docs: Update eBPF features list by kernel version (#717)

Following brendangregg's suggestion
(https://github.com/iovisor/bcc/pull/577#issuecomment-251052371), this
commit replaces the former list with a new one: more features are
listed, along with commit ids and references (but no comments detailing
the features, though).

docs/kernel-versions.md

 # BPF Features by Linux Kernel Version
 
-Major milestone releases: 4.1, 4.4.
+## eBPF support
 
-## 3.18
+Kernel version | Commit
+---------------|-------
+3.15 | [bd4cf0ed331a](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bd4cf0ed331a275e9bf5a49e6d0fd55dffc551b8)
 
-- bpf syscall.
+## JIT compiling
 
-## 3.19
+Feature / Architecture | Kernel version | Commit
+-----------------------|----------------|-------
+x86\_64 | 3.16 | [622582786c9e](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=622582786c9e041d0bd52bde201787adeab249f8)
+ARM64 | 3.18 | [e54bcde3d69d](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e54bcde3d69d40023ae77727213d14f920eb264a)
+s390 | 4.1 | [054623105728](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=054623105728b06852f077299e2bf1bf3d5f2b0b)
+Constant blinding for JIT machines | 4.7 | [4f3446bb809f](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4f3446bb809f20ad56cadf712e6006815ae7a8f9)
+PowerPC64 | 4.8 | [156d0e290e96](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=156d0e290e969caba25f1851c52417c14d141b24)
 
-- socket support: bpf can attach to sockets.
+## Main features
 
-## 4.1
+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)
+Kernel helpers | 3.15 | [bd4cf0ed331a](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bd4cf0ed331a275e9bf5a49e6d0fd55dffc551b8)
+`bpf()` syscall | 3.18 | [99c55f7d47c0](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=99c55f7d47c0dc6fc64729f37bf435abf43f4c60)
+Tables (_a.k.a._ Maps; details below) | 3.18 | [99c55f7d47c0](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=99c55f7d47c0dc6fc64729f37bf435abf43f4c60)
+BPF attached to sockets | 3.19 | [89aa075832b0](89aa075832b0da4402acebd698d0411dcc82d03e)
+BPF attached to `kprobes` | 4.1 | [2541517c32be](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2541517c32be2531e0da59dfd7efc1ce844644f5)
+`cls_bpf` / `act_bpf` for `tc` | 4.1 | [e2e9b6541dd4](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e2e9b6541dd4b31848079da80fe2253daaafb549)
+Tail calls | 4.2 | [04fd61ab36ec](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=04fd61ab36ec065e194ab5e74ae34a5240d992bb)
+Non-root programs on sockets | 4.4 | [1be7f75d1668](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1be7f75d1668d6296b80bf35dcf6762393530afc)
+Persistent maps and programs (virtual FS) | 4.4 | [b2197755b263](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b2197755b2633e164a439682fb05a9b5ea48f706)
+`tc`'s `direct_action` (`da`) mode | 4.4 | [045efa82ff56](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=045efa82ff563cd4e656ca1c2e354fa5bf6bbda4)
+`tc`'s `clsact` qdisc | 4.5 | [1f211a1b929c](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1f211a1b929c804100e138c5d3d656992cfd5622)
+BPF attached to tracepoints | 4.7 | [98b5c2c65c29](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=98b5c2c65c2951772a8fc661f50d675e450e8bce)
+Direct packet access | 4.7 | [969bf05eb3ce](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=969bf05eb3cedd5a8d4b7c346a85c2ede87a6d6d)
+XDP (see below) | 4.8 | [6a773a15a1e8](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=6a773a15a1e8874e5eccd2f29190c31085912c95)
+BPF attached to perf events | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=0515e5999a466dfe6e1924f460da599bb6821487) | [](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=)
 
-- kprobe support: BPF programs can now instrument any kernel function via kernel dynamic tracing.
+## Tables (_a.k.a._ Maps)
 
-## 4.3
+Table type | Kernel version | Commit
+-----------|----------------|-------
+Hash | 3.19 | [0f8e4bd8a1fc](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0f8e4bd8a1fc8c4185f1630061d0a1f2d197a475)
+Array | 3.19 | [28fbcfa08d8e](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=28fbcfa08d8ed7c5a50d41a0433aad222835e8e3)
+Tail call (`PROG_ARRAY`) | 4.2 | [04fd61ab36ec](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=04fd61ab36ec065e194ab5e74ae34a5240d992bb)
+Perf events | 4.3 | [ea317b267e9d](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ea317b267e9d03a8241893aa176fba7661d07579)
+Per-CPU hash | 4.6 | [824bd0ce6c7c](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=824bd0ce6c7c43a9e1e210abf124958e54d88342)
+Per-CPU array | 4.6 | [a10423b87a7e](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a10423b87a7eae75da79ce80a8d9475047a674ee)
+Stack trace | 4.6 | [d5a3b1f69186](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d5a3b1f691865be576c2bffa708549b8cdccda19)
+cgroup array | 4.8 | [4ed8ec521ed5](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4ed8ec521ed57c4e207ad464ca0388776de74d4b)
+Text string | _To be done?_ |
+Variable-length maps | _To be done?_ |
 
