linux-kernel - [PATCH 05/12] perf tools: Read also the end of the kernel

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Date:   Tue, 16 Apr 2019 18:01:20 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH 05/12] perf tools: Read also the end of the kernel

We mark the end of kernel based on the first module,
but that could cover some bpf program maps. Reading
_etext symbol if it's present to get precise kernel
map end.

Link: http://lkml.kernel.org/n/tip-ynut991ttyyhvo1sbhlm4c42@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/util/machine.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 3c520baa198c..ad0205fbb506 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -924,7 +924,8 @@ const char *ref_reloc_sym_names[] = {"_text", "_stext", NULL};
  * symbol_name if it's not that important.
  */
 static int machine__get_running_kernel_start(struct machine *machine,
-					     const char **symbol_name, u64 *start)
+					     const char **symbol_name,
+					     u64 *start, u64 *end)
 {
 	char filename[PATH_MAX];
 	int i, err = -1;
@@ -949,6 +950,11 @@ static int machine__get_running_kernel_start(struct machine *machine,
 		*symbol_name = name;
 
 	*start = addr;
+
+	err = kallsyms__get_function_start(filename, "_etext", &addr);
+	if (!err)
+		*end = addr;
+
 	return 0;
 }
 
@@ -1440,7 +1446,7 @@ int machine__create_kernel_maps(struct machine *machine)
 	struct dso *kernel = machine__get_kernel(machine);
 	const char *name = NULL;
 	struct map *map;
-	u64 addr = 0;
+	u64 start = 0, end = ~0ULL;
 	int ret;
 
 	if (kernel == NULL)
@@ -1459,9 +1465,9 @@ int machine__create_kernel_maps(struct machine *machine)
 				 "continuing anyway...\n", machine->pid);
 	}
 
-	if (!machine__get_running_kernel_start(machine, &name, &addr)) {
+	if (!machine__get_running_kernel_start(machine, &name, &start, &end)) {
 		if (name &&
-		    map__set_kallsyms_ref_reloc_sym(machine->vmlinux_map, name, addr)) {
+		    map__set_kallsyms_ref_reloc_sym(machine->vmlinux_map, name, start)) {
 			machine__destroy_kernel_maps(machine);
 			ret = -1;
 			goto out_put;
@@ -1471,16 +1477,19 @@ int machine__create_kernel_maps(struct machine *machine)
 		 * we have a real start address now, so re-order the kmaps
 		 * assume it's the last in the kmaps
 		 */
-		machine__update_kernel_mmap(machine, addr, ~0ULL);
+		machine__update_kernel_mmap(machine, start, end);
 	}
 
 	if (machine__create_extra_kernel_maps(machine, kernel))
 		pr_debug("Problems creating extra kernel maps, continuing anyway...\n");
 
-	/* update end address of the kernel map using adjacent module address */
-	map = map__next(machine__kernel_map(machine));
-	if (map)
-		machine__set_kernel_mmap(machine, addr, map->start);
+	if (end == ~0ULL) {
+		/* update end address of the kernel map using adjacent module address */
+		map = map__next(machine__kernel_map(machine));
+		if (map)
+			machine__set_kernel_mmap(machine, start, map->start);
+	}
+
 out_put:
 	dso__put(kernel);
 	return ret;
-- 
2.17.2