[PATCH V2 3/5] Force MAPPING_TYPE__IDENTIY for PIE

[Leo Yan]

On 8/26/2024 10:35 PM, Steve Clevenger wrote:
> 
> Changes in V2:
>   - Updated mailing list distribution
> 
> Use dso__is_pie() to check whether the DSO file is a Position
> Independent Executable (PIE). If PIE, change the MAPPING_TYPE to
> MAPPING_TYPE__IDENTITY so a zero map pgoff (text offset) is passed
> into the script.
> 
> 
> Signed-off-by: Steve Clevenger <scclevenger at os.amperecomputing.com>
> ---
>  tools/perf/util/map.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index e1d14936a60d..df7c06fc373e 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -171,8 +171,11 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
>                 assert(!dso__kernel(dso));
>                 map__init(result, start, start + len, pgoff, dso);
> 
> +               if (map->pgoff && !no_dso)
> +                       no_dso = dso__is_pie(dso);      // PIE check

Here the logic is whatever the `pgoff` is (zero or non-zero), we need to
always set the mapping type as MAPPING_TYPE__IDENTITY. It is no need to check
pgoff and is no matter with 'no_dso'. So we can simply check dso__is_pie() and
set IDENTITY flag for the true case.

    if (dso__is_pie(dso)) {
            map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
    } else if (anon || no_dso) {
            ...
    }

BTW, please rebase the series on the top of the perf-tools-next branch [1], I
saw this patch has merging conflict on it.

Thanks,
Leo

[1] https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
    branch: perf-tools-next
> +
>                 if (anon || no_dso) {
> -                       map->mapping_type = MAPPING_TYPE__IDENTITY;
> +                       map__set_mapping_type(map, MAPPING_TYPE__IDENTITY);
> 
>                         /*
>                          * Set memory without DSO as loaded. All map__find_*
> --
> 2.25.1
>