* [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page
@ 2018-04-10 14:41 Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation Quentin Monnet
` (7 more replies)
0 siblings, 8 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
eBPF helper functions can be called from within eBPF programs to perform
a variety of tasks that would be otherwise hard or impossible to do with
eBPF itself. There is a growing number of such helper functions in the
kernel, but documentation is scarce. The main user space header file
does contain a short commented description of most helpers, but it is
somewhat outdated and not complete. It is more a "cheat sheet" than a
real documentation accessible to new eBPF developers.
This commit attempts to improve the situation by replacing the existing
overview for the helpers with a more developed description. Furthermore,
a Python script is added to generate a manual page for eBPF helpers. The
workflow is the following, and requires the rst2man utility:
$ ./scripts/bpf_helpers_doc.py \
--filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
$ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
$ man /tmp/bpf-helpers.7
The objective is to keep all documentation related to the helpers in a
single place, and to be able to generate from here a manual page that
could be packaged in the man-pages repository and shipped with most
distributions.
Additionally, parsing the prototypes of the helper functions could
hopefully be reused, with a different Printer object, to generate
header files needed in some eBPF-related projects.
Regarding the description of each helper, it comprises several items:
- The function prototype.
- A description of the function and of its arguments (except for a
couple of cases, when there are no arguments and the return value
makes the function usage really obvious).
- A description of return values (if not void).
Additional items such as the list of compatible eBPF program and map
types for each helper, Linux kernel version that introduced the helper,
GPL-only restriction, and commit hash could be added in the future, but
it was decided on the mailing list to leave them aside for now.
For several helpers, descriptions are inspired (at times, nearly copied)
from the commit logs introducing them in the kernel--Many thanks to
their respective authors! They were completed as much as possible, the
objective being to have something easily accessible even for people just
starting with eBPF. There is probably a bit more work to do in this
direction for some helpers.
Some RST formatting is used in the descriptions (not in function
prototypes, to keep them readable, but the Python script provided in
order to generate the RST for the manual page does add formatting to
prototypes, to produce something pretty) to get "bold" and "italics" in
manual pages. Hopefully, the descriptions in bpf.h file remains
perfectly readable. Note that the few trailing white spaces are
intentional, removing them would break paragraphs for rst2man.
The descriptions should ideally be updated each time someone adds a new
helper, or updates the behaviour (new socket option supported, ...) or
the interface (new flags available, ...) of existing ones.
The second RFC for this set splits the documentation into several patches.
Ideally all helper descriptions should be reviewed by the respective
authors of the functions they describe. Please do not hesitate to suggest
improvements to make descriptions more complete or accessible.
v2:
- Remove "For" (compatible program and map types), "Since" (minimal
Linux kernel version required), "GPL only" sections and commit hashes
for the helpers.
- Add comment on top of the description list to explain how this
documentation is supposed to be processed.
- Update Python script accordingly (remove the same sections, and remove
paragraphs on program types and GPL restrictions from man page
header).
- Split series into several patches.
Cc: linux-doc@vger.kernel.org
Cc: linux-man@vger.kernel.org
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Quentin Monnet (8):
bpf: add script and prepare bpf.h for new helpers documentation
bpf: add documentation for eBPF helpers (01-11)
bpf: add documentation for eBPF helpers (12-22)
bpf: add documentation for eBPF helpers (23-32)
bpf: add documentation for eBPF helpers (33-41)
bpf: add documentation for eBPF helpers (42-50)
bpf: add documentation for eBPF helpers (51-57)
bpf: add documentation for eBPF helpers (58-64)
include/uapi/linux/bpf.h | 1580 +++++++++++++++++++++++++++++++++-----------
scripts/bpf_helpers_doc.py | 414 ++++++++++++
2 files changed, 1616 insertions(+), 378 deletions(-)
create mode 100755 scripts/bpf_helpers_doc.py
--
2.14.1
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
2018-04-10 18:16 ` Alexei Starovoitov
2018-04-10 14:41 ` [RFC bpf-next v2 2/8] bpf: add documentation for eBPF helpers (01-11) Quentin Monnet
` (6 subsequent siblings)
7 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
Remove previous "overview" of eBPF helpers from user bpf.h header.
Replace it by a comment explaining how to process the new documentation
(to come in following patches) with a Python script to produce RST, then
man page documentation.
Also add the aforementioned Python script under scripts/. It is used to
process include/uapi/linux/bpf.h and to extract helper descriptions, to
turn it into a RST document that can further be processed with rst2man
to produce a man page. The script takes one "--filename <path/to/file>"
option. If the script is launched from scripts/ in the kernel root
directory, it should be able to find the location of the header to
parse, and "--filename <path/to/file>" is then optional. If it cannot
find the file, then the option becomes mandatory. RST-formatted
documentation is printed to standard output.
Typical workflow for producing the final man page would be:
$ ./scripts/bpf_helpers_doc.py \
--filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
$ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
$ man /tmp/bpf-helpers.7
Note that the tool kernel-doc cannot be used to document eBPF helpers,
whose signatures are not available directly in the header files
(pre-processor directives are used to produce them at the beginning of
the compilation process).
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 406 ++------------------------------------------
scripts/bpf_helpers_doc.py | 414 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 430 insertions(+), 390 deletions(-)
create mode 100755 scripts/bpf_helpers_doc.py
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c5ec89732a8d..45f77f01e672 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -365,396 +365,22 @@ union bpf_attr {
} raw_tracepoint;
} __attribute__((aligned(8)));
-/* BPF helper function descriptions:
- *
- * void *bpf_map_lookup_elem(&map, &key)
- * Return: Map value or NULL
- *
- * int bpf_map_update_elem(&map, &key, &value, flags)
- * Return: 0 on success or negative error
- *
- * int bpf_map_delete_elem(&map, &key)
- * Return: 0 on success or negative error
- *
- * int bpf_probe_read(void *dst, int size, void *src)
- * Return: 0 on success or negative error
- *
- * u64 bpf_ktime_get_ns(void)
- * Return: current ktime
- *
- * int bpf_trace_printk(const char *fmt, int fmt_size, ...)
- * Return: length of buffer written or negative error
- *
- * u32 bpf_prandom_u32(void)
- * Return: random value
- *
- * u32 bpf_raw_smp_processor_id(void)
- * Return: SMP processor ID
- *
- * int bpf_skb_store_bytes(skb, offset, from, len, flags)
- * store bytes into packet
- * @skb: pointer to skb
- * @offset: offset within packet from skb->mac_header
- * @from: pointer where to copy bytes from
- * @len: number of bytes to store into packet
- * @flags: bit 0 - if true, recompute skb->csum
- * other bits - reserved
- * Return: 0 on success or negative error
- *
- * int bpf_l3_csum_replace(skb, offset, from, to, flags)
- * recompute IP checksum
- * @skb: pointer to skb
- * @offset: offset within packet where IP checksum is located
- * @from: old value of header field
- * @to: new value of header field
- * @flags: bits 0-3 - size of header field
- * other bits - reserved
- * Return: 0 on success or negative error
- *
- * int bpf_l4_csum_replace(skb, offset, from, to, flags)
- * recompute TCP/UDP checksum
- * @skb: pointer to skb
- * @offset: offset within packet where TCP/UDP checksum is located
- * @from: old value of header field
- * @to: new value of header field
- * @flags: bits 0-3 - size of header field
- * bit 4 - is pseudo header
- * other bits - reserved
- * Return: 0 on success or negative error
- *
- * int bpf_tail_call(ctx, prog_array_map, index)
- * jump into another BPF program
- * @ctx: context pointer passed to next program
- * @prog_array_map: pointer to map which type is BPF_MAP_TYPE_PROG_ARRAY
- * @index: 32-bit index inside array that selects specific program to run
- * Return: 0 on success or negative error
- *
- * int bpf_clone_redirect(skb, ifindex, flags)
- * redirect to another netdev
- * @skb: pointer to skb
- * @ifindex: ifindex of the net device
