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perf symbols: Apply the symfs flat layout to the composed filename

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--symfs=<dir>,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
<dir>/libc.so.6.debug.  It lands on
<dir>/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/<build id>.debug.  hierarchy is unchanged.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Zhan Xusheng 2026-09-22 21:19:52 +08:00 committed by Arnaldo Carvalho de Melo
parent 60d454456f
commit 7e27239d22
3 changed files with 44 additions and 19 deletions
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12
tools/perf/util/build-id.c
View File

@ -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);

8
tools/perf/util/disasm.c
View File

@ -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))

43
tools/perf/util/dso.c
View File

@ -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: