perf kallsyms: Introduce tool to look for extended symbol information on the running kernel

Its similar to doing grep on a /proc/kallsyms, but it also shows extra
information like the path to the kernel module and the unrelocated
addresses in it, to help in diagnosing problems.

It is also helps demonstrate the use of the symbols routines so that
tool writers can use them more effectively.

Using it:

  $ perf kallsyms e1000_xmit_frame netif_rx usb_stor_set_xfer_buf
  e1000_xmit_frame: [e1000e] /lib/modules/4.9.0+/kernel/drivers/net/ethernet/intel/e1000e/e1000e.ko 0xffffffffc046fc10-0xffffffffc0470bb0 (0x19c80-0x1ac20)
  netif_rx: [kernel] [kernel.kallsyms] 0xffffffff916f03a0-0xffffffff916f0410 (0xffffffff916f03a0-0xffffffff916f0410)
  usb_stor_set_xfer_buf: [usb_storage] /lib/modules/4.9.0+/kernel/drivers/usb/storage/usb-storage.ko 0xffffffffc057aea0-0xffffffffc057af19 (0xf10-0xf89)
  $

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-79bk9pakujn4l4vq0f90klv3@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-kallsyms.txt

@@ -0,0 +1,24 @@
+perf-kallsyms(1)
+==============
+
+NAME
+----
+perf-kallsyms - Searches running kernel for symbols
+
+SYNOPSIS
+--------
+[verse]
+'perf kallsyms <options> symbol_name[,symbol_name...]'
+
+DESCRIPTION
+-----------
+This command searches the running kernel kallsyms file for the given symbol(s)
+and prints information about it, including the DSO, the kallsyms begin/end
+addresses and the addresses in the ELF kallsyms symbol table (for symbols in
+modules).
+
+OPTIONS
+-------
+-v::
+--verbose=::
+	Increase verbosity level, showing details about symbol table loading, etc.