From 7e27239d2230394a797e2791bccf7ad24fc45c43 Mon Sep 17 00:00:00 2001 From: Zhan Xusheng Date: Tue, 22 Sep 2026 21:19:52 +0800 Subject: [PATCH] perf symbols: Apply the symfs flat layout to the composed filename --symfs=,flat documents itself as matching only the base name, so a debuginfo lookup for /usr/lib/x86_64-linux-gnu/libc.so.6 should land on /libc.so.6.debug. It lands on /debug/usr/lib/x86_64-linux-gnu/libc.so.6.debug instead, because the layout is applied to a fixed prefix and the file name arrives afterwards: len = __symbol__join_symfs(filename, size, "/usr/lib/debug"); snprintf(filename + len, size - len, "%s.debug", dso__long_name(dso)); perf_basename() only ever sees "/usr/lib/debug", so neither layout comes out of it. Compose the path as it would appear on the profiled system and join it once, which puts the layout on the whole name. That covers FEDORA_DEBUGINFO, UBUNTU_DEBUGINFO, MIXEDUP_UBUNTU_DEBUGINFO, OPENEMBEDDED_DEBUGINFO and BUILDID_DEBUGINFO, plus the same composition in build_id_cache__find_debug(). BUILDID_DEBUGINFO needs one more step: the build id cache splits the first two characters of the build id off into a directory name, so the basename of the hierarchy path is only part of the build id. Name the flat file after the whole build id. dso__disassemble_filename() passes a path from perf's own build id cache rather than one on the profiled system, and every entry there is named "elf" or "debug". Use path__join() so the layout does not apply. With --symfs /s,flat the lookups are now /s/libc.so.6, /s/libc.so.6.debug, /s/sleep and /s/.debug. hierarchy is unchanged. Reviewed-by: Namhyung Kim Signed-off-by: Zhan Xusheng Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/build-id.c | 12 +++++++---- tools/perf/util/disasm.c | 8 ++++++- tools/perf/util/dso.c | 43 +++++++++++++++++++++++++------------- 3 files changed, 44 insertions(+), 19 deletions(-) diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c index eb95ab90f974..02233ef0eaff 100644 --- a/tools/perf/util/build-id.c +++ b/tools/perf/util/build-id.c @@ -586,9 +586,9 @@ static char *build_id_cache__find_debug(const char *sbuild_id, const char *dirname = "/usr/lib/debug/.build-id/"; char *realname = NULL; char dirbuf[PATH_MAX]; + char pathbuf[PATH_MAX]; char *debugfile; struct nscookie nsc; - size_t len = 0; debugfile = calloc(1, PATH_MAX); if (!debugfile) @@ -599,9 +599,13 @@ static char *build_id_cache__find_debug(const char *sbuild_id, dirname = dirbuf; } - len = __symbol__join_symfs(debugfile, PATH_MAX, dirname); - snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id, - sbuild_id + 2); + /* See the build id note in dso__read_binary_type_filename(). */ + if (symbol_conf.symfs_layout_flat) + scnprintf(pathbuf, PATH_MAX, "/%s.debug", sbuild_id); + else + scnprintf(pathbuf, PATH_MAX, "%s%.2s/%s.debug", dirname, + sbuild_id, sbuild_id + 2); + __symbol__join_symfs(debugfile, PATH_MAX, pathbuf); nsinfo__mountns_enter(nsi, &nsc); realname = realpath(debugfile, NULL); diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c index b39636ec35c1..5478c134e7e3 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" @@ -1189,7 +1190,12 @@ 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); + /* + * This is a path in perf's own build id cache, not a path on + * the profiled system, so the symfs layout does not apply. + */ + 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 9e90de92fcfa..11db461f2032 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -121,6 +121,7 @@ int dso__read_binary_type_filename(const struct dso *dso, const char *root_dir, char *filename, size_t size) { char build_id_hex[SBUILD_ID_SIZE]; + char relative[PATH_MAX]; int ret = 0; size_t len; @@ -173,13 +174,15 @@ 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"); - snprintf(filename + len, size - len, "%s.debug", dso__long_name(dso)); + snprintf(relative, sizeof(relative), "/usr/lib/debug%s.debug", + dso__long_name(dso)); + __symbol__join_symfs(filename, size, relative); break; case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO: - len = __symbol__join_symfs(filename, size, "/usr/lib/debug"); - snprintf(filename + len, size - len, "%s", dso__long_name(dso)); + snprintf(relative, sizeof(relative), "/usr/lib/debug%s", + dso__long_name(dso)); + __symbol__join_symfs(filename, size, relative); break; case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO: @@ -193,8 +196,9 @@ int dso__read_binary_type_filename(const struct dso *dso, ret = -1; break; } - len = __symbol__join_symfs(filename, size, "/usr/lib/debug"); - snprintf(filename + len, size - len, "%s", dso__long_name(dso) + 4); + snprintf(relative, sizeof(relative), "/usr/lib/debug%s", + dso__long_name(dso) + 4); + __symbol__join_symfs(filename, size, relative); break; case DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO: @@ -206,15 +210,15 @@ 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, ""); dir_size = last_slash - dso__long_name(dso) + 2; - if (dir_size > (size - len)) { + if (dir_size > sizeof(relative)) { ret = -1; break; } - len += scnprintf(filename + len, dir_size, "%s", dso__long_name(dso)); - len += scnprintf(filename + len , size - len, ".debug%s", - last_slash); + len = scnprintf(relative, dir_size, "%s", dso__long_name(dso)); + scnprintf(relative + len, sizeof(relative) - len, ".debug%s", + last_slash); + __symbol__join_symfs(filename, size, relative); break; } @@ -225,9 +229,20 @@ 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/"); - snprintf(filename + len, size - len, "%.2s/%s.debug", - build_id_hex, build_id_hex + 2); + /* + * The build id cache layout splits the first two characters off + * into a directory name, so the basename of the hierarchy path + * is only part of the build id. Name the flat file after the + * whole build id instead. + */ + if (symbol_conf.symfs_layout_flat) + snprintf(relative, sizeof(relative), "/%s.debug", + build_id_hex); + else + snprintf(relative, sizeof(relative), + "/usr/lib/debug/.build-id/%.2s/%s.debug", + build_id_hex, build_id_hex + 2); + __symbol__join_symfs(filename, size, relative); break; case DSO_BINARY_TYPE__VMLINUX: