docs: update BPF features list and tell how to list components

Update list of main features and supported map types.

Also update list of architectures supporting JIT, and main features
list, with important upcoming changes (x86_32 for JIT, bpfilter and
AF_XDP for main features).

Also add notes on top of the lists about how to obtain the items of each
list.

Remove speculative map types with no link or schedule.

docs/kernel-versions.md

@@ -8,6 +8,10 @@ Kernel version | Commit
 
 ## JIT compiling
 
+The list of supported architectures for your kernel can be retrieved with:
+
+    git grep HAVE_EBPF_JIT arch/
+
 Feature / Architecture | Kernel version | Commit
 -----------------------|----------------|-------
 x86\_64 | 3.16 | [`622582786c9e`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=622582786c9e041d0bd52bde201787adeab249f8)
@@ -19,9 +23,16 @@ Constant blinding - PowerPC64 | 4.9 | [`b7b7013cac55`](https://git.kernel.org/cg
 Sparc64 | 4.12 | [`7a12b5031c6b`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7a12b5031c6b947cc13918237ae652b536243b76)
 MIPS | 4.13 | [`f381bf6d82f0`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=f381bf6d82f032b7410185b35d000ea370ac706b)
 ARM32 | 4.14 | [`39c13c204bb1`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=39c13c204bb1150d401e27d41a9d8b332be47c49)
+x86\_32 | ? | [Not upstream yet](https://lwn.net/Articles/752957/)
 
 ## Main features
 
+Several (but not all) of these _main features_ translate to an eBPF program type.
+The list of such program types supported in your kernel can be found in file
+[`include/uapi/linux/bpf.h`](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/bpf.h):
+
+    git grep -W 'bpf_prog_type {' include/uapi/linux/bpf.h
+
 Feature | Kernel version | Commit
 --------|----------------|-------
 `AF_PACKET` (libpcap/tcpdump, `cls_bpf` classifier, netfilter's `xt_bpf`, team driver's load-balancing mode…) | 3.15 | [`bd4cf0ed331a`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bd4cf0ed331a275e9bf5a49e6d0fd55dffc551b8)
@@ -51,9 +62,22 @@ Testing / benchmarking BPF programs | 4.12 | [`1cf1cae963c2`](https://git.kernel
 BPF programs and maps IDs | 4.13 | [`dc4bb0e23561`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=dc4bb0e2356149aee4cdae061936f3bbdd45595c)
 BPF support for `sock_ops` | 4.13 | [`40304b2a1567`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=40304b2a1567fecc321f640ee4239556dd0f3ee0)
 BPF support for skbs on sockets | 4.14 | [`b005fd189cec`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b005fd189cec9407b700599e1e80e0552446ee79)
+bpftool utility in kernel sources | 4.15 | [`71bb428fe2c1`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=71bb428fe2c19512ac671d5ee16ef3e73e1b49a8)
+BPF attached to cgroups as device controller | 4.15 | [`ebc614f68736`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ebc614f687369f9df99828572b1d85a7c2de3d92)
+BPF used for monitoring socket RX/TX data | 4.17 | [`4f738adba30a`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4f738adba30a7cfc006f605707e7aee847ffefa0)
+BPF attached to raw tracepoints | 4.17 | [`c4f6699dfcb8`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c4f6699dfcb8558d138fe838f741b2c10f416cf9)
+BPF attached to `bind()` system call | 4.17 | [`4fbac77d2d09`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4fbac77d2d092b475dda9eea66da674369665427)
+BPF Type Format (BTF) | 4.18 | [`69b693f0aefa`](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=69b693f0aefa0ed521e8bd02260523b5ae446ad7)
+AF_XDP | ? | [Not upstream yet](https://lwn.net/Articles/752959/)
+bpfilter | ? | [Not upstream yet](https://lwn.net/Articles/747504/)
 
 ## Tables (_a.k.a._ Maps)
 
+The list of map types supported in your kernel can be found in file
+[`include/uapi/linux/bpf.h`](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/bpf.h):
+
+    git grep -W 'bpf_map_type {' include/uapi/linux/bpf.h
+
 Table type | Kernel version | Commit
 -----------|----------------|-------
 Hash | 3.19 | [`0f8e4bd8a1fc`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0f8e4bd8a1fc8c4185f1630061d0a1f2d197a475)
@@ -72,11 +96,15 @@ Array of maps | 4.12 | [`56f668dfe00d`](https://git.kernel.org/cgit/linux/kernel
 Hash of maps | 4.12 | [`bcc6b1b7ebf8`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bcc6b1b7ebf857a9fe56202e2be3361131588c15)
 Netdevice references | 4.14 | [`546ac1ffb70d`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=546ac1ffb70d25b56c1126940e5ec639c4dd7413)
 Socket references | 4.14 | [`174a79ff9515`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=174a79ff9515f400b9a6115643dafd62a635b7e6)
-Text string | _To be done?_ |
-Variable-length maps | _To be done?_ |
+CPU references | 4.15 | [`6710e1126934`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6710e1126934d8b4372b4d2f9ae1646cd3f151bf)
 
 ## XDP
 
+An approximate list of drivers or components supporting XDP programs for your
+kernel can be retrieved with:
+
+    git grep -l XDP_SETUP_PROG drivers/
+
 Feature / Driver | Kernel version | Commit
 -----------------|----------------|-------
 XDP core architecture | 4.8 | [`6a773a15a1e8`](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6a773a15a1e8874e5eccd2f29190c31085912c95)
@@ -102,6 +130,11 @@ Intel `e1000e` driver | | [Not planned for upstream at this time](https://github
 
 ## Helpers
 
+The list of helpers supported in your kernel can be found in file
+[`include/uapi/linux/bpf.h`](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/bpf.h):
+
+    git grep '	FN(' include/uapi/linux/bpf.h
+
 Alphabetical order
 
 Helper | Kernel version | Commit