Merge branch 'bpf'

Daniel Borkmann says:

====================
bpf/filter updates

This set adds just two minimal helper tools that complement the
already available bpf_jit_disasm and complete BPF tooling; plus
it adds and an extensive documentation update of filter.txt.

Please see individual descriptions for details.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/filter.txt

@@ -1,49 +1,563 @@
-filter.txt: Linux Socket Filtering
-Written by: Jay Schulist <jschlst@samba.org>
+Linux Socket Filtering aka Berkeley Packet Filter (BPF)
+=======================================================
 
 Introduction
-============
-
-	Linux Socket Filtering is derived from the Berkeley
-Packet Filter. There are some distinct differences between
-the BSD and Linux Kernel Filtering.
-
-Linux Socket Filtering (LSF) allows a user-space program to
-attach a filter onto any socket and allow or disallow certain
-types of data to come through the socket. LSF follows exactly
-the same filter code structure as the BSD Berkeley Packet Filter
-(BPF), so referring to the BSD bpf.4 manpage is very helpful in
-creating filters.
-
-LSF is much simpler than BPF. One does not have to worry about
-devices or anything like that. You simply create your filter
-code, send it to the kernel via the SO_ATTACH_FILTER option and
-if your filter code passes the kernel check on it, you then
-immediately begin filtering data on that socket.
-
-You can also detach filters from your socket via the
-SO_DETACH_FILTER option. This will probably not be used much
-since when you close a socket that has a filter on it the
-filter is automagically removed. The other less common case
-may be adding a different filter on the same socket where you had another
-filter that is still running: the kernel takes care of removing
-the old one and placing your new one in its place, assuming your
-filter has passed the checks, otherwise if it fails the old filter
-will remain on that socket.
-
-SO_LOCK_FILTER option allows to lock the filter attached to a
-socket. Once set, a filter cannot be removed or changed. This allows
-one process to setup a socket, attach a filter, lock it then drop
-privileges and be assured that the filter will be kept until the
-socket is closed.
-
-Examples
-========
-
-Ioctls-
-setsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &Filter, sizeof(Filter));
-setsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &value, sizeof(value));
-setsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &value, sizeof(value));
-
-See the BSD bpf.4 manpage and the BSD Packet Filter paper written by
-Steven McCanne and Van Jacobson of Lawrence Berkeley Laboratory.
+------------
+
+Linux Socket Filtering (LSF) is derived from the Berkeley Packet Filter.
+Though there are some distinct differences between the BSD and Linux
+Kernel filtering, but when we speak of BPF or LSF in Linux context, we
+mean the very same mechanism of filtering in the Linux kernel.
+
+BPF allows a user-space program to attach a filter onto any socket and
+allow or disallow certain types of data to come through the socket. LSF
+follows exactly the same filter code structure as BSD's BPF, so referring
+to the BSD bpf.4 manpage is very helpful in creating filters.
+
+On Linux, BPF is much simpler than on BSD. One does not have to worry
+about devices or anything like that. You simply create your filter code,
+send it to the kernel via the SO_ATTACH_FILTER option and if your filter
+code passes the kernel check on it, you then immediately begin filtering
+data on that socket.
+
+You can also detach filters from your socket via the SO_DETACH_FILTER
+option. This will probably not be used much since when you close a socket
+that has a filter on it the filter is automagically removed. The other
+less common case may be adding a different filter on the same socket where
+you had another filter that is still running: the kernel takes care of
+removing the old one and placing your new one in its place, assuming your
+filter has passed the checks, otherwise if it fails the old filter will
+remain on that socket.
+
+SO_LOCK_FILTER option allows to lock the filter attached to a socket. Once
+set, a filter cannot be removed or changed. This allows one process to
+setup a socket, attach a filter, lock it then drop privileges and be
+assured that the filter will be kept until the socket is closed.
+
+The biggest user of this construct might be libpcap. Issuing a high-level
+filter command like `tcpdump -i em1 port 22` passes through the libpcap
+internal compiler that generates a structure that can eventually be loaded
+via SO_ATTACH_FILTER to the kernel. `tcpdump -i em1 port 22 -ddd`
+displays what is being placed into this structure.
+
+Although we were only speaking about sockets here, BPF in Linux is used
+in many more places. There's xt_bpf for netfilter, cls_bpf in the kernel
+qdisc layer, SECCOMP-BPF (SECure COMPuting [1]), and lots of other places
+such as team driver, PTP code, etc where BPF is being used.
+
+ [1] Documentation/prctl/seccomp_filter.txt
+
+Original BPF paper:
+
+Steven McCanne and Van Jacobson. 1993. The BSD packet filter: a new
+architecture for user-level packet capture. In Proceedings of the
+USENIX Winter 1993 Conference Proceedings on USENIX Winter 1993
+Conference Proceedings (USENIX'93). USENIX Association, Berkeley,
+CA, USA, 2-2. [http://www.tcpdump.org/papers/bpf-usenix93.pdf]
+
+Structure
+---------
+
+User space applications include <linux/filter.h> which contains the
+following relevant structures:
+
+struct sock_filter {	/* Filter block */
+	__u16	code;   /* Actual filter code */
+	__u8	jt;	/* Jump true */
+	__u8	jf;	/* Jump false */
+	__u32	k;      /* Generic multiuse field */
+};
+
+Such a structure is assembled as an array of 4-tuples, that contains
+a code, jt, jf and k value. jt and jf are jump offsets and k a generic
+value to be used for a provided code.
+
+struct sock_fprog {			/* Required for SO_ATTACH_FILTER. */
+	unsigned short		   len;	/* Number of filter blocks */
+	struct sock_filter __user *filter;
+};
+
+For socket filtering, a pointer to this structure (as shown in
+follow-up example) is being passed to the kernel through setsockopt(2).
+
+Example
+-------
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <arpa/inet.h>
+#include <linux/if_ether.h>
+/* ... */
+
+/* From the example above: tcpdump -i em1 port 22 -dd */
+struct sock_filter code[] = {
+	{ 0x28,  0,  0, 0x0000000c },
+	{ 0x15,  0,  8, 0x000086dd },
+	{ 0x30,  0,  0, 0x00000014 },
+	{ 0x15,  2,  0, 0x00000084 },
+	{ 0x15,  1,  0, 0x00000006 },
+	{ 0x15,  0, 17, 0x00000011 },
+	{ 0x28,  0,  0, 0x00000036 },
+	{ 0x15, 14,  0, 0x00000016 },
+	{ 0x28,  0,  0, 0x00000038 },
+	{ 0x15, 12, 13, 0x00000016 },
+	{ 0x15,  0, 12, 0x00000800 },
+	{ 0x30,  0,  0, 0x00000017 },
+	{ 0x15,  2,  0, 0x00000084 },
+	{ 0x15,  1,  0, 0x00000006 },
+	{ 0x15,  0,  8, 0x00000011 },
+	{ 0x28,  0,  0, 0x00000014 },
+	{ 0x45,  6,  0, 0x00001fff },
+	{ 0xb1,  0,  0, 0x0000000e },
+	{ 0x48,  0,  0, 0x0000000e },
+	{ 0x15,  2,  0, 0x00000016 },
+	{ 0x48,  0,  0, 0x00000010 },
+	{ 0x15,  0,  1, 0x00000016 },
+	{ 0x06,  0,  0, 0x0000ffff },
+	{ 0x06,  0,  0, 0x00000000 },
+};
+
+struct sock_fprog bpf = {
+	.len = ARRAY_SIZE(code),
+	.filter = code,
+};
+
+sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
+if (sock < 0)
+	/* ... bail out ... */
+
+ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf));
+if (ret < 0)
+	/* ... bail out ... */
+
+/* ... */
+close(sock);
+
+The above example code attaches a socket filter for a PF_PACKET socket
+in order to let all IPv4/IPv6 packets with port 22 pass. The rest will
+be dropped for this socket.
+
+The setsockopt(2) call to SO_DETACH_FILTER doesn't need any arguments
+and SO_LOCK_FILTER for preventing the filter to be detached, takes an
+integer value with 0 or 1.
+
+Note that socket filters are not restricted to PF_PACKET sockets only,
+but can also be used on other socket families.
+
+Summary of system calls:
+
+ * setsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &val, sizeof(val));
+ * setsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &val, sizeof(val));
+ * setsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER,   &val, sizeof(val));
+
+Normally, most use cases for socket filtering on packet sockets will be
+covered by libpcap in high-level syntax, so as an application developer
+you should stick to that. libpcap wraps its own layer around all that.
+
+Unless i) using/linking to libpcap is not an option, ii) the required BPF
+filters use Linux extensions that are not supported by libpcap's compiler,
+iii) a filter might be more complex and not cleanly implementable with
+libpcap's compiler, or iv) particular filter codes should be optimized
+differently than libpcap's internal compiler does; then in such cases
+writing such a filter "by hand" can be of an alternative. For example,
+xt_bpf and cls_bpf users might have requirements that could result in
+more complex filter code, or one that cannot be expressed with libpcap
+(e.g. different return codes for various code paths). Moreover, BPF JIT
+implementors may wish to manually write test cases and thus need low-level
+access to BPF code as well.
+
+BPF engine and instruction set
+------------------------------
+
+Under tools/net/ there's a small helper tool called bpf_asm which can
+be used to write low-level filters for example scenarios mentioned in the
+previous section. Asm-like syntax mentioned here has been implemented in
+bpf_asm and will be used for further explanations (instead of dealing with
+less readable opcodes directly, principles are the same). The syntax is
+closely modelled after Steven McCanne's and Van Jacobson's BPF paper.
+
+The BPF architecture consists of the following basic elements:
+
+  Element          Description
+
+  A                32 bit wide accumulator
+  X                32 bit wide X register
+  M[]              16 x 32 bit wide misc registers aka "scratch memory
+                   store", addressable from 0 to 15
+
+A program, that is translated by bpf_asm into "opcodes" is an array that
+consists of the following elements (as already mentioned):
+
+  op:16, jt:8, jf:8, k:32
+
+The element op is a 16 bit wide opcode that has a particular instruction
+encoded. jt and jf are two 8 bit wide jump targets, one for condition
+"jump if true", the other one "jump if false". Eventually, element k
+contains a miscellaneous argument that can be interpreted in different
+ways depending on the given instruction in op.
+
+The instruction set consists of load, store, branch, alu, miscellaneous
+and return instructions that are also represented in bpf_asm syntax. This
+table lists all bpf_asm instructions available resp. what their underlying
+opcodes as defined in linux/filter.h stand for:
+
+  Instruction      Addressing mode      Description
+
+  ld               1, 2, 3, 4, 10       Load word into A
+  ldi              4                    Load word into A
+  ldh              1, 2                 Load half-word into A
+  ldb              1, 2                 Load byte into A
+  ldx              3, 4, 5, 10          Load word into X
+  ldxi             4                    Load word into X
+  ldxb             5                    Load byte into X
+
+  st               3                    Store A into M[]
+  stx              3                    Store X into M[]
+
+  jmp              6                    Jump to label
+  ja               6                    Jump to label
+  jeq              7, 8                 Jump on k == A
+  jneq             8                    Jump on k != A
+  jne              8                    Jump on k != A
+  jlt              8                    Jump on k < A
+  jle              8                    Jump on k <= A
+  jgt              7, 8                 Jump on k > A
+  jge              7, 8                 Jump on k >= A
+  jset             7, 8                 Jump on k & A
