[PATCH bpf-next 00/13] docs: Convert BPF filter.txt to RST

[PATCH bpf-next 00/13] docs: Convert BPF filter.txt to RST

[Tobin C. Harding]

Hi,

Sending this to BPF maintainers.  Recent patch set to Documentation/bpf
went through bpf tree so I'm guessing this one will too.  I rekon there
will be less merge conflicts through your tree.  I do not know exactly
the path for docs into the mainline or who fixes up merge conflicts
though so if this is better done another way please say so.

Patch set applies on top of bpf-next commit: ("2e96187b6967 Merge branch
'bpf-docs-rst-improvements'")


Use of --subject-prefix='PATCH bpf-next' was a guess.

While doing the final read over of this set I realised that perhaps we
should have just moved this file to Documentation/bpf?

Anyways, here is the conversion of filter.txt to filter.rst split up
into a bunch of patches to ease review.  I failed to fully grok the
contents of this file so there may be mistakes in the 'Fix various
minor tyos' patch.

Also the diff looks like it contains spurious whitespace changes in
places, I think this is when spaces have been replaced by tabs.  I'm
guessing you guys are experienced at reading patches so can tell this
already - it took me a bit of thinking :)

Some of the formatting for code snippets is subjective, if you'd like me
to change it please say so.  In particular I added a line of whitespace
before error output in a bunch of the snippets.  Also indented slightly
differently to the original so it looks okay in HTML.  I did not check
any other rendered format.

thanks,
Tobin.


Tobin C. Harding (13):
  docs: net: Rename filter.txt to filter.rst
  docs: Update references to filter.rst
  docs: net: Add filter to index toctree
  docs: net: Use correct heading adornments
  docs: net: Fix indentation issues for code snippets
  docs: net: Remove non-standard identifiers
  docs: net: Use double ticks instead of single quote
  docs: net: Use double ticks instead of single tick
  docs: net: Use lowercase 'k' for kernel
  docs: net: Embed reference to seccomp_filter
  docs: net: Use correct RST list construct
  docs: net: Fix various minor typos
  docs: net: Fix authors list to render as a list

 Documentation/bpf/index.rst                   |    9 +-
 Documentation/networking/00-INDEX             |    2 -
 .../networking/{filter.txt => filter.rst}     | 1007 +++++++++--------
 Documentation/networking/index.rst            |    1 +
 Documentation/networking/packet_mmap.txt      |    2 +-
 .../userspace-api/seccomp_filter.rst          |    2 +
 MAINTAINERS                                   |    2 +-
 tools/bpf/bpf_asm.c                           |    2 +-
 tools/bpf/bpf_dbg.c                           |    2 +-
 9 files changed, 545 insertions(+), 484 deletions(-)
 rename Documentation/networking/{filter.txt => filter.rst} (69%)

-- 
2.17.1

[PATCH bpf-next 01/13] docs: net: Rename filter.txt to filter.rst

[Tobin C. Harding]

In preparation for conversion to RST format.  Rename file in a single
commit to ease review.

Rename Documentation/networking/filter.txt to
Documentation/networking/filter.rst

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/00-INDEX                   | 2 --
 Documentation/networking/{filter.txt => filter.rst} | 0
 MAINTAINERS                                         | 2 +-
 3 files changed, 1 insertion(+), 3 deletions(-)
 rename Documentation/networking/{filter.txt => filter.rst} (100%)

diff --git a/Documentation/networking/00-INDEX b/Documentation/networking/00-INDEX
index 1e5153ed8990..37c65b3a90be 100644
--- a/Documentation/networking/00-INDEX
+++ b/Documentation/networking/00-INDEX
@@ -78,8 +78,6 @@ eql.txt
 	- serial IP load balancing
 fib_trie.txt
 	- Level Compressed Trie (LC-trie) notes: a structure for routing.
-filter.txt
-	- Linux Socket Filtering
 fore200e.txt
 	- FORE Systems PCA-200E/SBA-200E ATM NIC driver info.
 framerelay.txt
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.rst
similarity index 100%
rename from Documentation/networking/filter.txt
rename to Documentation/networking/filter.rst
diff --git a/MAINTAINERS b/MAINTAINERS
index fce04d747a1a..a95431e90ab9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2746,7 +2746,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git
 Q:	https://patchwork.ozlabs.org/project/netdev/list/?delegate=77147
 S:	Supported
 F:	arch/x86/net/bpf_jit*
-F:	Documentation/networking/filter.txt
+F:	Documentation/networking/filter.rst
 F:	Documentation/bpf/
 F:	include/linux/bpf*
 F:	include/linux/filter.h
-- 
2.17.1

[PATCH bpf-next 02/13] docs: Update references to filter.rst

[Tobin C. Harding]

Documentation/networking/filter.rst was just renamed.  In order to use RST
references we need to add a label to filter.rst

Add label and update references from filter.txt to filter.rst

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/bpf/index.rst              | 9 ++++-----
 Documentation/networking/filter.rst      | 2 ++
 Documentation/networking/packet_mmap.txt | 2 +-
 tools/bpf/bpf_asm.c                      | 2 +-
 tools/bpf/bpf_dbg.c                      | 2 +-
 5 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 00a8450a602f..192393135c61 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -7,10 +7,10 @@ Filter) facility, with a focus on the extended BPF version (eBPF).
 
 This kernel side documentation is still work in progress.  The main
 textual documentation is (for historical reasons) described in
-`Documentation/networking/filter.txt`_, which describe both classical
-and extended BPF instruction-set.
-The Cilium project also maintains a `BPF and XDP Reference Guide`_
-that goes into great technical depth about the BPF Architecture.
+:ref:`Documentation/networking/filter.rst <bpf_filter>`, which describe
+both classical and extended BPF instruction-set.  The Cilium project also
+maintains a `BPF and XDP Reference Guide`_ that goes into great technical
+depth about the BPF Architecture.
 
 The primary info for the bpf syscall is available in the `man-pages`_
 for `bpf(2)`_.
@@ -30,7 +30,6 @@ Two sets of Questions and Answers (Q&A) are maintained.
 
 
 .. Links:
-.. _Documentation/networking/filter.txt: ../networking/filter.txt
 .. _man-pages: https://www.kernel.org/doc/man-pages/
 .. _bpf(2): http://man7.org/linux/man-pages/man2/bpf.2.html
 .. _BPF and XDP Reference Guide: http://cilium.readthedocs.io/en/latest/bpf/
diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index e6b4ebb2b243..14ce8901c245 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -1,6 +1,8 @@
 Linux Socket Filtering aka Berkeley Packet Filter (BPF)
 =======================================================
 
+.. _bpf_filter:
+
 Introduction
 ------------
 
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt
index 999eb41da81d..494614573c67 100644
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -1051,7 +1051,7 @@ for more information on hardware timestamps.
 -------------------------------------------------------------------------------
 
 - Packet sockets work well together with Linux socket filters, thus you also
-  might want to have a look at Documentation/networking/filter.txt
+  might want to have a look at Documentation/networking/filter.rst
 
 --------------------------------------------------------------------------------
 + THANKS
diff --git a/tools/bpf/bpf_asm.c b/tools/bpf/bpf_asm.c
index c15aef097b04..5040875735db 100644
--- a/tools/bpf/bpf_asm.c
+++ b/tools/bpf/bpf_asm.c
@@ -10,7 +10,7 @@
  *
  * How to get into it:
  *
- * 1) read Documentation/networking/filter.txt
+ * 1) read Documentation/networking/filter.rst
  * 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.
diff --git a/tools/bpf/bpf_dbg.c b/tools/bpf/bpf_dbg.c
index 61b9aa5d6415..d05d8df0ce3b 100644
--- a/tools/bpf/bpf_dbg.c
+++ b/tools/bpf/bpf_dbg.c
@@ -12,7 +12,7 @@
  * 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
+ * More on how to debug BPF opcodes see Documentation/networking/filter.rst
  * which is the main document on BPF. Mini howto for getting started:
  *
  *  1) `./bpf_dbg` to enter the shell (shell cmds denoted with '>'):
-- 
2.17.1

[PATCH bpf-next 03/13] docs: net: Add filter to index toctree

[Tobin C. Harding]

filter.rst was just created (from filter.txt).  We should include it in
the networking docs toctree.

Add filter to Documentation/networking/index.rst toctree.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst
index f0ae9b65dfba..1f926bb347b1 100644
--- a/Documentation/networking/index.rst
+++ b/Documentation/networking/index.rst
@@ -19,6 +19,7 @@ Contents:
    net_failover
    alias
    bridge
+   filter
 
 .. only::  subproject
 
-- 
2.17.1

[PATCH bpf-next 04/13] docs: net: Use correct heading adornments

[Tobin C. Harding]

Conversion to RST format requires the use of correct RST heading
adornments.  While we are at it we can make sure spacing around headings
is uniform.  Choose to use one empty line after any heading.

Use correct levels of heading adornment.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 36 +++++++++++++++++------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 14ce8901c245..19325286780b 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -1,10 +1,11 @@
+=======================================================
 Linux Socket Filtering aka Berkeley Packet Filter (BPF)
 =======================================================
 
 .. _bpf_filter:
 
 Introduction
-------------
+============
 
 Linux Socket Filtering (LSF) is derived from the Berkeley Packet Filter.
 Though there are some distinct differences between the BSD and Linux
@@ -58,7 +59,7 @@ 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:
@@ -169,7 +170,7 @@ 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/bpf/ there's a small helper tool called bpf_asm which can
 be used to write low-level filters for example scenarios mentioned in the
@@ -462,7 +463,7 @@ breakpoints: 0 1
   Exits bpf_dbg.
 
 JIT compiler
-------------
+============
 
 The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
 ARM, ARM64, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT
@@ -569,7 +570,8 @@ 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.
 
 BPF kernel internals
---------------------
+====================
+
 Internally, for the kernel interpreter, a different instruction set
 format with similar underlying principles from BPF described in previous
 paragraphs is being used. However, the instruction set format is modelled
@@ -843,7 +845,7 @@ descends all possible paths. It simulates execution of every insn and observes
 the state change of registers and stack.
 
 eBPF opcode encoding
---------------------
+====================
 
 eBPF is reusing most of the opcode encoding from classic to simplify conversion
 of classic BPF to eBPF. For arithmetic and jump instructions the 8-bit 'code'
@@ -1014,7 +1016,8 @@ Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads
 32-bit immediate value into a register.
 
 eBPF verifier
--------------
+=============
+
 The safety of the eBPF program is determined in two steps.
 
 First step does DAG check to disallow loops and other CFG validation.
@@ -1107,7 +1110,8 @@ all use cases.
 See details of eBPF verifier in kernel/bpf/verifier.c
 
 Register value tracking
------------------------
+=======================
+
 In order to determine the safety of an eBPF program, the verifier must track
 the range of possible values in each register and also in each stack slot.
 This is done with 'struct bpf_reg_state', defined in include/linux/
@@ -1175,7 +1179,7 @@ bytes (NET_IP_ALIGN) gives a 4-byte alignment and so word-sized accesses through
 that pointer are safe.
 
 Direct packet access
---------------------
+====================
 In cls_bpf and act_bpf programs the verifier allows direct access to the packet
 data via skb->data and skb->data_end pointers.
 Ex:
@@ -1261,7 +1265,8 @@ which makes such programs easier to write comparing to LD_ABS insn
 and significantly faster.
 
 eBPF maps
----------
+=========
+
 'maps' is a generic storage of different types for sharing data between kernel
 and userspace.
 
@@ -1300,7 +1305,8 @@ The map is defined by:
   . value size in bytes
 
 Pruning
--------
+=======
+
 The verifier does not actually walk all possible paths through the program.  For
 each new branch to analyse, the verifier looks at all the states it's previously
 been in when at this instruction.  If any of them contain the current state as a
@@ -1316,7 +1322,7 @@ registers it may hold).  They must all be safe for the branch to be pruned.
 This is implemented in states_equal().
 
