[PATCH] perf symbols: Skip dynamic symbols with invalid section indexes

[Zhanpeng Zhang]

RISC-V post-link processing can remove relocation sections from the final
vmlinux while some .dynsym entries retain stale section indexes. perf
aborts the whole ELF symbol load when elf_getscn() rejects one of them,
discarding otherwise valid .symtab symbols.

Skip only dynamic symbols whose normal section index is outside the final
section table. Keep the existing error path for .symtab, reserved indexes,
and other libelf failures.

On an affected system, the vmlinux symtab matches kallsyms test changes
from Skip to Ok. [unknown] rows in the same perf.data change from 41 to 0.

Signed-off-by: Zhanpeng Zhang <zhangzhanpeng.jasper at bytedance.com>
---
 tools/perf/util/symbol-elf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index f6f6b54da131..e955c3feddcd 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1681,8 +1681,13 @@ dso__load_sym_internal(struct dso *dso, struct map *map, struct symsrc *syms_ss,
 			continue;
 
 		sec = elf_getscn(syms_ss->elf, sym.st_shndx);
-		if (!sec)
+		if (!sec) {
+			if (dynsym && ehdr.e_shnum &&
+			    sym.st_shndx < SHN_LORESERVE &&
+			    sym.st_shndx >= ehdr.e_shnum)
+				continue;
 			goto out_elf_end;
+		}
 
 		gelf_getshdr(sec, &shdr);
 
-- 
2.50.1 (Apple Git-155)