perf record: Get ref_reloc_sym from kernel map

Now that ref_reloc_sym is set up when the kernel map is created,
'perf record' does not need to pass the symbol names to
perf_event__synthesize_kernel_mmap() which can read the values needed
from ref_reloc_sym directly.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1391004884-10334-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -287,10 +287,7 @@ static void perf_event__synthesize_guest_os(struct machine *machine, void *data)
 	 * have no _text sometimes.
 	 */
 	err = perf_event__synthesize_kernel_mmap(tool, process_synthesized_event,
-						 machine, "_text");
-	if (err < 0)
-		err = perf_event__synthesize_kernel_mmap(tool, process_synthesized_event,
-							 machine, "_stext");
+						 machine);
 	if (err < 0)
 		pr_err("Couldn't record guest kernel [%d]'s reference"
 		       " relocation symbol.\n", machine->pid);
@@ -457,10 +454,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	}
 
 	err = perf_event__synthesize_kernel_mmap(tool, process_synthesized_event,
-						 machine, "_text");
-	if (err < 0)
-		err = perf_event__synthesize_kernel_mmap(tool, process_synthesized_event,
-							 machine, "_stext");
+						 machine);
 	if (err < 0)
 		pr_err("Couldn't record kernel reference relocation symbol\n"
 		       "Symbol resolution may be skewed if relocation was used (e.g. kexec).\n"

tools/perf/util/event.c

@@ -483,15 +483,13 @@ u64 kallsyms__get_function_start(const char *kallsyms_filename,
 
 int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
 				       perf_event__handler_t process,
-				       struct machine *machine,
-				       const char *symbol_name)
+				       struct machine *machine)
 {
 	size_t size;
-	const char *filename, *mmap_name;
-	char path[PATH_MAX];
+	const char *mmap_name;
 	char name_buff[PATH_MAX];
 	struct map *map;
-	u64 start;
+	struct kmap *kmap;
 	int err;
 	/*
 	 * We should get this from /sys/kernel/sections/.text, but till that is
@@ -513,31 +511,19 @@ int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
 		 * see kernel/perf_event.c __perf_event_mmap
 		 */
 		event->header.misc = PERF_RECORD_MISC_KERNEL;
-		filename = "/proc/kallsyms";
 	} else {
 		event->header.misc = PERF_RECORD_MISC_GUEST_KERNEL;
-		if (machine__is_default_guest(machine))
-			filename = (char *) symbol_conf.default_guest_kallsyms;
-		else {
-			sprintf(path, "%s/proc/kallsyms", machine->root_dir);
-			filename = path;
-		}
-	}
-
-	start = kallsyms__get_function_start(filename, symbol_name);
-	if (!start) {
-		free(event);
-		return -ENOENT;
 	}
 
 	map = machine->vmlinux_maps[MAP__FUNCTION];
+	kmap = map__kmap(map);
 	size = snprintf(event->mmap.filename, sizeof(event->mmap.filename),
-			"%s%s", mmap_name, symbol_name) + 1;
+			"%s%s", mmap_name, kmap->ref_reloc_sym->name) + 1;
 	size = PERF_ALIGN(size, sizeof(u64));
 	event->mmap.header.type = PERF_RECORD_MMAP;
 	event->mmap.header.size = (sizeof(event->mmap) -
 			(sizeof(event->mmap.filename) - size) + machine->id_hdr_size);
-	event->mmap.pgoff = start;
+	event->mmap.pgoff = kmap->ref_reloc_sym->addr;
 	event->mmap.start = map->start;
 	event->mmap.len   = map->end - event->mmap.start;
 	event->mmap.pid   = machine->pid;

tools/perf/util/event.h

@@ -214,8 +214,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
 				   struct machine *machine, bool mmap_data);
 int perf_event__synthesize_kernel_mmap(struct perf_tool *tool,
 				       perf_event__handler_t process,
-				       struct machine *machine,
-				       const char *symbol_name);
+				       struct machine *machine);
 
 int perf_event__synthesize_modules(struct perf_tool *tool,
 				   perf_event__handler_t process,