 Understanding eBPF verifier messages
-------------------------------------
+====================================
 
 The following are few examples of invalid eBPF programs and verifier error
 messages as seen in the log:
@@ -1447,7 +1453,7 @@ Error:
   R0 invalid mem access 'imm'
 
 Testing
--------
+=======
 
 Next to the BPF toolchain, the kernel also ships a test module that contains
 various test cases for classic and internal BPF that can be executed against
@@ -1461,13 +1467,13 @@ via insmod or modprobe against 'test_bpf' module. Results of the test cases
 including timings in nsec can be found in the kernel log (dmesg).
 
 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
-- 
2.17.1

[PATCH bpf-next 05/13] docs: net: Fix indentation issues for code snippets

[Tobin C. Harding]

Recent conversion of filter.txt to RST format did not fix indentation.
Sphinx emits various warnings about indentation.  We should prefix all
code snippets with the RST identifier '::' and indent first column of
snippets 2 characters (inline with other docs in RST format).

Fix indentation issues for code snippets (including spaces to tabs when
appropriate).

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 746 +++++++++++++++-------------
 1 file changed, 398 insertions(+), 348 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 19325286780b..916e7ac01576 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -62,38 +62,40 @@ Structure
 =========
 
 User space applications include <linux/filter.h> which contains the
-following relevant structures:
+following relevant structures::
 
-struct sock_filter {	/* Filter block */
+  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. */
+  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>
-/* ... */
+  #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[] = {
+  /* 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 },
@@ -118,23 +120,23 @@ struct sock_filter code[] = {
 	{ 0x15,  0,  1, 0x00000016 },
 	{ 0x06,  0,  0, 0x0000ffff },
 	{ 0x06,  0,  0, 0x00000000 },
-};
+  };
 
-struct sock_fprog bpf = {
+  struct sock_fprog bpf = {
 	.len = ARRAY_SIZE(code),
 	.filter = code,
-};
+  };
 
-sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
-if (sock < 0)
+  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)
+  ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf));
+  if (ret < 0)
 	/* ... bail out ... */
 
-/* ... */
-close(sock);
+  /* ... */
+  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
@@ -179,17 +181,17 @@ 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:
+The BPF architecture consists of the following basic elements::
 
-  Element          Description
+  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		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):
+consists of the following elements (as already mentioned)::
 
   op:16, jt:8, jf:8, k:32
 
@@ -202,7 +204,7 @@ 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:
+opcodes as defined in linux/filter.h stand for::
 
   Instruction      Addressing mode      Description
 
@@ -245,7 +247,7 @@ opcodes as defined in linux/filter.h stand for:
 
   ret              4, 9                 Return
 
-The next table shows addressing formats from the 2nd column:
+The next table shows addressing formats from the 2nd column::
 
   Addressing mode  Syntax               Description
 
@@ -266,7 +268,7 @@ 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:
+Possible BPF extensions are shown in the following table::
 
   Extension                             Description
 
@@ -290,14 +292,14 @@ Possible BPF extensions are shown in the following table:
 These extensions can also be prefixed with '#'.
 Examples for low-level BPF:
 
-** ARP packets:
+** ARP packets::
 
   ldh [12]
   jne #0x806, drop
   ret #-1
   drop: ret #0
 
-** IPv4 TCP packets:
+** IPv4 TCP packets::
 
   ldh [12]
   jne #0x800, drop
@@ -306,14 +308,15 @@ Examples for low-level BPF:
   ret #-1
   drop: ret #0
 
-** (Accelerated) VLAN w/ id 10:
+** (Accelerated) VLAN w/ id 10::
 
   ld vlan_tci
   jneq #10, drop
   ret #-1
   drop: ret #0
 
-** icmp random packet sampling, 1 in 4
+** icmp random packet sampling, 1 in 4::
+
   ldh [12]
   jne #0x800, drop
   ldb [23]
@@ -325,7 +328,7 @@ Examples for low-level BPF:
   ret #-1
   drop: ret #0
 
-** SECCOMP filter example:
+** SECCOMP filter example::
 
   ld [4]                  /* offsetof(struct seccomp_data, arch) */
   jne #0xc000003e, bad    /* AUDIT_ARCH_X86_64 */
@@ -346,18 +349,18 @@ Examples for low-level BPF:
 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:
+ARP code::
 
-$ ./bpf_asm foo
-4,40 0 0 12,21 0 1 2054,6 0 0 4294967295,6 0 0 0,
+  $ ./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:
+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 },
+  $ ./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
@@ -366,9 +369,9 @@ bpf_dbg under tools/bpf/ 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:
+Starting bpf_dbg is trivial and just requires issuing::
 
-# ./bpf_dbg
+  # ./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
@@ -381,86 +384,87 @@ file "~/.bpf_dbg_init" and the command history is stored in the file
 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.
+::
+
+  > 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
 ============
@@ -468,23 +472,23 @@ JIT compiler
 The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
 ARM, ARM64, MIPS 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:
+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:
+opcode image into the kernel log via::
 
   echo 2 > /proc/sys/net/core/bpf_jit_enable
 
-Example output from dmesg:
+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
+  [ 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
 
 When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and
 setting any other value than that will return in failure. This is even the case for
@@ -493,77 +497,77 @@ is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is t
 generally recommended approach instead.
 
 In the kernel source tree under tools/bpf/, 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
+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:
+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
+  # ./bpf_jit_disasm -o
+  70 bytes emitted from JIT compiler (pass:3, flen:6)
+  ffffffffa0069c8f + <x>:
+     0:	push   %rbp
 	55
-   1:	mov    %rsp,%rbp
+     1:	mov    %rsp,%rbp
 	48 89 e5
-   4:	sub    $0x60,%rsp
+     4:	sub    $0x60,%rsp
 	48 83 ec 60
-   8:	mov    %rbx,-0x8(%rbp)
+     8:	mov    %rbx,-0x8(%rbp)
 	48 89 5d f8
-   c:	mov    0x68(%rdi),%r9d
+     c:	mov    0x68(%rdi),%r9d
 	44 8b 4f 68
-  10:	sub    0x6c(%rdi),%r9d
+    10:	sub    0x6c(%rdi),%r9d
 	44 2b 4f 6c
-  14:	mov    0xd8(%rdi),%r8
+    14:	mov    0xd8(%rdi),%r8
 	4c 8b 87 d8 00 00 00
-  1b:	mov    $0xc,%esi
+    1b:	mov    $0xc,%esi
 	be 0c 00 00 00
-  20:	callq  0xffffffffe0ff9442
+    20:	callq  0xffffffffe0ff9442
 	e8 1d 94 ff e0
-  25:	cmp    $0x800,%eax
+    25:	cmp    $0x800,%eax
 	3d 00 08 00 00
-  2a:	jne    0x0000000000000042
+    2a:	jne    0x0000000000000042
 	75 16
-  2c:	mov    $0x17,%esi
+    2c:	mov    $0x17,%esi
 	be 17 00 00 00
-  31:	callq  0xffffffffe0ff945e
+    31:	callq  0xffffffffe0ff945e
 	e8 28 94 ff e0
-  36:	cmp    $0x1,%eax
+    36:	cmp    $0x1,%eax
 	83 f8 01
-  39:	jne    0x0000000000000042
+    39:	jne    0x0000000000000042
 	75 07
-  3b:	mov    $0xffff,%eax
+    3b:	mov    $0xffff,%eax
 	b8 ff ff 00 00
-  40:	jmp    0x0000000000000044
+    40:	jmp    0x0000000000000044
 	eb 02
-  42:	xor    %eax,%eax
+    42:	xor    %eax,%eax
 	31 c0
-  44:	leaveq
+    44:	leaveq
 	c9
-  45:	retq
+    45:	retq
 	c3
 
 For BPF JIT developers, bpf_jit_disasm, bpf_asm and bpf_dbg provides a useful
@@ -663,9 +667,18 @@ Some core changes of the new internal format:
 
 - Conditional jt/jf targets replaced with jt/fall-through:
 
-  While the original design has constructs such as "if (cond) jump_true;
-  else jump_false;", they are being replaced into alternative constructs like
-  "if (cond) jump_true; /* else fall-through */".
+  While the original design has constructs such as::
+
+    if (cond)
+      jump_true;
+    else
+      jump_false;
+
+  they are being replaced into alternative constructs like::
+
+    if (cond)
+      jump_true;
+    /* else fall-through */
 
 - Introduces bpf_call insn and register passing convention for zero overhead
   calls from/to other kernel functions:
@@ -684,30 +697,30 @@ Some core changes of the new internal format:
   a return value of the function. Since R6 - R9 are callee saved, their state
   is preserved across the call.
 
-  For example, consider three C functions:
+  For example, consider three C functions::
 
-  u64 f1() { return (*_f2)(1); }
-  u64 f2(u64 a) { return f3(a + 1, a); }
-  u64 f3(u64 a, u64 b) { return a - b; }
+    u64 f1() { return (*_f2)(1); }
+    u64 f2(u64 a) { return f3(a + 1, a); }
+    u64 f3(u64 a, u64 b) { return a - b; }
 
-  GCC can compile f1, f3 into x86_64:
+  GCC can compile f1, f3 into x86_64::
 
-  f1:
-    movl $1, %edi
-    movq _f2(%rip), %rax
-    jmp  *%rax
-  f3:
-    movq %rdi, %rax
-    subq %rsi, %rax
-    ret
+    f1:
+      movl $1, %edi
+      movq _f2(%rip), %rax
+      jmp  *%rax
+    f3:
+      movq %rdi, %rax
+      subq %rsi, %rax
+      ret
 
-  Function f2 in eBPF may look like:
+  Function f2 in eBPF may look like::
 
-  f2:
-    bpf_mov R2, R1
-    bpf_add R1, 1
-    bpf_call f3
-    bpf_exit
+    f2:
+      bpf_mov R2, R1
+      bpf_add R1, 1
+      bpf_call f3
+      bpf_exit
 
   If f2 is JITed and the pointer stored to '_f2'. The calls f1 -> f2 -> f3 and
   returns will be seamless. Without JIT, __bpf_prog_run() interpreter needs to
@@ -720,7 +733,7 @@ Some core changes of the new internal format:
   in the future.
 
   On 64-bit architectures all register map to HW registers one to one. For
-  example, x86_64 JIT compiler can map them as ...
+  example, x86_64 JIT compiler can map them as ... ::
 
     R0 - rax
     R1 - rdi
@@ -737,7 +750,7 @@ Some core changes of the new internal format:
   ... since x86_64 ABI mandates rdi, rsi, rdx, rcx, r8, r9 for argument passing
   and rbx, r12 - r15 are callee saved.
 
-  Then the following internal BPF pseudo-program:
+  Then the following internal BPF pseudo-program::
 
     bpf_mov R6, R1 /* save ctx */
     bpf_mov R2, 2
@@ -755,7 +768,7 @@ Some core changes of the new internal format:
     bpf_add R0, R7
     bpf_exit
 
-  After JIT to x86_64 may look like:
+  After JIT to x86_64 may look like::
 
     push %rbp
     mov %rsp,%rbp
@@ -781,11 +794,11 @@ Some core changes of the new internal format:
     leaveq
     retq
 
-  Which is in this example equivalent in C to:
+  Which is in this example equivalent in C to::
 
     u64 bpf_filter(u64 ctx)
     {
-        return foo(ctx, 2, 3, 4, 5) + bar(ctx, 6, 7, 8, 9);
+	return foo(ctx, 2, 3, 4, 5) + bar(ctx, 6, 7, 8, 9);
     }
 
   In-kernel functions foo() and bar() with prototype: u64 (*)(u64 arg1, u64
@@ -795,7 +808,7 @@ Some core changes of the new internal format:
   interpreter. R0-R5 are scratch registers, so eBPF program needs to preserve
   them across the calls as defined by calling convention.
 
