perf powerpc: Unify the skip-callchain-idx libdw with that for addr2line

Rather than have 2 Dwfl unify the Dwfl in skip-callchain-idx with that
is used by libdw__addr2line().

Rename that variable in 'struct dso' from 'a2l_libdw' to just 'libdw' as
it is now used in more than addr2line.

The Dwfl in skip-callchain-idx uses a map address when being read with
dwfl_report_elf (rather than dwfl_report_offline that addr2line
uses).

skip-callchain-idx is wrong as the map address can vary between
processes because of ASLR, ie it should need a different Dwfl per
process.

In the code after this patch the base address becomes 0 and the mapped
PC is used with the dwfl functions.

This should increase the accuracy of skip-callchain-idx, but the impact
has only been build tested.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Aditya Bodkhe <aditya.b1@linux.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.ibm.com>
Cc: Chun-Tse Shao <ctshao@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Dr. David Alan Gilbert <linux@treblig.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Haibo Xu <haibo1.xu@intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Krzysztof Łopatowski <krzysztof.m.lopatowski@gmail.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mark Wielaard <mark@klomp.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergei Trofimovich <slyich@gmail.com>
Cc: Shimin Guo <shimin.guo@skydio.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/powerpc/util/skip-callchain-idx.c

@@ -30,14 +30,6 @@
  * The libdwfl code in this file is based on code from elfutils
  * (libdwfl/argp-std.c, libdwfl/tests/addrcfi.c, etc).
  */
-static char *debuginfo_path;
-
-static const Dwfl_Callbacks offline_callbacks = {
-	.debuginfo_path = &debuginfo_path,
-	.find_debuginfo = dwfl_standard_find_debuginfo,
-	.section_address = dwfl_offline_section_address,
-};
-
 
 /*
  * Use the DWARF expression for the Call-frame-address and determine
@@ -149,44 +141,22 @@ static Dwarf_Frame *get_dwarf_frame(Dwfl_Module *mod, Dwarf_Addr pc)
  *		yet used)
  *	-1 in case of errors
  */
-static int check_return_addr(struct dso *dso, u64 map_start, Dwarf_Addr pc)
+static int check_return_addr(struct dso *dso, Dwarf_Addr mapped_pc)
 {
 	int		rc = -1;
 	Dwfl		*dwfl;
 	Dwfl_Module	*mod;
 	Dwarf_Frame	*frame;
 	int		ra_regno;
-	Dwarf_Addr	start = pc;
+	Dwarf_Addr	start = mapped_pc;
-	Dwarf_Addr	end = pc;
+	Dwarf_Addr	end = mapped_pc;
 	bool		signalp;
-	const char	*exec_file = dso__long_name(dso);
 
-	dwfl = RC_CHK_ACCESS(dso)->dwfl;
+	dwfl = dso__libdw_dwfl(dso);
+	if (!dwfl)
+		return -1;
 
-	if (!dwfl) {
+	mod = dwfl_addrmodule(dwfl, mapped_pc);
-		dwfl = dwfl_begin(&offline_callbacks);
-		if (!dwfl) {
-			pr_debug("dwfl_begin() failed: %s\n", dwarf_errmsg(-1));
-			return -1;
-		}
-
-		mod = dwfl_report_elf(dwfl, exec_file, exec_file, -1,
-						map_start, false);
-		if (!mod) {
-			pr_debug("dwfl_report_elf() failed %s\n",
-						dwarf_errmsg(-1));
-			/*
-			 * We normally cache the DWARF debug info and never
-			 * call dwfl_end(). But to prevent fd leak, free in
-			 * case of error.
-			 */
-			dwfl_end(dwfl);
-			goto out;
-		}
-		RC_CHK_ACCESS(dso)->dwfl = dwfl;
-	}
-
-	mod = dwfl_addrmodule(dwfl, pc);
 	if (!mod) {
 		pr_debug("dwfl_addrmodule() failed, %s\n", dwarf_errmsg(-1));
 		goto out;
@@ -196,9 +166,9 @@ static int check_return_addr(struct dso *dso, u64 map_start, Dwarf_Addr pc)
 	 * To work with split debug info files (eg: glibc), check both
 	 * .eh_frame and .debug_frame sections of the ELF header.
 	 */
-	frame = get_eh_frame(mod, pc);
+	frame = get_eh_frame(mod, mapped_pc);
 	if (!frame) {
-		frame = get_dwarf_frame(mod, pc);
+		frame = get_dwarf_frame(mod, mapped_pc);
 		if (!frame)
 			goto out;
 	}
@@ -264,7 +234,7 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain)
 		return skip_slot;
 	}
 