+
+  add              0, 4                 A + <x>
+  sub              0, 4                 A - <x>
+  mul              0, 4                 A * <x>
+  div              0, 4                 A / <x>
+  mod              0, 4                 A % <x>
+  neg              0, 4                 !A
+  and              0, 4                 A & <x>
+  or               0, 4                 A | <x>
+  xor              0, 4                 A ^ <x>
+  lsh              0, 4                 A << <x>
+  rsh              0, 4                 A >> <x>
+
+  tax                                   Copy A into X
+  txa                                   Copy X into A
+
+  ret              4, 9                 Return
+
+The next table shows addressing formats from the 2nd column:
+
+  Addressing mode  Syntax               Description
+
+   0               x/%x                 Register X
+   1               [k]                  BHW at byte offset k in the packet
+   2               [x + k]              BHW at the offset X + k in the packet
+   3               M[k]                 Word at offset k in M[]
+   4               #k                   Literal value stored in k
+   5               4*([k]&0xf)          Lower nibble * 4 at byte offset k in the packet
+   6               L                    Jump label L
+   7               #k,Lt,Lf             Jump to Lt if true, otherwise jump to Lf
+   8               #k,Lt                Jump to Lt if predicate is true
+   9               a/%a                 Accumulator A
+  10               extension            BPF extension
+
+The Linux kernel also has a couple of BPF extensions that are used along
+with the class of load instructions by "overloading" the k argument with
+a negative offset + a particular extension offset. The result of such BPF
+extensions are loaded into A.
+
+Possible BPF extensions are shown in the following table:
+
+  Extension                             Description
+
+  len                                   skb->len
+  proto                                 skb->protocol
+  type                                  skb->pkt_type
+  poff                                  Payload start offset
+  ifidx                                 skb->dev->ifindex
+  nla                                   Netlink attribute of type X with offset A
+  nlan                                  Nested Netlink attribute of type X with offset A
+  mark                                  skb->mark
+  queue                                 skb->queue_mapping
+  hatype                                skb->dev->type
+  rxhash                                skb->rxhash
+  cpu                                   raw_smp_processor_id()
+  vlan_tci                              vlan_tx_tag_get(skb)
+  vlan_pr                               vlan_tx_tag_present(skb)
+
+These extensions can also be prefixed with '#'.
+Examples for low-level BPF:
+
+** ARP packets:
+
+  ldh [12]
+  jne #0x806, drop
+  ret #-1
+  drop: ret #0
+
+** IPv4 TCP packets:
+
+  ldh [12]
+  jne #0x800, drop
+  ldb [23]
+  jneq #6, drop
+  ret #-1
+  drop: ret #0
+
+** (Accelerated) VLAN w/ id 10:
+
+  ld vlan_tci
+  jneq #10, drop
+  ret #-1
+  drop: ret #0
+
+** SECCOMP filter example:
+
+  ld [4]                  /* offsetof(struct seccomp_data, arch) */
+  jne #0xc000003e, bad    /* AUDIT_ARCH_X86_64 */
+  ld [0]                  /* offsetof(struct seccomp_data, nr) */
+  jeq #15, good           /* __NR_rt_sigreturn */
+  jeq #231, good          /* __NR_exit_group */
+  jeq #60, good           /* __NR_exit */
+  jeq #0, good            /* __NR_read */
+  jeq #1, good            /* __NR_write */
+  jeq #5, good            /* __NR_fstat */
+  jeq #9, good            /* __NR_mmap */
+  jeq #14, good           /* __NR_rt_sigprocmask */
+  jeq #13, good           /* __NR_rt_sigaction */
+  jeq #35, good           /* __NR_nanosleep */
+  bad: ret #0             /* SECCOMP_RET_KILL */
+  good: ret #0x7fff0000   /* SECCOMP_RET_ALLOW */
+
+The above example code can be placed into a file (here called "foo"), and
+then be passed to the bpf_asm tool for generating opcodes, output that xt_bpf
+and cls_bpf understands and can directly be loaded with. Example with above
+ARP code:
+
+$ ./bpf_asm foo
+4,40 0 0 12,21 0 1 2054,6 0 0 4294967295,6 0 0 0,
+
+In copy and paste C-like output:
+
+$ ./bpf_asm -c foo
+{ 0x28,  0,  0, 0x0000000c },
+{ 0x15,  0,  1, 0x00000806 },
+{ 0x06,  0,  0, 0xffffffff },
+{ 0x06,  0,  0, 0000000000 },
+
+In particular, as usage with xt_bpf or cls_bpf can result in more complex BPF
+filters that might not be obvious at first, it's good to test filters before
+attaching to a live system. For that purpose, there's a small tool called
+bpf_dbg under tools/net/ in the kernel source directory. This debugger allows
+for testing BPF filters against given pcap files, single stepping through the
+BPF code on the pcap's packets and to do BPF machine register dumps.
+
+Starting bpf_dbg is trivial and just requires issuing:
+
+# ./bpf_dbg
+
+In case input and output do not equal stdin/stdout, bpf_dbg takes an
+alternative stdin source as a first argument, and an alternative stdout
+sink as a second one, e.g. `./bpf_dbg test_in.txt test_out.txt`.
+
+Other than that, a particular libreadline configuration can be set via
+file "~/.bpf_dbg_init" and the command history is stored in the file
+"~/.bpf_dbg_history".
+
+Interaction in bpf_dbg happens through a shell that also has auto-completion
+support (follow-up example commands starting with '>' denote bpf_dbg shell).
+The usual workflow would be to ...
+
+> load bpf 6,40 0 0 12,21 0 3 2048,48 0 0 23,21 0 1 1,6 0 0 65535,6 0 0 0
+  Loads a BPF filter from standard output of bpf_asm, or transformed via
+  e.g. `tcpdump -iem1 -ddd port 22 | tr '\n' ','`. Note that for JIT
+  debugging (next section), this command creates a temporary socket and
+  loads the BPF code into the kernel. Thus, this will also be useful for
+  JIT developers.
+
+> load pcap foo.pcap
+  Loads standard tcpdump pcap file.
+
+> run [<n>]
+bpf passes:1 fails:9
+  Runs through all packets from a pcap to account how many passes and fails
+  the filter will generate. A limit of packets to traverse can be given.
+
+> disassemble
+l0:	ldh [12]
+l1:	jeq #0x800, l2, l5
+l2:	ldb [23]
+l3:	jeq #0x1, l4, l5
+l4:	ret #0xffff
+l5:	ret #0
+  Prints out BPF code disassembly.
+
+> dump
+/* { op, jt, jf, k }, */
+{ 0x28,  0,  0, 0x0000000c },
+{ 0x15,  0,  3, 0x00000800 },
+{ 0x30,  0,  0, 0x00000017 },
+{ 0x15,  0,  1, 0x00000001 },
+{ 0x06,  0,  0, 0x0000ffff },
+{ 0x06,  0,  0, 0000000000 },
+  Prints out C-style BPF code dump.
+
+> breakpoint 0
+breakpoint at: l0:	ldh [12]
+> breakpoint 1
+breakpoint at: l1:	jeq #0x800, l2, l5
+  ...
+  Sets breakpoints at particular BPF instructions. Issuing a `run` command
+  will walk through the pcap file continuing from the current packet and
+  break when a breakpoint is being hit (another `run` will continue from
+  the currently active breakpoint executing next instructions):
+
+  > run
+  -- register dump --
+  pc:       [0]                       <-- program counter
+  code:     [40] jt[0] jf[0] k[12]    <-- plain BPF code of current instruction
+  curr:     l0:	ldh [12]              <-- disassembly of current instruction
+  A:        [00000000][0]             <-- content of A (hex, decimal)
+  X:        [00000000][0]             <-- content of X (hex, decimal)
+  M[0,15]:  [00000000][0]             <-- folded content of M (hex, decimal)
+  -- packet dump --                   <-- Current packet from pcap (hex)
+  len: 42
+    0: 00 19 cb 55 55 a4 00 14 a4 43 78 69 08 06 00 01
+   16: 08 00 06 04 00 01 00 14 a4 43 78 69 0a 3b 01 26
+   32: 00 00 00 00 00 00 0a 3b 01 01
+  (breakpoint)
+  >
+
+> breakpoint
+breakpoints: 0 1
+  Prints currently set breakpoints.
+
+> step [-<n>, +<n>]
+  Performs single stepping through the BPF program from the current pc
+  offset. Thus, on each step invocation, above register dump is issued.
+  This can go forwards and backwards in time, a plain `step` will break
+  on the next BPF instruction, thus +1. (No `run` needs to be issued here.)
+
+> select <n>
+  Selects a given packet from the pcap file to continue from. Thus, on
+  the next `run` or `step`, the BPF program is being evaluated against
+  the user pre-selected packet. Numbering starts just as in Wireshark
+  with index 1.
+
+> quit
+#
+  Exits bpf_dbg.
+
+JIT compiler
+------------
+
+The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
+ARM and s390 and can be enabled through CONFIG_BPF_JIT. The JIT compiler is
+transparently invoked for each attached filter from user space or for internal
+kernel users if it has been previously enabled by root:
+
+  echo 1 > /proc/sys/net/core/bpf_jit_enable
+
+For JIT developers, doing audits etc, each compile run can output the generated
+opcode image into the kernel log via:
+
+  echo 2 > /proc/sys/net/core/bpf_jit_enable
+
+Example output from dmesg:
+
+[ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f
+[ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68
+[ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00
+[ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00
+[ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00
+[ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3
+
+In the kernel source tree under tools/net/, there's bpf_jit_disasm for
+generating disassembly out of the kernel log's hexdump:
+
+# ./bpf_jit_disasm
+70 bytes emitted from JIT compiler (pass:3, flen:6)
+ffffffffa0069c8f + <x>:
+   0:	push   %rbp
+   1:	mov    %rsp,%rbp
+   4:	sub    $0x60,%rsp
+   8:	mov    %rbx,-0x8(%rbp)
+   c:	mov    0x68(%rdi),%r9d
+  10:	sub    0x6c(%rdi),%r9d
+  14:	mov    0xd8(%rdi),%r8
+  1b:	mov    $0xc,%esi
+  20:	callq  0xffffffffe0ff9442
+  25:	cmp    $0x800,%eax
+  2a:	jne    0x0000000000000042
+  2c:	mov    $0x17,%esi
+  31:	callq  0xffffffffe0ff945e
+  36:	cmp    $0x1,%eax
+  39:	jne    0x0000000000000042
+  3b:	mov    $0xffff,%eax
+  40:	jmp    0x0000000000000044
+  42:	xor    %eax,%eax
+  44:	leaveq
+  45:	retq
+
+Issuing option `-o` will "annotate" opcodes to resulting assembler
+instructions, which can be very useful for JIT developers:
+
+# ./bpf_jit_disasm -o
+70 bytes emitted from JIT compiler (pass:3, flen:6)
+ffffffffa0069c8f + <x>:
+   0:	push   %rbp
+	55
+   1:	mov    %rsp,%rbp
+	48 89 e5
+   4:	sub    $0x60,%rsp
+	48 83 ec 60
+   8:	mov    %rbx,-0x8(%rbp)
+	48 89 5d f8
+   c:	mov    0x68(%rdi),%r9d
+	44 8b 4f 68
+  10:	sub    0x6c(%rdi),%r9d
+	44 2b 4f 6c
+  14:	mov    0xd8(%rdi),%r8
+	4c 8b 87 d8 00 00 00
+  1b:	mov    $0xc,%esi
+	be 0c 00 00 00
+  20:	callq  0xffffffffe0ff9442
+	e8 1d 94 ff e0
+  25:	cmp    $0x800,%eax
+	3d 00 08 00 00
+  2a:	jne    0x0000000000000042
+	75 16
+  2c:	mov    $0x17,%esi
+	be 17 00 00 00
+  31:	callq  0xffffffffe0ff945e
+	e8 28 94 ff e0
+  36:	cmp    $0x1,%eax
+	83 f8 01
+  39:	jne    0x0000000000000042
+	75 07
+  3b:	mov    $0xffff,%eax
+	b8 ff ff 00 00
+  40:	jmp    0x0000000000000044
+	eb 02
+  42:	xor    %eax,%eax
+	31 c0
+  44:	leaveq
+	c9
+  45:	retq
+	c3
+
+For BPF JIT developers, bpf_jit_disasm, bpf_asm and bpf_dbg provides a useful
+toolchain for developing and testing the kernel's JIT compiler.
+
+Misc
+----
+
+Also trinity, the Linux syscall fuzzer, has built-in support for BPF and
+SECCOMP-BPF kernel fuzzing.
+
+Written by
+----------
+
+The document was written in the hope that it is found useful and in order
+to give potential BPF hackers or security auditors a better overview of
+the underlying architecture.
+
+Jay Schulist <jschlst@samba.org>
+Daniel Borkmann <dborkman@redhat.com>

tools/net/Makefile

@@ -1,15 +1,34 @@
 prefix = /usr
 
 CC = gcc
+LEX = flex
+YACC = bison
 
-all : bpf_jit_disasm
+%.yacc.c: %.y
+	$(YACC) -o $@ -d $<
+
+%.lex.c: %.l
+	$(LEX) -o $@ $<
+
+all : bpf_jit_disasm bpf_dbg bpf_asm
 
 bpf_jit_disasm : CFLAGS = -Wall -O2
 bpf_jit_disasm : LDLIBS = -lopcodes -lbfd -ldl
 bpf_jit_disasm : bpf_jit_disasm.o
 