-  For example the following program is invalid:
+  For example the following program is invalid::
 
     bpf_mov R1, 1
     bpf_call foo
@@ -814,7 +827,7 @@ The input context pointer for invoking the interpreter function is generic,
 its content is defined by a specific use case. For seccomp register R1 points
 to seccomp_data, for converted BPF filters R1 points to a skb.
 
-A program, that is translated internally consists of the following elements:
+A program, that is translated internally consists of the following elements::
 
   op:16, jt:8, jf:8, k:32    ==>    op:8, dst_reg:4, src_reg:4, off:16, imm:32
 
@@ -849,7 +862,7 @@ eBPF opcode encoding
 
 eBPF is reusing most of the opcode encoding from classic to simplify conversion
 of classic BPF to eBPF. For arithmetic and jump instructions the 8-bit 'code'
-field is divided into three parts:
+field is divided into three parts::
 
   +----------------+--------+--------------------+
   |   4 bits       |  1 bit |   3 bits           |
@@ -857,7 +870,7 @@ field is divided into three parts:
   +----------------+--------+--------------------+
   (MSB)                                      (LSB)
 
-Three LSB bits store instruction class which is one of:
+Three LSB bits store instruction class which is one of::
 
   Classic BPF classes:    eBPF classes:
 
@@ -871,23 +884,24 @@ Three LSB bits store instruction class which is one of:
   BPF_MISC  0x07          BPF_ALU64 0x07
 
 When BPF_CLASS(code) == BPF_ALU or BPF_JMP, 4th bit encodes source operand ...
+::
 
   BPF_K     0x00
   BPF_X     0x08
 
- * in classic BPF, this means:
+in classic BPF, this means::
 
   BPF_SRC(code) == BPF_X - use register X as source operand
   BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand
 
- * in eBPF, this means:
+in eBPF, this means::
 
   BPF_SRC(code) == BPF_X - use 'src_reg' register as source operand
   BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand
 
 ... and four MSB bits store operation code.
 
-If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:
+If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of::
 
   BPF_ADD   0x00
   BPF_SUB   0x10
@@ -904,7 +918,7 @@ If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:
   BPF_ARSH  0xc0  /* eBPF only: sign extending shift right */
   BPF_END   0xd0  /* eBPF only: endianness conversion */
 
-If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of:
+If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of::
 
   BPF_JA    0x00
   BPF_JEQ   0x10
@@ -941,7 +955,7 @@ in eBPF means function exit only. The eBPF program needs to store return
 value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is currently
 unused and reserved for future use.
 
-For load and store instructions the 8-bit 'code' field is divided as:
+For load and store instructions the 8-bit 'code' field is divided as::
 
   +--------+--------+-------------------+
   | 3 bits | 2 bits |   3 bits          |
@@ -949,21 +963,21 @@ For load and store instructions the 8-bit 'code' field is divided as:
   +--------+--------+-------------------+
   (MSB)                             (LSB)
 
-Size modifier is one of ...
+Size modifier is one of ... ::
 
   BPF_W   0x00    /* word */
   BPF_H   0x08    /* half word */
   BPF_B   0x10    /* byte */
   BPF_DW  0x18    /* eBPF only, double word */
 
-... which encodes size of load/store operation:
+... which encodes size of load/store operation::
 
- B  - 1 byte
- H  - 2 byte
- W  - 4 byte
- DW - 8 byte (eBPF only)
+  B  - 1 byte
+  H  - 2 byte
+  W  - 4 byte
+  DW - 8 byte (eBPF only)
 
-Mode modifier is one of:
+Mode modifier is one of::
 
   BPF_IMM  0x00  /* used for 32-bit mov in classic BPF and 64-bit in eBPF */
   BPF_ABS  0x20
@@ -991,20 +1005,20 @@ the interpreter will abort the execution of the program. JIT compilers
 therefore must preserve this property. src_reg and imm32 fields are
 explicit inputs to these instructions.
 
-For example:
+For example::
 
   BPF_IND | BPF_W | BPF_LD means:
 
     R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32))
     and R1 - R5 were scratched.
 
-Unlike classic BPF instruction set, eBPF has generic load/store operations:
+Unlike classic BPF instruction set, eBPF has generic load/store operations::
 
-BPF_MEM | <size> | BPF_STX:  *(size *) (dst_reg + off) = src_reg
-BPF_MEM | <size> | BPF_ST:   *(size *) (dst_reg + off) = imm32
-BPF_MEM | <size> | BPF_LDX:  dst_reg = *(size *) (src_reg + off)
-BPF_XADD | BPF_W  | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg
-BPF_XADD | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg
+  BPF_MEM | <size> | BPF_STX:  *(size *) (dst_reg + off) = src_reg
+  BPF_MEM | <size> | BPF_ST:   *(size *) (dst_reg + off) = imm32
+  BPF_MEM | <size> | BPF_LDX:  dst_reg = *(size *) (src_reg + off)
+  BPF_XADD | BPF_W  | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg
+  BPF_XADD | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg
 
 Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. Note that 1 and
 2 byte atomic increments are not supported.
@@ -1037,29 +1051,35 @@ since addition of two valid pointers makes invalid pointer.
 (In 'secure' mode verifier will reject any type of pointer arithmetic to make
 sure that kernel addresses don't leak to unprivileged users)
 
-If register was never written to, it's not readable:
+If register was never written to, it's not readable::
+
   bpf_mov R0 = R2
   bpf_exit
+
 will be rejected, since R2 is unreadable at the start of the program.
 
 After kernel function call, R1-R5 are reset to unreadable and
 R0 has a return type of the function.
 
-Since R6-R9 are callee saved, their state is preserved across the call.
+Since R6-R9 are callee saved, their state is preserved across the call. ::
+
   bpf_mov R6 = 1
   bpf_call foo
   bpf_mov R0 = R6
   bpf_exit
+
 is a correct program. If there was R1 instead of R6, it would have
 been rejected.
 
 load/store instructions are allowed only with registers of valid types, which
 are PTR_TO_CTX, PTR_TO_MAP, PTR_TO_STACK. They are bounds and alignment checked.
-For example:
+For example::
+
  bpf_mov R1 = 1
  bpf_mov R2 = 2
  bpf_xadd *(u32 *)(R1 + 3) += R2
  bpf_exit
+
 will be rejected, since R1 doesn't have a valid pointer type at the time of
 execution of instruction bpf_xadd.
 
@@ -1067,8 +1087,10 @@ At the start R1 type is PTR_TO_CTX (a pointer to generic 'struct bpf_context')
 A callback is used to customize verifier to restrict eBPF program access to only
 certain fields within ctx structure with specified size and alignment.
 
-For example, the following insn:
+For example, the following insn::
+
   bpf_ld R0 = *(u32 *)(R6 + 8)
+
 intends to load a word from address R6 + 8 and store it into R0
 If R6=PTR_TO_CTX, via is_valid_access() callback the verifier will know
 that offset 8 of size 4 bytes can be accessed for reading, otherwise
@@ -1080,9 +1102,11 @@ so it will fail verification, since it's out of bounds.
 The verifier will allow eBPF program to read data from stack only after
 it wrote into it.
 Classic BPF verifier does similar check with M[0-15] memory slots.
-For example:
+For example::
+
   bpf_ld R0 = *(u32 *)(R10 - 4)
   bpf_exit
+
 is invalid program.
 Though R10 is correct read-only register and has type PTR_TO_STACK
 and R10 - 4 is within stack bounds, there were no stores into that location.
@@ -1118,19 +1142,21 @@ This is done with 'struct bpf_reg_state', defined in include/linux/
 bpf_verifier.h, which unifies tracking of scalar and pointer values.  Each
 register state has a type, which is either NOT_INIT (the register has not been
 written to), SCALAR_VALUE (some value which is not usable as a pointer), or a
-pointer type.  The types of pointers describe their base, as follows:
+pointer type.  The types of pointers describe their base, as follows::
+
     PTR_TO_CTX          Pointer to bpf_context.
     CONST_PTR_TO_MAP    Pointer to struct bpf_map.  "Const" because arithmetic
-                        on these pointers is forbidden.
+			on these pointers is forbidden.
     PTR_TO_MAP_VALUE    Pointer to the value stored in a map element.
     PTR_TO_MAP_VALUE_OR_NULL
-                        Either a pointer to a map value, or NULL; map accesses
-                        (see section 'eBPF maps', below) return this type,
-                        which becomes a PTR_TO_MAP_VALUE when checked != NULL.
-                        Arithmetic on these pointers is forbidden.
+			Either a pointer to a map value, or NULL; map accesses
+			(see section 'eBPF maps', below) return this type,
+			which becomes a PTR_TO_MAP_VALUE when checked != NULL.
+			Arithmetic on these pointers is forbidden.
     PTR_TO_STACK        Frame pointer.
     PTR_TO_PACKET       skb->data.
     PTR_TO_PACKET_END   skb->data + headlen; arithmetic forbidden.
+
 However, a pointer may be offset from this base (as a result of pointer
 arithmetic), and this is tracked in two parts: the 'fixed offset' and 'variable
 offset'.  The former is used when an exactly-known value (e.g. an immediate
@@ -1182,14 +1208,15 @@ Direct packet access
 ====================
 In cls_bpf and act_bpf programs the verifier allows direct access to the packet
 data via skb->data and skb->data_end pointers.
-Ex:
-1:  r4 = *(u32 *)(r1 +80)  /* load skb->data_end */
-2:  r3 = *(u32 *)(r1 +76)  /* load skb->data */
-3:  r5 = r3
-4:  r5 += 14
-5:  if r5 > r4 goto pc+16
-R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp
-6:  r0 = *(u16 *)(r3 +12) /* access 12 and 13 bytes of the packet */
+Ex::
+
+  1:  r4 = *(u32 *)(r1 +80)  /* load skb->data_end */
+  2:  r3 = *(u32 *)(r1 +76)  /* load skb->data */
+  3:  r5 = r3
+  4:  r5 += 14
+  5:  if r5 > r4 goto pc+16
+   R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp
+  6:  r0 = *(u16 *)(r3 +12) /* access 12 and 13 bytes of the packet */
 
 this 2byte load from the packet is safe to do, since the program author
 did check 'if (skb->data + 14 > skb->data_end) goto err' at insn #5 which
@@ -1204,23 +1231,25 @@ to the packet data, but constant 14 was added to the register, so
 it now points to 'skb->data + 14' and accessible range is [R5, R5 + 14 - 14)
 which is zero bytes.
 
-More complex packet access may look like:
- R0=inv1 R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp
- 6:  r0 = *(u8 *)(r3 +7) /* load 7th byte from the packet */
- 7:  r4 = *(u8 *)(r3 +12)
- 8:  r4 *= 14
- 9:  r3 = *(u32 *)(r1 +76) /* load skb->data */
-10:  r3 += r4
-11:  r2 = r1
-12:  r2 <<= 48
-13:  r2 >>= 48
-14:  r3 += r2
-15:  r2 = r3
-16:  r2 += 8
-17:  r1 = *(u32 *)(r1 +80) /* load skb->data_end */
-18:  if r2 > r1 goto pc+2
- R0=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=pkt_end R2=pkt(id=2,off=8,r=8) R3=pkt(id=2,off=0,r=8) R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)) R5=pkt(id=0,off=14,r=14) R10=fp
-19:  r1 = *(u8 *)(r3 +4)
+More complex packet access may look like::
+
+  R0=inv1 R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp
+   6:  r0 = *(u8 *)(r3 +7) /* load 7th byte from the packet */
+   7:  r4 = *(u8 *)(r3 +12)
+   8:  r4 *= 14
+   9:  r3 = *(u32 *)(r1 +76) /* load skb->data */
+  10:  r3 += r4
+  11:  r2 = r1
+  12:  r2 <<= 48
+  13:  r2 >>= 48
+  14:  r3 += r2
+  15:  r2 = r3
+  16:  r2 += 8
+  17:  r1 = *(u32 *)(r1 +80) /* load skb->data_end */
+  18:  if r2 > r1 goto pc+2
+   R0=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=pkt_end R2=pkt(id=2,off=8,r=8) R3=pkt(id=2,off=0,r=8) R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)) R5=pkt(id=0,off=14,r=14) R10=fp
+  19:  r1 = *(u8 *)(r3 +4)
+
 The state of the register R3 is R3=pkt(id=2,off=0,r=8)
 id=2 means that two 'r3 += rX' instructions were seen, so r3 points to some
 offset within a packet and since the program author did
@@ -1246,7 +1275,8 @@ which calls adjust_ptr_min_max_vals() for adding pointer to scalar (or vice
 versa) and adjust_scalar_min_max_vals() for operations on two scalars.
 
