[PATCH v2 1/8] perf unwind: Refactor get_entries to allow dynamic libdw/libunwind selection

Ian Rogers
2026-03-05T22:19:42Z

Currently, both libdw and libunwind define 'unwind__get_entries'. This
causes a duplicate symbol build failure when both are compiled into
perf.

This commit refactors the DWARF unwind post-processing to be
configurable at runtime via the .perfconfig file option
'unwind.style', or using the argument '--unwind-style' in the commands
'perf report', 'perf script' and 'perf inject', in a similar manner to
the addr2line or the disassembler style.

The file 'tools/perf/util/unwind.c' adds the top-level dispatch
function 'unwind__get_entries'. The backend implementations are
renamed to 'libdw__get_entries' and 'libunwind__get_entries'. Both are
attempted as fallbacks if not configured, or if the primary backend
fails.

Fixes: 2e9191573a69 ("perf build: Remove NO_LIBDW_DWARF_UNWIND option")
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/builtin-inject.c | 4 ++
tools/perf/builtin-report.c | 4 ++
tools/perf/builtin-script.c | 4 ++
tools/perf/util/Build | 1 +
tools/perf/util/symbol_conf.h | 15 +++++
tools/perf/util/unwind-libdw.c | 2 +-
tools/perf/util/unwind-libunwind.c | 2 +-
tools/perf/util/unwind.c | 102 +++++++++++++++++++++++++++++
tools/perf/util/unwind.h | 40 +++++------
9 files changed, 149 insertions(+), 25 deletions(-)
create mode 100644 tools/perf/util/unwind.c

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index 5b29f4296861..9ad681b3c0dc 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -26,6 +26,7 @@
#include "util/synthetic-events.h"
#include "util/thread.h"
#include "util/namespaces.h"
+#include "util/unwind.h"
#include "util/util.h"
#include "util/tsc.h"

@@ -2539,6 +2540,9 @@ int cmd_inject(int argc, const char **argv)
OPT_STRING(0, "guestmount", &symbol_conf.guestmount, "directory",
"guest mount directory under which every guest os"
" instance has a subdir"),
+ OPT_CALLBACK(0, "unwind-style", NULL, "unwind style",
+ "unwind styles (libdw,libunwind)",
+ unwind__option),
OPT_BOOLEAN(0, "convert-callchain", &inject.convert_callchain,
"Generate callchains using DWARF and drop register/stack data"),
OPT_END()
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 3b81f4b3dc49..ae20c0679990 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -48,6 +48,7 @@
#include "util/time-utils.h"
#include "util/auxtrace.h"
#include "util/units.h"
+#include "util/unwind.h"
#include "util/util.h" // perf_tip()
#include "ui/ui.h"
#include "ui/progress.h"
@@ -1455,6 +1456,9 @@ int cmd_report(int argc, const char **argv)
OPT_CALLBACK(0, "addr2line-style", NULL, "addr2line style",
"addr2line styles (libdw,llvm,libbfd,addr2line)",
report_parse_addr2line_config),
+ OPT_CALLBACK(0, "unwind-style", NULL, "unwind style",
+ "unwind styles (libdw,libunwind)",
+ unwind__option),
OPT_BOOLEAN(0, "demangle", &symbol_conf.demangle,
"Symbol demangling. Enabled by default, use --no-demangle to disable."),
OPT_BOOLEAN(0, "demangle-kernel", &symbol_conf.demangle_kernel,
diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 9f8b0fd27a0a..b6c7c164d02d 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -63,6 +63,7 @@
#include <linux/err.h>
#include "util/dlfilter.h"
#include "util/record.h"
+#include "util/unwind.h"
#include "util/util.h"
#include "util/cgroup.h"
#include "util/annotate.h"
@@ -4164,6 +4165,9 @@ int cmd_script(int argc, const char **argv)
"Enable symbol demangling"),
OPT_BOOLEAN(0, "demangle-kernel", &symbol_conf.demangle_kernel,
"Enable kernel symbol demangling"),
+ OPT_CALLBACK(0, "unwind-style", NULL, "unwind style",
+ "unwind styles (libdw,libunwind)",
+ unwind__option),
OPT_STRING(0, "addr2line", &symbol_conf.addr2line_path, "path",
"addr2line binary to use for line numbers"),
OPT_STRING(0, "time", &script.time_str, "str",
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index bcccad7487a9..6190a8f5b0fa 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -218,6 +218,7 @@ ifndef CONFIG_SETNS
perf-util-y += setns.o
endif