+bpf_dbg : CFLAGS = -Wall -O2
+bpf_dbg : LDLIBS = -lreadline
+bpf_dbg : bpf_dbg.o
+
+bpf_asm : CFLAGS = -Wall -O2 -I.
+bpf_asm : LDLIBS =
+bpf_asm : bpf_asm.o bpf_exp.yacc.o bpf_exp.lex.o
+bpf_exp.lex.o : bpf_exp.yacc.c
+
 clean :
-	rm -rf *.o bpf_jit_disasm
+	rm -rf *.o bpf_jit_disasm bpf_dbg bpf_asm bpf_exp.yacc.* bpf_exp.lex.*
 
 install :
 	install bpf_jit_disasm $(prefix)/bin/bpf_jit_disasm
+	install bpf_dbg $(prefix)/bin/bpf_dbg
+	install bpf_asm $(prefix)/bin/bpf_asm

tools/net/bpf_asm.c

@@ -0,0 +1,52 @@
+/*
+ * Minimal BPF assembler
+ *
+ * Instead of libpcap high-level filter expressions, it can be quite
+ * useful to define filters in low-level BPF assembler (that is kept
+ * close to Steven McCanne and Van Jacobson's original BPF paper).
+ * In particular for BPF JIT implementors, JIT security auditors, or
+ * just for defining BPF expressions that contain extensions which are
+ * not supported by compilers.
+ *
+ * How to get into it:
+ *
+ * 1) read Documentation/networking/filter.txt
+ * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
+ *    blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
+ *    pretty print a C-like construct.
+ *
+ * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
+ * Licensed under the GNU General Public License, version 2.0 (GPLv2)
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+extern void bpf_asm_compile(FILE *fp, bool cstyle);
+
+int main(int argc, char **argv)
+{
+	FILE *fp = stdin;
+	bool cstyle = false;
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		if (!strncmp("-c", argv[i], 2)) {
+			cstyle = true;
+			continue;
+		}
+
+		fp = fopen(argv[i], "r");
+		if (!fp) {
+			fp = stdin;
+			continue;
+		}
+
+		break;
+	}
+
+	bpf_asm_compile(fp, cstyle);
+
+	return 0;
+}