 The end result is that bpf program author can access packet directly
-using normal C code as:
+using normal C code as::
+
   void *data = (void *)(long)skb->data;
   void *data_end = (void *)(long)skb->data_end;
   struct eth_hdr *eth = data;
@@ -1254,13 +1284,14 @@ using normal C code as:
   struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph);
 
   if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end)
-          return 0;
+	return 0;
   if (eth->h_proto != htons(ETH_P_IP))
-          return 0;
+	return 0;
   if (iph->protocol != IPPROTO_UDP || iph->ihl != 5)
-          return 0;
+	return 0;
   if (udp->dest == 53 || udp->source == 9)
-          ...;
+	...;
+
 which makes such programs easier to write comparing to LD_ABS insn
 and significantly faster.
 
@@ -1271,6 +1302,7 @@ eBPF maps
 and userspace.
 
 The maps are accessed from user space via BPF syscall, which has commands:
+
 - create a map with given type and attributes
   map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
   using attr->map_type, attr->key_size, attr->value_size, attr->max_entries
@@ -1327,66 +1359,79 @@ Understanding eBPF verifier messages
 The following are few examples of invalid eBPF programs and verifier error
 messages as seen in the log:
 
-Program with unreachable instructions:
-static struct bpf_insn prog[] = {
-  BPF_EXIT_INSN(),
-  BPF_EXIT_INSN(),
-};
-Error:
-  unreachable insn 1
+Program with unreachable instructions::
+
+  static struct bpf_insn prog[] = {
+    BPF_EXIT_INSN(),
+    BPF_EXIT_INSN(),
+  };
+
+  Error:
+    unreachable insn 1
+
+Program that reads uninitialized register::
 
-Program that reads uninitialized register:
   BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
   BPF_EXIT_INSN(),
-Error:
-  0: (bf) r0 = r2
-  R2 !read_ok
 
-Program that doesn't initialize R0 before exiting:
+  Error:
+    0: (bf) r0 = r2
+    R2 !read_ok
+
+Program that doesn't initialize R0 before exiting::
+
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_1),
   BPF_EXIT_INSN(),
-Error:
-  0: (bf) r2 = r1
-  1: (95) exit
-  R0 !read_ok
 
-Program that accesses stack out of bounds:
+  Error:
+    0: (bf) r2 = r1
+    1: (95) exit
+    R0 !read_ok
+
+Program that accesses stack out of bounds::
+
   BPF_ST_MEM(BPF_DW, BPF_REG_10, 8, 0),
   BPF_EXIT_INSN(),
-Error:
-  0: (7a) *(u64 *)(r10 +8) = 0
-  invalid stack off=8 size=8
 
-Program that doesn't initialize stack before passing its address into function:
+  Error:
+    0: (7a) *(u64 *)(r10 +8) = 0
+    invalid stack off=8 size=8
+
+Program that doesn't initialize stack before passing its address into function::
+
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
   BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
   BPF_LD_MAP_FD(BPF_REG_1, 0),
   BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
   BPF_EXIT_INSN(),
-Error:
-  0: (bf) r2 = r10
-  1: (07) r2 += -8
-  2: (b7) r1 = 0x0
-  3: (85) call 1
-  invalid indirect read from stack off -8+0 size 8
-
-Program that uses invalid map_fd=0 while calling to map_lookup_elem() function:
+
+  Error:
+    0: (bf) r2 = r10
+    1: (07) r2 += -8
+    2: (b7) r1 = 0x0
+    3: (85) call 1
+    invalid indirect read from stack off -8+0 size 8
+
+Program that uses invalid map_fd=0 while calling to map_lookup_elem() function::
+
   BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
   BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
   BPF_LD_MAP_FD(BPF_REG_1, 0),
   BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
   BPF_EXIT_INSN(),
-Error:
-  0: (7a) *(u64 *)(r10 -8) = 0
-  1: (bf) r2 = r10
-  2: (07) r2 += -8
-  3: (b7) r1 = 0x0
-  4: (85) call 1
-  fd 0 is not pointing to valid bpf_map
+
+  Error:
+    0: (7a) *(u64 *)(r10 -8) = 0
+    1: (bf) r2 = r10
+    2: (07) r2 += -8
+    3: (b7) r1 = 0x0
+    4: (85) call 1
+    fd 0 is not pointing to valid bpf_map
 
 Program that doesn't check return value of map_lookup_elem() before accessing
-map element:
+map element::
+
   BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
   BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
@@ -1394,17 +1439,19 @@ map element:
   BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
   BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 0),
   BPF_EXIT_INSN(),
-Error:
-  0: (7a) *(u64 *)(r10 -8) = 0
-  1: (bf) r2 = r10
-  2: (07) r2 += -8
-  3: (b7) r1 = 0x0
-  4: (85) call 1
-  5: (7a) *(u64 *)(r0 +0) = 0
-  R0 invalid mem access 'map_value_or_null'
+
+  Error:
+    0: (7a) *(u64 *)(r10 -8) = 0
+    1: (bf) r2 = r10
+    2: (07) r2 += -8
+    3: (b7) r1 = 0x0
+    4: (85) call 1
+    5: (7a) *(u64 *)(r0 +0) = 0
+    R0 invalid mem access 'map_value_or_null'
 
 Program that correctly checks map_lookup_elem() returned value for NULL, but
-accesses the memory with incorrect alignment:
+accesses the memory with incorrect alignment::
+
   BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
   BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
@@ -1413,20 +1460,22 @@ accesses the memory with incorrect alignment:
   BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
   BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0),
   BPF_EXIT_INSN(),
-Error:
-  0: (7a) *(u64 *)(r10 -8) = 0
-  1: (bf) r2 = r10
-  2: (07) r2 += -8
-  3: (b7) r1 = 1
-  4: (85) call 1
-  5: (15) if r0 == 0x0 goto pc+1
-   R0=map_ptr R10=fp
-  6: (7a) *(u64 *)(r0 +4) = 0
-  misaligned access off 4 size 8
+
+  Error:
+    0: (7a) *(u64 *)(r10 -8) = 0
+    1: (bf) r2 = r10
+    2: (07) r2 += -8
+    3: (b7) r1 = 1
+    4: (85) call 1
+    5: (15) if r0 == 0x0 goto pc+1
+     R0=map_ptr R10=fp
+    6: (7a) *(u64 *)(r0 +4) = 0
+    misaligned access off 4 size 8
 
 Program that correctly checks map_lookup_elem() returned value for NULL and
 accesses memory with correct alignment in one side of 'if' branch, but fails
-to do so in the other side of 'if' branch:
+to do so in the other side of 'if' branch::
+
   BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
   BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
   BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
@@ -1437,20 +1486,21 @@ to do so in the other side of 'if' branch:
   BPF_EXIT_INSN(),
   BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 1),
   BPF_EXIT_INSN(),
-Error:
-  0: (7a) *(u64 *)(r10 -8) = 0
-  1: (bf) r2 = r10
-  2: (07) r2 += -8
-  3: (b7) r1 = 1
-  4: (85) call 1
-  5: (15) if r0 == 0x0 goto pc+2
-   R0=map_ptr R10=fp
-  6: (7a) *(u64 *)(r0 +0) = 0
-  7: (95) exit
-
-  from 5 to 8: R0=imm0 R10=fp
-  8: (7a) *(u64 *)(r0 +0) = 1
-  R0 invalid mem access 'imm'
+
+  Error:
+    0: (7a) *(u64 *)(r10 -8) = 0
+    1: (bf) r2 = r10
+    2: (07) r2 += -8
+    3: (b7) r1 = 1
+    4: (85) call 1
+    5: (15) if r0 == 0x0 goto pc+2
+     R0=map_ptr R10=fp
+    6: (7a) *(u64 *)(r0 +0) = 0
+    7: (95) exit
+
+    from 5 to 8: R0=imm0 R10=fp
+    8: (7a) *(u64 *)(r0 +0) = 1
+    R0 invalid mem access 'imm'
 
 Testing
 =======
@@ -1458,7 +1508,7 @@ Testing
 Next to the BPF toolchain, the kernel also ships a test module that contains
 various test cases for classic and internal BPF that can be executed against
 the BPF interpreter and JIT compiler. It can be found in lib/test_bpf.c and
-enabled via Kconfig:
+enabled via Kconfig::
 
   CONFIG_TEST_BPF=m
 
-- 
2.17.1

[PATCH bpf-next 06/13] docs: net: Remove non-standard identifiers

[Tobin C. Harding]

File uses a custom identifier '**'.  Documentation build is cleaner if
we use standard identifiers.  Usage is not _really_ a list and its not
_really_ a section header.  Lets just remove the double stars since
we just added code snippet format for following text so the identifiers
are redundant now.

Remove non-standard identifiers '**'.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 916e7ac01576..62630e8f023a 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -292,14 +292,14 @@ Possible BPF extensions are shown in the following table::
 These extensions can also be prefixed with '#'.
 Examples for low-level BPF:
 
-** ARP packets::
+ARP packets::
 
   ldh [12]
   jne #0x806, drop
   ret #-1
   drop: ret #0
 
-** IPv4 TCP packets::
+IPv4 TCP packets::
 
   ldh [12]
   jne #0x800, drop
@@ -308,14 +308,14 @@ Examples for low-level BPF:
   ret #-1
   drop: ret #0
 
-** (Accelerated) VLAN w/ id 10::
+(Accelerated) VLAN w/ id 10::
 
   ld vlan_tci
   jneq #10, drop
   ret #-1
   drop: ret #0
 
-** icmp random packet sampling, 1 in 4::
+icmp random packet sampling, 1 in 4::
 
   ldh [12]
   jne #0x800, drop
@@ -328,7 +328,7 @@ Examples for low-level BPF:
   ret #-1
   drop: ret #0
 
-** SECCOMP filter example::
+SECCOMP filter example::
 
   ld [4]                  /* offsetof(struct seccomp_data, arch) */
   jne #0xc000003e, bad    /* AUDIT_ARCH_X86_64 */
-- 
2.17.1

[PATCH bpf-next 07/13] docs: net: Use double ticks instead of single quote

[Tobin C. Harding]

Currently there are many places that use single quote to guard text.
RST has the double tick for code.  Also the document is full of
identifiers.  Using too many double ticks hinders reading the file in
text format.  For this reason we only change a few select cases to use
the double tick.

Sphinx also emits a bunch of cryptic warnings due to not correctly
wrapping lines.

These two fixes touch the same lines so its all in one patch.

Use double ticks instead of single quote to guard inline code.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 100 ++++++++++++++--------------
 1 file changed, 49 insertions(+), 51 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 62630e8f023a..f9ec58144ed3 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -289,7 +289,7 @@ Possible BPF extensions are shown in the following table::
   vlan_tpid                             skb->vlan_proto
   rand                                  prandom_u32()
 
-These extensions can also be prefixed with '#'.
+These extensions can also be prefixed with ``#``.
 Examples for low-level BPF:
 
 ARP packets::
@@ -382,7 +382,7 @@ 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).
+support (follow-up example commands starting with ``>`` denote bpf_dbg shell).
 The usual workflow would be to ...
 ::
 
@@ -689,7 +689,7 @@ Some core changes of the new internal format:
   to in-kernel function. If R1 - R5 registers are mapped to CPU registers
   that are used for argument passing on given architecture, the JIT compiler
   doesn't need to emit extra moves. Function arguments will be in the correct
-  registers and BPF_CALL instruction will be JITed as single 'call' HW
+  registers and BPF_CALL instruction will be JITed as single ``call`` HW
   instruction. This calling convention was picked to cover common call
   situations without performance penalty.
 
