perf annotate: Properly notify the user that vmlinux is missing

Before this patch we would not find a vmlinux, then try to pass
objdump "[kernel.kallsyms]" as the filename, it would get
confused and produce no output:

 [root@doppio ~]# perf annotate n_tty_write

 ------------------------------------------------
  Percent |      Source code & Disassembly of [kernel.kallsyms]
 ------------------------------------------------

Now we check that and emit meaningful warning:

 [root@doppio ~]# perf annotate n_tty_write
 Can't annotate n_tty_write: No vmlinux file was found in the
 path: [0] vmlinux
 [1] /boot/vmlinux
 [2] /boot/vmlinux-2.6.34-rc1-tip+
 [3] /lib/modules/2.6.34-rc1-tip+/build/vmlinux
 [4] /usr/lib/debug/lib/modules/2.6.34-rc1-tip+/vmlinux
 [root@doppio ~]#

This bug was introduced when we added automatic search for
vmlinux, before that time the user had to specify a vmlinux
file.

v2: Print the warning just for the first symbol found when no
    symbol name is specified, otherwise it will spam the screen
    repeating the warning for each symbol.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NArnaldo Carvalho de Melo <acme@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>
Cc: <stable@kernel.org>
LKML-Reference: <1268669073-6856-1-git-send-email-acme@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/builtin-annotate.c

@@ -452,6 +452,16 @@ static void annotate_sym(struct hist_entry *he)
 	if (!filename)
 		return;
 
+	if (dso->origin == DSO__ORIG_KERNEL) {
+		if (dso->annotate_warned)
+			return;
+		dso->annotate_warned = 1;
+		pr_err("Can't annotate %s: No vmlinux file was found in the "
+		       "path:\n", sym->name);
+		vmlinux_path__fprintf(stderr);
+		return;
+	}
+
 	pr_debug("%s: filename=%s, sym=%s, start=%#Lx, end=%#Lx\n", __func__,
 		 filename, sym->name, map->unmap_ip(map, sym->start),
 		 map->unmap_ip(map, sym->end));

tools/perf/util/newt.c

@@ -63,7 +63,7 @@ static void hist_entry__annotate_browser(struct hist_entry *self)
 	if (self->sym == NULL)
 		return;
 
-	if (asprintf(&str, "perf annotate %s | expand", self->sym->name) < 0)
+	if (asprintf(&str, "perf annotate %s 2>&1 | expand", self->sym->name) < 0)
 		return;
 
 	fp = popen(str, "r");

tools/perf/util/symbol.h

@@ -106,6 +106,7 @@ struct dso {
 	u8		 has_build_id:1;
 	u8		 kernel:1;
 	u8		 hit:1;
+	u8		 annotate_warned:1;
 	unsigned char	 origin;
 	u8		 sorted_by_name;
 	u8		 loaded;