tools/net/bpf_dbg.c

@@ -0,0 +1,1404 @@
+/*
+ * Minimal BPF debugger
+ *
+ * Minimal BPF debugger that mimics the kernel's engine (w/o extensions)
+ * and allows for single stepping through selected packets from a pcap
+ * with a provided user filter in order to facilitate verification of a
+ * BPF program. Besides others, this is useful to verify BPF programs
+ * before attaching to a live system, and can be used in socket filters,
+ * cls_bpf, xt_bpf, team driver and e.g. PTP code; in particular when a
+ * single more complex BPF program is being used. Reasons for a more
+ * complex BPF program are likely primarily to optimize execution time
+ * for making a verdict when multiple simple BPF programs are combined
+ * into one in order to prevent parsing same headers multiple times.
+ *
+ * More on how to debug BPF opcodes see Documentation/networking/filter.txt
+ * which is the main document on BPF. Mini howto for getting started:
+ *
+ *  1) `./bpf_dbg` to enter the shell (shell cmds denoted with '>'):
+ *  2) > load bpf 6,40 0 0 12,21 0 3 20... (output from `bpf_asm` or
+ *     `tcpdump -iem1 -ddd port 22 | tr '\n' ','` to load as filter)
+ *  3) > load pcap foo.pcap
+ *  4) > run <n>/disassemble/dump/quit (self-explanatory)
+ *  5) > breakpoint 2 (sets bp at loaded BPF insns 2, do `run` then;
+ *       multiple bps can be set, of course, a call to `breakpoint`
+ *       w/o args shows currently loaded bps, `breakpoint reset` for
+ *       resetting all breakpoints)
+ *  6) > select 3 (`run` etc will start from the 3rd packet in the pcap)
+ *  7) > step [-<n>, +<n>] (performs single stepping through the BPF)
+ *
+ * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
+ * Licensed under the GNU General Public License, version 2.0 (GPLv2)
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <setjmp.h>
+#include <linux/filter.h>
+#include <linux/if_packet.h>
+#include <readline/readline.h>
+#include <readline/history.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <signal.h>
+#include <arpa/inet.h>
+#include <net/ethernet.h>
+
+#define TCPDUMP_MAGIC	0xa1b2c3d4
+
+#define BPF_LDX_B	(BPF_LDX | BPF_B)
+#define BPF_LDX_W	(BPF_LDX | BPF_W)
+#define BPF_JMP_JA	(BPF_JMP | BPF_JA)
+#define BPF_JMP_JEQ	(BPF_JMP | BPF_JEQ)
+#define BPF_JMP_JGT	(BPF_JMP | BPF_JGT)
+#define BPF_JMP_JGE	(BPF_JMP | BPF_JGE)
+#define BPF_JMP_JSET	(BPF_JMP | BPF_JSET)
+#define BPF_ALU_ADD	(BPF_ALU | BPF_ADD)
+#define BPF_ALU_SUB	(BPF_ALU | BPF_SUB)
+#define BPF_ALU_MUL	(BPF_ALU | BPF_MUL)
+#define BPF_ALU_DIV	(BPF_ALU | BPF_DIV)
+#define BPF_ALU_MOD	(BPF_ALU | BPF_MOD)
+#define BPF_ALU_NEG	(BPF_ALU | BPF_NEG)
+#define BPF_ALU_AND	(BPF_ALU | BPF_AND)
+#define BPF_ALU_OR	(BPF_ALU | BPF_OR)
+#define BPF_ALU_XOR	(BPF_ALU | BPF_XOR)
+#define BPF_ALU_LSH	(BPF_ALU | BPF_LSH)
+#define BPF_ALU_RSH	(BPF_ALU | BPF_RSH)
+#define BPF_MISC_TAX	(BPF_MISC | BPF_TAX)
+#define BPF_MISC_TXA	(BPF_MISC | BPF_TXA)
+#define BPF_LD_B	(BPF_LD | BPF_B)
+#define BPF_LD_H	(BPF_LD | BPF_H)
+#define BPF_LD_W	(BPF_LD | BPF_W)
+
+#ifndef array_size
+# define array_size(x)	(sizeof(x) / sizeof((x)[0]))
+#endif
+
+#ifndef __check_format_printf
+# define __check_format_printf(pos_fmtstr, pos_fmtargs) \
+	__attribute__ ((format (printf, (pos_fmtstr), (pos_fmtargs))))
+#endif
+
+#define CMD(_name, _func) { .name = _name, .func = _func, }
+#define OP(_op, _name)      [_op] = _name
+
+enum {
+	CMD_OK,
+	CMD_ERR,
+	CMD_EX,
+};
+
+struct shell_cmd {
+	const char *name;
+	int (*func)(char *args);
+};
+
+struct pcap_filehdr {
+	uint32_t magic;
+	uint16_t version_major;
+	uint16_t version_minor;
+	int32_t  thiszone;
+	uint32_t sigfigs;
+	uint32_t snaplen;
+	uint32_t linktype;
+};
+
+struct pcap_timeval {
+	int32_t tv_sec;
+	int32_t tv_usec;
+};
+
+struct pcap_pkthdr {
+	struct pcap_timeval ts;
+	uint32_t caplen;
+	uint32_t len;
+};
+
+struct bpf_regs {
+	uint32_t A;
+	uint32_t X;
+	uint32_t M[BPF_MEMWORDS];
+	uint32_t R;
+	bool     Rs;
+	uint16_t Pc;
+};
+
+static struct sock_filter bpf_image[BPF_MAXINSNS + 1];
+static unsigned int bpf_prog_len = 0;
+
+static int bpf_breakpoints[64];
+static struct bpf_regs bpf_regs[BPF_MAXINSNS + 1];
+static struct bpf_regs bpf_curr;
+static unsigned int bpf_regs_len = 0;
+
+static int pcap_fd = -1;
+static unsigned int pcap_packet = 0;
+static size_t pcap_map_size = 0;
+static char *pcap_ptr_va_start, *pcap_ptr_va_curr;
+
+static const char * const op_table[] = {
+	OP(BPF_ST, "st"),
+	OP(BPF_STX, "stx"),
+	OP(BPF_LD_B, "ldb"),
+	OP(BPF_LD_H, "ldh"),
+	OP(BPF_LD_W, "ld"),
+	OP(BPF_LDX, "ldx"),
+	OP(BPF_LDX_B, "ldxb"),
+	OP(BPF_JMP_JA, "ja"),
+	OP(BPF_JMP_JEQ, "jeq"),
+	OP(BPF_JMP_JGT, "jgt"),
+	OP(BPF_JMP_JGE, "jge"),
+	OP(BPF_JMP_JSET, "jset"),
+	OP(BPF_ALU_ADD, "add"),
+	OP(BPF_ALU_SUB, "sub"),
+	OP(BPF_ALU_MUL, "mul"),
+	OP(BPF_ALU_DIV, "div"),
+	OP(BPF_ALU_MOD, "mod"),
+	OP(BPF_ALU_NEG, "neg"),
+	OP(BPF_ALU_AND, "and"),
+	OP(BPF_ALU_OR, "or"),
+	OP(BPF_ALU_XOR, "xor"),
+	OP(BPF_ALU_LSH, "lsh"),
+	OP(BPF_ALU_RSH, "rsh"),
+	OP(BPF_MISC_TAX, "tax"),
+	OP(BPF_MISC_TXA, "txa"),
+	OP(BPF_RET, "ret"),
+};
+
+static __check_format_printf(1, 2) int rl_printf(const char *fmt, ...)
+{
+	int ret;
+	va_list vl;
+
+	va_start(vl, fmt);
+	ret = vfprintf(rl_outstream, fmt, vl);
+	va_end(vl);
+
+	return ret;
+}
+
+static int matches(const char *cmd, const char *pattern)
+{
+	int len = strlen(cmd);
+
+	if (len > strlen(pattern))
+		return -1;
+
+	return memcmp(pattern, cmd, len);
+}
+
+static void hex_dump(const uint8_t *buf, size_t len)
+{
+	int i;
+
+	rl_printf("%3u: ", 0);
+	for (i = 0; i < len; i++) {
+		if (i && !(i % 16))
+			rl_printf("\n%3u: ", i);
+		rl_printf("%02x ", buf[i]);
+	}
+	rl_printf("\n");
+}
+
+static bool bpf_prog_loaded(void)
+{
+	if (bpf_prog_len == 0)
+		rl_printf("no bpf program loaded!\n");
+
+	return bpf_prog_len > 0;
+}
+
+static void bpf_disasm(const struct sock_filter f, unsigned int i)
+{
+	const char *op, *fmt;
+	int val = f.k;
+	char buf[256];
+
+	switch (f.code) {
+	case BPF_RET | BPF_K:
+		op = op_table[BPF_RET];
+		fmt = "#%#x";
+		break;
+	case BPF_RET | BPF_A:
+		op = op_table[BPF_RET];
+		fmt = "a";
+		break;
+	case BPF_RET | BPF_X:
+		op = op_table[BPF_RET];
+		fmt = "x";
+		break;
+	case BPF_MISC_TAX:
+		op = op_table[BPF_MISC_TAX];
+		fmt = "";
+		break;
+	case BPF_MISC_TXA:
+		op = op_table[BPF_MISC_TXA];
+		fmt = "";
+		break;
+	case BPF_ST:
+		op = op_table[BPF_ST];
+		fmt = "M[%d]";
+		break;
+	case BPF_STX:
+		op = op_table[BPF_STX];
+		fmt = "M[%d]";
+		break;
+	case BPF_LD_W | BPF_ABS:
+		op = op_table[BPF_LD_W];
+		fmt = "[%d]";
+		break;
+	case BPF_LD_H | BPF_ABS:
+		op = op_table[BPF_LD_H];
+		fmt = "[%d]";
+		break;
+	case BPF_LD_B | BPF_ABS:
+		op = op_table[BPF_LD_B];
+		fmt = "[%d]";
+		break;
+	case BPF_LD_W | BPF_LEN:
+		op = op_table[BPF_LD_W];
+		fmt = "#len";
+		break;
+	case BPF_LD_W | BPF_IND:
+		op = op_table[BPF_LD_W];
+		fmt = "[x+%d]";
+		break;
+	case BPF_LD_H | BPF_IND:
+		op = op_table[BPF_LD_H];
+		fmt = "[x+%d]";
+		break;
+	case BPF_LD_B | BPF_IND:
+		op = op_table[BPF_LD_B];
+		fmt = "[x+%d]";
+		break;
+	case BPF_LD | BPF_IMM:
+		op = op_table[BPF_LD_W];
+		fmt = "#%#x";
+		break;
+	case BPF_LDX | BPF_IMM:
+		op = op_table[BPF_LDX];
+		fmt = "#%#x";
+		break;
+	case BPF_LDX_B | BPF_MSH:
+		op = op_table[BPF_LDX_B];
+		fmt = "4*([%d]&0xf)";
+		break;
+	case BPF_LD | BPF_MEM:
+		op = op_table[BPF_LD_W];
+		fmt = "M[%d]";
+		break;
+	case BPF_LDX | BPF_MEM:
+		op = op_table[BPF_LDX];
+		fmt = "M[%d]";
+		break;
+	case BPF_JMP_JA:
+		op = op_table[BPF_JMP_JA];
+		fmt = "%d";
+		val = i + 1 + f.k;
+		break;
+	case BPF_JMP_JGT | BPF_X:
+		op = op_table[BPF_JMP_JGT];
+		fmt = "x";
+		break;
+	case BPF_JMP_JGT | BPF_K:
+		op = op_table[BPF_JMP_JGT];
+		fmt = "#%#x";
+		break;
+	case BPF_JMP_JGE | BPF_X:
+		op = op_table[BPF_JMP_JGE];
+		fmt = "x";
+		break;
+	case BPF_JMP_JGE | BPF_K:
+		op = op_table[BPF_JMP_JGE];
+		fmt = "#%#x";
+		break;
+	case BPF_JMP_JEQ | BPF_X:
+		op = op_table[BPF_JMP_JEQ];
+		fmt = "x";
+		break;
+	case BPF_JMP_JEQ | BPF_K:
+		op = op_table[BPF_JMP_JEQ];
+		fmt = "#%#x";
+		break;
+	case BPF_JMP_JSET | BPF_X:
+		op = op_table[BPF_JMP_JSET];
+		fmt = "x";
+		break;
+	case BPF_JMP_JSET | BPF_K:
+		op = op_table[BPF_JMP_JSET];
+		fmt = "#%#x";
+		break;
+	case BPF_ALU_NEG:
+		op = op_table[BPF_ALU_NEG];
+		fmt = "";
+		break;
+	case BPF_ALU_LSH | BPF_X:
+		op = op_table[BPF_ALU_LSH];
+		fmt = "x";
+		break;
+	case BPF_ALU_LSH | BPF_K:
+		op = op_table[BPF_ALU_LSH];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_RSH | BPF_X:
+		op = op_table[BPF_ALU_RSH];
+		fmt = "x";
+		break;
+	case BPF_ALU_RSH | BPF_K:
+		op = op_table[BPF_ALU_RSH];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_ADD | BPF_X:
+		op = op_table[BPF_ALU_ADD];
+		fmt = "x";
+		break;
+	case BPF_ALU_ADD | BPF_K:
+		op = op_table[BPF_ALU_ADD];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_SUB | BPF_X:
+		op = op_table[BPF_ALU_SUB];
+		fmt = "x";
+		break;
+	case BPF_ALU_SUB | BPF_K:
+		op = op_table[BPF_ALU_SUB];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_MUL | BPF_X:
+		op = op_table[BPF_ALU_MUL];
+		fmt = "x";
+		break;
+	case BPF_ALU_MUL | BPF_K:
+		op = op_table[BPF_ALU_MUL];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_DIV | BPF_X:
+		op = op_table[BPF_ALU_DIV];
+		fmt = "x";
+		break;
+	case BPF_ALU_DIV | BPF_K:
+		op = op_table[BPF_ALU_DIV];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_MOD | BPF_X:
+		op = op_table[BPF_ALU_MOD];
+		fmt = "x";
+		break;
+	case BPF_ALU_MOD | BPF_K:
+		op = op_table[BPF_ALU_MOD];
+		fmt = "#%d";
+		break;
+	case BPF_ALU_AND | BPF_X:
+		op = op_table[BPF_ALU_AND];
+		fmt = "x";
+		break;
+	case BPF_ALU_AND | BPF_K:
+		op = op_table[BPF_ALU_AND];
+		fmt = "#%#x";
+		break;
+	case BPF_ALU_OR | BPF_X:
+		op = op_table[BPF_ALU_OR];
+		fmt = "x";
+		break;
+	case BPF_ALU_OR | BPF_K:
+		op = op_table[BPF_ALU_OR];
+		fmt = "#%#x";
+		break;
+	case BPF_ALU_XOR | BPF_X:
+		op = op_table[BPF_ALU_XOR];
+		fmt = "x";
+		break;
+	case BPF_ALU_XOR | BPF_K:
+		op = op_table[BPF_ALU_XOR];
+		fmt = "#%#x";
+		break;
+	default:
+		op = "nosup";
+		fmt = "%#x";