@@ -803,7 +803,7 @@ Some core changes of the new internal format:
 
   In-kernel functions foo() and bar() with prototype: u64 (*)(u64 arg1, u64
   arg2, u64 arg3, u64 arg4, u64 arg5); will receive arguments in proper
-  registers and place their return value into '%rax' which is R0 in eBPF.
+  registers and place their return value into ``%rax`` which is R0 in eBPF.
   Prologue and epilogue are emitted by JIT and are implicit in the
   interpreter. R0-R5 are scratch registers, so eBPF program needs to preserve
   them across the calls as defined by calling convention.
@@ -831,7 +831,7 @@ A program, that is translated internally consists of the following elements::
 
   op:16, jt:8, jf:8, k:32    ==>    op:8, dst_reg:4, src_reg:4, off:16, imm:32
 
-So far 87 internal BPF instructions were implemented. 8-bit 'op' opcode field
+So far 87 internal BPF instructions were implemented. 8-bit ``op`` opcode field
 has room for new instructions. Some of them may use 16/24/32 byte encoding. New
 instructions must be multiple of 8 bytes to preserve backward compatibility.
 
@@ -992,7 +992,7 @@ eBPF has two non-generic instructions: (BPF_ABS | <size> | BPF_LD) and
 
 They had to be carried over from classic to have strong performance of
 socket filters running in eBPF interpreter. These instructions can only
-be used when interpreter context is a pointer to 'struct sk_buff' and
+be used when interpreter context is a pointer to ``struct sk_buff`` and
 have seven implicit operands. Register R6 is an implicit input that must
 contain pointer to sk_buff. Register R0 is an implicit output which contains
 the data fetched from the packet. Registers R1-R5 are scratch registers
@@ -1024,7 +1024,7 @@ Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. Note that 1 and
 2 byte atomic increments are not supported.
 
 eBPF has one 16-byte instruction: BPF_LD | BPF_DW | BPF_IMM which consists
-of two consecutive 'struct bpf_insn' 8-byte blocks and interpreted as single
+of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single
 instruction that loads 64-bit immediate value into a dst_reg.
 Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads
 32-bit immediate value into a register.
@@ -1083,7 +1083,7 @@ For example::
 will be rejected, since R1 doesn't have a valid pointer type at the time of
 execution of instruction bpf_xadd.
 
-At the start R1 type is PTR_TO_CTX (a pointer to generic 'struct bpf_context')
+At the start R1 type is PTR_TO_CTX (a pointer to generic ``struct bpf_context``)
 A callback is used to customize verifier to restrict eBPF program access to only
 certain fields within ctx structure with specified size and alignment.
 
@@ -1138,7 +1138,7 @@ Register value tracking
 
 In order to determine the safety of an eBPF program, the verifier must track
 the range of possible values in each register and also in each stack slot.
-This is done with 'struct bpf_reg_state', defined in include/linux/
+This is done with ``struct bpf_reg_state``, defined in include/linux/
 bpf_verifier.h, which unifies tracking of scalar and pointer values.  Each
 register state has a type, which is either NOT_INIT (the register has not been
 written to), SCALAR_VALUE (some value which is not usable as a pointer), or a
@@ -1219,7 +1219,7 @@ Ex::
   6:  r0 = *(u16 *)(r3 +12) /* access 12 and 13 bytes of the packet */
 
 this 2byte load from the packet is safe to do, since the program author
-did check 'if (skb->data + 14 > skb->data_end) goto err' at insn #5 which
+did check ``if (skb->data + 14 > skb->data_end) goto err`` at insn #5 which
 means that in the fall-through case the register R3 (which points to skb->data)
 has at least 14 directly accessible bytes. The verifier marks it
 as R3=pkt(id=0,off=0,r=14).
@@ -1228,7 +1228,7 @@ off=0 means that no additional constants were added.
 r=14 is the range of safe access which means that bytes [R3, R3 + 14) are ok.
 Note that R5 is marked as R5=pkt(id=0,off=14,r=14). It also points
 to the packet data, but constant 14 was added to the register, so
-it now points to 'skb->data + 14' and accessible range is [R5, R5 + 14 - 14)
+it now points to ``skb->data + 14`` and accessible range is [R5, R5 + 14 - 14)
 which is zero bytes.
 
 More complex packet access may look like::
@@ -1250,29 +1250,30 @@ More complex packet access may look like::
    R0=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=pkt_end R2=pkt(id=2,off=8,r=8) R3=pkt(id=2,off=0,r=8) R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)) R5=pkt(id=0,off=14,r=14) R10=fp
   19:  r1 = *(u8 *)(r3 +4)
 
-The state of the register R3 is R3=pkt(id=2,off=0,r=8)
-id=2 means that two 'r3 += rX' instructions were seen, so r3 points to some
-offset within a packet and since the program author did
-'if (r3 + 8 > r1) goto err' at insn #18, the safe range is [R3, R3 + 8).
-The verifier only allows 'add'/'sub' operations on packet registers. Any other
-operation will set the register state to 'SCALAR_VALUE' and it won't be
-available for direct packet access.
-Operation 'r3 += rX' may overflow and become less than original skb->data,
-therefore the verifier has to prevent that.  So when it sees 'r3 += rX'
-instruction and rX is more than 16-bit value, any subsequent bounds-check of r3
-against skb->data_end will not give us 'range' information, so attempts to read
-through the pointer will give "invalid access to packet" error.
-Ex. after insn 'r4 = *(u8 *)(r3 +12)' (insn #7 above) the state of r4 is
-R4=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) which means that upper 56 bits
-of the register are guaranteed to be zero, and nothing is known about the lower
-8 bits. After insn 'r4 *= 14' the state becomes
-R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)), since multiplying an 8-bit
-value by constant 14 will keep upper 52 bits as zero, also the least significant
-bit will be zero as 14 is even.  Similarly 'r2 >>= 48' will make
-R2=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)), since the shift is not sign
-extending.  This logic is implemented in adjust_reg_min_max_vals() function,
-which calls adjust_ptr_min_max_vals() for adding pointer to scalar (or vice
-versa) and adjust_scalar_min_max_vals() for operations on two scalars.
+The state of the register R3 is R3=pkt(id=2,off=0,r=8) id=2 means that
+two ``r3 += rX`` instructions were seen, so r3 points to some offset within
+a packet and since the program author did ``if (r3 + 8 > r1) goto err`` at
+insn #18, the safe range is [R3, R3 + 8).  The verifier only allows
+'add'/'sub' operations on packet registers. Any other operation will set
+the register state to 'SCALAR_VALUE' and it won't be available for direct
+packet access.  Operation ``r3 += rX`` may overflow and become less than
+original skb->data, therefore the verifier has to prevent that.  So when it
+sees ``r3 += rX`` instruction and rX is more than 16-bit value, any
+subsequent bounds-check of r3 against skb->data_end will not give us
+'range' information, so attempts to read through the pointer will give
+"invalid access to packet" error.  Ex. after insn ``r4 = *(u8 *)(r3 +12)``
+(insn #7 above) the state of r4 is
+R4=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) which means that upper
+56 bits of the register are guaranteed to be zero, and nothing is known
+about the lower 8 bits. After insn ``r4 *= 14`` the state becomes
+R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)), since multiplying
+an 8-bit value by constant 14 will keep upper 52 bits as zero, also the
+least significant bit will be zero as 14 is even.  Similarly ``r2 >>= 48``
+will make R2=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)), since
+the shift is not sign extending.  This logic is implemented in
+adjust_reg_min_max_vals() function, which calls adjust_ptr_min_max_vals()
+for adding pointer to scalar (or vice versa) and
+adjust_scalar_min_max_vals() for operations on two scalars.
 
 The end result is that bpf program author can access packet directly
 using normal C code as::
@@ -1303,27 +1304,24 @@ and userspace.
 
 The maps are accessed from user space via BPF syscall, which has commands:
 
-- create a map with given type and attributes
-  map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
-  using attr->map_type, attr->key_size, attr->value_size, attr->max_entries
-  returns process-local file descriptor or negative error
+- create a map with given type and attributes ``map_fd =
+  bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)`` using
+  attr->map_type, attr->key_size, attr->value_size, attr->max_entries
+  returns process-local file descriptor or negative error.
 
-- lookup key in a given map
-  err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
-  using attr->map_fd, attr->key, attr->value
-  returns zero and stores found elem into value or negative error
+- lookup key in a given map ``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr
+  *attr, u32 size)`` using attr->map_fd, attr->key, attr->value returns
+  zero and stores found elem into value or negative error.
 
-- create or update key/value pair in a given map
-  err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
-  using attr->map_fd, attr->key, attr->value
-  returns zero or negative error
+- create or update key/value pair in a given map ``err =
+  bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)`` using
+  attr->map_fd, attr->key, attr->value returns zero or negative error.
 
-- find and delete element by key in a given map
-  err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
-  using attr->map_fd, attr->key
+- find and delete element by key in a given map ``err =
+  bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)`` using
+  attr->map_fd, attr->key.
 
-- to delete map: close(fd)
-  Exiting process will delete maps automatically
+- to delete map: close(fd) Exiting process will delete maps automatically.
 
 userspace programs use this syscall to create/access maps that eBPF programs
 are concurrently updating.
-- 
2.17.1

[PATCH bpf-next 08/13] docs: net: Use double ticks instead of single tick

[Tobin C. Harding]

Single tick around a command should  be converted to a double
tick for RST files (excluding ticks in a code snippet section).

Use double ticks instead of single tick.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index f9ec58144ed3..dda1afdb5f26 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -38,9 +38,9 @@ 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
+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`
+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
@@ -375,7 +375,7 @@ Starting bpf_dbg is trivial and just requires issuing::
 
 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`.
+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
@@ -388,7 +388,7 @@ 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
+    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.
@@ -523,7 +523,7 @@ generating disassembly out of the kernel log's hexdump::
     44:	leaveq
     45:	retq
 
-Issuing option `-o` will "annotate" opcodes to resulting assembler
+Issuing option ``-o`` will "annotate" opcodes to resulting assembler
 instructions, which can be very useful for JIT developers::
 
   # ./bpf_jit_disasm -o
-- 
2.17.1

[PATCH bpf-next 09/13] docs: net: Use lowercase 'k' for kernel

[Tobin C. Harding]

The whole document uses a lowercase 'k' for 'kernel' except in one
instance.  The kernel community also favours a lowercase 'k'.

Use lowercase 'k' for kernel instead of uppercase 'K'.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index dda1afdb5f26..10c4eab042df 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -9,7 +9,7 @@ Introduction
 
 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
+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
-- 
2.17.1

[PATCH bpf-next 10/13] docs: net: Embed reference to seccomp_filter

[Tobin C. Harding]

Typical RST documents embed the reference link straight in the text.
Currently document uses a '[1]' with the reference below that
paragraph.

Use RST :ref:`path/to/file` <label>` format and embed the reference to
seccomp_filter directly in the text.  Add a label to seccomp_filter.rst
to enable the reference to function correctly.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst            | 12 ++++++------
 Documentation/userspace-api/seccomp_filter.rst |  2 ++
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 10c4eab042df..1ed6972c3544 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -43,12 +43,12 @@ 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/userspace-api/seccomp_filter.rst
+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
+:ref:`Documentation/userspace-api/seccomp_filter.rst <seccomp_filter>`),
+and lots of other places such as team driver, PTP code, etc where BPF is
+being used.
 
 Original BPF paper:
 
diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst
index 82a468bc7560..6c3eb4908818 100644
--- a/Documentation/userspace-api/seccomp_filter.rst
+++ b/Documentation/userspace-api/seccomp_filter.rst
@@ -2,6 +2,8 @@
 Seccomp BPF (SECure COMPuting with filters)
 ===========================================
 
+.. _seccomp_filter:
+
 Introduction
 ============
 
-- 
2.17.1

[PATCH bpf-next 11/13] docs: net: Use correct RST list construct

[Tobin C. Harding]

Currently we are using a custom list format.  We should use the correct
standard list construct.  Also lists require a newline before and after
the list items.

