perf symbol: Add filename__has_section()

The filename__has_section() is to check if the given section name is in
the binary.  It'd be used for checking debug info for srcline.

Committer notes:

Added missing  __maybe_unused to the unused filename__has_section()
arguments in tools/perf/util/symbol-minimal.c.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221215192817.2734573-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol-elf.c

@@ -233,6 +233,34 @@ Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
 	return NULL;
 }
 
+bool filename__has_section(const char *filename, const char *sec)
+{
+	int fd;
+	Elf *elf;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+	bool found = false;
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0)
+		return false;
+
+	elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+	if (elf == NULL)
+		goto out;
+
+	if (gelf_getehdr(elf, &ehdr) == NULL)
+		goto elf_out;
+
+	found = !!elf_section_by_name(elf, &ehdr, &shdr, sec, NULL);
+
+elf_out:
+	elf_end(elf);
+out:
+	close(fd);
+	return found;
+}
+
 static int elf_read_program_header(Elf *elf, u64 vaddr, GElf_Phdr *phdr)
 {
 	size_t i, phdrnum;

tools/perf/util/symbol-minimal.c

@@ -385,3 +385,8 @@ char *dso__demangle_sym(struct dso *dso __maybe_unused,
 {
 	return NULL;
 }
+
+bool filename__has_section(const char *filename __maybe_unused, const char *sec __maybe_unused)
+{
+	return false;
+}

tools/perf/util/symbol.h

@@ -165,6 +165,7 @@ int modules__parse(const char *filename, void *arg,
 					 u64 start, u64 size));
 int filename__read_debuglink(const char *filename, char *debuglink,
 			     size_t size);
+bool filename__has_section(const char *filename, const char *sec);
 
 struct perf_env;
 int symbol__init(struct perf_env *env);