perf report/top: Add 'k' hotkey to zoom directly into the kernel map

As a convenience, equivalent to pressing Enter in a line with a kernel
symbol and then selecting "Zoom" into the kernel DSO.

Reviewed-by: Jiri Olsa <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Jin Yao <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/browsers/hists.c

···
 #include "../../util/evlist.h"
 #include "../../util/header.h"
 #include "../../util/hist.h"
+#include "../../util/machine.h"
 #include "../../util/map.h"
+#include "../../util/maps.h"
 #include "../../util/symbol.h"
 #include "../../util/map_symbol.h"
 #include "../../util/branch.h"
···
 	if (!hists__has(browser->hists, dso) || map == NULL)
 		return 0;
 
-	if (asprintf(optstr, "Zoom %s %s DSO",
+	if (asprintf(optstr, "Zoom %s %s DSO (use the 'k' hotkey to zoom directly into the kernel)",
 		     browser->hists->dso_filter ? "out of" : "into",
 		     __map__is_kernel(map) ? "the Kernel" : map->dso->short_name) < 0)
 		return 0;
···
 	"E             Expand all callchains\n"				\
 	"F             Toggle percentage of filtered entries\n"		\
 	"H             Display column headers\n"			\
+	"k             Zoom into the kernel map\n"			\
 	"L             Change percent limit\n"				\
 	"m             Display context menu\n"				\
 	"S             Zoom into current Processor Socket\n"		\
···
 		case 'd':
 			actions->ms.map = map;
 			do_zoom_dso(browser, actions);
+			continue;
+		case 'k':
+			if (browser->selection != NULL)
+				hists_browser__zoom_map(browser, browser->selection->maps->machine->vmlinux_map);
 			continue;
 		case 'V':
 			verbose = (verbose + 1) % 4;