Use correct RST list construct.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 30 ++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 1ed6972c3544..99dfa74fc4f7 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -1162,18 +1162,21 @@ arithmetic), and this is tracked in two parts: the 'fixed offset' and 'variable
 offset'.  The former is used when an exactly-known value (e.g. an immediate
 operand) is added to a pointer, while the latter is used for values which are
 not exactly known.  The variable offset is also used in SCALAR_VALUEs, to track
-the range of possible values in the register.
-The verifier's knowledge about the variable offset consists of:
+the range of possible values in the register.  The verifier's knowledge
+about the variable offset consists of:
+
 * minimum and maximum values as unsigned
 * minimum and maximum values as signed
 * knowledge of the values of individual bits, in the form of a 'tnum': a u64
-'mask' and a u64 'value'.  1s in the mask represent bits whose value is unknown;
-1s in the value represent bits known to be 1.  Bits known to be 0 have 0 in both
-mask and value; no bit should ever be 1 in both.  For example, if a byte is read
-into a register from memory, the register's top 56 bits are known zero, while
-the low 8 are unknown - which is represented as the tnum (0x0; 0xff).  If we
-then OR this with 0x40, we get (0x40; 0xbf), then if we add 1 we get (0x0;
-0x1ff), because of potential carries.
+  'mask' and a u64 'value'
+
+1s in the mask represent bits whose value is unknown; 1s in the value
+represent bits known to be 1.  Bits known to be 0 have 0 in both mask and
+value; no bit should ever be 1 in both.  For example, if a byte is read
+into a register from memory, the register's top 56 bits are known zero,
+while the low 8 are unknown - which is represented as the tnum (0x0; 0xff).
+If we then OR this with 0x40, we get (0x40; 0xbf), then if we add 1 we get
+(0x0; 0x1ff), because of potential carries.
 
 Besides arithmetic, the register state can also be updated by conditional
 branches.  For instance, if a SCALAR_VALUE is compared > 8, in the 'true' branch
@@ -1329,10 +1332,11 @@ are concurrently updating.
 maps can have different types: hash, array, bloom filter, radix-tree, etc.
 
 The map is defined by:
-  . type
-  . max number of elements
-  . key size in bytes
-  . value size in bytes
+
+- type
+- max number of elements
+- key size in bytes
+- value size in bytes
 
 Pruning
 =======
-- 
2.17.1

[PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Tobin C. Harding]

There are a few minor typos and grammatical issues.  We should however
try to keep the current flavour of the document.

Fix typos and grammar if glaringly required.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 65 +++++++++++++++--------------
 1 file changed, 33 insertions(+), 32 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 99dfa74fc4f7..b989a6c882b8 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -32,10 +32,10 @@ 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
+SO_LOCK_FILTER option allows locking of 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.
+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
@@ -470,7 +470,7 @@ JIT compiler
 ============
 
 The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
-ARM, ARM64, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT
+ARM, ARM64, MIPS and s390 which 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::
 
@@ -580,7 +580,7 @@ Internally, for the kernel interpreter, a different instruction set
 format with similar underlying principles from BPF described in previous
 paragraphs is being used. However, the instruction set format is modelled
 closer to the underlying architecture to mimic native instruction sets, so
-that a better performance can be achieved (more details later). This new
+that better performance can be achieved (more details later). This new
 ISA is called 'eBPF' or 'internal BPF' interchangeably. (Note: eBPF which
 originates from [e]xtended BPF is not the same as BPF extensions! While
 eBPF is an ISA, BPF extensions date back to classic BPF's 'overloading'
@@ -655,12 +655,12 @@ Some core changes of the new internal format:
 
   32-bit architectures run 64-bit internal BPF programs via interpreter.
   Their JITs may convert BPF programs that only use 32-bit subregisters into
-  native instruction set and let the rest being interpreted.
+  native instruction set and let the rest be interpreted.
 
-  Operation is 64-bit, because on 64-bit architectures, pointers are also
-  64-bit wide, and we want to pass 64-bit values in/out of kernel functions,
-  so 32-bit eBPF registers would otherwise require to define register-pair
-  ABI, thus, there won't be able to use a direct eBPF register to HW register
+  Operation is 64-bit since on 64-bit architectures pointers are also
+  64-bit wide and we want to pass 64-bit values in/out of kernel functions.
+  32-bit eBPF registers would otherwise require us to define a register-pair
+  ABI, thus we would not be able to use a direct eBPF register to HW register
   mapping and JIT would need to do combine/split/move operations for every
   register in and out of the function, which is complex, bug prone and slow.
   Another reason is the use of atomic 64-bit counters.
@@ -694,7 +694,7 @@ Some core changes of the new internal format:
   situations without performance penalty.
 
   After an in-kernel function call, R1 - R5 are reset to unreadable and R0 has
-  a return value of the function. Since R6 - R9 are callee saved, their state
+  the return value of the function. Since R6 - R9 are callee saved, their state
   is preserved across the call.
 
   For example, consider three C functions::
@@ -732,7 +732,7 @@ Some core changes of the new internal format:
   are currently not supported, but these restrictions can be lifted if necessary
   in the future.
 
-  On 64-bit architectures all register map to HW registers one to one. For
+  On 64-bit architectures all registers map to HW registers one to one. For
   example, x86_64 JIT compiler can map them as ... ::
 
     R0 - rax
@@ -831,9 +831,10 @@ A program, that is translated internally consists of the following elements::
 
   op:16, jt:8, jf:8, k:32    ==>    op:8, dst_reg:4, src_reg:4, off:16, imm:32
 
-So far 87 internal BPF instructions were implemented. 8-bit ``op`` opcode field
-has room for new instructions. Some of them may use 16/24/32 byte encoding. New
-instructions must be multiple of 8 bytes to preserve backward compatibility.
+So far 87 internal BPF instructions have been implemented. 8-bit ``op``
+opcode field has room for new instructions. Some of them may use 16/24/32
+byte encoding. New instructions must be a multiple of 8 bytes to preserve
+backward compatibility.
 
 Internal BPF is a general purpose RISC instruction set. Not every register and
 every instruction are used during translation from original BPF to new format.
@@ -844,11 +845,11 @@ out of registers and would have to resort to spill/fill to stack.
 
 Internal BPF can used as generic assembler for last step performance
 optimizations, socket filters and seccomp are using it as assembler. Tracing
-filters may use it as assembler to generate code from kernel. In kernel usage
+filters may use it as assembler to generate code from kernel.  In-kernel usage
 may not be bounded by security considerations, since generated internal BPF code
-may be optimizing internal code path and not being exposed to the user space.
-Safety of internal BPF can come from a verifier (TBD). In such use cases as
-described, it may be used as safe instruction set.
+may use an optimised internal code path and may not be being exposed to user
+space. Safety of internal BPF can come from a verifier (TBD). In such use cases
+as described, it may be used as safe as the instruction set.
 
 Just like the original BPF, the new format runs within a controlled environment,
 is deterministic and the kernel can easily prove that. The safety of the program
@@ -945,7 +946,7 @@ Classic BPF is using BPF_MISC class to represent A = X and X = A moves.
 eBPF is using BPF_MOV | BPF_X | BPF_ALU code instead. Since there are no
 BPF_MISC operations in eBPF, the class 7 is used as BPF_ALU64 to mean
 exactly the same operations as BPF_ALU, but with 64-bit wide operands
-instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition, i.e.:
+instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition i.e.
 dst_reg = dst_reg + src_reg
 
 Classic BPF wastes the whole BPF_RET class to represent a single 'ret'
@@ -1024,8 +1025,8 @@ Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. Note that 1 and
 2 byte atomic increments are not supported.
 
 eBPF has one 16-byte instruction: BPF_LD | BPF_DW | BPF_IMM which consists
-of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single
-instruction that loads 64-bit immediate value into a dst_reg.
+of two consecutive ``struct bpf_insn`` 8-byte blocks and is interpreted as
+a single instruction that loads 64-bit immediate value into a dst_reg.
 Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads
 32-bit immediate value into a register.
 
@@ -1035,8 +1036,8 @@ eBPF verifier
 The safety of the eBPF program is determined in two steps.
 
 First step does DAG check to disallow loops and other CFG validation.
-In particular it will detect programs that have unreachable instructions.
-(though classic BPF checker allows them)
+In particular it will detect programs that have unreachable instructions
+(though classic BPF checker allows them).
 
 Second step starts from the first insn and descends all possible paths.
 It simulates execution of every insn and observes the state change of
@@ -1107,7 +1108,7 @@ For example::
   bpf_ld R0 = *(u32 *)(R10 - 4)
   bpf_exit
 
-is invalid program.
+is an invalid program.
 Though R10 is correct read-only register and has type PTR_TO_STACK
 and R10 - 4 is within stack bounds, there were no stores into that location.
 
@@ -1118,13 +1119,13 @@ Allowed function calls are customized with bpf_verifier_ops->get_func_proto()
 The eBPF verifier will check that registers match argument constraints.
 After the call register R0 will be set to return type of the function.
 
-Function calls is a main mechanism to extend functionality of eBPF programs.
-Socket filters may let programs to call one set of functions, whereas tracing
-filters may allow completely different set.
+Function calls is an important mechanism to extend functionality of eBPF
+programs.  Socket filters may let programs call one set of functions,
+whereas tracing filters may allow a completely different set.
 
-If a function made accessible to eBPF program, it needs to be thought through
-from safety point of view. The verifier will guarantee that the function is
-called with valid arguments.
+If a function is made accessible to eBPF program, it needs to be thought
+through from a safety point of view. The verifier will guarantee that the
+function is called with valid arguments.
 
 seccomp vs socket filters have different security restrictions for classic BPF.
 Seccomp solves this by two stage verifier: classic BPF verifier is followed
@@ -1202,7 +1203,7 @@ checked and found to be non-NULL, all copies can become PTR_TO_MAP_VALUEs.
 As well as range-checking, the tracked information is also used for enforcing
 alignment of pointer accesses.  For instance, on most systems the packet pointer
 is 2 bytes after a 4-byte alignment.  If a program adds 14 bytes to that to jump
-over the Ethernet header, then reads IHL and addes (IHL * 4), the resulting
+over the Ethernet header, then reads IHL and adds (IHL * 4), the resulting
 pointer will have a variable offset known to be 4n+2 for some n, so adding the 2
 bytes (NET_IP_ALIGN) gives a 4-byte alignment and so word-sized accesses through
 that pointer are safe.
-- 
2.17.1

[PATCH bpf-next 13/13] docs: net: Fix authors list to render as a list

[Tobin C. Harding]

Currently authors list renders on a single line in HTML.  The text
format implies that a list was meant.

Use RST list construct to fix authors contact details to be rendered as
a list.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 Documentation/networking/filter.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index b989a6c882b8..1913718e3f2a 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst
@@ -1532,6 +1532,6 @@ 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 <daniel@iogearbox.net>
-Alexei Starovoitov <ast@kernel.org>
+- Jay Schulist <jschlst@samba.org>
+- Daniel Borkmann <daniel@iogearbox.net>
+- Alexei Starovoitov <ast@kernel.org>
-- 
2.17.1

Re: [PATCH bpf-next 03/13] docs: net: Add filter to index toctree

[Jonathan Corbet]

On Wed,  1 Aug 2018 15:08:58 +1000
"Tobin C. Harding" <me@tobin.cc> wrote:

> filter.rst was just created (from filter.txt).  We should include it in
> the networking docs toctree.
> 
> Add filter to Documentation/networking/index.rst toctree.

So...the minorest of nits just to prove that I actually looked at
this...:)  Adding it to the toctree at this point is going to make the
docs build messy (OK, even messier than it already is) because the RST
conversion hasn't really been done yet.  I'd do this at the end of the
series, just in case somebody, somewhere, is crazy enough to try to
bisect a docs build.

