perf symbols: Capture the running kernel buildid too

[root@doppio linux-2.6-tip]# perf record -a -f sleep 3s ; perf
buildid-list | grep vmlinux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.171 MB perf.data (~7489
samples) ] 18e7cc53db62a7d35e9d6f6c9ddc23017d38ee9a vmlinux
[root@doppio linux-2.6-tip]#

Several refactorings were needed so that we can have symmetry
between dsos__load_modules() and dsos__load_kernel(), i.e. those
functions will respectively create and add to the dsos list the
loaded modules and kernel, with its buildids, but not load its
symbols. That is something the subcomands that need will have to
call dso__load_kernel_sym(), just like we do with modules with
dsos__load_module_sym()/dso__load_module_sym().

Next csets will actually use this info to stop producing bogus
results using mismatched vmlinux and .ko files.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1258582853-8579-4-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-top.c

@@ -948,7 +948,12 @@ static int symbol_filter(struct map *map, struct symbol *sym)
 
 static int parse_symbols(void)
 {
-	if (dsos__load_kernel(vmlinux_name, symbol_filter, 1) <= 0)
+	struct dso *kernel = dsos__load_kernel();
+
+	if (kernel == NULL)
+		return -1;
+
+	if (dso__load_kernel_sym(kernel, symbol_filter, 1) <= 0)
 		return -1;
 
 	if (dump_symtab)

tools/perf/util/header.c

@@ -241,6 +241,7 @@ perf_header__adds_write(struct perf_header *self, int fd)
 
 		buildid_sec = &feat_sec[idx++];
 
+		dsos__load_kernel();
 		/*
 		 * Read the list of loaded modules with its build_ids
 		 */

tools/perf/util/symbol.c

@@ -1352,17 +1352,11 @@ static int dso__load_vmlinux(struct dso *self, struct map *map,
 	return err;
 }
 
-int dsos__load_kernel(const char *vmlinux, symbol_filter_t filter,
-		      int use_modules)
+int dso__load_kernel_sym(struct dso *self, symbol_filter_t filter, int use_modules)
 {
 	int err = -1;
-	struct dso *dso = dso__new(vmlinux);
 
-	if (dso == NULL)
-		return -1;
-
-	dso->short_name = "[kernel]";
-	kernel_map = map__new2(0, dso);
+	kernel_map = map__new2(0, self);
 	if (kernel_map == NULL)
 		goto out_delete_dso;
 
@@ -1374,8 +1368,7 @@ int dsos__load_kernel(const char *vmlinux, symbol_filter_t filter,
 		use_modules = 0;
 	}
 
-	if (vmlinux) {
-		err = dso__load_vmlinux(dso, kernel_map, vmlinux, filter);
+	err = dso__load_vmlinux(self, kernel_map, self->name, filter);
 	if (err > 0 && use_modules) {
 		int syms = dsos__load_modules_sym(filter);
 
@@ -1385,28 +1378,26 @@ int dsos__load_kernel(const char *vmlinux, symbol_filter_t filter,
 		else
 			err += syms;
 	}
-	}
 
 	if (err <= 0)
 		err = kernel_maps__load_kallsyms(filter, use_modules);
 
 	if (err > 0) {
-		struct rb_node *node = rb_first(&dso->syms);
+		struct rb_node *node = rb_first(&self->syms);
 		struct symbol *sym = rb_entry(node, struct symbol, rb_node);
 
 		kernel_map->start = sym->start;
-		node = rb_last(&dso->syms);
+		node = rb_last(&self->syms);
 		sym = rb_entry(node, struct symbol, rb_node);
 		kernel_map->end = sym->end;
 
-		dso->origin = DSO__ORIG_KERNEL;
+		self->origin = DSO__ORIG_KERNEL;
 		kernel_maps__insert(kernel_map);
 		/*
 		 * Now that we have all sorted out, just set the ->end of all
 		 * maps:
 		 */
 		kernel_maps__fixup_end();
-		dsos__add(dso);
 
 		if (verbose)
 			kernel_maps__fprintf(stderr);
@@ -1415,7 +1406,7 @@ int dsos__load_kernel(const char *vmlinux, symbol_filter_t filter,
 	return err;
 
 out_delete_dso:
-	dso__delete(dso);
+	dso__delete(self);
 	return -1;
 }
 
@@ -1475,18 +1466,36 @@ size_t dsos__fprintf_buildid(FILE *fp)
 	return ret;
 }
 
-int load_kernel(symbol_filter_t filter)
+struct dso *dsos__load_kernel(void)
 {
-	if (dsos__load_kernel(vmlinux_name, filter, modules) <= 0)
-		return -1;
+	struct dso *kernel = dso__new(vmlinux_name);
 
+	if (kernel == NULL)
+		return NULL;
+
+	kernel->short_name = "[kernel]";
 	vdso = dso__new("[vdso]");
 	if (!vdso)
-		return -1;
+		return NULL;
+
+	if (sysfs__read_build_id("/sys/kernel/notes", kernel->build_id,
+				 sizeof(kernel->build_id)) == 0)
+		kernel->has_build_id = true;
 
+	dsos__add(kernel);
 	dsos__add(vdso);
 
-	return 0;
+	return kernel;
+}
+
+int load_kernel(symbol_filter_t filter)
+{
+	struct dso *kernel = dsos__load_kernel();
+
+	if (kernel == NULL)
+		return -1;
+
+	return dso__load_kernel_sym(kernel, filter, modules);
 }
 
 void symbol__init(unsigned int priv_size)

tools/perf/util/symbol.h

@@ -77,10 +77,10 @@ void dso__delete(struct dso *self);
 
 struct symbol *dso__find_symbol(struct dso *self, u64 ip);
 
-int dsos__load_kernel(const char *vmlinux, symbol_filter_t filter, int modules);
 int dsos__load_modules(void);
 struct dso *dsos__findnew(const char *name);
 int dso__load(struct dso *self, struct map *map, symbol_filter_t filter);
+int dso__load_kernel_sym(struct dso *self, symbol_filter_t filter, int modules);
 void dsos__fprintf(FILE *fp);
 size_t dsos__fprintf_buildid(FILE *fp);
 
@@ -94,6 +94,7 @@ int sysfs__read_build_id(const char *filename, void *bf, size_t size);
 bool dsos__read_build_ids(void);
 int build_id__sprintf(u8 *self, int len, char *bf);
 
+struct dso *dsos__load_kernel(void);
 int load_kernel(symbol_filter_t filter);
 
 void symbol__init(unsigned int priv_size);