- * @flags: bit 0 - if set, redirect to ingress instead of egress
- * other bits - reserved
- * Return: 0 on success or negative error
- *
- * u64 bpf_get_current_pid_tgid(void)
- * Return: current->tgid << 32 | current->pid
- *
- * u64 bpf_get_current_uid_gid(void)
- * Return: current_gid << 32 | current_uid
- *
- * int bpf_get_current_comm(char *buf, int size_of_buf)
- * stores current->comm into buf
- * Return: 0 on success or negative error
- *
- * u32 bpf_get_cgroup_classid(skb)
- * retrieve a proc's classid
- * @skb: pointer to skb
- * Return: classid if != 0
- *
- * int bpf_skb_vlan_push(skb, vlan_proto, vlan_tci)
- * Return: 0 on success or negative error
- *
- * int bpf_skb_vlan_pop(skb)
- * Return: 0 on success or negative error
- *
- * int bpf_skb_get_tunnel_key(skb, key, size, flags)
- * int bpf_skb_set_tunnel_key(skb, key, size, flags)
- * retrieve or populate tunnel metadata
- * @skb: pointer to skb
- * @key: pointer to 'struct bpf_tunnel_key'
- * @size: size of 'struct bpf_tunnel_key'
- * @flags: room for future extensions
- * Return: 0 on success or negative error
- *
- * u64 bpf_perf_event_read(map, flags)
- * read perf event counter value
- * @map: pointer to perf_event_array map
- * @flags: index of event in the map or bitmask flags
- * Return: value of perf event counter read or error code
- *
- * int bpf_redirect(ifindex, flags)
- * redirect to another netdev
- * @ifindex: ifindex of the net device
- * @flags:
- * cls_bpf:
- * bit 0 - if set, redirect to ingress instead of egress
- * other bits - reserved
- * xdp_bpf:
- * all bits - reserved
- * Return: cls_bpf: TC_ACT_REDIRECT on success or TC_ACT_SHOT on error
- * xdp_bfp: XDP_REDIRECT on success or XDP_ABORT on error
- * int bpf_redirect_map(map, key, flags)
- * redirect to endpoint in map
- * @map: pointer to dev map
- * @key: index in map to lookup
- * @flags: --
- * Return: XDP_REDIRECT on success or XDP_ABORT on error
- *
- * u32 bpf_get_route_realm(skb)
- * retrieve a dst's tclassid
- * @skb: pointer to skb
- * Return: realm if != 0
- *
- * int bpf_perf_event_output(ctx, map, flags, data, size)
- * output perf raw sample
- * @ctx: struct pt_regs*
- * @map: pointer to perf_event_array map
- * @flags: index of event in the map or bitmask flags
- * @data: data on stack to be output as raw data
- * @size: size of data
- * Return: 0 on success or negative error
- *
- * int bpf_get_stackid(ctx, map, flags)
- * walk user or kernel stack and return id
- * @ctx: struct pt_regs*
- * @map: pointer to stack_trace map
- * @flags: bits 0-7 - numer of stack frames to skip
- * bit 8 - collect user stack instead of kernel
- * bit 9 - compare stacks by hash only
- * bit 10 - if two different stacks hash into the same stackid
- * discard old
- * other bits - reserved
- * Return: >= 0 stackid on success or negative error
- *
- * s64 bpf_csum_diff(from, from_size, to, to_size, seed)
- * calculate csum diff
- * @from: raw from buffer
- * @from_size: length of from buffer
- * @to: raw to buffer
- * @to_size: length of to buffer
- * @seed: optional seed
- * Return: csum result or negative error code
- *
- * int bpf_skb_get_tunnel_opt(skb, opt, size)
- * retrieve tunnel options metadata
- * @skb: pointer to skb
- * @opt: pointer to raw tunnel option data
- * @size: size of @opt
- * Return: option size
- *
- * int bpf_skb_set_tunnel_opt(skb, opt, size)
- * populate tunnel options metadata
- * @skb: pointer to skb
- * @opt: pointer to raw tunnel option data
- * @size: size of @opt
- * Return: 0 on success or negative error
- *
- * int bpf_skb_change_proto(skb, proto, flags)
- * Change protocol of the skb. Currently supported is v4 -> v6,
- * v6 -> v4 transitions. The helper will also resize the skb. eBPF
- * program is expected to fill the new headers via skb_store_bytes
- * and lX_csum_replace.
- * @skb: pointer to skb
- * @proto: new skb->protocol type
- * @flags: reserved
- * Return: 0 on success or negative error
- *
- * int bpf_skb_change_type(skb, type)
- * Change packet type of skb.
- * @skb: pointer to skb
- * @type: new skb->pkt_type type
- * Return: 0 on success or negative error
- *
- * int bpf_skb_under_cgroup(skb, map, index)
- * Check cgroup2 membership of skb
- * @skb: pointer to skb
- * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
- * @index: index of the cgroup in the bpf_map
- * Return:
- * == 0 skb failed the cgroup2 descendant test
- * == 1 skb succeeded the cgroup2 descendant test
- * < 0 error
- *
- * u32 bpf_get_hash_recalc(skb)
- * Retrieve and possibly recalculate skb->hash.
- * @skb: pointer to skb
- * Return: hash
- *
- * u64 bpf_get_current_task(void)
- * Returns current task_struct
- * Return: current
- *
- * int bpf_probe_write_user(void *dst, void *src, int len)
- * safely attempt to write to a location
- * @dst: destination address in userspace
- * @src: source address on stack
- * @len: number of bytes to copy
- * Return: 0 on success or negative error
- *
- * int bpf_current_task_under_cgroup(map, index)
- * Check cgroup2 membership of current task
- * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
- * @index: index of the cgroup in the bpf_map
- * Return:
- * == 0 current failed the cgroup2 descendant test
- * == 1 current succeeded the cgroup2 descendant test
- * < 0 error
- *
- * int bpf_skb_change_tail(skb, len, flags)
- * The helper will resize the skb to the given new size, to be used f.e.
- * with control messages.
- * @skb: pointer to skb
- * @len: new skb length
- * @flags: reserved
- * Return: 0 on success or negative error
- *
- * int bpf_skb_pull_data(skb, len)
- * The helper will pull in non-linear data in case the skb is non-linear
- * and not all of len are part of the linear section. Only needed for
- * read/write with direct packet access.
- * @skb: pointer to skb
- * @len: len to make read/writeable
- * Return: 0 on success or negative error
- *
- * s64 bpf_csum_update(skb, csum)
- * Adds csum into skb->csum in case of CHECKSUM_COMPLETE.
- * @skb: pointer to skb
- * @csum: csum to add
- * Return: csum on success or negative error
- *
- * void bpf_set_hash_invalid(skb)
- * Invalidate current skb->hash.
- * @skb: pointer to skb
- *
- * int bpf_get_numa_node_id()
- * Return: Id of current NUMA node.
- *
- * int bpf_skb_change_head()
- * Grows headroom of skb and adjusts MAC header offset accordingly.
- * Will extends/reallocae as required automatically.
- * May change skb data pointer and will thus invalidate any check
- * performed for direct packet access.
- * @skb: pointer to skb
- * @len: length of header to be pushed in front
- * @flags: Flags (unused for now)
- * Return: 0 on success or negative error
- *
- * int bpf_xdp_adjust_head(xdp_md, delta)
- * Adjust the xdp_md.data by delta
- * @xdp_md: pointer to xdp_md
- * @delta: An positive/negative integer to be added to xdp_md.data
- * Return: 0 on success or negative on error
- *
- * int bpf_probe_read_str(void *dst, int size, const void *unsafe_ptr)
- * Copy a NUL terminated string from unsafe address. In case the string
- * length is smaller than size, the target is not padded with further NUL
- * bytes. In case the string length is larger than size, just count-1
- * bytes are copied and the last byte is set to NUL.
- * @dst: destination address
- * @size: maximum number of bytes to copy, including the trailing NUL
- * @unsafe_ptr: unsafe address
- * Return:
- * > 0 length of the string including the trailing NUL on success
- * < 0 error
- *
- * u64 bpf_get_socket_cookie(skb)
- * Get the cookie for the socket stored inside sk_buff.
- * @skb: pointer to skb
- * Return: 8 Bytes non-decreasing number on success or 0 if the socket
- * field is missing inside sk_buff
- *
- * u32 bpf_get_socket_uid(skb)
- * Get the owner uid of the socket stored inside sk_buff.
- * @skb: pointer to skb
- * Return: uid of the socket owner on success or overflowuid if failed.
- *
- * u32 bpf_set_hash(skb, hash)
- * Set full skb->hash.
- * @skb: pointer to skb
- * @hash: hash to set
- *
- * int bpf_setsockopt(bpf_socket, level, optname, optval, optlen)
- * Calls setsockopt. Not all opts are available, only those with
- * integer optvals plus TCP_CONGESTION.
- * Supported levels: SOL_SOCKET and IPPROTO_TCP
- * @bpf_socket: pointer to bpf_socket
- * @level: SOL_SOCKET or IPPROTO_TCP
- * @optname: option name
- * @optval: pointer to option value
- * @optlen: length of optval in bytes
- * Return: 0 or negative error
- *
- * int bpf_getsockopt(bpf_socket, level, optname, optval, optlen)
- * Calls getsockopt. Not all opts are available.
- * Supported levels: IPPROTO_TCP
- * @bpf_socket: pointer to bpf_socket
- * @level: IPPROTO_TCP
- * @optname: option name
- * @optval: pointer to option value
- * @optlen: length of optval in bytes
- * Return: 0 or negative error
- *
- * int bpf_sock_ops_cb_flags_set(bpf_sock_ops, flags)
- * Set callback flags for sock_ops
- * @bpf_sock_ops: pointer to bpf_sock_ops_kern struct
- * @flags: flags value
- * Return: 0 for no error
- * -EINVAL if there is no full tcp socket
- * bits in flags that are not supported by current kernel
- *
- * int bpf_skb_adjust_room(skb, len_diff, mode, flags)
- * Grow or shrink room in sk_buff.