+		val = f.code;
+		break;
+	}
+
+	memset(buf, 0, sizeof(buf));
+	snprintf(buf, sizeof(buf), fmt, val);
+	buf[sizeof(buf) - 1] = 0;
+
+	if ((BPF_CLASS(f.code) == BPF_JMP && BPF_OP(f.code) != BPF_JA))
+		rl_printf("l%d:\t%s %s, l%d, l%d\n", i, op, buf,
+			  i + 1 + f.jt, i + 1 + f.jf);
+	else
+		rl_printf("l%d:\t%s %s\n", i, op, buf);
+}
+
+static void bpf_dump_curr(struct bpf_regs *r, struct sock_filter *f)
+{
+	int i, m = 0;
+
+	rl_printf("pc:       [%u]\n", r->Pc);
+	rl_printf("code:     [%u] jt[%u] jf[%u] k[%u]\n",
+		  f->code, f->jt, f->jf, f->k);
+	rl_printf("curr:     ");
+	bpf_disasm(*f, r->Pc);
+
+	if (f->jt || f->jf) {
+		rl_printf("jt:       ");
+		bpf_disasm(*(f + f->jt + 1), r->Pc + f->jt + 1);
+		rl_printf("jf:       ");
+		bpf_disasm(*(f + f->jf + 1), r->Pc + f->jf + 1);
+	}
+
+	rl_printf("A:        [%#08x][%u]\n", r->A, r->A);
+	rl_printf("X:        [%#08x][%u]\n", r->X, r->X);
+	if (r->Rs)
+		rl_printf("ret:      [%#08x][%u]!\n", r->R, r->R);
+
+	for (i = 0; i < BPF_MEMWORDS; i++) {
+		if (r->M[i]) {
+			m++;
+			rl_printf("M[%d]: [%#08x][%u]\n", i, r->M[i], r->M[i]);
+		}
+	}
+	if (m == 0)
+		rl_printf("M[0,%d]:  [%#08x][%u]\n", BPF_MEMWORDS - 1, 0, 0);
+}
+
+static void bpf_dump_pkt(uint8_t *pkt, uint32_t pkt_caplen, uint32_t pkt_len)
+{
+	if (pkt_caplen != pkt_len)
+		rl_printf("cap: %u, len: %u\n", pkt_caplen, pkt_len);
+	else
+		rl_printf("len: %u\n", pkt_len);
+
+	hex_dump(pkt, pkt_caplen);
+}
+
+static void bpf_disasm_all(const struct sock_filter *f, unsigned int len)
+{
+	unsigned int i;
+
+	for (i = 0; i < len; i++)
+		bpf_disasm(f[i], i);
+}
+
+static void bpf_dump_all(const struct sock_filter *f, unsigned int len)
+{
+	unsigned int i;
+
+	rl_printf("/* { op, jt, jf, k }, */\n");
+	for (i = 0; i < len; i++)
+		rl_printf("{ %#04x, %2u, %2u, %#010x },\n",
+			  f[i].code, f[i].jt, f[i].jf, f[i].k);
+}
+
+static bool bpf_runnable(struct sock_filter *f, unsigned int len)
+{
+	int sock, ret, i;
+	struct sock_fprog bpf = {
+		.filter = f,
+		.len = len,
+	};
+
+	sock = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sock < 0) {
+		rl_printf("cannot open socket!\n");
+		return false;
+	}
+	ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf));
+	if (ret < 0) {
+		rl_printf("program not allowed to run by kernel!\n");
+		return false;
+	}
+	close(sock);
+	for (i = 0; i < len; i++) {
+		if (BPF_CLASS(f[i].code) == BPF_LD &&
+		    f[i].k > SKF_AD_OFF) {
+			rl_printf("extensions currently not supported!\n");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static void bpf_reset_breakpoints(void)
+{
+	int i;
+
+	for (i = 0; i < array_size(bpf_breakpoints); i++)
+		bpf_breakpoints[i] = -1;
+}
+
+static void bpf_set_breakpoints(unsigned int where)
+{
+	int i;
+	bool set = false;
+
+	for (i = 0; i < array_size(bpf_breakpoints); i++) {
+		if (bpf_breakpoints[i] == (int) where) {
+			rl_printf("breakpoint already set!\n");
+			set = true;
+			break;
+		}
+
+		if (bpf_breakpoints[i] == -1 && set == false) {
+			bpf_breakpoints[i] = where;
+			set = true;
+		}
+	}
+
+	if (!set)
+		rl_printf("too many breakpoints set, reset first!\n");
+}
+
+static void bpf_dump_breakpoints(void)
+{
+	int i;
+
+	rl_printf("breakpoints: ");
+
+	for (i = 0; i < array_size(bpf_breakpoints); i++) {
+		if (bpf_breakpoints[i] < 0)
+			continue;
+		rl_printf("%d ", bpf_breakpoints[i]);
+	}
+
+	rl_printf("\n");
+}
+
+static void bpf_reset(void)
+{
+	bpf_regs_len = 0;
+
+	memset(bpf_regs, 0, sizeof(bpf_regs));
+	memset(&bpf_curr, 0, sizeof(bpf_curr));
+}
+
+static void bpf_safe_regs(void)
+{
+	memcpy(&bpf_regs[bpf_regs_len++], &bpf_curr, sizeof(bpf_curr));
+}
+
+static bool bpf_restore_regs(int off)
+{
+	unsigned int index = bpf_regs_len - 1 + off;
+
+	if (index == 0) {
+		bpf_reset();
+		return true;
+	} else if (index < bpf_regs_len) {
+		memcpy(&bpf_curr, &bpf_regs[index], sizeof(bpf_curr));
+		bpf_regs_len = index;
+		return true;
+	} else {
+		rl_printf("reached bottom of register history stack!\n");
+		return false;
+	}
+}
+
+static uint32_t extract_u32(uint8_t *pkt, uint32_t off)
+{
+	uint32_t r;
+
+	memcpy(&r, &pkt[off], sizeof(r));
+
+	return ntohl(r);
+}
+
+static uint16_t extract_u16(uint8_t *pkt, uint32_t off)
+{
+	uint16_t r;
+
+	memcpy(&r, &pkt[off], sizeof(r));
+
+	return ntohs(r);
+}
+
+static uint8_t extract_u8(uint8_t *pkt, uint32_t off)
+{
+	return pkt[off];
+}
+
+static void set_return(struct bpf_regs *r)
+{
+	r->R = 0;
+	r->Rs = true;
+}
+
+static void bpf_single_step(struct bpf_regs *r, struct sock_filter *f,
+			    uint8_t *pkt, uint32_t pkt_caplen,
+			    uint32_t pkt_len)
+{
+	uint32_t K = f->k;
+	int d;
+
+	switch (f->code) {
+	case BPF_RET | BPF_K:
+		r->R = K;
+		r->Rs = true;
+		break;
+	case BPF_RET | BPF_A:
+		r->R = r->A;
+		r->Rs = true;
+		break;
+	case BPF_RET | BPF_X:
+		r->R = r->X;
+		r->Rs = true;
+		break;
+	case BPF_MISC_TAX:
+		r->X = r->A;
+		break;
+	case BPF_MISC_TXA:
+		r->A = r->X;
+		break;
+	case BPF_ST:
+		r->M[K] = r->A;
+		break;
+	case BPF_STX:
+		r->M[K] = r->X;
+		break;
+	case BPF_LD_W | BPF_ABS:
+		d = pkt_caplen - K;
+		if (d >= sizeof(uint32_t))
+			r->A = extract_u32(pkt, K);
+		else
+			set_return(r);
+		break;
+	case BPF_LD_H | BPF_ABS:
+		d = pkt_caplen - K;
+		if (d >= sizeof(uint16_t))
+			r->A = extract_u16(pkt, K);
+		else
+			set_return(r);
+		break;
+	case BPF_LD_B | BPF_ABS:
+		d = pkt_caplen - K;
+		if (d >= sizeof(uint8_t))
+			r->A = extract_u8(pkt, K);
+		else
+			set_return(r);
+		break;
+	case BPF_LD_W | BPF_IND:
+		d = pkt_caplen - (r->X + K);
+		if (d >= sizeof(uint32_t))
+			r->A = extract_u32(pkt, r->X + K);
+		break;
+	case BPF_LD_H | BPF_IND:
+		d = pkt_caplen - (r->X + K);
+		if (d >= sizeof(uint16_t))
+			r->A = extract_u16(pkt, r->X + K);
+		else
+			set_return(r);
+		break;
+	case BPF_LD_B | BPF_IND:
+		d = pkt_caplen - (r->X + K);
+		if (d >= sizeof(uint8_t))
+			r->A = extract_u8(pkt, r->X + K);
+		else
+			set_return(r);
+		break;
+	case BPF_LDX_B | BPF_MSH:
+		d = pkt_caplen - K;
+		if (d >= sizeof(uint8_t)) {
+			r->X = extract_u8(pkt, K);
+			r->X = (r->X & 0xf) << 2;
+		} else
+			set_return(r);
+		break;
+	case BPF_LD_W | BPF_LEN:
+		r->A = pkt_len;
+		break;
+	case BPF_LDX_W | BPF_LEN:
+		r->A = pkt_len;
+		break;
+	case BPF_LD | BPF_IMM:
+		r->A = K;
+		break;
+	case BPF_LDX | BPF_IMM:
+		r->X = K;
+		break;
+	case BPF_LD | BPF_MEM:
+		r->A = r->M[K];
+		break;
+	case BPF_LDX | BPF_MEM:
+		r->X = r->M[K];
+		break;
+	case BPF_JMP_JA:
+		r->Pc += K;
+		break;
+	case BPF_JMP_JGT | BPF_X:
+		r->Pc += r->A > r->X ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JGT | BPF_K:
+		r->Pc += r->A > K ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JGE | BPF_X:
+		r->Pc += r->A >= r->X ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JGE | BPF_K:
+		r->Pc += r->A >= K ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JEQ | BPF_X:
+		r->Pc += r->A == r->X ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JEQ | BPF_K:
+		r->Pc += r->A == K ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JSET | BPF_X:
+		r->Pc += r->A & r->X ? f->jt : f->jf;
+		break;
+	case BPF_JMP_JSET | BPF_K:
+		r->Pc += r->A & K ? f->jt : f->jf;
+		break;
+	case BPF_ALU_NEG:
+		r->A = -r->A;
+		break;
+	case BPF_ALU_LSH | BPF_X:
+		r->A <<= r->X;
+		break;
+	case BPF_ALU_LSH | BPF_K:
+		r->A <<= K;
+		break;
+	case BPF_ALU_RSH | BPF_X:
+		r->A >>= r->X;
+		break;
+	case BPF_ALU_RSH | BPF_K:
+		r->A >>= K;
+		break;
+	case BPF_ALU_ADD | BPF_X:
+		r->A += r->X;
+		break;
+	case BPF_ALU_ADD | BPF_K:
+		r->A += K;
+		break;
+	case BPF_ALU_SUB | BPF_X:
+		r->A -= r->X;
+		break;
+	case BPF_ALU_SUB | BPF_K:
+		r->A -= K;
+		break;
+	case BPF_ALU_MUL | BPF_X:
+		r->A *= r->X;
+		break;
+	case BPF_ALU_MUL | BPF_K:
+		r->A *= K;
+		break;
+	case BPF_ALU_DIV | BPF_X:
+	case BPF_ALU_MOD | BPF_X:
+		if (r->X == 0) {
+			set_return(r);
+			break;
+		}
+		goto do_div;
+	case BPF_ALU_DIV | BPF_K:
+	case BPF_ALU_MOD | BPF_K:
+		if (K == 0) {
+			set_return(r);
+			break;
+		}
+do_div:
+		switch (f->code) {
+		case BPF_ALU_DIV | BPF_X:
+			r->A /= r->X;
+			break;
+		case BPF_ALU_DIV | BPF_K:
+			r->A /= K;
+			break;
+		case BPF_ALU_MOD | BPF_X:
+			r->A %= r->X;
+			break;
+		case BPF_ALU_MOD | BPF_K:
+			r->A %= K;
+			break;
+		}
+		break;
+	case BPF_ALU_AND | BPF_X:
+		r->A &= r->X;
+		break;
+	case BPF_ALU_AND | BPF_K:
+		r->A &= r->X;
+		break;
+	case BPF_ALU_OR | BPF_X:
+		r->A |= r->X;
+		break;
+	case BPF_ALU_OR | BPF_K:
+		r->A |= K;
+		break;
+	case BPF_ALU_XOR | BPF_X:
+		r->A ^= r->X;
+		break;
+	case BPF_ALU_XOR | BPF_K:
+		r->A ^= K;
+		break;
+	}
+}
+
+static bool bpf_pc_has_breakpoint(uint16_t pc)
+{
+	int i;
+
+	for (i = 0; i < array_size(bpf_breakpoints); i++) {
+		if (bpf_breakpoints[i] < 0)
+			continue;
+		if (bpf_breakpoints[i] == pc)
+			return true;
+	}
+
+	return false;
+}
+
+static bool bpf_handle_breakpoint(struct bpf_regs *r, struct sock_filter *f,
+				  uint8_t *pkt, uint32_t pkt_caplen,
+				  uint32_t pkt_len)
+{
+	rl_printf("-- register dump --\n");
+	bpf_dump_curr(r, &f[r->Pc]);
+	rl_printf("-- packet dump --\n");
+	bpf_dump_pkt(pkt, pkt_caplen, pkt_len);
+	rl_printf("(breakpoint)\n");
+	return true;
+}
+
+static int bpf_run_all(struct sock_filter *f, uint16_t bpf_len, uint8_t *pkt,
+		       uint32_t pkt_caplen, uint32_t pkt_len)
+{
+	bool stop = false;
+
+	while (bpf_curr.Rs == false && stop == false) {
+		bpf_safe_regs();
+
+		if (bpf_pc_has_breakpoint(bpf_curr.Pc))
+			stop = bpf_handle_breakpoint(&bpf_curr, f, pkt,
+						     pkt_caplen, pkt_len);
+
+		bpf_single_step(&bpf_curr, &f[bpf_curr.Pc], pkt, pkt_caplen,
+				pkt_len);
+		bpf_curr.Pc++;
+	}
+
+	return stop ? -1 : bpf_curr.R;
+}
+
+static int bpf_run_stepping(struct sock_filter *f, uint16_t bpf_len,
+			    uint8_t *pkt, uint32_t pkt_caplen,
+			    uint32_t pkt_len, int next)
+{
+	bool stop = false;
+	int i = 1;
+
+	while (bpf_curr.Rs == false && stop == false) {
+		bpf_safe_regs();
+
+		if (i++ == next)
+			stop = bpf_handle_breakpoint(&bpf_curr, f, pkt,
+						     pkt_caplen, pkt_len);
+
+		bpf_single_step(&bpf_curr, &f[bpf_curr.Pc], pkt, pkt_caplen,
+				pkt_len);
