linux-kernel - [tip:perf/core] perf tools: Use the "_stest" symbol to identify the kernel map when loading kcore

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Date:   Wed, 16 May 2018 11:04:56 -0700
From:   tip-bot for Adrian Hunter <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jolsa@...hat.com, dave.hansen@...ux.intel.com, ak@...ux.intel.com,
        hpa@...or.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de,
        alexander.shishkin@...ux.intel.com, adrian.hunter@...el.com,
        joro@...tes.org, acme@...hat.com, luto@...nel.org
Subject: [tip:perf/core] perf tools: Use the "_stest" symbol to identify the
 kernel map when loading kcore

Commit-ID:  5654997838c2ac9b1950d633fc97f354cc4180e7
Gitweb:     https://git.kernel.org/tip/5654997838c2ac9b1950d633fc97f354cc4180e7
Author:     Adrian Hunter <adrian.hunter@...el.com>
AuthorDate: Wed, 9 May 2018 14:43:34 +0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 15 May 2018 14:31:25 -0300

perf tools: Use the "_stest" symbol to identify the kernel map when loading kcore

The first symbol is not necessarily in the kernel text.  Instead of
using the first symbol, use the _stest symbol to identify the kernel map
when loading kcore.

This allows for the introduction of symbols to identify the x86_64 PTI
entry trampolines.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org
Link: http://lkml.kernel.org/r/1525866228-30321-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/symbol.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index f48dc157c2bd..4a39f4d0a174 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1149,7 +1149,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	bool is_64_bit;
 	int err, fd;
 	char kcore_filename[PATH_MAX];
-	struct symbol *sym;
+	u64 stext;
 
 	if (!kmaps)
 		return -EINVAL;
@@ -1198,13 +1198,13 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 		old_map = next;
 	}
 
-	/* Find the kernel map using the first symbol */
-	sym = dso__first_symbol(dso);
-	list_for_each_entry(new_map, &md.maps, node) {
-		if (sym && sym->start >= new_map->start &&
-		    sym->start < new_map->end) {
-			replacement_map = new_map;
-			break;
+	/* Find the kernel map using the '_stext' symbol */
+	if (!kallsyms__get_function_start(kallsyms_filename, "_stext", &stext)) {
+		list_for_each_entry(new_map, &md.maps, node) {
+			if (stext >= new_map->start && stext < new_map->end) {
+				replacement_map = new_map;
+				break;
+			}
 		}
 	}