- * @skb: pointer to skb
- * @len_diff: (signed) amount of room to grow/shrink
- * @mode: operation mode (enum bpf_adj_room_mode)
- * @flags: reserved for future use
- * Return: 0 on success or negative error code
- *
- * int bpf_sk_redirect_map(map, key, flags)
- * Redirect skb to a sock in map using key as a lookup key for the
- * sock in map.
- * @map: pointer to sockmap
- * @key: key to lookup sock in map
- * @flags: reserved for future use
- * Return: SK_PASS
- *
- * int bpf_sock_map_update(skops, map, key, flags)
- * @skops: pointer to bpf_sock_ops
- * @map: pointer to sockmap to update
- * @key: key to insert/update sock in map
- * @flags: same flags as map update elem
- *
- * int bpf_xdp_adjust_meta(xdp_md, delta)
- * Adjust the xdp_md.data_meta by delta
- * @xdp_md: pointer to xdp_md
- * @delta: An positive/negative integer to be added to xdp_md.data_meta
- * Return: 0 on success or negative on error
- *
- * int bpf_perf_event_read_value(map, flags, buf, buf_size)
- * read perf event counter value and perf event enabled/running time
- * @map: pointer to perf_event_array map
- * @flags: index of event in the map or bitmask flags
- * @buf: buf to fill
- * @buf_size: size of the buf
- * Return: 0 on success or negative error code
- *
- * int bpf_perf_prog_read_value(ctx, buf, buf_size)
- * read perf prog attached perf event counter and enabled/running time
- * @ctx: pointer to ctx
- * @buf: buf to fill
- * @buf_size: size of the buf
- * Return : 0 on success or negative error code
- *
- * int bpf_override_return(pt_regs, rc)
- * @pt_regs: pointer to struct pt_regs
- * @rc: the return value to set
- *
- * int bpf_msg_redirect_map(map, key, flags)
- * Redirect msg to a sock in map using key as a lookup key for the
- * sock in map.
- * @map: pointer to sockmap
- * @key: key to lookup sock in map
- * @flags: reserved for future use
- * Return: SK_PASS
- *
- * int bpf_bind(ctx, addr, addr_len)
- * Bind socket to address. Only binding to IP is supported, no port can be
- * set in addr.
- * @ctx: pointer to context of type bpf_sock_addr
- * @addr: pointer to struct sockaddr to bind socket to
- * @addr_len: length of sockaddr structure
- * Return: 0 on success or negative error code
+/* The description below is an attempt at providing documentation to eBPF
+ * developers about the multiple available eBPF helper functions. It can be
+ * parsed and used to produce a manual page. The workflow is the following,
+ * and requires the rst2man utility:
+ *
+ * $ ./scripts/bpf_helpers_doc.py \
+ * --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
+ * $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
+ * $ man /tmp/bpf-helpers.7
+ *
+ * Note that in order to produce this external documentation, some RST
+ * formatting is used in the descriptions to get "bold" and "italics" in
+ * manual pages. Also note that the few trailing white spaces are
+ * intentional, removing them would break paragraphs for rst2man.
+ *
+ * Start of BPF helper function descriptions:
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
new file mode 100755
index 000000000000..3a15ba3f0a83
--- /dev/null
+++ b/scripts/bpf_helpers_doc.py
@@ -0,0 +1,414 @@
+#!/usr/bin/python3
+#
+# Copyright (C) 2018 Netronome Systems, Inc.
+#
+# This software is licensed under the GNU General License Version 2,
+# June 1991 as shown in the file COPYING in the top-level directory of this
+# source tree.
+#
+# THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
+# WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
+# BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
+# OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
+# THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+# In case user attempts to run with Python 2.
+from __future__ import print_function
+
+import argparse
+import re
+import sys, os
+
+class NoHelperFound(BaseException):
+ pass
+
+class ParsingError(BaseException):
+ def __init__(self, line='<line not provided>', reader=None):
+ if reader:
+ BaseException.__init__(self,
+ 'Error at file offset %d, parsing line: %s' %
+ (reader.tell(), line))
+ else:
+ BaseException.__init__(self, 'Error parsing line: %s' % line)
+
+class Helper(object):
+ """
+ An object representing the description of an eBPF helper function.
+ @proto: function prototype of the helper function
+ @desc: textual description of the helper function
+ @ret: description of the return value of the helper function
+ """
+ def __init__(self, proto='', desc='', ret=''):
+ self.proto = proto
+ self.desc = desc
+ self.ret = ret
+
+ def proto_break_down(self):
+ """
+ Break down helper function protocol into smaller chunks: return type,
+ name, distincts arguments.
+ """
+ arg_re = re.compile('^((const )?(struct )?(\w+|...))( (\**)(\w+))?$')
+ res = {}
+ proto_re = re.compile('^(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
+
+ capture = proto_re.match(self.proto)
+ res['ret_type'] = capture.group(1)
+ res['ret_star'] = capture.group(2)
+ res['name'] = capture.group(3)
+ res['args'] = []
+
+ args = capture.group(4).split(', ')
+ for a in args:
+ capture = arg_re.match(a)
+ res['args'].append({
+ 'type' : capture.group(1),
+ 'star' : capture.group(6),
+ 'name' : capture.group(7)
+ })
+
+ return res
+
+class HeaderParser(object):
+ """
+ An object used to parse a file in order to extract the documentation of a
+ list of eBPF helper functions. All the helpers that can be retrieved are
+ stored as Helper object, in the self.helpers() array.
+ @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
+ kernel tree
+ """
+ def __init__(self, filename):
+ self.reader = open(filename, 'r')
+ self.line = ''
+ self.helpers = []
+
+ def parse_helper(self):
+ proto = self.parse_proto()
+ desc = self.parse_desc()
+ ret = self.parse_ret()
+ return Helper(proto=proto, desc=desc, ret=ret)
+
+ def parse_proto(self):
+ # Argument can be of shape:
+ # - "void"
+ # - "type name"
+ # - "type *name"
+ # - Same as above, with "const" and/or "struct" in front of type
+ # - "..." (undefined number of arguments, for bpf_trace_printk())
+ # There is at least one term ("void"), and at most five arguments.
+ p = re.compile('^ \* ((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
+ capture = p.match(self.line)
+ if not capture:
+ raise NoHelperFound
+ self.line = self.reader.readline()
+ return capture.group(1)
+
+ def parse_desc(self):
+ p = re.compile('^ \* \tDescription$')
+ capture = p.match(self.line)
+ if not capture:
+ # Helper can have empty description and we might be parsing another
+ # attribute: return but do not consume.
+ return ''
+ # Description can be several lines, some of them possibly empty, and it
+ # stops when another subsection title is met.
+ desc = ''
+ while True:
+ self.line = self.reader.readline()
+ if self.line == ' *\n':
+ desc += '\n'
+ else:
+ p = re.compile('^ \* \t\t(.*)')
+ capture = p.match(self.line)
+ if capture:
+ desc += capture.group(1) + '\n'
+ else:
+ break
+ return desc
+
+ def parse_ret(self):
+ p = re.compile('^ \* \tReturn$')
+ capture = p.match(self.line)
+ if not capture:
+ # Helper can have empty retval and we might be parsing another
+ # attribute: return but do not consume.
+ return ''
+ # Return value description can be several lines, some of them possibly
+ # empty, and it stops when another subsection title is met.
+ ret = ''
+ while True:
+ self.line = self.reader.readline()
+ if self.line == ' *\n':
+ ret += '\n'
+ else:
+ p = re.compile('^ \* \t\t(.*)')
+ capture = p.match(self.line)
+ if capture:
+ ret += capture.group(1) + '\n'
+ else:
+ break
+ return ret
+
+ def run(self):
+ # Advance to start of helper function descriptions.
+ offset = self.reader.read().find('* Start of BPF helper function descriptions:')
+ if offset == -1:
+ raise Exception('Could not find start of eBPF helper descriptions list')
+ self.reader.seek(offset)
+ self.reader.readline()
+ self.reader.readline()
+ self.line = self.reader.readline()
+
+ while True:
+ try:
+ helper = self.parse_helper()
+ self.helpers.append(helper)
+ except NoHelperFound:
+ break
+
+ self.reader.close()
+ print('Parsed description of %d helper function(s)' % len(self.helpers),
+ file=sys.stderr)
+
+###############################################################################
+
+class Printer(object):
+ """
+ A generic class for printers. Printers should be created with an array of
+ Helper objects, and implement a way to print them in the desired fashion.
