linux-kernel - [PATCH] perf symbols: Ignore mapping symbols on riscv

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Message-ID: <20250409025202.201046-1-haibo1.xu@intel.com>
Date: Wed,  9 Apr 2025 10:51:56 +0800
From: Haibo Xu <haibo1.xu@...el.com>
To: 
Cc: xiaobo55x@...il.com,
	Haibo Xu <haibo1.xu@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Stephen Brennan <stephen.s.brennan@...cle.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org
Subject: [PATCH] perf symbols: Ignore mapping symbols on riscv

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@...el.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