-- debug string support: bpf_trace_printk() supports strings.
+## XDP
 
-## 4.4
+Feature / Driver | Kernel version | Commit
+-----------------|----------------|-------
+XDP core architecture | 4.8 | [6a773a15a1e8](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=6a773a15a1e8874e5eccd2f29190c31085912c95)
+Action: drop | 4.8 | [6a773a15a1e8](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=6a773a15a1e8874e5eccd2f29190c31085912c95)
+Action: pass on to stack | 4.8 | [6a773a15a1e8](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=6a773a15a1e8874e5eccd2f29190c31085912c95)
+Action: direct forwarding (on same port) | 4.8 | [6ce96ca348a9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=6ce96ca348a9e949f8c43f4d3e98db367d93cffd)
+Direct packet data write | 4.8 | [4acf6c0b84c9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=4acf6c0b84c91243c705303cd9ff16421914150d)
+Mellanox `mlx4` driver | 4.8 | [47a38e155037](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=47a38e155037f417c5740e24ccae6482aedf4b68)
+Mellanox `mlx5` driver | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=86994156c736978d113e7927455d4eeeb2128b9f) | [](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=)
+`e1000` driver  | ? | [](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=)
 
-- bpf_perf_event_output: used by many tools that print per-event output. Eg, opensnoop.
-- unprivileged BPF for sockets: non-root usage for socket-based programs.
+## Helpers
 