+ @helpers: array of Helper objects to print to standard output
+ """
+ def __init__(self, helpers):
+ self.helpers = helpers
+
+ def print_header(self):
+ pass
+
+ def print_footer(self):
+ pass
+
+ def print_one(self, helper):
+ pass
+
+ def print_all(self):
+ self.print_header()
+ for helper in self.helpers:
+ self.print_one(helper)
+ self.print_footer()
+
+class PrinterRST(Printer):
+ """
+ A printer for dumping collected information about helpers as a ReStructured
+ Text page compatible with the rst2man program, which can be used to
+ generate a manual page for the helpers.
+ @helpers: array of Helper objects to print to standard output
+ """
+ def print_header(self):
+ header = '''\
+.. Copyright (C) 2018 Netronome Systems, Inc.
+..
+.. %%%LICENSE_START(VERBATIM)
+.. Permission is granted to make and distribute verbatim copies of this
+.. manual provided the copyright notice and this permission notice are
+.. preserved on all copies.
+..
+.. Permission is granted to copy and distribute modified versions of this
+.. manual under the conditions for verbatim copying, provided that the
+.. entire resulting derived work is distributed under the terms of a
+.. permission notice identical to this one.
+..
+.. Since the Linux kernel and libraries are constantly changing, this
+.. manual page may be incorrect or out-of-date. The author(s) assume no
+.. responsibility for errors or omissions, or for damages resulting from
+.. the use of the information contained herein. The author(s) may not
+.. have taken the same level of care in the production of this manual,
+.. which is licensed free of charge, as they might when working
+.. professionally.
+..
+.. Formatted or processed versions of this manual, if unaccompanied by
+.. the source, must acknowledge the copyright and authors of this work.
+.. %%%LICENSE_END
+..
+.. Please do not edit this file. It was generated from the documentation
+.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
+.. (helpers description), and from scripts/bpf_helpers_doc.py in the same
+.. repository (header and footer).
+
+===========
+BPF-HELPERS
+===========
+-------------------------------------------------------------------------------
+list of eBPF helper functions
+-------------------------------------------------------------------------------
+
+:Manual section: 7
+
+DESCRIPTION
+===========
+
+The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
+written in a pseudo-assembly language, then attached to one of the several
+kernel hooks and run in reaction of specific events. This framework differs
+from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
+the ability to call special functions (or "helpers") from within a program. For
+security reasons, these functions are restricted to a white-list of helpers
+defined in the kernel.
+
+These helpers are used by eBPF programs to interact with the system, or with
+the context in which they work. For instance, they can be used to print
+debugging messages, to get the time since the system was booted, to interact
+with eBPF maps, or to manipulate network packets metadata. Since there are
+several eBPF program types, and that they do not run in the same context, each
+program type can only call a subset of those helpers.
+
+Due to eBPF conventions, a helper can not have more than five arguments.
+
+This document is an attempt to list and document the helpers available to eBPF
+developers. They are sorted by chronological order (the oldest helpers in the
+kernel at the top).
+
+HELPERS
+=======
+'''
+ print(header)
+
+ def print_footer(self):
+ footer = '''
+NOTES
+=====
+
+On the performance side, eBPF programs move to the stack all arguments to pass
+to the helpers, and call directly into the compiled helper functions without
+requiring any foreign-function interface. As a result, calling helpers
+introduce very little overhead.
+
+EXAMPLES
+========
+
+Example usage for most of the eBPF helpers listed in this manual page are
+available within the Linux kernel sources, at the following locations:
+
+* *samples/bpf/*
+* *tools/testing/selftests/bpf/*
+
+IMPLEMENTATION
+==============
+
+This manual page is an effort to document the existing eBPF helper functions.
+But as of this writing, the BPF sub-system is under heavy development. New eBPF
+program or map types are added, along with new helper functions. Some helpers
+are occasionally made available for additional program types. So in spite of
+the efforts of the community, this page might not be up-to-date. If you want to
+check by yourself what helper functions exist in your kernel, or what types of
+programs they can support, here are some files among the kernel tree that you
+may be interested in:
+
+* *include/uapi/linux/bpf.h* contains the full list of all helper functions.
+* *net/core/filter.c* contains the definition of most network-related helper
+ functions, and the list of program types from which they can be used.
+* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
+ helpers.
+* *kernel/bpf/verifier.c* contains the functions used to check that valid types
+ of eBPF maps are used with a given helper function.
+* *kernel/bpf/* directory contains other files in which additional helpers are
+ defined (for cgroups, sockmaps, etc.).
+
+Compatibility between helper functions and program types can generally be found
+in the files where helper functions are defined. Look for the **struct
+bpf_func_proto** objects and for functions returning them: these functions
+contain a list of helpers that a given program type can call. Note that the
+**default:** label of the **switch ... case** used to filter helpers can call
+other functions, themselves allowing access to additional helpers. The
+requirement for GPL license is also in those **struct bpf_func_proto**.
+
+Compatibility between helper functions and map types can be found in the
+**check_map_func_compatibility**\ () function in file *kernel/bpf/verifier.c*.
+
+Helper functions that invalidate the checks on **data** and **data_end**
+pointers for network processing are listed in function
+**bpf_helper_changes_pkt_data**\ () in file *net/core/filter.c*.
+
+SEE ALSO
+========
+
+**bpf**\ (2),
+**cgroups**\ (7),
+**ip**\ (8),
+**perf_event_open**\ (2),
+**sendmsg**\ (2),
+**socket**\ (7),
+**tc-bpf**\ (8)'''
+ print(footer)
+
+ def print_proto(self, helper):
+ """
+ Format function protocol with bold and italics markers. This makes RST
+ file less readable, but gives nice results in the manual page.
+ """
+ proto = helper.proto_break_down()
+
+ print('**%s %s%s(' % (proto['ret_type'],
+ proto['ret_star'].replace('*', '\\*'),
+ proto['name']),
+ end='')
+
+ comma = ''
+ for a in proto['args']:
+ one_arg = '{}{}'.format(comma, a['type'])
+ if a['name']:
+ if a['star']:
+ one_arg += ' {}**\ '.format(a['star'].replace('*', '\\*'))
+ else:
+ one_arg += '** '
+ one_arg += '*{}*\\ **'.format(a['name'])
+ comma = ', '
+ print(one_arg, end='')
+
+ print(')**')
+
+ def print_one(self, helper):
+ self.print_proto(helper)
+
+ if (helper.desc):
+ print('\tDescription')
+ # Do not strip all newline characters: formatted code at the end of
+ # a section must be followed by a blank line.
+ for line in re.sub('\n$', '', helper.desc, count=1).split('\n'):
+ print('{}{}'.format('\t\t' if line else '', line))
+
+ if (helper.ret):
+ print('\tReturn')
+ for line in helper.ret.rstrip().split('\n'):
+ print('{}{}'.format('\t\t' if line else '', line))
+
+ print('')
+
+###############################################################################
+
+# If script is launched from scripts/ from kernel tree and can access
+# ../include/uapi/linux/bpf.h, use it as a default name for the file to parse,
+# otherwise the --filename argument will be required from the command line.
+script = os.path.abspath(sys.argv[0])
+linuxRoot = os.path.dirname(os.path.dirname(script))
+bpfh = os.path.join(linuxRoot, 'include/uapi/linux/bpf.h')
+
+argParser = argparse.ArgumentParser(description="""
+Parse eBPF header file and generate documentation for eBPF helper functions.
+The RST-formatted output produced can be turned into a manual page with the
+rst2man utility.
+""")
+if (os.path.isfile(bpfh)):
+ argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
+ default=bpfh)
+else:
+ argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h')
+args = argParser.parse_args()
+
+# Parse file.
+headerParser = HeaderParser(args.filename)
+headerParser.run()
+
+# Print formatted output to standard output.
+printer = PrinterRST(headerParser.helpers)
+printer.print_all()
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 2/8] bpf: add documentation for eBPF helpers (01-11)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
[not found] ` <20180410175605.2wqhaqx34a4o3gdi@ast-mbp.dhcp.thefacebook.com>
2018-04-10 14:41 ` [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22) Quentin Monnet
` (5 subsequent siblings)
7 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Alexei:
- bpf_map_lookup_elem()
- bpf_map_update_elem()
- bpf_map_delete_elem()
- bpf_probe_read()
- bpf_ktime_get_ns()
- bpf_trace_printk()
- bpf_skb_store_bytes()
- bpf_l3_csum_replace()
- bpf_l4_csum_replace()
- bpf_tail_call()
- bpf_clone_redirect()
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 199 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 199 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 45f77f01e672..2bc653a3a20f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -381,6 +381,205 @@ union bpf_attr {
* intentional, removing them would break paragraphs for rst2man.
*
* Start of BPF helper function descriptions:
+ *
+ * void *bpf_map_lookup_elem(struct bpf_map *map, void *key)
+ * Description
+ * Perform a lookup in *map* for an entry associated to *key*.
+ * Return
+ * Map value associated to *key*, or **NULL** if no entry was
+ * found.
+ *
+ * int bpf_map_update_elem(struct bpf_map *map, void *key, void *value, u64 flags)
+ * Description
+ * Add or update the value of the entry associated to *key* in
+ * *map* with *value*. *flags* is one of:
+ *
+ * **BPF_NOEXIST**
+ * The entry for *key* must not exist in the map.
