[tip:perf/urgent] perf s390: Fix 'start' address of module's map

[tip-bot for Song Shan Gong]

Commit-ID:  203d8a4aa6edf2c19206316d439ec5dae52ce581
Gitweb:     http://git.kernel.org/tip/203d8a4aa6edf2c19206316d439ec5dae52ce581
Author:     Song Shan Gong <gongss@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 21 Jul 2016 11:10:51 +0800
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 26 Jul 2016 16:46:12 -0300

perf s390: Fix 'start' address of module's map

At present, when creating module's map, perf gets 'start' address by
parsing '/proc/modules', but it's the module base address, it isn't the
start address of the '.text' section.

In most arches, it's OK. But for s390, it places 'GOT' and 'PLT'
relocations before '.text' section. So there exists an offset between
module base address and '.text' section, which will incur wrong symbol
resolution for modules.

Fix this bug by getting 'start' address of module's map from parsing
'/sys/module/[module name]/sections/.text', not from '/proc/modules'.

Signed-off-by: Song Shan Gong <gongss@xxxxxxxxxxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1469070651-6447-2-git-send-email-gongss@xxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/arch/s390/util/Build     |  2 ++
 tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
 tools/perf/util/machine.c           |  8 ++++++++
 tools/perf/util/machine.h           |  1 +
 4 files changed, 30 insertions(+)

diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
index 8a61372..5bd7b92 100644
--- a/tools/perf/arch/s390/util/Build
+++ b/tools/perf/arch/s390/util/Build
@@ -2,3 +2,5 @@ libperf-y += header.o
 libperf-y += kvm-stat.o
 
 libperf-$(CONFIG_DWARF) += dwarf-regs.o
+
+libperf-y += machine.o
diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
new file mode 100644
index 0000000..b9a95a1
--- /dev/null
+++ b/tools/perf/arch/s390/util/machine.c
@@ -0,0 +1,19 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include "util.h"
+#include "machine.h"
+#include "api/fs/fs.h"
+
+int arch__fix_module_text_start(u64 *start, const char *name)
+{
+	char path[PATH_MAX];
+
+	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
+				(int)strlen(name) - 2, name + 1);
+
+	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
+		return -1;
+
+	return 0;
+}
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index bc2cdbd..cb6388d 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1093,12 +1093,20 @@ static int machine__set_modules_path(struct machine *machine)
 
 	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
 }
+int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
+				const char *name __maybe_unused)
+{
+	return 0;
+}
 
 static int machine__create_module(void *arg, const char *name, u64 start)
 {
 	struct machine *machine = arg;
 	struct map *map;
 
+	if (arch__fix_module_text_start(&start, name) < 0)
+		return -1;
+
 	map = machine__findnew_module_map(machine, start, name);
 	if (map == NULL)
 		return -1;
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index 41ac9cf..20739f7 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
 
 struct map *machine__findnew_module_map(struct machine *machine, u64 start,
 					const char *filename);
+int arch__fix_module_text_start(u64 *start, const char *name);
 
 int __machine__load_kallsyms(struct machine *machine, const char *filename,
 			     enum map_type type, bool no_kcore, symbol_filter_t filter);