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

On Thu, Mar 05, 2026 at 02:19:20PM -0800, Ian Rogers wrote:
> 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;


What if the user asks for one of the unwinders, symbol_conf.unwind_style
will be populated with the user's choices, but then here in
unwind__get_entries() we end up returning 0 because the user choice is
not built-in?

Also no warning will be emitted that what was asked for is not
available?

Maybe remove the ifdefs here and have a dummy libdw__get_entries() when
HAVE_LIBDW_SUPPORT ins't defined that emits the warning and returns -1?
Ditto for UNWIND_STYLE_LIBUNWIND?

- Arnaldo

> +		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

On Tue, Mar 31, 2026 at 1:42 PM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> On Thu, Mar 05, 2026 at 02:19:20PM -0800, Ian Rogers wrote:
> > 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,
> > +
> > +};

I'll remove the blank lines in the next version.

> > +
> > +#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;
>
>
> What if the user asks for one of the unwinders, symbol_conf.unwind_style
> will be populated with the user's choices, but then here in
> unwind__get_entries() we end up returning 0 because the user choice is
> not built-in?
>
> Also no warning will be emitted that what was asked for is not
> available?
>
> Maybe remove the ifdefs here and have a dummy libdw__get_entries() when
> HAVE_LIBDW_SUPPORT ins't defined that emits the warning and returns -1?
> Ditto for UNWIND_STYLE_LIBUNWIND?

Makes sense, I'll add it to the next version. Since the later patches
are larger I'll wait to address review feedback there before sending
out the next version - this will avoid unnecessary mailing list churn.

Thanks,
Ian

> - Arnaldo
>
> > +             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

On Thu, Mar 05, 2026 at 02:19:20PM -0800, Ian Rogers wrote:
> 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,
> +

Please remove the blank lines.

- Arnaldo