+ * **BPF_EXIST**
+ * The entry for *key* must already exist in the map.
+ * **BPF_ANY**
+ * No condition on the existence of the entry for *key*.
+ *
+ * These flags are only useful for maps of type
+ * **BPF_MAP_TYPE_HASH**. For all other map types, **BPF_ANY**
+ * should be used.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_map_delete_elem(struct bpf_map *map, void *key)
+ * Description
+ * Delete entry with *key* from *map*.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_probe_read(void *dst, u32 size, const void *src)
+ * Description
+ * For tracing programs, safely attempt to read *size* bytes from
+ * address *src* and store the data in *dst*.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * u64 bpf_ktime_get_ns(void)
+ * Description
+ * Return the time elapsed since system boot, in nanoseconds.
+ * Return
+ * Current *ktime*.
+ *
+ * int bpf_trace_printk(const char *fmt, u32 fmt_size, ...)
+ * Description
+ * This helper is a "printk()-like" facility for debugging. It
+ * prints a message defined by format *fmt* (of size *fmt_size*)
+ * to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
+ * available. It can take up to three additional **u64**
+ * arguments (as an eBPF helpers, the total number of arguments is
+ * limited to five). Each time the helper is called, it appends a
+ * line that looks like the following:
+ *
+ * ::
+ *
+ * telnet-470 [001] .N.. 419421.045894: 0x00000001: BPF command: 2
+ *
+ * In the above:
+ *
+ * * ``telnet`` is the name of the current task.
+ * * ``470`` is the PID of the current task.
+ * * ``001`` is the CPU number on which the task is
+ * running.
+ * * In ``.N..``, each character refers to a set of
+ * options (whether irqs are enabled, scheduling
+ * options, whether hard/softirqs are running, level of
+ * preempt_disabled respectively). **N** means that
+ * **TIF_NEED_RESCHED** and **PREEMPT_NEED_RESCHED**
+ * are set.
+ * * ``419421.045894`` is a timestamp.
+ * * ``0x00000001`` is a fake value used by BPF for the
+ * instruction pointer register.
+ * * ``BPF command: 2`` is the message formatted with
+ * *fmt*.
+ *
+ * The conversion specifiers supported by *fmt* are similar, but
+ * more limited than for printk(). They are **%d**, **%i**,
+ * **%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
+ * **%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
+ * of field, padding with zeroes, etc.) is available, and the
+ * helper will silently fail if it encounters an unknown
+ * specifier.
+ *
+ * Also, note that **bpf_trace_printk**\ () is slow, and should
+ * only be used for debugging purposes. For passing values to user
+ * space, perf events should be preferred.
+ * Return
+ * The number of bytes written to the buffer, or a negative error
+ * in case of failure.
+ *
+ * int bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len, u64 flags)
+ * Description
+ * Store *len* bytes from address *from* into the packet
+ * associated to *skb*, at *offset*. *flags* are a combination of
+ * **BPF_F_RECOMPUTE_CSUM** (automatically recompute the
+ * checksum for the packet after storing the bytes) and
+ * **BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\
+ * **->swhash** and *skb*\ **->l4hash** to 0).
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_l3_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 size)
+ * Description
+ * Recompute the IP checksum for the packet associated to *skb*.
+ * Computation is incremental, so the helper must know the former
+ * value of the header field that was modified (*from*), the new
+ * value of this field (*to*), and the number of bytes (2 or 4)
+ * for this field, stored in *size*. Alternatively, it is possible
+ * to store the difference between the previous and the new values
+ * of the header field in *to*, by setting *from* and *size* to 0.
+ * For both methods, *offset* indicates the location of the IP
+ * checksum within the packet.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_l4_csum_replace(struct sk_buff *skb, u32 offset, u64 from, u64 to, u64 flags)
+ * Description
+ * Recompute the TCP or UDP checksum for the packet associated to
+ * *skb*. Computation is incremental, so the helper must know the
+ * former value of the header field that was modified (*from*),
+ * the new value of this field (*to*), and the number of bytes (2
+ * or 4) for this field, stored on the lowest four bits of
+ * *flags*. Alternatively, it is possible to store the difference
+ * between the previous and the new values of the header field in
+ * *to*, by setting *from* and the four lowest bits of *flags* to
+ * 0. For both methods, *offset* indicates the location of the IP
+ * checksum within the packet. In addition to the size of the
+ * field, *flags* can be added (bitwise OR) actual flags. With
+ * **BPF_F_MARK_MANGLED_0**, a null checksum is left untouched
+ * (unless **BPF_F_MARK_ENFORCE** is added as well), and for
+ * updates resulting in a null checksum the value is set to
+ * **CSUM_MANGLED_0** instead. Flag **BPF_F_PSEUDO_HDR**
+ * indicates the checksum is to be computed against a
+ * pseudo-header.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_tail_call(void *ctx, struct bpf_map *prog_array_map, u32 index)
+ * Description
+ * This special helper is used to trigger a "tail call", or in
+ * other words, to jump into another eBPF program. The contents of
+ * eBPF registers and stack are not modified, the new program
+ * "inherits" them from the caller. This mechanism allows for
+ * program chaining, either for raising the maximum number of
+ * available eBPF instructions, or to execute given programs in
+ * conditional blocks. For security reasons, there is an upper
+ * limit to the number of successive tail calls that can be
+ * performed.
+ *
+ * Upon call of this helper, the program attempts to jump into a
+ * program referenced at index *index* in *prog_array_map*, a
+ * special map of type **BPF_MAP_TYPE_PROG_ARRAY**, and passes
+ * *ctx*, a pointer to the context.
+ *
+ * If the call succeeds, the kernel immediately runs the first
+ * instruction of the new program. This is not a function call,
+ * and it never goes back to the previous program. If the call
+ * fails, then the helper has no effect, and the caller continues
+ * to run its own instructions. A call can fail if the destination
+ * program for the jump does not exist (i.e. *index* is superior
+ * to the number of entries in *prog_array_map*), or if the
+ * maximum number of tail calls has been reached for this chain of
+ * programs. This limit is defined in the kernel by the macro
+ * **MAX_TAIL_CALL_CNT** (not accessible to user space), which
+ * is currently set to 32.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_clone_redirect(struct sk_buff *skb, u32 ifindex, u64 flags)
+ * Description
+ * Clone and redirect the packet associated to *skb* to another
+ * net device of index *ifindex*. The only flag supported for now
+ * is **BPF_F_INGRESS**, which indicates the packet is to be
+ * redirected to the ingress interface instead of (by default)
+ * egress.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 2/8] bpf: add documentation for eBPF helpers (01-11) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
2018-04-10 22:43 ` Alexei Starovoitov
2018-04-10 14:41 ` [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32) Quentin Monnet
` (4 subsequent siblings)
7 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
writter by Alexei:
- bpf_get_current_pid_tgid()
- bpf_get_current_uid_gid()
- bpf_get_current_comm()
- bpf_skb_vlan_push()
- bpf_skb_vlan_pop()
- bpf_skb_get_tunnel_key()
- bpf_skb_set_tunnel_key()
- bpf_redirect()
- bpf_perf_event_output()
- bpf_get_stackid()
- bpf_get_current_task()
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 237 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 237 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2bc653a3a20f..f3ea8824efbc 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -580,6 +580,243 @@ union bpf_attr {
* performed again.
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * u64 bpf_get_current_pid_tgid(void)
+ * Return
+ * A 64-bit integer containing the current tgid and pid, and
+ * created as such:
+ * *current_task*\ **->tgid << 32 \|**
+ * *current_task*\ **->pid**.
+ *
+ * u64 bpf_get_current_uid_gid(void)
+ * Return
+ * A 64-bit integer containing the current GID and UID, and
+ * created as such: *current_gid* **<< 32 \|** *current_uid*.
+ *
+ * int bpf_get_current_comm(char *buf, u32 size_of_buf)
+ * Description
+ * Copy the **comm** attribute of the current task into *buf* of
+ * *size_of_buf*. The **comm** attribute contains the name of
+ * the executable (excluding the path) for the current task. The
+ * *size_of_buf* must be strictly positive. On success, the
+ * helper makes sure that the *buf* is NUL-terminated. On failure,
+ * it is filled with zeroes.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
+ * Description
+ * Push a *vlan_tci* (VLAN tag control information) of protocol
+ * *vlan_proto* to the packet associated to *skb*, then update
+ * the checksum. Note that if *vlan_proto* is different from
+ * **ETH_P_8021Q** and **ETH_P_8021AD**, it is considered to
+ * be **ETH_P_8021Q**.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_vlan_pop(struct sk_buff *skb)
+ * Description
+ * Pop a VLAN header from the packet associated to *skb*.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_get_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
+ * Description
+ * Get tunnel metadata. This helper takes a pointer *key* to an
+ * empty **struct bpf_tunnel_key** of **size**, that will be
+ * filled with tunnel metadata for the packet associated to *skb*.
