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* [PATCH] perf symbols: Don't apply the symfs layout to synthesised paths
@ 2026-08-11  5:00 Zhan Xusheng
  2026-08-17 21:42 ` Ian Rogers
  0 siblings, 1 reply; 3+ messages in thread
From: Zhan Xusheng @ 2026-08-11  5:00 UTC (permalink / raw)
  To: Arnaldo Carvalho de Melo, Namhyung Kim, Ian Rogers
  Cc: Changbin Du, Peter Zijlstra, Ingo Molnar, Jiri Olsa,
	Adrian Hunter, linux-perf-users, linux-kernel, zhanxusheng

The flat symfs layout was implemented inside __symbol__join_symfs() alone,
which went from

	return path__join(bf, size, symbol_conf.symfs, path);

to taking perf_basename(path) first.  No caller was changed, so all of them
got it.  Most pass dso__long_name(), which is what the option is about, but
some pass a path perf built itself:

  dso.c        "/usr/lib/debug"             -> "debug"
  dso.c        "/usr/lib/debug/.build-id/"  -> ""
  build-id.c   "/usr/lib/debug/.build-id/"  -> ""
  disasm.c     <file under buildid_dir>     -> last component

perf_basename() yields "" for a path ending in '/'.  So with --symfs
DIR,flat the FEDORA, UBUNTU and MIXEDUP_UBUNTU debuginfo lookups land in
<symfs>/debug/, the two build-id ones in <symfs> itself, and disasm.c
flattens a path under perf's own build-id cache.

Use path__join() at those sites, which is what the helper did for them
before.  A hierarchy layout is unaffected, being that same call.  The
OPENEMBEDDED site passes "", where perf_basename() is already a no-op;
it is converted for uniformity.  Every remaining __symbol__join_symfs()
caller passes a path from the profiled system.

Fixes: f182573e06ab ("perf tools: Add layout support for --symfs option")
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 tools/perf/util/build-id.c |  2 +-
 tools/perf/util/disasm.c   |  4 +++-
 tools/perf/util/dso.c      | 11 ++++++-----
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index eb95ab90f974..0c89fe75a650 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -599,7 +599,7 @@ static char *build_id_cache__find_debug(const char *sbuild_id,
 		dirname = dirbuf;
 	}
 
-	len = __symbol__join_symfs(debugfile, PATH_MAX, dirname);
+	len = path__join(debugfile, PATH_MAX, symbol_conf.symfs, dirname);
 	snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
 		 sbuild_id + 2);
 
diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index 0a1a7e9cf3ef..decf9348d735 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -31,6 +31,7 @@
 #include "map.h"
 #include "maps.h"
 #include "namespaces.h"
+#include "path.h"
 #include "srcline.h"
 #include "symbol.h"
 #include "thread.h"
@@ -1173,7 +1174,8 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
 
 	build_id_filename = dso__build_id_filename(dso, NULL, 0, false);
 	if (build_id_filename) {
-		__symbol__join_symfs(filename, filename_size, build_id_filename);
+		path__join(filename, filename_size, symbol_conf.symfs,
+			   build_id_filename);
 		free(build_id_filename);
 	} else {
 		if (dso__has_build_id(dso))
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 2309196d8df3..314c9a0edf28 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -167,12 +167,12 @@ int dso__read_binary_type_filename(const struct dso *dso,
 		break;
 
 	case DSO_BINARY_TYPE__FEDORA_DEBUGINFO:
-		len = __symbol__join_symfs(filename, size, "/usr/lib/debug");
+		len = path__join(filename, size, symbol_conf.symfs, "/usr/lib/debug");
 		snprintf(filename + len, size - len, "%s.debug", dso__long_name(dso));
 		break;
 
 	case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO:
-		len = __symbol__join_symfs(filename, size, "/usr/lib/debug");
+		len = path__join(filename, size, symbol_conf.symfs, "/usr/lib/debug");
 		snprintf(filename + len, size - len, "%s", dso__long_name(dso));
 		break;
 
@@ -187,7 +187,7 @@ int dso__read_binary_type_filename(const struct dso *dso,
 			ret = -1;
 			break;
 		}
-		len = __symbol__join_symfs(filename, size, "/usr/lib/debug");
+		len = path__join(filename, size, symbol_conf.symfs, "/usr/lib/debug");
 		snprintf(filename + len, size - len, "%s", dso__long_name(dso) + 4);
 		break;
 
@@ -200,7 +200,7 @@ int dso__read_binary_type_filename(const struct dso *dso,
 		while (last_slash != dso__long_name(dso) && *last_slash != '/')
 			last_slash--;
 
-		len = __symbol__join_symfs(filename, size, "");
+		len = path__join(filename, size, symbol_conf.symfs, "");
 		dir_size = last_slash - dso__long_name(dso) + 2;
 		if (dir_size > (size - len)) {
 			ret = -1;
@@ -219,7 +219,8 @@ int dso__read_binary_type_filename(const struct dso *dso,
 		}
 
 		build_id__snprintf(dso__bid(dso), build_id_hex, sizeof(build_id_hex));
-		len = __symbol__join_symfs(filename, size, "/usr/lib/debug/.build-id/");
+		len = path__join(filename, size, symbol_conf.symfs,
+				 "/usr/lib/debug/.build-id/");
 		snprintf(filename + len, size - len, "%.2s/%s.debug",
 			 build_id_hex, build_id_hex + 2);
 		break;
-- 
2.43.0


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2026-08-11  5:00 [PATCH] perf symbols: Don't apply the symfs layout to synthesised paths Zhan Xusheng
2026-08-17 21:42 ` Ian Rogers
2026-08-18  2:08   ` Zhan Xusheng

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