From: Ian Rogers Date: Wed, 13 May 2026 23:31:45 +0000 (-0700) Subject: perf unwind: Refactor get_entries to allow dynamic libdw/libunwind selection X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4248ae6e799605b3e62855be6085935d89de50d1;p=thirdparty%2Fkernel%2Fstable.git perf unwind: Refactor get_entries to allow dynamic libdw/libunwind selection 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: 2e9191573a69ff96 ("perf build: Remove NO_LIBDW_DWARF_UNWIND option") Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Albert Ou Cc: Alexander Shishkin Cc: Alexandre Ghiti Cc: Andrew Jones Cc: Athira Rajeev Cc: Dapeng Mi Cc: Dmitrii Dolgov <9erthalion6@gmail.com> Cc: Florian Fainelli Cc: Howard Chu Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: John Garry Cc: Leo Yan Cc: libunwind-devel@nongnu.org Cc: Li Guan Cc: Namhyung Kim Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Peter Zijlstra Cc: Shimin Guo Cc: Thomas Richter Cc: Tomas Glozar Cc: Will Deacon [ Don't mix declarations and code, move 'entries' variable to the start of scope ] [ Use pr_warning_once() instead of pr_err() in stubs for get_entries(), suggested by a local sashiko instance ] Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c index 6ab20df358c4..a2493f1097df 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" @@ -2563,6 +2564,9 @@ 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 95c0bdba6b11..0b0966d94128 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" @@ -1449,6 +1450,9 @@ 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 c8ac9f01a36b..fd0b4609516b 100644 --- a/tools/perf/builtin-script.c +++ b/tools/perf/builtin-script.c @@ -63,6 +63,7 @@ #include #include "util/dlfilter.h" #include "util/record.h" +#include "util/unwind.h" #include "util/util.h" #include "util/cgroup.h" #include "util/annotate.h" @@ -4159,6 +4160,9 @@ 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 70cc91d00804..01edfccebb88 100644 --- a/tools/perf/util/Build +++ b/tools/perf/util/Build @@ -216,6 +216,7 @@ 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/config.c b/tools/perf/util/config.c index 087002fb1b9b..7988149dc7ed 100644 --- a/tools/perf/util/config.c +++ b/tools/perf/util/config.c @@ -23,6 +23,7 @@ #include "build-id.h" #include "debug.h" #include "config.h" +#include "unwind.h" #include #include #include @@ -525,6 +526,9 @@ int perf_default_config(const char *var, const char *value, if (strstarts(var, "addr2line.")) return addr2line_configure(var, value, dummy); + if (strstarts(var, "unwind.")) + return unwind__configure(var, value, dummy); + /* Add other config variables here. */ return 0; } diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h index 6cd454d7c98e..0dee5aa6a534 100644 --- a/tools/perf/util/symbol_conf.h +++ b/tools/perf/util/symbol_conf.h @@ -9,6 +9,15 @@ 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, @@ -81,6 +90,7 @@ struct symbol_conf { const char *addr2line_path; enum a2l_style addr2line_style[MAX_A2L_STYLE]; int addr2line_timeout_ms; + enum unwind_style unwind_style[MAX_UNWIND_STYLE]; unsigned long time_quantum; struct strlist *dso_list, *comm_list, diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c index 05e8e68bd49c..7f35042be567 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, @@ -353,10 +353,10 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg, static struct unwind_info *ui; Dwfl *dwfl; Dwarf_Word ip; - int err = -EINVAL, i; + int err = -EINVAL, i, entries; if (!data->user_regs || !data->user_regs->regs) - return -EINVAL; + return 0; ui = zalloc(sizeof(*ui) + sizeof(ui->entries[0]) * max_stack); if (!ui) @@ -430,6 +430,18 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg, map_symbol__exit(&ui->entries[i].ms); dwfl_ui_ti->ui = NULL; + entries = (int)ui->idx; free(ui); - return 0; + /* + * Unwinder return contract: + * > 0 : unwinding succeeded (stops fallback). If we found frames but hit an error + * (e.g. truncated stack), report success to preserve existing frames. + * 0 : unwinding failed without yielding frames. Ignore non-fatal errors + * (e.g. missing debug info, DWARF corruption) to allow fallback unwinder or + * kernel callchain resolution to proceed. + * < 0 : fatal error (e.g. -ENOMEM). Aborts unwinding entirely. + */ + if (err) + return (err == -ENOMEM) ? -ENOMEM : (entries > 0 ? 