-	rc = check_return_addr(dso, map__start(al.map), ip);
+	rc = check_return_addr(dso, map__map_ip(al.map, ip));
 
 	pr_debug("[DSO %s, sym %s, ip 0x%" PRIx64 "] rc %d\n",
 		dso__long_name(dso), al.sym->name, ip, rc);

tools/perf/util/dso.c

@@ -1612,7 +1612,7 @@ void dso__delete(struct dso *dso)
 	auxtrace_cache__free(RC_CHK_ACCESS(dso)->auxtrace_cache);
 	dso_cache__free(dso);
 	dso__free_a2l(dso);
-	dso__free_a2l_libdw(dso);
+	dso__free_libdw(dso);
 	dso__free_symsrc_filename(dso);
 	nsinfo__zput(RC_CHK_ACCESS(dso)->nsinfo);
 	mutex_destroy(dso__lock(dso));

tools/perf/util/dso.h

@@ -268,11 +268,8 @@ DECLARE_RC_STRUCT(dso) {
 	const char	 *short_name;
 	const char	 *long_name;
 	void		 *a2l;
-	void		 *a2l_libdw;
+	void		 *libdw;
 	char		 *symsrc_filename;
-#if defined(__powerpc__)
-	void		*dwfl;			/* DWARF debug info */
-#endif
 	struct nsinfo	*nsinfo;
 	struct auxtrace_cache *auxtrace_cache;
 	union { /* Tool specific area */
@@ -335,16 +332,26 @@ static inline void dso__set_a2l(struct dso *dso, void *val)
 	RC_CHK_ACCESS(dso)->a2l = val;
 }
 
-static inline void *dso__a2l_libdw(const struct dso *dso)
+static inline void *dso__libdw(const struct dso *dso)
 {
-	return RC_CHK_ACCESS(dso)->a2l_libdw;
+	return RC_CHK_ACCESS(dso)->libdw;
 }
 
-static inline void dso__set_a2l_libdw(struct dso *dso, void *val)
+static inline void dso__set_libdw(struct dso *dso, void *val)
 {
-	RC_CHK_ACCESS(dso)->a2l_libdw = val;
+	RC_CHK_ACCESS(dso)->libdw = val;
 }
 
+struct Dwfl;
+#ifdef HAVE_LIBDW_SUPPORT
+struct Dwfl *dso__libdw_dwfl(struct dso *dso);
+#else
+static inline struct Dwfl *dso__libdw_dwfl(struct dso *dso __maybe_unused)
+{
+	return NULL;
+}
+#endif
+
 static inline unsigned int dso__a2l_fails(const struct dso *dso)
 {
 	return RC_CHK_ACCESS(dso)->a2l_fails;

tools/perf/util/libdw.c

@@ -8,16 +8,64 @@
 #include <unistd.h>
 #include <elfutils/libdwfl.h>
 
-void dso__free_a2l_libdw(struct dso *dso)
+static const Dwfl_Callbacks offline_callbacks = {
+	.find_debuginfo = dwfl_standard_find_debuginfo,
+	.section_address = dwfl_offline_section_address,
+	.find_elf = dwfl_build_id_find_elf,
+};
+
+void dso__free_libdw(struct dso *dso)
 {
-	Dwfl *dwfl = dso__a2l_libdw(dso);
+	Dwfl *dwfl = dso__libdw(dso);
 
 	if (dwfl) {
 		dwfl_end(dwfl);
-		dso__set_a2l_libdw(dso, NULL);
+		dso__set_libdw(dso, NULL);
 	}
 }
 
+struct Dwfl *dso__libdw_dwfl(struct dso *dso)
+{
+	Dwfl *dwfl = dso__libdw(dso);
+	const char *dso_name;
+	Dwfl_Module *mod;
+	int fd;
+
+	if (dwfl)
+		return dwfl;
+
+	dso_name = dso__long_name(dso);
+	/*
+	 * Initialize Dwfl session.
+	 * We need to open the DSO file to report it to libdw.
+	 */
+	fd = open(dso_name, O_RDONLY);
+	if (fd < 0)
+		return NULL;
+
+	dwfl = dwfl_begin(&offline_callbacks);
+	if (!dwfl) {
+		close(fd);
+		return NULL;
+	}
+
+	/*
+	 * If the report is successful, the file descriptor fd is consumed
+	 * and closed by the Dwfl. If not, it is not closed.
+	 */
+	mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
+	if (!mod) {
+		dwfl_end(dwfl);
+		close(fd);
+		return NULL;
+	}
+
+	dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
+	dso__set_libdw(dso, dwfl);
+
+	return dwfl;
+}
+
 struct libdw_a2l_cb_args {
 	struct dso *dso;
 	struct symbol *sym;
@@ -63,58 +111,21 @@ static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
 	return 0;
 }
 
