Re: [PATCH v2 01/10] perf dwarf-aux: Use signed variable types in match_var_offset

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Wed, Aug 27, 2025 at 11:52:02PM -0700, Namhyung Kim wrote:
> On Mon, Aug 25, 2025 at 07:54:03PM +0000, Zecheng Li wrote:
> > match_var_offset compares address offsets to determine if an access
> > falls within a variable's bounds. The offsets involved for those
> > relative to base registers from DW_OP_breg can be negative.

> > The current implementation uses unsigned types (u64) for these offsets,
> > which rejects almost all negative values.
 
> Right, I thought it cannot get negative offsets except for stack access
> (e.g. fbreg).  But it turns out that container_of() trick can generate
> them with optimizing compilers.
 
> > Change the signature of match_var_offset to use signed types (s64). This
> > ensures correct behavior when addr_offset or addr_type are negative.

> > Signed-off-by: Zecheng Li <zecheng@google.com>
 
> I've confirmed it produced slightly better results on my test sets.
 
> Reviewed-by: Namhyung Kim <namhyung@kernel.org>

Cherry picked this first patch to make a bit of progress in the
perf-tools-next front.

- Arnaldo