perf symbols: Ignore mapping symbols on riscv

[PATCH] perf symbols: Ignore mapping symbols on riscv

Posted by Haibo Xu 10 months ago

RISCV ELF use mapping symbols with special names $x, $d to
identify regions of RISCV code or code with different ISAs[1].
These symbols don't identify functions, so will confuse the
perf output.

The patch filters out these symbols at load time, similar to
"4886f2ca perf symbols: Ignore mapping symbols on aarch64".

[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/
    master/riscv-elf.adoc#mapping-symbol

Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
---
 tools/perf/util/symbol-elf.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index fbf6d0f73af9..55b1409b0593 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1733,6 +1733,12 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss,
 				continue;
 		}
 
+		/* Reject RISCV ELF "mapping symbols" */
+		if (ehdr.e_machine == EM_RISCV) {
+			if (elf_name[0] == '$' && strchr("dx", elf_name[1]))
+				continue;
+		}
+
 		if (runtime_ss->opdsec && sym.st_shndx == runtime_ss->opdidx) {
 			u32 offset = sym.st_value - syms_ss->opdshdr.sh_addr;
 			u64 *opd = opddata->d_buf + offset;
-- 
2.43.0

Re: [PATCH] perf symbols: Ignore mapping symbols on riscv

Posted by Namhyung Kim 10 months ago

Hello,

On Wed, Apr 09, 2025 at 10:51:56AM +0800, Haibo Xu wrote:
> RISCV ELF use mapping symbols with special names $x, $d to
> identify regions of RISCV code or code with different ISAs[1].
> These symbols don't identify functions, so will confuse the
> perf output.
> 
> The patch filters out these symbols at load time, similar to
> "4886f2ca perf symbols: Ignore mapping symbols on aarch64".
> 
> [1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/
>     master/riscv-elf.adoc#mapping-symbol
> 
> Signed-off-by: Haibo Xu <haibo1.xu@intel.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


> ---
>  tools/perf/util/symbol-elf.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index fbf6d0f73af9..55b1409b0593 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -1733,6 +1733,12 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss,
>  				continue;
>  		}
>  
> +		/* Reject RISCV ELF "mapping symbols" */
> +		if (ehdr.e_machine == EM_RISCV) {
> +			if (elf_name[0] == '$' && strchr("dx", elf_name[1]))
> +				continue;
> +		}
> +
>  		if (runtime_ss->opdsec && sym.st_shndx == runtime_ss->opdidx) {
>  			u32 offset = sym.st_value - syms_ss->opdshdr.sh_addr;
>  			u64 *opd = opddata->d_buf + offset;
> -- 
> 2.43.0
>

Re: [PATCH] perf symbols: Ignore mapping symbols on riscv

Posted by Haibo Xu 8 months, 3 weeks ago

kindly ping.

Regards,
Haibo

On Fri, Apr 11, 2025 at 8:53 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello,
>
> On Wed, Apr 09, 2025 at 10:51:56AM +0800, Haibo Xu wrote:
> > RISCV ELF use mapping symbols with special names $x, $d to
> > identify regions of RISCV code or code with different ISAs[1].
> > These symbols don't identify functions, so will confuse the
> > perf output.
> >
> > The patch filters out these symbols at load time, similar to
> > "4886f2ca perf symbols: Ignore mapping symbols on aarch64".
> >
> > [1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/
> >     master/riscv-elf.adoc#mapping-symbol
> >
> > Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
>
> Acked-by: Namhyung Kim <namhyung@kernel.org>
>
> Thanks,
> Namhyung
>
>
> > ---
> >  tools/perf/util/symbol-elf.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> > index fbf6d0f73af9..55b1409b0593 100644
> > --- a/tools/perf/util/symbol-elf.c
> > +++ b/tools/perf/util/symbol-elf.c
> > @@ -1733,6 +1733,12 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss,
> >                               continue;
> >               }
> >
> > +             /* Reject RISCV ELF "mapping symbols" */
> > +             if (ehdr.e_machine == EM_RISCV) {
> > +                     if (elf_name[0] == '$' && strchr("dx", elf_name[1]))
> > +                             continue;
> > +             }
> > +
> >               if (runtime_ss->opdsec && sym.st_shndx == runtime_ss->opdidx) {
> >                       u32 offset = sym.st_value - syms_ss->opdshdr.sh_addr;
> >                       u64 *opd = opddata->d_buf + offset;
> > --
> > 2.43.0
> >