+		bpf_curr.Pc++;
+	}
+
+	return stop ? -1 : bpf_curr.R;
+}
+
+static bool pcap_loaded(void)
+{
+	if (pcap_fd < 0)
+		rl_printf("no pcap file loaded!\n");
+
+	return pcap_fd >= 0;
+}
+
+static struct pcap_pkthdr *pcap_curr_pkt(void)
+{
+	return (void *) pcap_ptr_va_curr;
+}
+
+static bool pcap_next_pkt(void)
+{
+	struct pcap_pkthdr *hdr = pcap_curr_pkt();
+
+	if (pcap_ptr_va_curr + sizeof(*hdr) -
+	    pcap_ptr_va_start >= pcap_map_size)
+		return false;
+	if (hdr->caplen == 0 || hdr->len == 0 || hdr->caplen > hdr->len)
+		return false;
+	if (pcap_ptr_va_curr + sizeof(*hdr) + hdr->caplen -
+	    pcap_ptr_va_start >= pcap_map_size)
+		return false;
+
+	pcap_ptr_va_curr += (sizeof(*hdr) + hdr->caplen);
+	return true;
+}
+
+static void pcap_reset_pkt(void)
+{
+	pcap_ptr_va_curr = pcap_ptr_va_start + sizeof(struct pcap_filehdr);
+}
+
+static int try_load_pcap(const char *file)
+{
+	struct pcap_filehdr *hdr;
+	struct stat sb;
+	int ret;
+
+	pcap_fd = open(file, O_RDONLY);
+	if (pcap_fd < 0) {
+		rl_printf("cannot open pcap [%s]!\n", strerror(errno));
+		return CMD_ERR;
+	}
+
+	ret = fstat(pcap_fd, &sb);
+	if (ret < 0) {
+		rl_printf("cannot fstat pcap file!\n");
+		return CMD_ERR;
+	}
+
+	if (!S_ISREG(sb.st_mode)) {
+		rl_printf("not a regular pcap file, duh!\n");
+		return CMD_ERR;
+	}
+
+	pcap_map_size = sb.st_size;
+	if (pcap_map_size <= sizeof(struct pcap_filehdr)) {
+		rl_printf("pcap file too small!\n");
+		return CMD_ERR;
+	}
+
+	pcap_ptr_va_start = mmap(NULL, pcap_map_size, PROT_READ,
+				 MAP_SHARED | MAP_LOCKED, pcap_fd, 0);
+	if (pcap_ptr_va_start == MAP_FAILED) {
+		rl_printf("mmap of file failed!");
+		return CMD_ERR;
+	}
+
+	hdr = (void *) pcap_ptr_va_start;
+	if (hdr->magic != TCPDUMP_MAGIC) {
+		rl_printf("wrong pcap magic!\n");
+		return CMD_ERR;
+	}
+
+	pcap_reset_pkt();
+
+	return CMD_OK;
+
+}
+
+static void try_close_pcap(void)
+{
+	if (pcap_fd >= 0) {
+		munmap(pcap_ptr_va_start, pcap_map_size);
+		close(pcap_fd);
+
+		pcap_ptr_va_start = pcap_ptr_va_curr = NULL;
+		pcap_map_size = 0;
+		pcap_packet = 0;
+		pcap_fd = -1;
+	}
+}
+
+static int cmd_load_bpf(char *bpf_string)
+{
+	char sp, *token, separator = ',';
+	unsigned short bpf_len, i = 0;
+	struct sock_filter tmp;
+
+	bpf_prog_len = 0;
+	memset(bpf_image, 0, sizeof(bpf_image));
+
+	if (sscanf(bpf_string, "%hu%c", &bpf_len, &sp) != 2 ||
+	    sp != separator || bpf_len > BPF_MAXINSNS || bpf_len == 0) {
+		rl_printf("syntax error in head length encoding!\n");
+		return CMD_ERR;
+	}
+
+	token = bpf_string;
+	while ((token = strchr(token, separator)) && (++token)[0]) {
+		if (i >= bpf_len) {
+			rl_printf("program exceeds encoded length!\n");
+			return CMD_ERR;
+		}
+
+		if (sscanf(token, "%hu %hhu %hhu %u,",
+			   &tmp.code, &tmp.jt, &tmp.jf, &tmp.k) != 4) {
+			rl_printf("syntax error at instruction %d!\n", i);
+			return CMD_ERR;
+		}
+
+		bpf_image[i].code = tmp.code;
+		bpf_image[i].jt = tmp.jt;
+		bpf_image[i].jf = tmp.jf;
+		bpf_image[i].k = tmp.k;
+
+		i++;
+	}
+
+	if (i != bpf_len) {
+		rl_printf("syntax error exceeding encoded length!\n");
+		return CMD_ERR;
+	} else
+		bpf_prog_len = bpf_len;
+	if (!bpf_runnable(bpf_image, bpf_prog_len))
+		bpf_prog_len = 0;
+
+	return CMD_OK;
+}
+
+static int cmd_load_pcap(char *file)
+{
+	char *file_trim, *tmp;
+
+	file_trim = strtok_r(file, " ", &tmp);
+	if (file_trim == NULL)
+		return CMD_ERR;
+
+	try_close_pcap();
+
+	return try_load_pcap(file_trim);
+}
+
+static int cmd_load(char *arg)
+{
+	char *subcmd, *cont, *tmp = strdup(arg);
+	int ret = CMD_OK;
+
+	subcmd = strtok_r(tmp, " ", &cont);
+	if (subcmd == NULL)
+		goto out;
+	if (matches(subcmd, "bpf") == 0) {
+		bpf_reset();
+		bpf_reset_breakpoints();
+
+		ret = cmd_load_bpf(cont);
+	} else if (matches(subcmd, "pcap") == 0) {
+		ret = cmd_load_pcap(cont);
+	} else {
+out:
+		rl_printf("bpf <code>:  load bpf code\n");
+		rl_printf("pcap <file>: load pcap file\n");
+		ret = CMD_ERR;
+	}
+
+	free(tmp);
+	return ret;
+}
+
+static int cmd_step(char *num)
+{
+	struct pcap_pkthdr *hdr;
+	int steps, ret;
+
+	if (!bpf_prog_loaded() || !pcap_loaded())
+		return CMD_ERR;
+
+	steps = strtol(num, NULL, 10);
+	if (steps == 0 || strlen(num) == 0)
+		steps = 1;
+	if (steps < 0) {
+		if (!bpf_restore_regs(steps))
+			return CMD_ERR;
+		steps = 1;
+	}
+
+	hdr = pcap_curr_pkt();
+	ret = bpf_run_stepping(bpf_image, bpf_prog_len,
+			       (uint8_t *) hdr + sizeof(*hdr),
+			       hdr->caplen, hdr->len, steps);
+	if (ret >= 0 || bpf_curr.Rs) {
+		bpf_reset();
+		if (!pcap_next_pkt()) {
+			rl_printf("(going back to first packet)\n");
+			pcap_reset_pkt();
+		} else {
+			rl_printf("(next packet)\n");
+		}
+	}
+
+	return CMD_OK;
+}
+
+static int cmd_select(char *num)
+{
+	unsigned int which, i;
+	struct pcap_pkthdr *hdr;
+	bool have_next = true;
+
+	if (!pcap_loaded() || strlen(num) == 0)
+		return CMD_ERR;
+
+	which = strtoul(num, NULL, 10);
+	if (which == 0) {
+		rl_printf("packet count starts with 1, clamping!\n");
+		which = 1;
+	}
+
+	pcap_reset_pkt();
+	bpf_reset();
+
+	for (i = 0; i < which && (have_next = pcap_next_pkt()); i++)
+		/* noop */;
+	if (!have_next || (hdr = pcap_curr_pkt()) == NULL) {
+		rl_printf("no packet #%u available!\n", which);
+		pcap_reset_pkt();
+		return CMD_ERR;
+	}
+
+	return CMD_OK;
+}
+
+static int cmd_breakpoint(char *subcmd)
+{
+	if (!bpf_prog_loaded())
+		return CMD_ERR;
+	if (strlen(subcmd) == 0)
+		bpf_dump_breakpoints();
+	else if (matches(subcmd, "reset") == 0)
+		bpf_reset_breakpoints();
+	else {
+		unsigned int where = strtoul(subcmd, NULL, 10);
+
+		if (where < bpf_prog_len) {
+			bpf_set_breakpoints(where);
+			rl_printf("breakpoint at: ");
+			bpf_disasm(bpf_image[where], where);
+		}
+	}
+
+	return CMD_OK;
+}
+
+static int cmd_run(char *num)
+{
+	static uint32_t pass = 0, fail = 0;
+	struct pcap_pkthdr *hdr;
+	bool has_limit = true;
+	int ret, pkts = 0, i = 0;
+
+	if (!bpf_prog_loaded() || !pcap_loaded())
+		return CMD_ERR;
+
+	pkts = strtol(num, NULL, 10);
+	if (pkts == 0 || strlen(num) == 0)
+		has_limit = false;
+
+	do {
+		hdr = pcap_curr_pkt();
+		ret = bpf_run_all(bpf_image, bpf_prog_len,
+				  (uint8_t *) hdr + sizeof(*hdr),
+				  hdr->caplen, hdr->len);
+		if (ret > 0)
+			pass++;
+		else if (ret == 0)
+			fail++;
+		else
+			return CMD_OK;
+		bpf_reset();
+	} while (pcap_next_pkt() && (!has_limit || (has_limit && ++i < pkts)));
+
+	rl_printf("bpf passes:%u fails:%u\n", pass, fail);
+
+	pcap_reset_pkt();
+	bpf_reset();
+
+	pass = fail = 0;
+	return CMD_OK;
+}
+
+static int cmd_disassemble(char *line_string)
+{
+	bool single_line = false;
+	unsigned long line;
+
+	if (!bpf_prog_loaded())
+		return CMD_ERR;
+	if (strlen(line_string) > 0 &&
+	    (line = strtoul(line_string, NULL, 10)) < bpf_prog_len)
+		single_line = true;
+	if (single_line)
+		bpf_disasm(bpf_image[line], line);
+	else
+		bpf_disasm_all(bpf_image, bpf_prog_len);
+
+	return CMD_OK;
+}
+
+static int cmd_dump(char *dontcare)
+{
+	if (!bpf_prog_loaded())
+		return CMD_ERR;
+
+	bpf_dump_all(bpf_image, bpf_prog_len);
+
+	return CMD_OK;
+}
+
+static int cmd_quit(char *dontcare)
+{
+	return CMD_EX;
+}
+
+static const struct shell_cmd cmds[] = {
+	CMD("load",		cmd_load),
+	CMD("select",		cmd_select),
+	CMD("step",		cmd_step),
+	CMD("run",		cmd_run),
+	CMD("breakpoint",	cmd_breakpoint),
+	CMD("disassemble",	cmd_disassemble),
+	CMD("dump",		cmd_dump),
+	CMD("quit",		cmd_quit),
+};
+
+static int execf(char *arg)
+{
+	char *cmd, *cont, *tmp = strdup(arg);
+	int i, ret = 0, len;
+
+	cmd = strtok_r(tmp, " ", &cont);
+	if (cmd == NULL)
+		goto out;
+	len = strlen(cmd);
+	for (i = 0; i < array_size(cmds); i++) {
+		if (len != strlen(cmds[i].name))
+			continue;
+		if (strncmp(cmds[i].name, cmd, len) == 0) {
+			ret = cmds[i].func(cont);
+			break;
+		}
+	}
+out:
+	free(tmp);
+	return ret;
+}
+
+static char *shell_comp_gen(const char *buf, int state)
+{
+	static int list_index, len;
+	const char *name;
+
+	if (!state) {
+		list_index = 0;
+		len = strlen(buf);
+	}
+
+	for (; list_index < array_size(cmds); ) {
+		name = cmds[list_index].name;
+		list_index++;
+
+		if (strncmp(name, buf, len) == 0)
+			return strdup(name);
+	}
+
+	return NULL;
+}
+
+static char **shell_completion(const char *buf, int start, int end)
+{
+	char **matches = NULL;
+
+	if (start == 0)
+		matches = rl_completion_matches(buf, shell_comp_gen);
+
+	return matches;
+}
+
+static void intr_shell(int sig)
+{
+	if (rl_end)
+		rl_kill_line(-1, 0);
+
+	rl_crlf();
+	rl_refresh_line(0, 0);
+	rl_free_line_state();
+}
+
+static void init_shell(FILE *fin, FILE *fout)
+{
+	char file[128];
+
+	memset(file, 0, sizeof(file));
+	snprintf(file, sizeof(file) - 1,
+		 "%s/.bpf_dbg_history", getenv("HOME"));
+
+	read_history(file);
+
+	memset(file, 0, sizeof(file));
+	snprintf(file, sizeof(file) - 1,
+		 "%s/.bpf_dbg_init", getenv("HOME"));
+
+	rl_instream = fin;
+	rl_outstream = fout;
+
+	rl_readline_name = "bpf_dbg";
+	rl_terminal_name = getenv("TERM");
+
+	rl_catch_signals = 0;
+	rl_catch_sigwinch = 1;
+
+	rl_attempted_completion_function = shell_completion;
+
+	rl_bind_key('\t', rl_complete);
+
+	rl_bind_key_in_map('\t', rl_complete, emacs_meta_keymap);
+	rl_bind_key_in_map('\033', rl_complete, emacs_meta_keymap);
+
+	rl_read_init_file(file);
+	rl_prep_terminal(0);
+	rl_set_signals();
+
+	signal(SIGINT, intr_shell);
+}
+
+static void exit_shell(void)
+{
+	char file[128];
+
+	memset(file, 0, sizeof(file));
+	snprintf(file, sizeof(file) - 1,
+		 "%s/.bpf_dbg_history", getenv("HOME"));
+
+	write_history(file);
+	clear_history();
+	rl_deprep_terminal();
+
+	try_close_pcap();
+}
+
+static int run_shell_loop(FILE *fin, FILE *fout)
+{
+	char *buf;
+	int ret;
+
+	init_shell(fin, fout);
+
+	while ((buf = readline("> ")) != NULL) {
+		ret = execf(buf);
+		if (ret == CMD_EX)
+			break;
+		if (ret == CMD_OK && strlen(buf) > 0)
+			add_history(buf);
+
+		free(buf);
+	}
+
+	exit_shell();
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	FILE *fin = NULL, *fout = NULL;
+
+	if (argc >= 2)
+		fin = fopen(argv[1], "r");
+	if (argc >= 3)
+		fout = fopen(argv[2], "w");
+
+	return run_shell_loop(fin ? : stdin, fout ? : stdout);
+}

