perf jevents: Program to convert JSON file

This is a modified version of an earlier patch by Andi Kleen.

We expect architectures to create JSON files describing the performance
monitoring (PMU) events that each CPU model/family of the architecture
supports.

Following is an example of the JSON file entry for an x86 event:

    	[
    	...
    	{
    	"EventCode": "0x00",
    	"UMask": "0x01",
    	"EventName": "INST_RETIRED.ANY",
    	"BriefDescription": "Instructions retired from execution.",
    	"PublicDescription": "Instructions retired from execution.",
    	"Counter": "Fixed counter 1",
    	"CounterHTOff": "Fixed counter 1",
    	"SampleAfterValue": "2000003",
    	"SampleAfterValue": "2000003",
    	"MSRIndex": "0",
    	"MSRValue": "0",
    	"TakenAlone": "0",
    	"CounterMask": "0",
    	"Invert": "0",
    	"AnyThread": "0",
    	"EdgeDetect": "0",
    	"PEBS": "0",
    	"PRECISE_STORE": "0",
    	"Errata": "null",
    	"Offcore": "0"
    	},
    	...

    	]

All the PMU events supported by a CPU model/family must be grouped into
"topics" such as "Pipelining", "Floating-point", "Virtual-memory" etc.

All events belonging to a topic must be placed in a separate JSON file
(eg: "Pipelining.json") and all the topic JSON files for a CPU model must
be in a separate directory.

	Eg: for the CPU model "Silvermont_core":

    	$ ls tools/perf/pmu-events/arch/x86/Silvermont_core
    	Floating-point.json
    	Memory.json
    	Other.json
    	Pipelining.json
    	Virtualmemory.json

Finally, to allow multiple CPU models to share a single set of JSON files,
architectures must provide a mapping between a model and its set of events:

    	$ grep Silvermont tools/perf/pmu-events/arch/x86/mapfile.csv
    	GenuineIntel-6-4D,V13,Silvermont_core,core
    	GenuineIntel-6-4C,V13,Silvermont_core,core

which maps each CPU, identified by [vendor, family, model, version, type]
to a directory of JSON files. Thus two (or more) CPU models support the
set of PMU events listed in the directory.

    	tools/perf/pmu-events/arch/x86/Silvermont_core/

Given this organization of files, the program, jevents:

	- locates all JSON files for each CPU-model of the architecture,

	- parses all JSON files for the CPU-model and generates a C-style
	  "PMU-events table" (pmu-events.c) for the model

	- locates a mapfile for the architecture

	- builds a global table, mapping each model of CPU to the corresponding
	  PMU-events table.

The 'pmu-events.c' is generated when building perf and added to libperf.a.
The global table pmu_events_map[] table in this pmu-events.c will be used
in perf in a follow-on patch.

If the architecture does not have any JSON files or there is an error in
processing them, an empty mapping file is created. This would allow the
build of perf to proceed even if we are not able to provide aliases for
events.

The parser for JSON files allows parsing Intel style JSON event files. This
allows to use an Intel event list directly with perf. The Intel event lists
can be quite large and are too big to store in unswappable kernel memory.

The conversion from JSON to C-style is straight forward.  The parser knows
(very little) Intel specific information, and can be easily extended to
handle fields for other CPUs.

The parser code is partially shared with an independent parsing library,
which is 2-clause BSD licensed. To avoid any conflicts I marked those
files as BSD licensed too. As part of perf they become GPLv2.

Committer notes:

Fixes:

1) Limit maxfds to 512 to avoid nftd() segfaulting on alloca() with a
   big rlim_max, as in docker containers - acme

2) Make jevents a hostprog, supporting cross compilation - jolsa

3) Use HOSTCC for jevents final step - acme

4) Define _GNU_SOURCE for asprintf, as we can't use CC's EXTRA_CFLAGS,
  that has to have --sysroot on the Android NDK 24 - acme

5) Removed $(srctree)/tools/perf/pmu-events/pmu-events.c from the
   'clean' target, it is generated on $(OUTPUT)pmu-events/pmu-events.c,
   which is already taken care of in the original patch - acme

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1473978296-20712-3-git-send-email-sukadev@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/20160927141846.GA6589@krava


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>