1 : 0); + return entries; } diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c index 87d496e9dfa6..27e2f7b31789 100644 --- a/tools/perf/util/unwind-libunwind-local.c +++ b/tools/perf/util/unwind-libunwind-local.c @@ -744,7 +744,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, ret = perf_reg_value(&val, perf_sample__user_regs(ui->sample), perf_arch_reg_ip(e_machine)); if (ret) - return ret; + return 0; ips[i++] = (unw_word_t) val; @@ -757,7 +757,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, addr_space = maps__addr_space(thread__maps(ui->thread)); if (addr_space == NULL) - return -1; + return 0; ret = unw_init_remote(&c, addr_space, ui); if (ret && !ui->best_effort) @@ -785,15 +785,30 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, /* * Display what we got based on the order setup. */ + int entries = 0; for (i = 0; i < max_stack && !ret; i++) { int j = i; if (callchain_param.order == ORDER_CALLER) j = max_stack - i - 1; - ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; + if (ips[j]) { + ret = entry(ips[j], ui->thread, cb, arg); + if (ret) + break; + entries++; + } } - return ret; + /* + * Unwinder return contract: + * > 0 : unwinding succeeded (stops fallback). + * 0 : unwinding failed without yielding frames. Ignore non-fatal errors + * (e.g. stepping failure) to allow fallback unwinder or kernel callchains. + * < 0 : fatal error (e.g. -ENOMEM). Aborts unwinding entirely. + */ + if (ret == -ENOMEM) + return -ENOMEM; + return (entries > 0 || ret == 0) ? entries : 0; } static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, @@ -809,10 +824,10 @@ static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, }; if (!data->user_regs || !data->user_regs->regs) - return -EINVAL; + return 0; if (max_stack <= 0) - return -EINVAL; + return 0; return get_entries(&ui, cb, arg, 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..4ed4b1d55c69 --- /dev/null +++ b/tools/perf/util/unwind.c @@ -0,0 +1,104 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "debug.h" +#include "symbol_conf.h" +#include "unwind.h" +#include +#include +#include + +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: + ret = libdw__get_entries(cb, arg, thread, data, max_stack, best_effort); + break; + case UNWIND_STYLE_LIBUNWIND: + ret = libunwind__get_entries(cb, arg, thread, data, max_stack, best_effort); + 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 = 0; + break; + } + if (ret > 0) { + ret = 0; + 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; + + memset(symbol_conf.unwind_style, 0, sizeof(symbol_conf.unwind_style)); + + 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..69ba08afda79 100644 --- a/tools/perf/util/unwind.h +++ b/tools/perf/util/unwind.h @@ -4,9 +4,10 @@ #include #include -#include "util/map_symbol.h" +#include "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 +39,31 @@ 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); +#else +#include "debug.h" +static inline int libdw__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) +{ + pr_warning_once("Error: libdw dwarf unwinding not built into perf\n"); + return 0; +} +#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 @@ -47,25 +73,15 @@ int unwind__prepare_access(struct maps *maps, struct map *map, bool *initialized void unwind__flush_access(struct maps *maps); void unwind__finish_access(struct maps *maps); #else -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 -#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) +#include "debug.h" +static inline int libunwind__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) { + pr_warning_once("Error: libunwind dwarf unwinding not built into perf\n"); return 0; } @@ -78,5 +94,6 @@ 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 /* HAVE_DWARF_UNWIND_SUPPORT */ +#endif + #endif /* __UNWIND_H */