Something that's a bit more relevant, perhaps: this document is a bit of
a mishmash.  It starts by talking about how to use cBPF for socket
filters, then includes a long discussion about the features of eBPF
which, as I understand it, is still not accessible to user space for
socket filters. That latter part certainly merits being in its own file
where people will actually find it?  And if it were me, I would move that
file into the core API guide, since it will be relevant beyond networking.

Thanks,

jon

Re: [PATCH bpf-next 03/13] docs: net: Add filter to index toctree

[Tobin C. Harding]

On Wed, Aug 01, 2018 at 07:52:12AM -0600, Jonathan Corbet wrote:
> On Wed,  1 Aug 2018 15:08:58 +1000
> "Tobin C. Harding" <me@tobin.cc> wrote:
> 
> > filter.rst was just created (from filter.txt).  We should include it in
> > the networking docs toctree.
> > 
> > Add filter to Documentation/networking/index.rst toctree.
> 
> So...the minorest of nits just to prove that I actually looked at
> this...:)

Thanks for the feedback Jon, I like when I get feedback as apposed to
just patches being applied - makes me feel like the work actually
matters, thanks.

> Adding it to the toctree at this point is going to make the
> docs build messy (OK, even messier than it already is) because the RST
> conversion hasn't really been done yet.  I'd do this at the end of the
> series, just in case somebody, somewhere, is crazy enough to try to
> bisect a docs build.

Will use this method for re-spin of this set and for future conversions.

> Something that's a bit more relevant, perhaps: this document is a bit of
> a mishmash.  It starts by talking about how to use cBPF for socket
> filters, then includes a long discussion about the features of eBPF
> which, as I understand it, is still not accessible to user space for
> socket filters. That latter part certainly merits being in its own file
> where people will actually find it?  And if it were me, I would move that
> file into the core API guide, since it will be relevant beyond networking.

And we have Documentation/bpf as well?  I'll have a go at splitting this
file up and/or moving it around.  The content is pretty heavy so I may
need some comments/ideas from the original authors.

I'll spin up a V2 and we can see how it looks.

thanks,
Tobin.

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Daniel Borkmann]

On 08/01/2018 07:09 AM, Tobin C. Harding wrote:
> There are a few minor typos and grammatical issues.  We should however
> try to keep the current flavour of the document.
> 
> Fix typos and grammar if glaringly required.
> 
> Signed-off-by: Tobin C. Harding <me@tobin.cc>

Overall looks good, just some minor nits:

>  Documentation/networking/filter.rst | 65 +++++++++++++++--------------
>  1 file changed, 33 insertions(+), 32 deletions(-)
> 
> diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
> index 99dfa74fc4f7..b989a6c882b8 100644
> --- a/Documentation/networking/filter.rst
> +++ b/Documentation/networking/filter.rst
> @@ -32,10 +32,10 @@ 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
> +SO_LOCK_FILTER option allows locking of 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.
> +assured  that the filter will be kept until the socket is closed.

          ^-- looks like extra whitespace slipped in?

>  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
> @@ -470,7 +470,7 @@ JIT compiler
>  ============
>  
>  The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
> -ARM, ARM64, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT
> +ARM, ARM64, MIPS and s390 which 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::
>  
> @@ -580,7 +580,7 @@ Internally, for the kernel interpreter, a different instruction set
>  format with similar underlying principles from BPF described in previous
>  paragraphs is being used. However, the instruction set format is modelled
>  closer to the underlying architecture to mimic native instruction sets, so
> -that a better performance can be achieved (more details later). This new
> +that better performance can be achieved (more details later). This new
>  ISA is called 'eBPF' or 'internal BPF' interchangeably. (Note: eBPF which
>  originates from [e]xtended BPF is not the same as BPF extensions! While
>  eBPF is an ISA, BPF extensions date back to classic BPF's 'overloading'
> @@ -655,12 +655,12 @@ Some core changes of the new internal format:
>  
>    32-bit architectures run 64-bit internal BPF programs via interpreter.
>    Their JITs may convert BPF programs that only use 32-bit subregisters into
> -  native instruction set and let the rest being interpreted.
> +  native instruction set and let the rest be interpreted.
>  
> -  Operation is 64-bit, because on 64-bit architectures, pointers are also
> -  64-bit wide, and we want to pass 64-bit values in/out of kernel functions,
> -  so 32-bit eBPF registers would otherwise require to define register-pair
> -  ABI, thus, there won't be able to use a direct eBPF register to HW register
> +  Operation is 64-bit since on 64-bit architectures pointers are also
> +  64-bit wide and we want to pass 64-bit values in/out of kernel functions.
> +  32-bit eBPF registers would otherwise require us to define a register-pair
> +  ABI, thus we would not be able to use a direct eBPF register to HW register
>    mapping and JIT would need to do combine/split/move operations for every
>    register in and out of the function, which is complex, bug prone and slow.
>    Another reason is the use of atomic 64-bit counters.
> @@ -694,7 +694,7 @@ Some core changes of the new internal format:
>    situations without performance penalty.
>  
>    After an in-kernel function call, R1 - R5 are reset to unreadable and R0 has
> -  a return value of the function. Since R6 - R9 are callee saved, their state
> +  the return value of the function. Since R6 - R9 are callee saved, their state
>    is preserved across the call.
>  
>    For example, consider three C functions::
> @@ -732,7 +732,7 @@ Some core changes of the new internal format:
>    are currently not supported, but these restrictions can be lifted if necessary
>    in the future.
>  
> -  On 64-bit architectures all register map to HW registers one to one. For
> +  On 64-bit architectures all registers map to HW registers one to one. For
>    example, x86_64 JIT compiler can map them as ... ::
>  
>      R0 - rax
> @@ -831,9 +831,10 @@ A program, that is translated internally consists of the following elements::
>  
>    op:16, jt:8, jf:8, k:32    ==>    op:8, dst_reg:4, src_reg:4, off:16, imm:32
>  
> -So far 87 internal BPF instructions were implemented. 8-bit ``op`` opcode field
> -has room for new instructions. Some of them may use 16/24/32 byte encoding. New
> -instructions must be multiple of 8 bytes to preserve backward compatibility.
> +So far 87 internal BPF instructions have been implemented. 8-bit ``op``
> +opcode field has room for new instructions. Some of them may use 16/24/32
> +byte encoding. New instructions must be a multiple of 8 bytes to preserve
> +backward compatibility.
>  
>  Internal BPF is a general purpose RISC instruction set. Not every register and
>  every instruction are used during translation from original BPF to new format.
> @@ -844,11 +845,11 @@ out of registers and would have to resort to spill/fill to stack.
>  
>  Internal BPF can used as generic assembler for last step performance
>  optimizations, socket filters and seccomp are using it as assembler. Tracing
> -filters may use it as assembler to generate code from kernel. In kernel usage
> +filters may use it as assembler to generate code from kernel.  In-kernel usage

                                                                ^-- ditto

>  may not be bounded by security considerations, since generated internal BPF code
> -may be optimizing internal code path and not being exposed to the user space.
> -Safety of internal BPF can come from a verifier (TBD). In such use cases as
> -described, it may be used as safe instruction set.
> +may use an optimised internal code path and may not be being exposed to user
> +space. Safety of internal BPF can come from a verifier (TBD). In such use cases
> +as described, it may be used as safe as the instruction set.
>  
>  Just like the original BPF, the new format runs within a controlled environment,
>  is deterministic and the kernel can easily prove that. The safety of the program
> @@ -945,7 +946,7 @@ Classic BPF is using BPF_MISC class to represent A = X and X = A moves.
>  eBPF is using BPF_MOV | BPF_X | BPF_ALU code instead. Since there are no
>  BPF_MISC operations in eBPF, the class 7 is used as BPF_ALU64 to mean
>  exactly the same operations as BPF_ALU, but with 64-bit wide operands
> -instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition, i.e.:
> +instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition i.e.
>  dst_reg = dst_reg + src_reg
>  
>  Classic BPF wastes the whole BPF_RET class to represent a single 'ret'
> @@ -1024,8 +1025,8 @@ Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. Note that 1 and
>  2 byte atomic increments are not supported.
>  
>  eBPF has one 16-byte instruction: BPF_LD | BPF_DW | BPF_IMM which consists
> -of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single
> -instruction that loads 64-bit immediate value into a dst_reg.
> +of two consecutive ``struct bpf_insn`` 8-byte blocks and is interpreted as
> +a single instruction that loads 64-bit immediate value into a dst_reg.
>  Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads
>  32-bit immediate value into a register.
>  
> @@ -1035,8 +1036,8 @@ eBPF verifier
>  The safety of the eBPF program is determined in two steps.
>  
>  First step does DAG check to disallow loops and other CFG validation.
> -In particular it will detect programs that have unreachable instructions.
> -(though classic BPF checker allows them)
> +In particular it will detect programs that have unreachable instructions
> +(though classic BPF checker allows them).
>  
>  Second step starts from the first insn and descends all possible paths.
>  It simulates execution of every insn and observes the state change of
> @@ -1107,7 +1108,7 @@ For example::
>    bpf_ld R0 = *(u32 *)(R10 - 4)
>    bpf_exit
>  
> -is invalid program.
> +is an invalid program.
>  Though R10 is correct read-only register and has type PTR_TO_STACK
>  and R10 - 4 is within stack bounds, there were no stores into that location.
>  
> @@ -1118,13 +1119,13 @@ Allowed function calls are customized with bpf_verifier_ops->get_func_proto()
>  The eBPF verifier will check that registers match argument constraints.
>  After the call register R0 will be set to return type of the function.
>  
> -Function calls is a main mechanism to extend functionality of eBPF programs.
> -Socket filters may let programs to call one set of functions, whereas tracing
> -filters may allow completely different set.
> +Function calls is an important mechanism to extend functionality of eBPF
> +programs.  Socket filters may let programs call one set of functions,

             ^-- ditto

> +whereas tracing filters may allow a completely different set.
>  
> -If a function made accessible to eBPF program, it needs to be thought through
> -from safety point of view. The verifier will guarantee that the function is
> -called with valid arguments.
> +If a function is made accessible to eBPF program, it needs to be thought
> +through from a safety point of view. The verifier will guarantee that the
> +function is called with valid arguments.
>  
>  seccomp vs socket filters have different security restrictions for classic BPF.
>  Seccomp solves this by two stage verifier: classic BPF verifier is followed
> @@ -1202,7 +1203,7 @@ checked and found to be non-NULL, all copies can become PTR_TO_MAP_VALUEs.
>  As well as range-checking, the tracked information is also used for enforcing
>  alignment of pointer accesses.  For instance, on most systems the packet pointer
>  is 2 bytes after a 4-byte alignment.  If a program adds 14 bytes to that to jump
> -over the Ethernet header, then reads IHL and addes (IHL * 4), the resulting
> +over the Ethernet header, then reads IHL and adds (IHL * 4), the resulting
>  pointer will have a variable offset known to be 4n+2 for some n, so adding the 2
>  bytes (NET_IP_ALIGN) gives a 4-byte alignment and so word-sized accesses through
>  that pointer are safe.
> 

Re: [PATCH bpf-next 05/13] docs: net: Fix indentation issues for code snippets

[Daniel Borkmann]

On 08/01/2018 07:09 AM, Tobin C. Harding wrote:
[...]
> -Starting bpf_dbg is trivial and just requires issuing:
> +Starting bpf_dbg is trivial and just requires issuing::
>  
> -# ./bpf_dbg
> +  # ./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
> @@ -381,86 +384,87 @@ file "~/.bpf_dbg_init" and the command history is stored in the file
>  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.
> +::
> +
> +  > 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.

Here for the bpf_dbg howto, it would be good to separate explanation from
the cmdline code snippets. This would more easily clarify the commands
themselves if we already go the rst route, so I'd prefer splitting this up.