+ * The *flags* can be set to **BPF_F_TUNINFO_IPV6**, which
+ * indicates that the tunnel is based on IPv6 protocol instead of
+ * IPv4.
+ *
+ * This is typically used on the receive path to perform a lookup
+ * or a packet redirection based on the value of *key*:
+ *
+ * ::
+ *
+ * struct bpf_tunnel_key key = {};
+ * bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
+ * lookup or redirect based on key ...
+ *
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_set_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
+ * Description
+ * Populate tunnel metadata for packet associated to *skb.* The
+ * tunnel metadata is set to the contents of *key*, of *size*. The
+ * *flags* can be set to a combination of the following values:
+ *
+ * **BPF_F_TUNINFO_IPV6**
+ * Indicate that the tunnel is based on IPv6 protocol
+ * instead of IPv4.
+ * **BPF_F_ZERO_CSUM_TX**
+ * For IPv4 packets, add a flag to tunnel metadata
+ * indicating that checksum computation should be skipped
+ * and checksum set to zeroes.
+ * **BPF_F_DONT_FRAGMENT**
+ * Add a flag to tunnel metadata indicating that the
+ * packet should not be fragmented.
+ * **BPF_F_SEQ_NUMBER**
+ * Add a flag to tunnel metadata indicating that a
+ * sequence number should be added to tunnel header before
+ * sending the packet. This flag was added for GRE
+ * encapsulation, but might be used with other protocols
+ * as well in the future.
+ *
+ * Here is a typical usage on the transmit path:
+ *
+ * ::
+ *
+ * struct bpf_tunnel_key key;
+ * populate key ...
+ * bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
+ * bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
+ *
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_redirect(u32 ifindex, u64 flags)
+ * Description
+ * Redirect the packet to another net device of index *ifindex*.
+ * This helper is somewhat similar to **bpf_clone_redirect**\
+ * (), except that the packet is not cloned, which provides
+ * increased performance.
+ *
+ * For hooks other than XDP, *flags* can be set to
+ * **BPF_F_INGRESS**, which indicates the packet is to be
+ * redirected to the ingress interface instead of (by default)
+ * egress. Currently, XDP does not support any flag.
+ * Return
+ * For XDP, the helper returns **XDP_REDIRECT** on success or
+ * **XDP_ABORT** on error. For other program types, the values
+ * are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
+ * error.
+ *
+ * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
+ * Description
+ * Write perf raw sample into a perf event held by *map* of type
+ * **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf event must
+ * have the following attributes: **PERF_SAMPLE_RAW** as
+ * **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
+ * **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
+ *
+ * The *flags* are used to indicate the index in *map* for which
+ * the value must be put, masked with **BPF_F_INDEX_MASK**.
+ * Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
+ * to indicate that the index of the current CPU core should be
+ * used.
+ *
+ * The value to write, of *size*, is passed through eBPF stack and
+ * pointed by *data*.
+ *
+ * The context of the program *ctx* needs also be passed to the
+ * helper, and will get interpreted as a pointer to a **struct
+ * pt_reg**.
+ *
+ * On user space, a program willing to read the values needs to
+ * call **perf_event_open**\ () on the perf event (either for
+ * one or for all CPUs) and to store the file descriptor into the
+ * *map*. This must be done before the eBPF program can send data
+ * into it. An example is available in file
+ * *samples/bpf/trace_output_user.c* in the Linux kernel source
+ * tree (the eBPF program counterpart is in
+ * *samples/bpf/trace_output_kern.c*). It looks like the
+ * following snippet:
+ *
+ * ::
+ *
+ * volatile struct perf_event_mmap_page *header;
+ * struct perf_event_attr attr = {
+ * .sample_type = PERF_SAMPLE_RAW,
+ * .type = PERF_TYPE_SOFTWARE,
+ * .config = PERF_COUNT_SW_BPF_OUTPUT,
+ * };
+ * int page_size;
+ * int mmap_size;
+ * int key = 0;
+ * int pmu_fd;
+ * void *base;
+ *
+ * if (load_bpf_file(filename))
+ * return -1;
+ *
+ * pmu_fd = sys_perf_event_open(&attr,
+ * -1, // pid
+ * 0, // cpu
+ * -1, // group_fd
+ * 0);
+ *
+ * assert(pmu_fd >= 0);
+ * assert(bpf_map_update_elem(map_fd[0], &key,
+ * &pmu_fd, BPF_ANY) == 0);
+ * assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0) == 0);
+ *
+ * page_size = getpagesize();
+ * mmap_size = page_size * (page_cnt + 1);
+ *
+ * base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
+ * MAP_SHARED, fd, 0);
+ * if (base == MAP_FAILED)
+ * return -1;
+ *
+ * header = base;
+ *
+ * **bpf_perf_event_output**\ () achieves better performance
+ * than **bpf_trace_printk**\ () for sharing data with user
+ * space, and is much better suitable for streaming data from eBPF
+ * programs.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
+ * Description
+ * Walk a user or a kernel stack and return its id. To achieve
+ * this, the helper needs *ctx*, which is a pointer to the context
+ * on which the tracing program is executed, and a pointer to a
+ * *map* of type **BPF_MAP_TYPE_STACK_TRACE**.
+ *
+ * The last argument, *flags*, holds the number of stack frames to
+ * skip (from 0 to 255), masked with
+ * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
+ * a combination of the following flags:
+ *
+ * **BPF_F_USER_STACK**
+ * Collect a user space stack instead of a kernel stack.
+ * **BPF_F_FAST_STACK_CMP**
+ * Compare stacks by hash only.
+ * **BPF_F_REUSE_STACKID**
+ * If two different stacks hash into the same *stackid*,
+ * discard the old one.
+ *
+ * The stack id retrieved is a 32 bit long integer handle which
+ * can be further combined with other data (including other stack
+ * ids) and used as a key into maps. This can be useful for
+ * generating a variety of graphs (such as flame graphs or off-cpu
+ * graphs).
+ *
+ * For walking a stack, this helper is an improvement over
+ * **bpf_probe_read**\ (), which can be used with unrolled loops
+ * but is not efficient and consumes a lot of eBPF instructions.
+ * Instead, **bpf_get_stackid**\ () can collect up to
+ * **PERF_MAX_STACK_DEPTH** both kernel and user frames.
+ * Return
+ * The positive or null stack id on success, or a negative error
+ * in case of failure.
+ *
+ * u64 bpf_get_current_task(void)
+ * Return
+ * A pointer to the current task struct.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
` (2 preceding siblings ...)
2018-04-10 14:41 ` [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
2018-04-13 0:28 ` Alexei Starovoitov
2018-04-10 14:41 ` [RFC bpf-next v2 5/8] bpf: add documentation for eBPF helpers (33-41) Quentin Monnet
` (3 subsequent siblings)
7 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Daniel:
- bpf_get_prandom_u32()
- bpf_get_smp_processor_id()
- bpf_get_cgroup_classid()
- bpf_get_route_realm()
- bpf_skb_load_bytes()
- bpf_csum_diff()
- bpf_skb_get_tunnel_opt()
- bpf_skb_set_tunnel_opt()
- bpf_skb_change_proto()
- bpf_skb_change_type()
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 125 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 125 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f3ea8824efbc..d147d9dd6a83 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -473,6 +473,14 @@ union bpf_attr {
* The number of bytes written to the buffer, or a negative error
* in case of failure.
*
+ * u32 bpf_prandom_u32(void)
+ * Return
+ * A random 32-bit unsigned value.
+ *
+ * u32 bpf_get_smp_processor_id(void)
+ * Return
+ * The SMP (Symmetric multiprocessing) processor id.
+ *
* int bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len, u64 flags)
* Description
* Store *len* bytes from address *from* into the packet
@@ -604,6 +612,13 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * u32 bpf_get_cgroup_classid(struct sk_buff *skb)
+ * Description
+ * Retrieve the classid for the current task, i.e. for the
+ * net_cls (network classifier) cgroup to which *skb* belongs.
+ * Return
+ * The classid, or 0 for the default unconfigured classid.
+ *
* int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
* Description
* Push a *vlan_tci* (VLAN tag control information) of protocol
@@ -703,6 +718,14 @@ union bpf_attr {
* are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
* error.
*
+ * u32 bpf_get_route_realm(struct sk_buff *skb)
+ * Description
+ * Retrieve the realm or the route, that is to say the
+ * **tclassid** field of the destination for the *skb*.
+ * Return
+ * The realm of the route for the packet associated to *sdb*, or 0
+ * if none was found.
+ *
* int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
* Description
* Write perf raw sample into a perf event held by *map* of type
@@ -779,6 +802,21 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * int bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len)
+ * Description
+ * This helper was provided as an easy way to load data from a
+ * packet. It can be used to load *len* bytes from *offset* from
+ * the packet associated to *skb*, into the buffer pointed by
+ * *to*.