+perf-util-y += unwind.o
perf-util-$(CONFIG_LIBDW) += probe-finder.o
perf-util-$(CONFIG_LIBDW) += dwarf-aux.o
perf-util-$(CONFIG_LIBDW) += dwarf-regs.o
diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h
index 71bb17372a6c..25d92bbbfee7 100644
--- a/tools/perf/util/symbol_conf.h
+++ b/tools/perf/util/symbol_conf.h
@@ -9,6 +9,19 @@
struct strlist;
struct intlist;

+enum unwind_style {
+
+ UNWIND_STYLE_UNKNOWN = 0,
+
+ UNWIND_STYLE_LIBDW,
+
+ UNWIND_STYLE_LIBUNWIND,
+
+};
+
+#define MAX_UNWIND_STYLE (UNWIND_STYLE_LIBUNWIND + 1)
+
+
enum a2l_style {
A2L_STYLE_UNKNOWN = 0,
A2L_STYLE_LIBDW,
@@ -80,6 +93,7 @@ struct symbol_conf {
*bt_stop_list_str;
const char *addr2line_path;
enum a2l_style addr2line_style[MAX_A2L_STYLE];
+ enum unwind_style unwind_style[MAX_UNWIND_STYLE];
unsigned long time_quantum;
struct strlist *dso_list,
*comm_list,
@@ -103,3 +117,4 @@ struct symbol_conf {
extern struct symbol_conf symbol_conf;

#endif // __PERF_SYMBOL_CONF
+
diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
index 05e8e68bd49c..d8a5b7d54192 100644
--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -339,7 +339,7 @@ frame_callback(Dwfl_Frame *state, void *arg)
DWARF_CB_ABORT : DWARF_CB_OK;
}

-int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
+int libdw__get_entries(unwind_entry_cb_t cb, void *arg,
struct thread *thread,
struct perf_sample *data,
int max_stack,
diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index cb8be6acfb6f..a0016b897dae 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -79,7 +79,7 @@ void unwind__finish_access(struct maps *maps)
ops->finish_access(maps);
}

-int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
+int libunwind__get_entries(unwind_entry_cb_t cb, void *arg,
struct thread *thread,
struct perf_sample *data, int max_stack,
bool best_effort)
diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c
new file mode 100644
index 000000000000..9ae7d5ad246d
--- /dev/null
+++ b/tools/perf/util/unwind.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "debug.h"
+#include "symbol_conf.h"
+#include "unwind.h"
+#include <linux/string.h>
+#include <string.h>
+#include <stdlib.h>
+
+int unwind__get_entries(unwind_entry_cb_t cb __maybe_unused, void *arg __maybe_unused,
+ struct thread *thread __maybe_unused,
+ struct perf_sample *data __maybe_unused,
+ int max_stack __maybe_unused,
+ bool best_effort __maybe_unused)
+{
+ int ret = 0;
+
+#if defined(HAVE_LIBDW_SUPPORT) || defined(HAVE_LIBUNWIND_SUPPORT)
+ if (symbol_conf.unwind_style[0] == UNWIND_STYLE_UNKNOWN) {
+ int i = 0;
+#ifdef HAVE_LIBDW_SUPPORT
+ symbol_conf.unwind_style[i++] = UNWIND_STYLE_LIBDW;
+#endif
+#ifdef HAVE_LIBUNWIND_SUPPORT
+ symbol_conf.unwind_style[i++] = UNWIND_STYLE_LIBUNWIND;
+#endif
+ }
+#endif //defined(HAVE_LIBDW_SUPPORT) || defined(HAVE_LIBUNWIND_SUPPORT)
+
+ for (size_t i = 0; i < ARRAY_SIZE(symbol_conf.unwind_style); i++) {
+ switch (symbol_conf.unwind_style[i]) {
+ case UNWIND_STYLE_LIBDW:
+#ifdef HAVE_LIBDW_SUPPORT
+ ret = libdw__get_entries(cb, arg, thread, data, max_stack, best_effort);
+#endif
+ break;
+ case UNWIND_STYLE_LIBUNWIND:
+#ifdef HAVE_LIBUNWIND_SUPPORT
+ ret = libunwind__get_entries(cb, arg, thread, data, max_stack, best_effort);
+#endif
+ break;
+ case UNWIND_STYLE_UNKNOWN:
+ default:
+#if !defined(HAVE_LIBDW_SUPPORT) && !defined(HAVE_LIBUNWIND_SUPPORT)
+ pr_warning_once(
+ "Error: dwarf unwinding not supported, build perf with libdw or libunwind.\n");
+#endif
+ ret = -1;
+ break;
+ }
+ if (ret == 0)
+ break;
+ }
+ return ret;
+}
+
+int unwind__configure(const char *var, const char *value, void *cb __maybe_unused)
+{
+ static const char * const unwind_style_names[] = {
+ [UNWIND_STYLE_LIBDW] = "libdw",
+ [UNWIND_STYLE_LIBUNWIND] = "libunwind",
+ NULL
+ };
+ char *s, *p, *saveptr;
+ size_t i = 0;
+
+ if (strcmp(var, "unwind.style"))
+ return 0;
+
+ if (!value)
+ return -1;
+
+ s = strdup(value);
+ if (!s)
+ return -1;
+
+ p = strtok_r(s, ",", &saveptr);
+ while (p && i < ARRAY_SIZE(symbol_conf.unwind_style)) {
+ bool found = false;
+ char *q = strim(p);
+
+ for (size_t j = UNWIND_STYLE_LIBDW; j < MAX_UNWIND_STYLE; j++) {
+ if (!strcasecmp(q, unwind_style_names[j])) {
+ symbol_conf.unwind_style[i++] = j;
+ found = true;
+ break;
+ }
+ }
+ if (!found)
+ pr_warning("Unknown unwind style: %s\n", q);
+ p = strtok_r(NULL, ",", &saveptr);
+ }
+
+ free(s);
+ return 0;
+}
+
+int unwind__option(const struct option *opt __maybe_unused,
+ const char *arg,
+ int unset __maybe_unused)
+{
+ return unwind__configure("unwind.style", arg, NULL);
+}
diff --git a/tools/perf/util/unwind.h b/tools/perf/util/unwind.h
index 9f7164c6d9aa..581d042e170a 100644
--- a/tools/perf/util/unwind.h
+++ b/tools/perf/util/unwind.h
@@ -7,6 +7,7 @@
#include "util/map_symbol.h"

