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>

1 files changed, 37 insertions, 28 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 7b4cedeb3020..4d75e745288f 100644
--- a/tools/perf/util/symbol.c
+++ b/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;
 
@@ -1374,39 +1368,36 @@ 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);
-                if (err > 0 && use_modules) {
-                        int syms = dsos__load_modules_sym(filter);
+        err = dso__load_vmlinux(self, kernel_map, self->name, filter);
+        if (err > 0 && use_modules) {
+                int syms = dsos__load_modules_sym(filter);
 
-                        if (syms < 0)
-                                pr_warning("Failed to read module symbols!"
-                                           " Continuing...\n");
-                        else
-                                err += syms;
-                }
+                if (syms < 0)
+                        pr_warning("Failed to read module symbols!"
+                                   " Continuing...\n");
+                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)