+ *
+ * Since Linux 4.7, this helper is deprecated in favor of
+ * "direct packet access", enabling packet data to be manipulated
+ * with *skb*\ **->data** and *skb*\ **->data_end** pointing
+ * respectively to the first byte of packet data and to the byte
+ * after the last byte of packet data.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
* int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
* Description
* Walk a user or a kernel stack and return its id. To achieve
@@ -814,6 +852,93 @@ union bpf_attr {
* The positive or null stack id on success, or a negative error
* in case of failure.
*
+ * s64 bpf_csum_diff(__be32 *from, u32 from_size, __be32 *to, u32 to_size, __wsum seed)
+ * Description
+ * Compute a checksum difference, from the raw buffer pointed by
+ * *from*, of length *from_size* (that must be a multiple of 4),
+ * towards the raw buffer pointed by *to*, of size *to_size*
+ * (same remark). An optional *seed* can be added to the value.
+ *
+ * This is flexible enough to be used in several ways:
+ *
+ * * With *from_size* == 0, *to_size* > 0 and *seed* set to
+ * checksum, it can be used when pushing new data.
+ * * With *from_size* > 0, *to_size* == 0 and *seed* set to
+ * checksum, it can be used when removing data from a packet.
+ * * With *from_size* > 0, *to_size* > 0 and *seed* set to 0, it
+ * can be used to compute a diff. Note that *from_size* and
+ * *to_size* do not need to be equal.
+ * Return
+ * The checksum result, or a negative error code in case of
+ * failure.
+ *
+ * int bpf_skb_get_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
+ * Description
+ * Retrieve tunnel options metadata for the packet associated to
+ * *skb*, and store the raw tunnel option data to the buffer *opt*
+ * of *size*.
+ * Return
+ * The size of the option data retrieved.
+ *
+ * int bpf_skb_set_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
+ * Description
+ * Set tunnel options metadata for the packet associated to *skb*
+ * to the option data contained in the raw buffer *opt* of *size*.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_change_proto(struct sk_buff *skb, __be16 proto, u64 flags)
+ * Description
+ * Change the protocol of the *skb* to *proto*. Currently
+ * supported are transition from IPv4 to IPv6, and from IPv6 to
+ * IPv4. The helper takes care of the groundwork for the
+ * transition, including resizing the socket buffer. The eBPF
+ * program is expected to fill the new headers, if any, via
+ * **skb_store_bytes**\ () and to recompute the checksums with
+ * **bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\
+ * ().
+ *
+ * Internally, the GSO type is marked as dodgy so that headers are
+ * checked and segments are recalculated by the GSO/GRO engine.
+ * The size for GSO target is adapted as well.
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_change_type(struct sk_buff *skb, u32 type)
+ * Description
+ * Change the packet type for the packet associated to *skb*. This
+ * comes down to setting *skb*\ **->pkt_type** to *type*, except
+ * the eBPF program does not have a write access to *skb*\
+ * **->pkt_type** beside this helper. Using a helper here allows
+ * for graceful handling of errors.
+ *
+ * The major use case is to change incoming *skb*s to
+ * **PACKET_HOST** in a programmatic way instead of having to
+ * recirculate via **redirect**\ (..., **BPF_F_INGRESS**), for
+ * example.
+ *
+ * Note that *type* only allows certain values. At this time, they
+ * are:
+ *
+ * **PACKET_HOST**
+ * Packet is for us.
+ * **PACKET_BROADCAST**
+ * Send packet to all.
+ * **PACKET_MULTICAST**
+ * Send packet to group.
+ * **PACKET_OTHERHOST**
+ * Send packet to someone else.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
* u64 bpf_get_current_task(void)
* Return
* A pointer to the current task struct.
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 5/8] bpf: add documentation for eBPF helpers (33-41)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
` (3 preceding siblings ...)
2018-04-10 14:41 ` [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 6/8] bpf: add documentation for eBPF helpers (42-50) Quentin Monnet
` (2 subsequent siblings)
7 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast; +Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by Daniel:
- bpf_get_hash_recalc()
- bpf_skb_change_tail()
- bpf_skb_pull_data()
- bpf_csum_update()
- bpf_set_hash_invalid()
- bpf_get_numa_node_id()
- bpf_set_hash()
- bpf_skb_adjust_room()
- bpf_xdp_adjust_meta()
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 155 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 155 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d147d9dd6a83..af429ec79f50 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -939,9 +939,164 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * u32 bpf_get_hash_recalc(struct sk_buff *skb)
+ * Description
+ * Retrieve the hash of the packet, *skb*\ **->hash**. If it is
+ * not set, in particular if the hash was cleared due to mangling,
+ * recompute this hash. Later accesses to the hash can be done
+ * directly with *skb*\ **->hash**.
+ *
+ * Calling **bpf_set_hash_invalid**\ (), changing a packet
+ * prototype with **bpf_skb_change_proto**\ (), or calling
+ * **bpf_skb_store_bytes**\ () with the
+ * **BPF_F_INVALIDATE_HASH** are actions susceptible to clear
+ * the hash and to trigger a new computation for the next call to
+ * **bpf_get_hash_recalc**\ ().
+ * Return
+ * The 32-bit hash.
+ *
* u64 bpf_get_current_task(void)
* Return
* A pointer to the current task struct.
+ *
+ * int bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)
+ * Description
+ * Resize (trim or grow) the packet associated to *skb* to the
+ * new *len*. The *flags* are reserved for future usage, and must
+ * be left at zero.
+ *
+ * The basic idea is that the helper performs the needed work to
+ * change the size of the packet, then the eBPF program rewrites
+ * the rest via helpers like **bpf_skb_store_bytes**\ (),
+ * **bpf_l3_csum_replace**\ (), **bpf_l3_csum_replace**\ ()
+ * and others. This helper is a slow path utility intended for
+ * replies with control messages. And because it is targeted for
+ * slow path, the helper itself can afford to be slow: it
+ * implicitly linearizes, unclones and drops offloads from the
+ * *skb*.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_skb_pull_data(struct sk_buff *skb, u32 len)
+ * Description
+ * Pull in non-linear data in case the *skb* is non-linear and not
+ * all of *len* are part of the linear section. Make *len* bytes
+ * from *skb* readable and writable. If a zero value is passed for
+ * *len*, then the whole length of the *skb* is pulled.
+ *
+ * This helper is only needed for reading and writing with direct
+ * packet access.
+ *
+ * For direct packet access, when testing that offsets to access
+ * are within packet boundaries (test on *skb*\ **->data_end**)
+ * fails, programs just bail out, or, in the direct read case, use
+ * **bpf_skb_load_bytes()** as an alternative to overcome this
+ * limitation. If such data sits in non-linear parts, it is
+ * possible to pull them in once with the new helper, retest and
+ * eventually access them.
+ *
+ * At the same time, this also makes sure the skb is uncloned,
+ * which is a necessary condition for direct write. As this needs
+ * to be an invariant for the write part only, the verifier
+ * detects writes and adds a prologue that is calling
+ * **bpf_skb_pull_data()** to effectively unclone the skb from the
+ * very beginning in case it is indeed cloned.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * s64 bpf_csum_update(struct sk_buff *skb, __wsum csum)
+ * Description
+ * Add the checksum *csum* into *skb*\ **->csum** in case the
+ * driver fed us an IP checksum. Return an error otherwise. This
+ * header is intended to be used in combination with
+ * **bpf_csum_diff()** helper, in particular when the checksum
+ * needs to be updated after data has been written into the packet
+ * through direct packet access.
+ * Return
+ * The checksum on success, or a negative error code in case of
+ * failure.
+ *
+ * void bpf_set_hash_invalid(struct sk_buff *skb)
+ * Description
+ * Invalidate the current *skb*\ **->hash**. It can be used after
+ * mangling on headers through direct packet access, in order to
+ * indicate that the hash is outdated and to trigger a
+ * recalculation the next time the kernel tries to access this
+ * hash.
+ *
+ * int bpf_get_numa_node_id(void)
+ * Description
+ * Return the id of the current NUMA node. The primary use case
+ * for this helper is the selection of sockets for the local NUMA
+ * node, when the program is attached to sockets using the
+ * **SO_ATTACH_REUSEPORT_EBPF** option (see also **socket(7)**).
+ * Return
+ * The id of current NUMA node.
+ *
+ * u32 bpf_set_hash(struct sk_buff *skb, u32 hash)
+ * Description
+ * Set the full hash for *skb* (set the field *skb*\ **->hash**)
+ * to value *hash*.
+ * Return
+ * 0
+ *
+ * int bpf_skb_adjust_room(struct sk_buff *skb, u32 len_diff, u32 mode, u64 flags)
+ * Description
+ * Grow or shrink the room for data in the packet associated to
+ * *skb* by *len_diff*, and according to the selected *mode*.
