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

Arnaldo Carvalho de Melo
2026-03-31T20:39:03Z

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