tools/net/bpf_exp.l

@@ -0,0 +1,143 @@
+/*
+ * BPF asm code lexer
+ *
+ * This program is free software; you can distribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License,
+ * or (at your option) any later version.
+ *
+ * Syntax kept close to:
+ *
+ * Steven McCanne and Van Jacobson. 1993. The BSD packet filter: a new
+ * architecture for user-level packet capture. In Proceedings of the
+ * USENIX Winter 1993 Conference Proceedings on USENIX Winter 1993
+ * Conference Proceedings (USENIX'93). USENIX Association, Berkeley,
+ * CA, USA, 2-2.
+ *
+ * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
+ * Licensed under the GNU General Public License, version 2.0 (GPLv2)
+ */
+
+%{
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "bpf_exp.yacc.h"
+
+extern void yyerror(const char *str);
+
+%}
+
+%option align
+%option ecs
+
+%option nounput
+%option noreject
+%option noinput
+%option noyywrap
+
+%option 8bit
+%option caseless
+%option yylineno
+
+%%
+
+"ldb"		{ return OP_LDB; }
+"ldh"		{ return OP_LDH; }
+"ld"		{ return OP_LD; }
+"ldi"		{ return OP_LDI; }
+"ldx"		{ return OP_LDX; }
+"ldxi"		{ return OP_LDXI; }
+"ldxb"		{ return OP_LDXB; }
+"st"		{ return OP_ST; }
+"stx"		{ return OP_STX; }
+"jmp"		{ return OP_JMP; }
+"ja"		{ return OP_JMP; }
+"jeq"		{ return OP_JEQ; }
+"jneq"		{ return OP_JNEQ; }
+"jne"		{ return OP_JNEQ; }
+"jlt"		{ return OP_JLT; }
+"jle"		{ return OP_JLE; }
+"jgt"		{ return OP_JGT; }
+"jge"		{ return OP_JGE; }
+"jset"		{ return OP_JSET; }
+"add"		{ return OP_ADD; }
+"sub"		{ return OP_SUB; }
+"mul"		{ return OP_MUL; }
+"div"		{ return OP_DIV; }
+"mod"		{ return OP_MOD; }
+"neg"		{ return OP_NEG; }
+"and"		{ return OP_AND; }
+"xor"		{ return OP_XOR; }
+"or"		{ return OP_OR; }
+"lsh"		{ return OP_LSH; }
+"rsh"		{ return OP_RSH; }
+"ret"		{ return OP_RET; }
+"tax"		{ return OP_TAX; }
+"txa"		{ return OP_TXA; }
+
+"#"?("len")	{ return K_PKT_LEN; }
+"#"?("proto")	{ return K_PROTO; }
+"#"?("type")	{ return K_TYPE; }
+"#"?("poff")	{ return K_POFF; }
+"#"?("ifidx")	{ return K_IFIDX; }
+"#"?("nla")	{ return K_NLATTR; }
+"#"?("nlan")	{ return K_NLATTR_NEST; }
+"#"?("mark")	{ return K_MARK; }
+"#"?("queue")	{ return K_QUEUE; }
+"#"?("hatype")	{ return K_HATYPE; }
+"#"?("rxhash")	{ return K_RXHASH; }
+"#"?("cpu")	{ return K_CPU; }
+"#"?("vlan_tci") { return K_VLANT; }
+"#"?("vlan_pr")	{ return K_VLANP; }
+
+":"		{ return ':'; }
+","		{ return ','; }
+"#"		{ return '#'; }
+"%"		{ return '%'; }
+"["		{ return '['; }
+"]"		{ return ']'; }
+"("		{ return '('; }
+")"		{ return ')'; }
+"x"		{ return 'x'; }
+"a"		{ return 'a'; }
+"+"		{ return '+'; }
+"M"		{ return 'M'; }
+"*"		{ return '*'; }
+"&"		{ return '&'; }
+
+([0][x][a-fA-F0-9]+) {
+			yylval.number = strtoul(yytext, NULL, 16);
+			return number;
+		}
+([0][b][0-1]+)	{
+			yylval.number = strtol(yytext + 2, NULL, 2);
+			return number;
+		}
+(([0])|([-+]?[1-9][0-9]*)) {
+			yylval.number = strtol(yytext, NULL, 10);
+			return number;
+		}
+([0][0-9]+)	{
+			yylval.number = strtol(yytext + 1, NULL, 8);
+			return number;
+		}
+[a-zA-Z_][a-zA-Z0-9_]+ {
+			yylval.label = strdup(yytext);
+			return label;
+		}
+
+"/*"([^\*]|\*[^/])*"*/"		{ /* NOP */ }
+";"[^\n]*			{ /* NOP */ }
+^#.*				{ /* NOP */ }
+[ \t]+				{ /* NOP */ }
+[ \n]+				{ /* NOP */ }
+
+.		{
+			printf("unknown character \'%s\'", yytext);
+			yyerror("lex unknown character");
+		}
+
+%%

