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>

1 files changed, 11 insertions, 41 deletions

diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
index 356786432fd3..e57f10798fa6 100644
--- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c
+++ b/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	end = pc;
+	Dwarf_Addr	start = mapped_pc;
+	Dwarf_Addr	end = mapped_pc;
 	bool		signalp;
-	const char	*exec_file = dso__long_name(dso);
-
-	dwfl = RC_CHK_ACCESS(dso)->dwfl;
-
-	if (!dwfl) {
-		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);
+	dwfl = dso__libdw_dwfl(dso);
+	if (!dwfl)
+		return -1;
+
+	mod = dwfl_addrmodule(dwfl, mapped_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);