[PATCH perf-tools-next v8 3/6] perf symbol: Introduce vmlinux_path__find() helper

[Aaron Tomlin <atomlin@atomlin.com>]

The vmlinux_path array maintains standard paths used by perf to locate
the kernel image (e.g. "vmlinux", "/boot/vmlinux",
"/lib/modules/%s/build/vmlinux", "/usr/lib/debug/..."). While
vmlinux_path__init() populates these candidates and dso__load_vmlinux_path()
loads symbols into a DSO/map, callers (such as test suites or probing tools)
often need to verify the existence of an accessible vmlinux on disk before
attempting machine setup or test execution.

Introduce vmlinux_path__find() to search through the configured vmlinux_path
entries (or symbol_conf.vmlinux_name if explicitly set) and return the
path to the first readable vmlinux file, or NULL if none is accessible.

Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
 tools/perf/util/symbol.c | 30 ++++++++++++++++++++++++++++++
 tools/perf/util/symbol.h |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index b61a574ce9a3..a0fc430be13a 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2372,6 +2372,36 @@ static int vmlinux_path__init(struct perf_env *env)
 	return -1;
 }
 
+/**
+ * vmlinux_path__find - Locate the first accessible vmlinux file
+ *
+ * Check symbol_conf.vmlinux_name first if set, then search through the
+ * initialized paths in vmlinux_path.
+ *
+ * Return: A pointer to the path of the first readable vmlinux file, or NULL if
+ * none is accessible.
+ */
+const char *vmlinux_path__find(void)
+{
+	int i;
+
+	if (symbol_conf.vmlinux_name && access(symbol_conf.vmlinux_name, R_OK) == 0)
+		return symbol_conf.vmlinux_name;
+
+	if (!vmlinux_path) {
+		symbol_conf.try_vmlinux_path = true;
+		if (vmlinux_path__init(NULL) < 0)
+			return NULL;
+	}
+
+	for (i = 0; i < vmlinux_path__nr_entries; ++i) {
+		if (access(vmlinux_path[i], R_OK) == 0)
+			return vmlinux_path[i];
+	}
+
+	return NULL;
+}
+
 int setup_list(struct strlist **list, const char *list_str,
 		      const char *list_name)
 {
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index d0bac824c79c..6d1eb08076ab 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -184,6 +184,8 @@ static inline int __symbol__join_symfs(char *bf, size_t size, const char *path)
 extern int vmlinux_path__nr_entries;
 extern char **vmlinux_path;
 
+const char *vmlinux_path__find(void);
+
 static inline void *symbol__priv(struct symbol *sym)
 {
 	return ((void *)sym) - symbol_conf.priv_size;
-- 
2.55.0