> +  > 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.
>  

Re: [PATCH bpf-next 05/13] docs: net: Fix indentation issues for code snippets

[Tobin C. Harding]

On Fri, Aug 03, 2018 at 10:44:23AM +0200, Daniel Borkmann wrote:
> On 08/01/2018 07:09 AM, Tobin C. Harding wrote:
> [...]
> > -Starting bpf_dbg is trivial and just requires issuing:
> > +Starting bpf_dbg is trivial and just requires issuing::
> >  
> > -# ./bpf_dbg
> > +  # ./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
> > @@ -381,86 +384,87 @@ file "~/.bpf_dbg_init" and the command history is stored in the file
> >  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.
> > +::
> > +
> > +  > 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.
> 
> Here for the bpf_dbg howto, it would be good to separate explanation from
> the cmdline code snippets. This would more easily clarify the commands
> themselves if we already go the rst route, so I'd prefer splitting this up.

Sure thing.  Will do as suggested. Thanks for the review.


	Tobin

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Tobin C. Harding]

On Fri, Aug 03, 2018 at 10:41:12AM +0200, Daniel Borkmann wrote:
> On 08/01/2018 07:09 AM, Tobin C. Harding wrote:
> > There are a few minor typos and grammatical issues.  We should however
> > try to keep the current flavour of the document.
> > 
> > Fix typos and grammar if glaringly required.
> > 
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> 
> Overall looks good, just some minor nits:
> 
> >  Documentation/networking/filter.rst | 65 +++++++++++++++--------------
> >  1 file changed, 33 insertions(+), 32 deletions(-)
> > 
> > diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
> > index 99dfa74fc4f7..b989a6c882b8 100644
> > --- a/Documentation/networking/filter.rst
> > +++ b/Documentation/networking/filter.rst
> > @@ -32,10 +32,10 @@ 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
> > +SO_LOCK_FILTER option allows locking of 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.
> > +assured  that the filter will be kept until the socket is closed.
> 
>           ^-- looks like extra whitespace slipped in?

Fixed in the RFC.  Thanks for taking the time review.

	Tobin

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Tobin C. Harding]

On Fri, Aug 03, 2018 at 10:41:12AM +0200, Daniel Borkmann wrote:
> On 08/01/2018 07:09 AM, Tobin C. Harding wrote:
> > There are a few minor typos and grammatical issues.  We should however
> > try to keep the current flavour of the document.
> > 
> > Fix typos and grammar if glaringly required.
> > 
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> 
> Overall looks good, just some minor nits:
> 
> >  Documentation/networking/filter.rst | 65 +++++++++++++++--------------
> >  1 file changed, 33 insertions(+), 32 deletions(-)
> > 
> > diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
> > index 99dfa74fc4f7..b989a6c882b8 100644
> > --- a/Documentation/networking/filter.rst
> > +++ b/Documentation/networking/filter.rst
> > @@ -32,10 +32,10 @@ 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
> > +SO_LOCK_FILTER option allows locking of 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.
> > +assured  that the filter will be kept until the socket is closed.
> 
>           ^-- looks like extra whitespace slipped in?
> 
> >  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
> > @@ -470,7 +470,7 @@ JIT compiler
> >  ============
> >  
> >  The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC,
> > -ARM, ARM64, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT
> > +ARM, ARM64, MIPS and s390 which 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::
> >  
> > @@ -580,7 +580,7 @@ Internally, for the kernel interpreter, a different instruction set
> >  format with similar underlying principles from BPF described in previous
> >  paragraphs is being used. However, the instruction set format is modelled
> >  closer to the underlying architecture to mimic native instruction sets, so
> > -that a better performance can be achieved (more details later). This new
> > +that better performance can be achieved (more details later). This new
> >  ISA is called 'eBPF' or 'internal BPF' interchangeably. (Note: eBPF which
> >  originates from [e]xtended BPF is not the same as BPF extensions! While
> >  eBPF is an ISA, BPF extensions date back to classic BPF's 'overloading'
> > @@ -655,12 +655,12 @@ Some core changes of the new internal format:
> >  
> >    32-bit architectures run 64-bit internal BPF programs via interpreter.
> >    Their JITs may convert BPF programs that only use 32-bit subregisters into
> > -  native instruction set and let the rest being interpreted.
> > +  native instruction set and let the rest be interpreted.
> >  
> > -  Operation is 64-bit, because on 64-bit architectures, pointers are also
> > -  64-bit wide, and we want to pass 64-bit values in/out of kernel functions,
> > -  so 32-bit eBPF registers would otherwise require to define register-pair
> > -  ABI, thus, there won't be able to use a direct eBPF register to HW register
> > +  Operation is 64-bit since on 64-bit architectures pointers are also
> > +  64-bit wide and we want to pass 64-bit values in/out of kernel functions.
> > +  32-bit eBPF registers would otherwise require us to define a register-pair
> > +  ABI, thus we would not be able to use a direct eBPF register to HW register
> >    mapping and JIT would need to do combine/split/move operations for every
> >    register in and out of the function, which is complex, bug prone and slow.
> >    Another reason is the use of atomic 64-bit counters.
> > @@ -694,7 +694,7 @@ Some core changes of the new internal format:
> >    situations without performance penalty.
> >  
> >    After an in-kernel function call, R1 - R5 are reset to unreadable and R0 has
> > -  a return value of the function. Since R6 - R9 are callee saved, their state
> > +  the return value of the function. Since R6 - R9 are callee saved, their state
> >    is preserved across the call.
> >  
> >    For example, consider three C functions::
> > @@ -732,7 +732,7 @@ Some core changes of the new internal format:
> >    are currently not supported, but these restrictions can be lifted if necessary
> >    in the future.
> >  
> > -  On 64-bit architectures all register map to HW registers one to one. For
> > +  On 64-bit architectures all registers map to HW registers one to one. For
> >    example, x86_64 JIT compiler can map them as ... ::
> >  
> >      R0 - rax
> > @@ -831,9 +831,10 @@ A program, that is translated internally consists of the following elements::
> >  
> >    op:16, jt:8, jf:8, k:32    ==>    op:8, dst_reg:4, src_reg:4, off:16, imm:32
> >  
> > -So far 87 internal BPF instructions were implemented. 8-bit ``op`` opcode field
> > -has room for new instructions. Some of them may use 16/24/32 byte encoding. New
> > -instructions must be multiple of 8 bytes to preserve backward compatibility.
> > +So far 87 internal BPF instructions have been implemented. 8-bit ``op``
> > +opcode field has room for new instructions. Some of them may use 16/24/32
> > +byte encoding. New instructions must be a multiple of 8 bytes to preserve
> > +backward compatibility.
> >  
> >  Internal BPF is a general purpose RISC instruction set. Not every register and
> >  every instruction are used during translation from original BPF to new format.
> > @@ -844,11 +845,11 @@ out of registers and would have to resort to spill/fill to stack.
> >  
> >  Internal BPF can used as generic assembler for last step performance
> >  optimizations, socket filters and seccomp are using it as assembler. Tracing
> > -filters may use it as assembler to generate code from kernel. In kernel usage
> > +filters may use it as assembler to generate code from kernel.  In-kernel usage
> 
>                                                                 ^-- ditto

Hi Daniel,

Thanks for doing such a careful review that you noticed this.  I'm
working on this more ATM and I've moved the document to use double
spaces between _all_ full stops.  Currently the document uses mostly
single spaces but there are some sections with double space.  The
internet tells me this is a 'style' issue not a rule.  And I've seen
single and double spacing in tree and do not know if one is favoured.

Do you care?  If you do not care I'll just use double spaces.  If you do
care and would prefer me to uniformly use a single space I can do that
also.  Oh, and FTR filter.txt looks like its going into userspace-api/
so you may care even less with that move.

If this is overly pedantic just tell me to go away :)

thanks,
Tobin.

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Jonathan Corbet]

On Wed, 8 Aug 2018 11:42:48 +1000
"Tobin C. Harding" <me@tobin.cc> wrote:

> Hi Daniel,
> 
> Thanks for doing such a careful review that you noticed this.  I'm
> working on this more ATM and I've moved the document to use double
> spaces between _all_ full stops.  Currently the document uses mostly
> single spaces but there are some sections with double space.  The
> internet tells me this is a 'style' issue not a rule.  And I've seen
> single and double spacing in tree and do not know if one is favoured.
> 
> Do you care? 

I'm not Daniel, but let me just say that, for docs in general, I'm
absolutely uninterested in patches adjusting the number of spaces after
periods.  It really doesn't matter one way or the other, and I don't think
we benefit from that kind of churn.

Thanks,

jon

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Daniel Borkmann]

On 08/08/2018 03:23 PM, Jonathan Corbet wrote:
> On Wed, 8 Aug 2018 11:42:48 +1000
> "Tobin C. Harding" <me@tobin.cc> wrote:
> 
>> Thanks for doing such a careful review that you noticed this.  I'm
>> working on this more ATM and I've moved the document to use double
>> spaces between _all_ full stops.  Currently the document uses mostly
>> single spaces but there are some sections with double space.  The
>> internet tells me this is a 'style' issue not a rule.  And I've seen
>> single and double spacing in tree and do not know if one is favoured.
>>
>> Do you care? 
> 
> I'm not Daniel, but let me just say that, for docs in general, I'm
> absolutely uninterested in patches adjusting the number of spaces after
> periods.  It really doesn't matter one way or the other, and I don't think
> we benefit from that kind of churn.

Yep, agree.

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Markus Heiser]

Am Mittwoch, den 08.08.2018, 15:45 +0200 schrieb Daniel Borkmann:
> On 08/08/2018 03:23 PM, Jonathan Corbet wrote:
> > On Wed, 8 Aug 2018 11:42:48 +1000
> > "Tobin C. Harding" <me@tobin.cc> wrote:
> > 
> > > Thanks for doing such a careful review that you noticed this.  I'm
> > > working on this more ATM and I've moved the document to use double
> > > spaces between _all_ full stops.  Currently the document uses mostly
> > > single spaces but there are some sections with double space.  The
> > > internet tells me this is a 'style' issue not a rule.  And I've seen
> > > single and double spacing in tree and do not know if one is favoured.
> > > 
> > > Do you care? 
> > 
> > I'm not Daniel, but let me just say that, for docs in general, I'm
> > absolutely uninterested in patches adjusting the number of spaces after
> > periods.  It really doesn't matter one way or the other, and I don't think
> > we benefit from that kind of churn.
> 
> Yep, agree.

FWIW: even if it is not a patch worth, 'fill-paragraph' within emacs benefit
from.


-- Markus --

Re: [PATCH bpf-next 12/13] docs: net: Fix various minor typos

[Tobin C. Harding]

On Wed, Aug 08, 2018 at 06:26:50PM +0200, Markus Heiser wrote:
> 
> 
> Am Mittwoch, den 08.08.2018, 15:45 +0200 schrieb Daniel Borkmann:
> > On 08/08/2018 03:23 PM, Jonathan Corbet wrote:
> > > On Wed, 8 Aug 2018 11:42:48 +1000
> > > "Tobin C. Harding" <me@tobin.cc> wrote:
> > > 
> > > > Thanks for doing such a careful review that you noticed this.  I'm
> > > > working on this more ATM and I've moved the document to use double
> > > > spaces between _all_ full stops.  Currently the document uses mostly
> > > > single spaces but there are some sections with double space.  The
> > > > internet tells me this is a 'style' issue not a rule.  And I've seen
> > > > single and double spacing in tree and do not know if one is favoured.
> > > > 
> > > > Do you care? 
> > > 
> > > I'm not Daniel, but let me just say that, for docs in general, I'm
> > > absolutely uninterested in patches adjusting the number of spaces after
> > > periods.  It really doesn't matter one way or the other, and I don't think
> > > we benefit from that kind of churn.
> > 
> > Yep, agree.
> 
> FWIW: even if it is not a patch worth, 'fill-paragraph' within emacs benefit
> from.

That's why I originally started using double spaces :)

thanks,
Tobin.