi reg,reg,(name - 0b)@l;
> >
> >The code ended each line with a semicolon before, for absolutely no
> >reason that I can see, but still. Fixing that would be nice, but only
> >doing it on one line isn't good.
>
> Sure, forgetting the semicolon broke the build. That's because the
> backslash removes the newline.

Ah right, one of the surprises you get from using the C preprocessor on
non-C code :-)

> The cleanest way I found to fix that quite of stuff is by using GAS macro,
> as I did for LOAD_REG_IMMEDIATE() some time ago.

Yeah, good plan. You can use loops and saner parameters etc. as well if
you do :-)

> >Btw. Both the 7450 and the modern cores implementing this really need
> >this to be $+4, so it is a lot clearer to write that instead of 1f or
> >a named label.
>
> I like that, removing unneeded labels will make it smoother and clearer.
> I'll do it.

Cool, thanks!

Segher