-int libdw__addr2line(const char *dso_name, u64 addr,
+int libdw__addr2line(u64 addr, char **file, unsigned int *line_nr,
-		     char **file, unsigned int *line_nr,
 		     struct dso *dso, bool unwind_inlines,
 		     struct inline_node *node, struct symbol *sym)
 {
-	static const Dwfl_Callbacks offline_callbacks = {
+	Dwfl *dwfl = dso__libdw_dwfl(dso);
-		.find_debuginfo = dwfl_standard_find_debuginfo,
-		.section_address = dwfl_offline_section_address,
-		.find_elf = dwfl_build_id_find_elf,
-	};
-	Dwfl *dwfl = dso__a2l_libdw(dso);
 	Dwfl_Module *mod;
 	Dwfl_Line *dwline;
 	Dwarf_Addr bias;
 	const char *src;
 	int lineno = 0;
 
-	if (!dwfl) {
+	if (!dwfl)
-		/*
+		return 0;
-		 * Initialize Dwfl session.
-		 * We need to open the DSO file to report it to libdw.
-		 */
-		int fd;
-
-		fd = open(dso_name, O_RDONLY);
-		if (fd < 0)
-			return 0;
-
-		dwfl = dwfl_begin(&offline_callbacks);
-		if (!dwfl) {
-			close(fd);
-			return 0;
-		}
-
-		/*
-		 * If the report is successful, the file descriptor fd is consumed
-		 * and closed by the Dwfl. If not, it is not closed.
-		 */
-		mod = dwfl_report_offline(dwfl, dso_name, dso_name, fd);
-		if (!mod) {
-			dwfl_end(dwfl);
-			close(fd);
-			return 0;
-		}
-
-		dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
-		dso__set_a2l_libdw(dso, dwfl);
-	} else {
-		/* Dwfl session already initialized, get module for address. */
-		mod = dwfl_addrmodule(dwfl, addr);
-	}
 
+	mod = dwfl_addrmodule(dwfl, addr);
 	if (!mod)
 		return 0;
 

tools/perf/util/libdw.h

@@ -11,7 +11,6 @@ struct symbol;
 #ifdef HAVE_LIBDW_SUPPORT
 /*
  * libdw__addr2line - Convert address to source location using libdw
- * @dso_name: Name of the DSO
  * @addr: Address to resolve
  * @file: Pointer to return filename (caller must free)
  * @line_nr: Pointer to return line number
@@ -26,23 +25,22 @@ struct symbol;
  *
  * Returns 1 on success (found), 0 on failure (not found).
  */
-int libdw__addr2line(const char *dso_name, u64 addr, char **file,
+int libdw__addr2line(u64 addr, char **file,
 		     unsigned int *line_nr, struct dso *dso,
 		     bool unwind_inlines, struct inline_node *node,
 		     struct symbol *sym);
 
 /*
- * dso__free_a2l_libdw - Free libdw resources associated with the DSO
+ * dso__free_libdw - Free libdw resources associated with the DSO
  * @dso: The dso to free resources for
  *
  * This function cleans up the Dwfl context used for addr2line lookups.
  */
-void dso__free_a2l_libdw(struct dso *dso);
+void dso__free_libdw(struct dso *dso);
 
 #else /* HAVE_LIBDW_SUPPORT */
 
-static inline int libdw__addr2line(const char *dso_name __maybe_unused,
+static inline int libdw__addr2line(u64 addr __maybe_unused, char **file __maybe_unused,
-				   u64 addr __maybe_unused, char **file __maybe_unused,
 				   unsigned int *line_nr __maybe_unused,
 				   struct dso *dso __maybe_unused,
 				   bool unwind_inlines __maybe_unused,
@@ -52,7 +50,7 @@ static inline int libdw__addr2line(const char *dso_name __maybe_unused,
 	return 0;
 }
 
-static inline void dso__free_a2l_libdw(struct dso *dso __maybe_unused)
+static inline void dso__free_libdw(struct dso *dso __maybe_unused)
 {
 }
 #endif /* HAVE_LIBDW_SUPPORT */

tools/perf/util/srcline.c

@@ -161,7 +161,7 @@ static int addr2line(const char *dso_name, u64 addr, char **file, unsigned int *
 	for (size_t i = 0; i < ARRAY_SIZE(symbol_conf.addr2line_style); i++) {
 		switch (symbol_conf.addr2line_style[i]) {
 		case A2L_STYLE_LIBDW:
-			ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines,
+			ret = libdw__addr2line(addr, file, line_nr, dso, unwind_inlines,
 					       node, sym);
 			break;
 		case A2L_STYLE_LLVM: