perf buildid-cache: Add guestmount'd files to the build ID cache

When the guestmount option is used, a guest machine's file system mount
point is recorded in machine->root_dir.

perf already iterates guest machines when adding files to the build ID
cache, but does not take machine->root_dir into account.

Use machine->root_dir to find files for guest build IDs, and add them to
the build ID cache using the "proper" name i.e. relative to the guest root
directory not the host root directory.

Signed-off-by: Adrian Hunter <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/build-id.c

···
 #endif
 
 static char *build_id_cache__find_debug(const char *sbuild_id,
-					struct nsinfo *nsi)
+					struct nsinfo *nsi,
+					const char *root_dir)
 {
+	const char *dirname = "/usr/lib/debug/.build-id/";
 	char *realname = NULL;
+	char dirbuf[PATH_MAX];
 	char *debugfile;
 	struct nscookie nsc;
 	size_t len = 0;
···
 	if (!debugfile)
 		goto out;
 
-	len = __symbol__join_symfs(debugfile, PATH_MAX,
-				   "/usr/lib/debug/.build-id/");
+	if (root_dir) {
+		path__join(dirbuf, PATH_MAX, root_dir, dirname);
+		dirname = dirbuf;
+	}
+
+	len = __symbol__join_symfs(debugfile, PATH_MAX, dirname);
 	snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
 		 sbuild_id + 2);
 
···
 
 int
 build_id_cache__add(const char *sbuild_id, const char *name, const char *realname,
-		    struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
+		    struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
+		    const char *proper_name, const char *root_dir)
 {
 	const size_t size = PATH_MAX;
 	char *filename = NULL, *dir_name = NULL, *linkname = zalloc(size), *tmp;
 	char *debugfile = NULL;
 	int err = -1;
 
-	dir_name = build_id_cache__cachedir(sbuild_id, name, nsi, is_kallsyms,
+	if (!proper_name)
+		proper_name = name;
+
+	dir_name = build_id_cache__cachedir(sbuild_id, proper_name, nsi, is_kallsyms,
 					    is_vdso);
 	if (!dir_name)
 		goto out_free;
···
 	 */
 	if (!is_kallsyms && !is_vdso &&
 	    strncmp(".ko", name + strlen(name) - 3, 3)) {
-		debugfile = build_id_cache__find_debug(sbuild_id, nsi);
+		debugfile = build_id_cache__find_debug(sbuild_id, nsi, root_dir);
 		if (debugfile) {
 			zfree(&filename);
 			if (asprintf(&filename, "%s/%s", dir_name,
···
 	return err;
 }
 
-int build_id_cache__add_s(const char *sbuild_id, const char *name,
-			  struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
+int __build_id_cache__add_s(const char *sbuild_id, const char *name,
+			    struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
+			    const char *proper_name, const char *root_dir)
 {
 	char *realname = NULL;
 	int err = -1;
···
 			goto out_free;
 	}
 
-	err = build_id_cache__add(sbuild_id, name, realname, nsi, is_kallsyms, is_vdso);
-
+	err = build_id_cache__add(sbuild_id, name, realname, nsi,
+				  is_kallsyms, is_vdso, proper_name, root_dir);
 out_free:
 	if (!is_kallsyms)
 		free(realname);
···
 
 static int build_id_cache__add_b(const struct build_id *bid,
 				 const char *name, struct nsinfo *nsi,
-				 bool is_kallsyms, bool is_vdso)
+				 bool is_kallsyms, bool is_vdso,
+				 const char *proper_name,
+				 const char *root_dir)
 {
 	char sbuild_id[SBUILD_ID_SIZE];
 
 	build_id__sprintf(bid, sbuild_id);
 
-	return build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
-				     is_vdso);
+	return __build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
+				       is_vdso, proper_name, root_dir);
 }
 
 bool build_id_cache__cached(const char *sbuild_id)
···
 	bool is_kallsyms = dso__is_kallsyms(dso);
 	bool is_vdso = dso__is_vdso(dso);
 	const char *name = dso->long_name;
+	const char *proper_name = NULL;
+	const char *root_dir = NULL;
+	char *allocated_name = NULL;
+	int ret = 0;
 
 	if (!dso->has_build_id)
 		return 0;
···
 		name = machine->mmap_name;
 	}
 
-	if (!is_kallsyms && dso__build_id_mismatch(dso, name))
-		return 0;
+	if (!machine__is_host(machine)) {
+		if (*machine->root_dir) {
+			root_dir = machine->root_dir;
+			ret = asprintf(&allocated_name, "%s/%s", root_dir, name);
+			if (ret < 0)
+				return ret;
+			proper_name = name;
+			name = allocated_name;
+		} else if (is_kallsyms) {
+			/* Cannot get guest kallsyms */
+			return 0;
+		}
+	}
 
-	return build_id_cache__add_b(&dso->bid, name, dso->nsinfo,
-				     is_kallsyms, is_vdso);
+	if (!is_kallsyms && dso__build_id_mismatch(dso, name))
+		goto out_free;
+
+	ret = build_id_cache__add_b(&dso->bid, name, dso->nsinfo,
+				    is_kallsyms, is_vdso, proper_name, root_dir);
+out_free:
+	free(allocated_name);
+	return ret;
 }
 
 static int

tools/perf/util/build-id.h

···
 				   struct strlist **result);
 bool build_id_cache__cached(const char *sbuild_id);
 int build_id_cache__add(const char *sbuild_id, const char *name, const char *realname,
-			struct nsinfo *nsi, bool is_kallsyms, bool is_vdso);
-int build_id_cache__add_s(const char *sbuild_id,
-			  const char *name, struct nsinfo *nsi,
-			  bool is_kallsyms, bool is_vdso);
+			struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
+			const char *proper_name, const char *root_dir);
+int __build_id_cache__add_s(const char *sbuild_id,
+			    const char *name, struct nsinfo *nsi,
+			    bool is_kallsyms, bool is_vdso,
+			    const char *proper_name, const char *root_dir);
+static inline int build_id_cache__add_s(const char *sbuild_id,
+					const char *name, struct nsinfo *nsi,
+					bool is_kallsyms, bool is_vdso)
+{
+	return __build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms, is_vdso, NULL, NULL);
+}
 int build_id_cache__remove_s(const char *sbuild_id);
 
 extern char buildid_dir[];