-## 4.6
+Alphabetical order
 
-- stack traces (BPF_MAP_TYPE_STACK_TRACE): for capturing stack traces as keys in maps. Eg, stackcount.
-
-## 4.7
-
-- tracepoint support (BPF_PROG_TYPE_TRACEPOINT): BPF programs can now use static kernel tracepoints.
+Helper | Kernel version | Commit
+-------|----------------|-------
+`BPF_FUNC_clone_redirect()` | 4.2 | [3896d655f4d4](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3896d655f4d491c67d669a15f275a39f713410f8)
+`BPF_FUNC_csum_diff()` | 4.6 | [7d672345ed29](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7d672345ed295b1356a5d9f7111da1d1d7d65867)
+`BPF_FUNC_csum_update()` | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=36bbef52c7eb646ed6247055a2acd3851e317857) | [](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=)
+`BPF_FUNC_current_task_under_cgroup()` | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=60d20f9195b260bdf0ac10c275ae9f6016f9c069) | [](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=)
+`BPF_FUNC_get_cgroup_classid()` | 4.3 | [8d20aabe1c76](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8d20aabe1c76cccac544d9fcc3ad7823d9e98a2d)
+`BPF_FUNC_get_current_comm()` | 4.2 | [ffeedafbf023](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ffeedafbf0236f03aeb2e8db273b3e5ae5f5bc89)
+`BPF_FUNC_get_current_pid_tgid()` | 4.2 | [ffeedafbf023](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ffeedafbf0236f03aeb2e8db273b3e5ae5f5bc89)
+`BPF_FUNC_get_current_task()` | 4.8 | [606274c5abd8](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=606274c5abd8e245add01bc7145a8cbb92b69ba8)
+`BPF_FUNC_get_current_uid_gid()` | 4.2 | [ffeedafbf023](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ffeedafbf0236f03aeb2e8db273b3e5ae5f5bc89)
+`BPF_FUNC_get_hash_recalc()` | 4.8 | [13c5c240f789](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=13c5c240f789bbd2bcacb14a23771491485ae61f)
+`BPF_FUNC_get_prandom_u32()` | 4.1 | [03e69b508b6f](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=03e69b508b6f7c51743055c9f61d1dfeadf4b635)
+`BPF_FUNC_get_route_realm()` | 4.4 | [c46646d0484f](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c46646d0484f5d08e2bede9b45034ba5b8b489cc)
+`BPF_FUNC_get_smp_processor_id()` | 4.1 | [c04167ce2ca0](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c04167ce2ca0ecaeaafef006cb0d65cf01b68e42)
+`BPF_FUNC_get_stackid()` | 4.6 | [d5a3b1f69186](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d5a3b1f691865be576c2bffa708549b8cdccda19)
+`BPF_FUNC_ktime_get_ns()` | 4.1 | [d9847d310ab4](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d9847d310ab4003725e6ed1822682e24bd406908)
+`BPF_FUNC_l3_csum_replace()` | 4.1 | [91bc4822c3d6](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=91bc4822c3d61b9bb7ef66d3b77948a4f9177954)
+`BPF_FUNC_l4_csum_replace()` | 4.1 | [91bc4822c3d6](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=91bc4822c3d61b9bb7ef66d3b77948a4f9177954)
+`BPF_FUNC_map_delete_elem()` | 3.19 | [d0003ec01c66](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d0003ec01c667b731c139e23de3306a8b328ccf5)
+`BPF_FUNC_map_lookup_elem()` | 3.19 | [d0003ec01c66](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d0003ec01c667b731c139e23de3306a8b328ccf5)
+`BPF_FUNC_map_update_elem()` | 3.19 | [d0003ec01c66](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d0003ec01c667b731c139e23de3306a8b328ccf5)
+`BPF_FUNC_perf_event_output()` | 4.4 | [a43eec304259](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a43eec304259a6c637f4014a6d4767159b6a3aa3)
+`BPF_FUNC_perf_event_read()` | 4.3 | [35578d798400](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=35578d7984003097af2b1e34502bc943d40c1804)
+`BPF_FUNC_probe_read()` | 4.1 | [2541517c32be](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2541517c32be2531e0da59dfd7efc1ce844644f5)
+`BPF_FUNC_probe_write_user()` | 4.8 | [96ae52279594](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=96ae52279594470622ff0585621a13e96b700600)
+`BPF_FUNC_redirect()` | 4.4 | [27b29f63058d](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=27b29f63058d26c6c1742f1993338280d5a41dc6)
+`BPF_FUNC_set_hash_invalid()` | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=7a4b28c6cc9ffac50f791b99cc7e46106436e5d8) | [](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=)
+`BPF_FUNC_skb_change_proto()` | 4.8 | [6578171a7ff0](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6578171a7ff0c31dc73258f93da7407510abf085)
+`BPF_FUNC_skb_change_tail()` | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=5293efe62df81908f2e90c9820c7edcc8e61f5e9) | [](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=)
+`BPF_FUNC_skb_change_type()` | 4.8 | [d2485c4242a82](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2485c4242a826fdf493fd3a27b8b792965b9b9e)
+`BPF_FUNC_skb_get_tunnel_key()` | 4.3 | [d3aa45ce6b94](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d3aa45ce6b94c65b83971257317867db13e5f492)
+`BPF_FUNC_skb_get_tunnel_opt()` | 4.6 | [14ca0751c96f](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=14ca0751c96f8d3d0f52e8ed3b3236f8b34d3460)
+`BPF_FUNC_skb_load_bytes()` | 4.5 | [05c74e5e53f6](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=05c74e5e53f6cb07502c3e6a820f33e2777b6605)
+`BPF_FUNC_skb_pull_data()` | [4.9](https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=36bbef52c7eb646ed6247055a2acd3851e317857) | [](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=)
+`BPF_FUNC_skb_set_tunnel_key()` | 4.3 | [d3aa45ce6b94](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d3aa45ce6b94c65b83971257317867db13e5f492)
+`BPF_FUNC_skb_set_tunnel_opt()` | 4.6 | [14ca0751c96f](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=14ca0751c96f8d3d0f52e8ed3b3236f8b34d3460)
+`BPF_FUNC_skb_store_bytes()` | 4.1 | [91bc4822c3d6](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=91bc4822c3d61b9bb7ef66d3b77948a4f9177954)
+`BPF_FUNC_skb_under_cgroup()` | 4.8 | [4a482f34afcc](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4a482f34afcc162d8456f449b137ec2a95be60d8)
+`BPF_FUNC_skb_vlan_pop()` | 4.3 | [4e10df9a60d9](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4e10df9a60d96ced321dd2af71da558c6b750078)
+`BPF_FUNC_skb_vlan_push()` | 4.3 | [4e10df9a60d9](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4e10df9a60d96ced321dd2af71da558c6b750078)
+`BPF_FUNC_tail_call()` | 4.2 | [04fd61ab36ec](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=04fd61ab36ec065e194ab5e74ae34a5240d992bb)
+`BPF_FUNC_trace_printk()` | 4.1 | [9c959c863f82](https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=9c959c863f8217a2ff3d7c296e8223654d240569)