tools/net/bpf_exp.y

@@ -0,0 +1,749 @@
+/*
+ * BPF asm code parser
+ *
+ * This program is free software; you can distribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License,
+ * or (at your option) any later version.
+ *
+ * Syntax kept close to:
+ *
+ * Steven McCanne and Van Jacobson. 1993. The BSD packet filter: a new
+ * architecture for user-level packet capture. In Proceedings of the
+ * USENIX Winter 1993 Conference Proceedings on USENIX Winter 1993
+ * Conference Proceedings (USENIX'93). USENIX Association, Berkeley,
+ * CA, USA, 2-2.
+ *
+ * Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
+ * Licensed under the GNU General Public License, version 2.0 (GPLv2)
+ */
+
+%{
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <errno.h>
+#include <assert.h>
+#include <linux/filter.h>
+
+#include "bpf_exp.yacc.h"
+
+enum jmp_type { JTL, JFL, JKL };
+
+extern FILE *yyin;
+extern int yylex(void);
+extern void yyerror(const char *str);
+
+extern void bpf_asm_compile(FILE *fp, bool cstyle);
+static void bpf_set_curr_instr(uint16_t op, uint8_t jt, uint8_t jf, uint32_t k);
+static void bpf_set_curr_label(const char *label);
+static void bpf_set_jmp_label(const char *label, enum jmp_type type);
+
+%}
+
+%union {
+	char *label;
+	uint32_t number;
+}
+
+%token OP_LDB OP_LDH OP_LD OP_LDX OP_ST OP_STX OP_JMP OP_JEQ OP_JGT OP_JGE
+%token OP_JSET OP_ADD OP_SUB OP_MUL OP_DIV OP_AND OP_OR OP_XOR OP_LSH OP_RSH
+%token OP_RET OP_TAX OP_TXA OP_LDXB OP_MOD OP_NEG OP_JNEQ OP_JLT OP_JLE OP_LDI
+%token OP_LDXI
+
+%token K_PKT_LEN K_PROTO K_TYPE K_NLATTR K_NLATTR_NEST K_MARK K_QUEUE K_HATYPE
+%token K_RXHASH K_CPU K_IFIDX K_VLANT K_VLANP K_POFF
+
+%token ':' ',' '[' ']' '(' ')' 'x' 'a' '+' 'M' '*' '&' '#' '%'
+
+%token number label
+
+%type <label> label
+%type <number> number
+
+%%
+
+prog
+	: line
+	| prog line
+	;
+
+line
+	: instr
+	| labelled_instr
+	;
+
+labelled_instr
+	: labelled instr
+	;
+
+instr
+	: ldb
+	| ldh
+	| ld
+	| ldi
+	| ldx
+	| ldxi
+	| st
+	| stx
+	| jmp
+	| jeq
+	| jneq
+	| jlt
+	| jle
+	| jgt
+	| jge
+	| jset
+	| add
+	| sub
+	| mul
+	| div
+	| mod
+	| neg
+	| and
+	| or
+	| xor
+	| lsh
+	| rsh
+	| ret
+	| tax
+	| txa
+	;
+
+labelled
+	: label ':' { bpf_set_curr_label($1); }
+	;
+
+ldb
+	: OP_LDB '[' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_IND, 0, 0, $5); }
+	| OP_LDB '[' '%' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_IND, 0, 0, $6); }
+	| OP_LDB '[' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0, $3); }
+	| OP_LDB K_PROTO {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PROTOCOL); }
+	| OP_LDB K_TYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PKTTYPE); }
+	| OP_LDB K_IFIDX {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_IFINDEX); }
+	| OP_LDB K_NLATTR {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR); }
+	| OP_LDB K_NLATTR_NEST {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
+	| OP_LDB K_MARK {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_MARK); }
+	| OP_LDB K_QUEUE {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_QUEUE); }
+	| OP_LDB K_HATYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_HATYPE); }
+	| OP_LDB K_RXHASH {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_RXHASH); }
+	| OP_LDB K_CPU {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_CPU); }
+	| OP_LDB K_VLANT {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG); }
+	| OP_LDB K_VLANP {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LDB K_POFF {
+		bpf_set_curr_instr(BPF_LD | BPF_B | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+	;
+
+ldh
+	: OP_LDH '[' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_IND, 0, 0, $5); }
+	| OP_LDH '[' '%' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_IND, 0, 0, $6); }
+	| OP_LDH '[' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0, $3); }
+	| OP_LDH K_PROTO {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PROTOCOL); }
+	| OP_LDH K_TYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PKTTYPE); }
+	| OP_LDH K_IFIDX {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_IFINDEX); }
+	| OP_LDH K_NLATTR {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR); }
+	| OP_LDH K_NLATTR_NEST {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
+	| OP_LDH K_MARK {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_MARK); }
+	| OP_LDH K_QUEUE {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_QUEUE); }
+	| OP_LDH K_HATYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_HATYPE); }
+	| OP_LDH K_RXHASH {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_RXHASH); }
+	| OP_LDH K_CPU {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_CPU); }
+	| OP_LDH K_VLANT {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG); }
+	| OP_LDH K_VLANP {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LDH K_POFF {
+		bpf_set_curr_instr(BPF_LD | BPF_H | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+	;
+
+ldi
+	: OP_LDI '#' number {
+		bpf_set_curr_instr(BPF_LD | BPF_IMM, 0, 0, $3); }
+	| OP_LDI number {
+		bpf_set_curr_instr(BPF_LD | BPF_IMM, 0, 0, $2); }
+	;
+
+ld
+	: OP_LD '#' number {
+		bpf_set_curr_instr(BPF_LD | BPF_IMM, 0, 0, $3); }
+	| OP_LD K_PKT_LEN {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_LEN, 0, 0, 0); }
+	| OP_LD K_PROTO {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PROTOCOL); }
+	| OP_LD K_TYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PKTTYPE); }
+	| OP_LD K_IFIDX {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_IFINDEX); }
+	| OP_LD K_NLATTR {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR); }
+	| OP_LD K_NLATTR_NEST {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_NLATTR_NEST); }
+	| OP_LD K_MARK {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_MARK); }
+	| OP_LD K_QUEUE {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_QUEUE); }
+	| OP_LD K_HATYPE {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_HATYPE); }
+	| OP_LD K_RXHASH {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_RXHASH); }
+	| OP_LD K_CPU {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_CPU); }
+	| OP_LD K_VLANT {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG); }
+	| OP_LD K_VLANP {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT); }
+	| OP_LD K_POFF {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0,
+				   SKF_AD_OFF + SKF_AD_PAY_OFFSET); }
+	| OP_LD 'M' '[' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_MEM, 0, 0, $4); }
+	| OP_LD '[' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_IND, 0, 0, $5); }
+	| OP_LD '[' '%' 'x' '+' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_IND, 0, 0, $6); }
+	| OP_LD '[' number ']' {
+		bpf_set_curr_instr(BPF_LD | BPF_W | BPF_ABS, 0, 0, $3); }
+	;
+
+ldxi
+	: OP_LDXI '#' number {
+		bpf_set_curr_instr(BPF_LDX | BPF_IMM, 0, 0, $3); }
+	| OP_LDXI number {
+		bpf_set_curr_instr(BPF_LDX | BPF_IMM, 0, 0, $2); }
+	;
+
+ldx
+	: OP_LDX '#' number {
+		bpf_set_curr_instr(BPF_LDX | BPF_IMM, 0, 0, $3); }
+	| OP_LDX K_PKT_LEN {
+		bpf_set_curr_instr(BPF_LDX | BPF_W | BPF_LEN, 0, 0, 0); }
+	| OP_LDX 'M' '[' number ']' {
+		bpf_set_curr_instr(BPF_LDX | BPF_MEM, 0, 0, $4); }
+	| OP_LDXB number '*' '(' '[' number ']' '&' number ')' {
+		if ($2 != 4 || $9 != 0xf) {
+			fprintf(stderr, "ldxb offset not supported!\n");
+			exit(0);
+		} else {
+			bpf_set_curr_instr(BPF_LDX | BPF_MSH | BPF_B, 0, 0, $6); } }
+	| OP_LDX number '*' '(' '[' number ']' '&' number ')' {
+		if ($2 != 4 || $9 != 0xf) {
+			fprintf(stderr, "ldxb offset not supported!\n");
+			exit(0);
+		} else {
+			bpf_set_curr_instr(BPF_LDX | BPF_MSH | BPF_B, 0, 0, $6); } }
+	;
+
+st
+	: OP_ST 'M' '[' number ']' {
+		bpf_set_curr_instr(BPF_ST, 0, 0, $4); }
+	;
+
+stx
+	: OP_STX 'M' '[' number ']' {
+		bpf_set_curr_instr(BPF_STX, 0, 0, $4); }
+	;
+
+jmp
+	: OP_JMP label {
+		bpf_set_jmp_label($2, JKL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JA, 0, 0, 0); }
+	;
+
+jeq
+	: OP_JEQ '#' number ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_K, 0, 0, $3); }
+	| OP_JEQ 'x' ',' label ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_jmp_label($6, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	| OP_JEQ '%' 'x' ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	| OP_JEQ '#' number ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_K, 0, 0, $3); }
+	| OP_JEQ 'x' ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	| OP_JEQ '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	;
+
+jneq
+	: OP_JNEQ '#' number ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_K, 0, 0, $3); }
+	| OP_JNEQ 'x' ',' label {
+		bpf_set_jmp_label($4, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	| OP_JNEQ '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JEQ | BPF_X, 0, 0, 0); }
+	;
+
+jlt
+	: OP_JLT '#' number ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_K, 0, 0, $3); }
+	| OP_JLT 'x' ',' label {
+		bpf_set_jmp_label($4, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	| OP_JLT '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	;
+
+jle
+	: OP_JLE '#' number ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_K, 0, 0, $3); }
+	| OP_JLE 'x' ',' label {
+		bpf_set_jmp_label($4, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	| OP_JLE '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	;
+
+jgt
+	: OP_JGT '#' number ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_K, 0, 0, $3); }
+	| OP_JGT 'x' ',' label ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_jmp_label($6, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	| OP_JGT '%' 'x' ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	| OP_JGT '#' number ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_K, 0, 0, $3); }
+	| OP_JGT 'x' ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	| OP_JGT '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGT | BPF_X, 0, 0, 0); }
+	;
+
+jge
+	: OP_JGE '#' number ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_K, 0, 0, $3); }
+	| OP_JGE 'x' ',' label ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_jmp_label($6, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	| OP_JGE '%' 'x' ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	| OP_JGE '#' number ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_K, 0, 0, $3); }
+	| OP_JGE 'x' ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	| OP_JGE '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JGE | BPF_X, 0, 0, 0); }
+	;
+
+jset
+	: OP_JSET '#' number ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_K, 0, 0, $3); }
+	| OP_JSET 'x' ',' label ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_jmp_label($6, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_X, 0, 0, 0); }
+	| OP_JSET '%' 'x' ',' label ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_jmp_label($7, JFL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_X, 0, 0, 0); }
+	| OP_JSET '#' number ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_K, 0, 0, $3); }
+	| OP_JSET 'x' ',' label {
+		bpf_set_jmp_label($4, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_X, 0, 0, 0); }
+	| OP_JSET '%' 'x' ',' label {
+		bpf_set_jmp_label($5, JTL);
+		bpf_set_curr_instr(BPF_JMP | BPF_JSET | BPF_X, 0, 0, 0); }
+	;
+
+add
+	: OP_ADD '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_ADD | BPF_K, 0, 0, $3); }
+	| OP_ADD 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_ADD | BPF_X, 0, 0, 0); }
+	| OP_ADD '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_ADD | BPF_X, 0, 0, 0); }
+	;
+
+sub
+	: OP_SUB '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_SUB | BPF_K, 0, 0, $3); }
+	| OP_SUB 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_SUB | BPF_X, 0, 0, 0); }
+	| OP_SUB '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_SUB | BPF_X, 0, 0, 0); }
+	;
+
+mul
+	: OP_MUL '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_MUL | BPF_K, 0, 0, $3); }
+	| OP_MUL 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_MUL | BPF_X, 0, 0, 0); }
+	| OP_MUL '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_MUL | BPF_X, 0, 0, 0); }
+	;
+
+div
+	: OP_DIV '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_DIV | BPF_K, 0, 0, $3); }
+	| OP_DIV 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_DIV | BPF_X, 0, 0, 0); }
+	| OP_DIV '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_DIV | BPF_X, 0, 0, 0); }
+	;
+
+mod
+	: OP_MOD '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_MOD | BPF_K, 0, 0, $3); }
+	| OP_MOD 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_MOD | BPF_X, 0, 0, 0); }
+	| OP_MOD '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_MOD | BPF_X, 0, 0, 0); }
+	;
+
+neg
+	: OP_NEG {
+		bpf_set_curr_instr(BPF_ALU | BPF_NEG, 0, 0, 0); }
+	;
+
+and
+	: OP_AND '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_AND | BPF_K, 0, 0, $3); }
+	| OP_AND 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_AND | BPF_X, 0, 0, 0); }
+	| OP_AND '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_AND | BPF_X, 0, 0, 0); }
+	;
+
+or
+	: OP_OR '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_OR | BPF_K, 0, 0, $3); }
+	| OP_OR 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_OR | BPF_X, 0, 0, 0); }
+	| OP_OR '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_OR | BPF_X, 0, 0, 0); }
+	;
+
+xor
+	: OP_XOR '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_XOR | BPF_K, 0, 0, $3); }
+	| OP_XOR 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_XOR | BPF_X, 0, 0, 0); }
+	| OP_XOR '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_XOR | BPF_X, 0, 0, 0); }
+	;
+
+lsh
+	: OP_LSH '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_LSH | BPF_K, 0, 0, $3); }
+	| OP_LSH 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_LSH | BPF_X, 0, 0, 0); }
+	| OP_LSH '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_LSH | BPF_X, 0, 0, 0); }
+	;
+
+rsh
+	: OP_RSH '#' number {
+		bpf_set_curr_instr(BPF_ALU | BPF_RSH | BPF_K, 0, 0, $3); }
+	| OP_RSH 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_RSH | BPF_X, 0, 0, 0); }
+	| OP_RSH '%' 'x' {
+		bpf_set_curr_instr(BPF_ALU | BPF_RSH | BPF_X, 0, 0, 0); }
+	;
+
+ret
+	: OP_RET 'a' {
+		bpf_set_curr_instr(BPF_RET | BPF_A, 0, 0, 0); }
+	| OP_RET '%' 'a' {
+		bpf_set_curr_instr(BPF_RET | BPF_A, 0, 0, 0); }
+	| OP_RET 'x' {
+		bpf_set_curr_instr(BPF_RET | BPF_X, 0, 0, 0); }
+	| OP_RET '%' 'x' {
+		bpf_set_curr_instr(BPF_RET | BPF_X, 0, 0, 0); }
+	| OP_RET '#' number {
+		bpf_set_curr_instr(BPF_RET | BPF_K, 0, 0, $3); }
+	;
+
+tax
+	: OP_TAX {
+		bpf_set_curr_instr(BPF_MISC | BPF_TAX, 0, 0, 0); }
+	;
+
+txa
+	: OP_TXA {
+		bpf_set_curr_instr(BPF_MISC | BPF_TXA, 0, 0, 0); }
+	;
+
+%%
+
+static int curr_instr = 0;
+static struct sock_filter out[BPF_MAXINSNS];
+static const char **labels, **labels_jt, **labels_jf, **labels_k;
+
+static void bpf_assert_max(void)
+{
+	if (curr_instr >= BPF_MAXINSNS) {
+		fprintf(stderr, "only max %u insns allowed!\n", BPF_MAXINSNS);
+		exit(0);
+	}
+}
+
+static void bpf_set_curr_instr(uint16_t code, uint8_t jt, uint8_t jf,
+			       uint32_t k)
+{
+	bpf_assert_max();
+	out[curr_instr].code = code;
+	out[curr_instr].jt = jt;
+	out[curr_instr].jf = jf;
+	out[curr_instr].k = k;
+	curr_instr++;
+}
+
+static void bpf_set_curr_label(const char *label)
+{
+	bpf_assert_max();
+        labels[curr_instr] = label;
+}
+
+static void bpf_set_jmp_label(const char *label, enum jmp_type type)
+{
+	bpf_assert_max();
+	switch (type) {
+	case JTL:
+		labels_jt[curr_instr] = label;
+		break;
+	case JFL:
+		labels_jf[curr_instr] = label;
+		break;
+	case JKL:
+		labels_k[curr_instr] = label;
+		break;
+	}
+}
+
+static int bpf_find_insns_offset(const char *label)
+{
+	int i, max = curr_instr, ret = -ENOENT;
+
+	for (i = 0; i < max; i++) {
+		if (labels[i] && !strcmp(label, labels[i])) {
+			ret = i;
+			break;
+		}
+	}
+
+	if (ret == -ENOENT) {
+		fprintf(stderr, "no such label \'%s\'!\n", label);
+		exit(0);
+	}
+
+	return ret;
+}
+
+static void bpf_stage_1_insert_insns(void)
+{
+	yyparse();
+}
+
+static void bpf_reduce_k_jumps(void)
+{
+	int i;
+
+	for (i = 0; i < curr_instr; i++) {
+		if (labels_k[i]) {
+			int off = bpf_find_insns_offset(labels_k[i]);
+			out[i].k = (uint32_t) (off - i - 1);
+		}
+	}
+}
+
+static void bpf_reduce_jt_jumps(void)
+{
+	int i;
+
+	for (i = 0; i < curr_instr; i++) {
+		if (labels_jt[i]) {
+			int off = bpf_find_insns_offset(labels_jt[i]);
+			out[i].jt = (uint8_t) (off - i -1);
+		}
+	}
+}
+
+static void bpf_reduce_jf_jumps(void)
+{
+	int i;
+
+	for (i = 0; i < curr_instr; i++) {
+		if (labels_jf[i]) {
+			int off = bpf_find_insns_offset(labels_jf[i]);
+			out[i].jf = (uint8_t) (off - i - 1);
+		}
+	}
+}
+
+static void bpf_stage_2_reduce_labels(void)
+{
+	bpf_reduce_k_jumps();
+	bpf_reduce_jt_jumps();
+	bpf_reduce_jf_jumps();
+}
+
+static void bpf_pretty_print_c(void)
+{
+	int i;
+
+	for (i = 0; i < curr_instr; i++)
+		printf("{ %#04x, %2u, %2u, %#010x },\n", out[i].code,
+		       out[i].jt, out[i].jf, out[i].k);
+}
+
+static void bpf_pretty_print(void)
+{
+	int i;
+
+	printf("%u,", curr_instr);
+	for (i = 0; i < curr_instr; i++)
+		printf("%u %u %u %u,", out[i].code,
+		       out[i].jt, out[i].jf, out[i].k);
+	printf("\n");
+}
+
+static void bpf_init(void)
+{
+	memset(out, 0, sizeof(out));
+
+	labels = calloc(BPF_MAXINSNS, sizeof(*labels));
+	assert(labels);
+	labels_jt = calloc(BPF_MAXINSNS, sizeof(*labels_jt));
+	assert(labels_jt);
+	labels_jf = calloc(BPF_MAXINSNS, sizeof(*labels_jf));
+	assert(labels_jf);
+	labels_k = calloc(BPF_MAXINSNS, sizeof(*labels_k));
+	assert(labels_k);
+}
+
+static void bpf_destroy(void)
+{
+	free(labels);
+	free(labels_jt);
+	free(labels_jf);
+	free(labels_k);
+}
+
+void bpf_asm_compile(FILE *fp, bool cstyle)
+{
+	yyin = fp;
+
+	bpf_init();
+	bpf_stage_1_insert_insns();
+	bpf_stage_2_reduce_labels();
+	bpf_destroy();
+
+	if (cstyle)
+		bpf_pretty_print_c();
+	else
+		bpf_pretty_print();
+
+	if (fp != stdin)
+		fclose(yyin);
+}
+
+void yyerror(const char *str)
+{
+	exit(1);
+}