[DTrace-devel] [PATCH 4/6] Add macro to access stack slots past the register spill area

[Kris Van Hees]

On Tue, Mar 08, 2022 at 12:42:13AM -0500, Eugene Loh via DTrace-devel wrote:
> Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
> FWIW, it'd be nice if the ASCII-art figure that appears just above this
> change (describing the stack layout of a clause function) would show where
> the DT_STK_SP(n) appear... or a one-line comment for the below addition that
> explains that these slots come out of scratch memory.

Indeed, and in fact I am modifying the patch to also remove the SCRATCH_*
macros (and their ref in the comment block) because there is no code that
uses them at this point.

> On 3/7/22 2:50 PM, Kris Van Hees via DTrace-devel wrote:
> > Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> > ---
> >   libdtrace/dt_dctx.h | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/libdtrace/dt_dctx.h b/libdtrace/dt_dctx.h
> > index 7d38dfd8..77eb9a92 100644
> > --- a/libdtrace/dt_dctx.h
> > +++ b/libdtrace/dt_dctx.h
> > @@ -159,6 +159,9 @@ typedef struct dt_dctx {
> >   #define DT_STK_SPILL_BASE	(DT_STK_DCTX - DT_STK_SLOT_SZ)
> >   #define DT_STK_SPILL(n)		(DT_STK_SPILL_BASE - (n) * DT_STK_SLOT_SZ)
> > +#define DT_STK_SP_BASE		DT_STK_SPILL(DT_STK_NREGS)
> > +#define DT_STK_SP(n)		(DT_STK_SP_BASE - (n) * DT_STK_SLOT_SZ)
> > +
> >   #define DT_STK_SCRATCH_BASE	(-MAX_BPF_STACK)
> >   #define DT_STK_SCRATCH_SZ	(MAX_BPF_STACK + DT_STK_SPILL(DT_STK_NREGS - 1))
> 
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