struct maps;
+struct option;
struct perf_sample;
struct thread;

@@ -26,7 +27,9 @@ struct unwind_libunwind_ops {
struct perf_sample *data, int max_stack, bool best_effort);
};

-#ifdef HAVE_DWARF_UNWIND_SUPPORT
+int unwind__configure(const char *var, const char *value, void *cb);
+int unwind__option(const struct option *opt, const char *arg, int unset);
+
/*
* When best_effort is set, don't report errors and fail silently. This could
* be expanded in the future to be more permissive about things other than
@@ -36,8 +39,20 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
struct thread *thread,
struct perf_sample *data, int max_stack,
bool best_effort);
-/* libunwind specific */
+
+#ifdef HAVE_LIBDW_SUPPORT
+int libdw__get_entries(unwind_entry_cb_t cb, void *arg,
+ struct thread *thread,
+ struct perf_sample *data, int max_stack,
+ bool best_effort);
+#endif
+
#ifdef HAVE_LIBUNWIND_SUPPORT
+/* libunwind specific */
+int libunwind__get_entries(unwind_entry_cb_t cb, void *arg,
+ struct thread *thread,
+ struct perf_sample *data, int max_stack,
+ bool best_effort);
#ifndef LIBUNWIND__ARCH_REG_ID
#define LIBUNWIND__ARCH_REG_ID(regnum) libunwind__arch_reg_id(regnum)
#endif
@@ -57,26 +72,5 @@ static inline int unwind__prepare_access(struct maps *maps __maybe_unused,
static inline void unwind__flush_access(struct maps *maps __maybe_unused) {}
static inline void unwind__finish_access(struct maps *maps __maybe_unused) {}
#endif
-#else
-static inline int
-unwind__get_entries(unwind_entry_cb_t cb __maybe_unused,
- void *arg __maybe_unused,
- struct thread *thread __maybe_unused,
- struct perf_sample *data __maybe_unused,
- int max_stack __maybe_unused,
- bool best_effort __maybe_unused)
-{
- return 0;
-}
-
-static inline int unwind__prepare_access(struct maps *maps __maybe_unused,
- struct map *map __maybe_unused,
- bool *initialized __maybe_unused)
-{
- return 0;
-}

-static inline void unwind__flush_access(struct maps *maps __maybe_unused) {}
-static inline void unwind__finish_access(struct maps *maps __maybe_unused) {}
-#endif /* HAVE_DWARF_UNWIND_SUPPORT */
#endif /* __UNWIND_H */
--
2.53.0.473.g4a7958ca14-goog