[PATCH v1 1/2] perf libdw: Pass dso_name explicitly to properly anchor split-debug builds

[Ian Rogers]

When resolving source lines via get_srcline(), srcline_dso_name()
explicitly checks for and returns the split-debug file path
(dso__symsrc_filename, which is cached during dso__load()) rather than
the default executable path (dso__long_name). Because libdw__addr2line
defaulted to dso__long_name without accepting a passed dso_name, the
Dwfl_Module was hardcoded to initialize against the stripped
executable instead of the intended split debug file.

By explicitly passing the successfully resolved dso_name down the call
path from addr2line() to dso__libdw_dwfl(), libdw accurately anchors to
the dynamically discovered split-debug file, fixing dwarf resolution for
these binaries.

Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/arch/powerpc/util/skip-callchain-idx.c |  2 +-
 tools/perf/util/dso.h                             |  5 +++--
 tools/perf/util/libdw.c                           | 10 +++++-----
 tools/perf/util/libdw.h                           |  5 +++--
 tools/perf/util/srcline.c                         |  2 +-
 5 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
index e57f10798fa6..f7dd27faaec2 100644
--- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c
+++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
@@ -152,7 +152,7 @@ static int check_return_addr(struct dso *dso, Dwarf_Addr mapped_pc)
 	Dwarf_Addr	end = mapped_pc;
 	bool		signalp;
 
-	dwfl = dso__libdw_dwfl(dso);
+	dwfl = dso__libdw_dwfl(dso, NULL);
 	if (!dwfl)
 		return -1;
 
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 55c4aaa53c38..3271e1ecaa9e 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -380,9 +380,10 @@ static inline void dso__set_libdw(struct dso *dso, void *val)
 
 struct Dwfl;
 #ifdef HAVE_LIBDW_SUPPORT
-struct Dwfl *dso__libdw_dwfl(struct dso *dso);
+struct Dwfl *dso__libdw_dwfl(struct dso *dso, const char *dso_name);
 #else
-static inline struct Dwfl *dso__libdw_dwfl(struct dso *dso __maybe_unused)
+static inline struct Dwfl *dso__libdw_dwfl(struct dso *dso __maybe_unused,
+					   const char *dso_name __maybe_unused)
 {
 	return NULL;
 }
diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
index 4ca7e7e4fbe9..f53caee980b0 100644
--- a/tools/perf/util/libdw.c
+++ b/tools/perf/util/libdw.c
@@ -25,17 +25,17 @@ void dso__free_libdw(struct dso *dso)
 	}
 }
 
-struct Dwfl *dso__libdw_dwfl(struct dso *dso)
+struct Dwfl *dso__libdw_dwfl(struct dso *dso, const char *dso_name)
 {
 	Dwfl *dwfl = dso__libdw(dso);
-	const char *dso_name;
 	Dwfl_Module *mod;
 	int fd;
 
 	if (dwfl)
 		return dwfl;
 
-	dso_name = dso__long_name(dso);
+	if (!dso_name)
+		dso_name = dso__long_name(dso);
 	/*
 	 * Initialize Dwfl session.
 	 * We need to open the DSO file to report it to libdw.
@@ -163,11 +163,11 @@ static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
 	return DWARF_CB_ABORT;
 }
 
-int libdw__addr2line(u64 addr, char **file, unsigned int *line_nr,
+int libdw__addr2line(const char *dso_name, u64 addr, char **file, unsigned int *line_nr,
 		     struct dso *dso, bool unwind_inlines,
 		     struct inline_node *node, struct symbol *sym)
 {
-	Dwfl *dwfl = dso__libdw_dwfl(dso);
+	Dwfl *dwfl = dso__libdw_dwfl(dso, dso_name);
 	Dwfl_Module *mod;
 	Dwfl_Line *dwline;
 	Dwarf_Addr bias;
diff --git a/tools/perf/util/libdw.h b/tools/perf/util/libdw.h
index b12094737415..4bdd28d44e25 100644
--- a/tools/perf/util/libdw.h
+++ b/tools/perf/util/libdw.h
@@ -25,7 +25,7 @@ struct symbol;
  *
  * Returns 1 on success (found), 0 on failure (not found).
  */
-int libdw__addr2line(u64 addr, char **file,
+int libdw__addr2line(const char *dso_name, u64 addr, char **file,
 		     unsigned int *line_nr, struct dso *dso,
 		     bool unwind_inlines, struct inline_node *node,
 		     struct symbol *sym);
@@ -40,7 +40,8 @@ void dso__free_libdw(struct dso *dso);
 
 #else /* HAVE_LIBDW_SUPPORT */
 
-static inline int libdw__addr2line(u64 addr __maybe_unused, char **file __maybe_unused,
+static inline int libdw__addr2line(const char *dso_name, u64 addr __maybe_unused,
+				   char **file __maybe_unused,
 				   unsigned int *line_nr __maybe_unused,
 				   struct dso *dso __maybe_unused,
 				   bool unwind_inlines __maybe_unused,
diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index b082178c279b..8e954f0c860a 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -155,7 +155,7 @@ 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(addr, file, line_nr, dso, unwind_inlines,
+			ret = libdw__addr2line(dso_name, addr, file, line_nr, dso, unwind_inlines,
 					       node, sym);
 			break;
 		case A2L_STYLE_LLVM:
-- 
2.55.0.766.g2966f0265a-goog