+ *
+ * There is a single supported mode at this time:
+ *
+ * * **BPF_ADJ_ROOM_NET**: Adjust room at the network layer
+ * (room space is added or removed below the layer 3 header).
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
+ * Description
+ * Adjust the address pointed by *xdp_md*\ **->data_meta** by
+ * *delta* (which can be positive or negative). Note that this
+ * operation modifies the address stored in *xdp_md*\ **->data**,
+ * so the latter must be loaded only after the helper has been
+ * called.
+ *
+ * The use of *xdp_md*\ **->data_meta** is optional and programs
+ * are not required to use it. The rationale is that when the
+ * packet is processed with XDP (e.g. as DoS filter), it is
+ * possible to push further meta data along with it before passing
+ * to the stack, and to give the guarantee that an ingress eBPF
+ * program attached as a TC classifier on the same device can pick
+ * this up for further post-processing. Since TC works with socket
+ * buffers, it remains possible to set from XDP the **mark** or
+ * **priority** pointers, or other pointers for the socket buffer.
+ * Having this scratch space generic and programmable allows for
+ * more flexibility as the user is free to store whatever meta
+ * data they need.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 6/8] bpf: add documentation for eBPF helpers (42-50)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
` (4 preceding siblings ...)
2018-04-10 14:41 ` [RFC bpf-next v2 5/8] bpf: add documentation for eBPF helpers (33-41) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57) Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 8/8] bpf: add documentation for eBPF helpers (58-64) Quentin Monnet
7 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast
Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man,
Kaixu Xia, Martin KaFai Lau, Sargun Dhillon, Thomas Graf,
Gianluca Borello, Chenbo Feng
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions:
Helper from Kaixu:
- bpf_perf_event_read()
Helpers from Martin:
- bpf_skb_under_cgroup()
- bpf_xdp_adjust_head()
Helpers from Sargun:
- bpf_probe_write_user()
- bpf_current_task_under_cgroup()
Helper from Thomas:
- bpf_skb_change_head()
Helper from Gianluca:
- bpf_probe_read_str()
Helpers from Chenbo:
- bpf_get_socket_cookie()
- bpf_get_socket_uid()
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Gianluca Borello <g.borello@gmail.com>
Cc: Chenbo Feng <fengc@google.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 158 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 158 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index af429ec79f50..15d9ccafebbe 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -701,6 +701,25 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * u64 bpf_perf_event_read(struct bpf_map *map, u64 flags)
+ * Description
+ * Read the value of a perf event counter. This helper relies on a
+ * *map* of type **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The
+ * nature of the perf event counter is selected at the creation of
+ * the *map*. The *map* is an array whose size is the number of
+ * available CPU cores, and each cell contains a value relative to
+ * one core. The value to retrieve is indicated by *flags*, that
+ * contains the index of the core to look up, masked with
+ * **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
+ * **BPF_F_CURRENT_CPU** to indicate that the value for the
+ * current CPU core should be retrieved.
+ *
+ * Note that before Linux 4.13, only hardware perf event can be
+ * retrieved.
+ * Return
+ * The value of the perf event counter read from the map, or a
+ * negative error code in case of failure.
+ *
* int bpf_redirect(u32 ifindex, u64 flags)
* Description
* Redirect the packet to another net device of index *ifindex*.
@@ -939,6 +958,17 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * int bpf_skb_under_cgroup(struct sk_buff *skb, struct bpf_map *map, u32 index)
+ * Description
+ * Check whether *skb* is a descendant of the cgroup2 held by
+ * *map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
+ * Return
+ * The return value depends on the result of the test, and can be:
+ *
+ * * 0, if the *skb* failed the cgroup2 descendant test.
+ * * 1, if the *skb* succeeded the cgroup2 descendant test.
+ * * A negative error code, if an error occurred.
+ *
* u32 bpf_get_hash_recalc(struct sk_buff *skb)
* Description
* Retrieve the hash of the packet, *skb*\ **->hash**. If it is
@@ -959,6 +989,37 @@ union bpf_attr {
* Return
* A pointer to the current task struct.
*
+ * int bpf_probe_write_user(void *dst, const void *src, u32 len)
+ * Description
+ * Attempt in a safe way to write *len* bytes from the buffer
+ * *src* to *dst* in memory. It only works for threads that are in
+ * user context.
+ *
+ * This helper should not be used to implement any kind of
+ * security mechanism because of TOC-TOU attacks, but rather to
+ * debug, divert, and manipulate execution of semi-cooperative
+ * processes.
+ *
+ * Keep in mind that this feature is meant for experiments, and it
+ * has a risk of crashing the system and running programs.
+ * Therefore, when an eBPF program using this helper is attached,
+ * a warning including PID and process name is printed to kernel
+ * logs.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_current_task_under_cgroup(struct bpf_map *map, u32 index)
+ * Description
+ * Check whether the probe is being run is the context of a given
+ * subset of the cgroup2 hierarchy. The cgroup2 to test is held by
+ * *map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
+ * Return
+ * The return value depends on the result of the test, and can be:
+ *
+ * * 0, if the *skb* task belongs to the cgroup2.
+ * * 1, if the *skb* task does not belong to the cgroup2.
+ * * A negative error code, if an error occurred.
+ *
* int bpf_skb_change_tail(struct sk_buff *skb, u32 len, u64 flags)
* Description
* Resize (trim or grow) the packet associated to *skb* to the
@@ -1043,6 +1104,103 @@ union bpf_attr {
* Return
* The id of current NUMA node.
*
+ * int bpf_skb_change_head(struct sk_buff *skb, u32 len, u64 flags)
+ * Description
+ * Grows headroom of packet associated to *skb* and adjusts the
+ * offset of the MAC header accordingly, adding *len* bytes of
+ * space. It automatically extends and reallocates memory as
+ * required.
+ *
+ * This helper can be used on a layer 3 *skb* to push a MAC header
+ * for redirection into a layer 2 device.
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
+ * Description
+ * Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
+ * it is possible to use a negative value for *delta*. This helper
+ * can be used to prepare the packet for pushing or popping
+ * headers.
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_probe_read_str(void *dst, int size, const void *unsafe_ptr)
+ * Description
+ * Copy a NUL terminated string from an unsafe address
+ * *unsafe_ptr* to *dst*. The *size* should include the
+ * terminating NUL byte. In case the string length is smaller than
+ * *size*, the target is not padded with further NUL bytes. If the
+ * string length is larger than *size*, just *size*-1 bytes are
+ * copied and the last byte is set to NUL.
+ *
+ * On success, the length of the copied string is returned. This
+ * makes this helper useful in tracing programs for reading
+ * strings, and more importantly to get its length at runtime. See
+ * the following snippet:
+ *
+ * ::
+ *
+ * SEC("kprobe/sys_open")
+ * void bpf_sys_open(struct pt_regs *ctx)
+ * {
+ * char buf[PATHLEN]; // PATHLEN is defined to 256
+ * int res = bpf_probe_read_str(buf, sizeof(buf),
+ * ctx->di);
+ *
+ * // Consume buf, for example push it to
+ * // userspace via bpf_perf_event_output(); we
+ * // can use res (the string length) as event
+ * // size, after checking its boundaries.
+ * }
+ *
+ * In comparison, using **bpf_probe_read()** helper here instead
+ * to read the string would require to estimate the length at
+ * compile time, and would often result in copying more memory
+ * than necessary.
+ *
+ * Another useful use case is when parsing individual process
+ * arguments or individual environment variables navigating
+ * *current*\ **->mm->arg_start** and *current*\
+ * **->mm->env_start**: using this helper and the return value,
+ * one can quickly iterate at the right offset of the memory area.
+ * Return
+ * On success, the strictly positive length of the string,
+ * including the trailing NUL character. On error, a negative
+ * value.
+ *
+ * u64 bpf_get_socket_cookie(struct sk_buff *skb)
+ * Description
+ * Retrieve the socket cookie generated by the kernel from a
+ * **struct sk_buff** with a known socket. If none has been set
+ * yet, generate a new cookie. This helper can be useful for
+ * monitoring per socket networking traffic statistics as it
+ * provides a unique socket identifier per namespace.
+ * Return
+ * A 8-byte long non-decreasing number on success, or 0 if the
+ * socket field is missing inside *skb*.
+ *
+ * u32 bpf_get_socket_uid(struct sk_buff *skb)
+ * Return
+ * The owner UID of the socket associated to *skb*. If the socket
+ * is **NULL**, or if it is not a full socket (i.e. if it is a
+ * time-wait or a request socket instead), **overflowuid** value
+ * is returned (note that **overflowuid** might also be the actual
+ * UID value for the socket).
+ *
* u32 bpf_set_hash(struct sk_buff *skb, u32 hash)
* Description
* Set the full hash for *skb* (set the field *skb*\ **->hash**)
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
` (5 preceding siblings ...)
2018-04-10 14:41 ` [RFC bpf-next v2 6/8] bpf: add documentation for eBPF helpers (42-50) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
[not found] ` <cc54b41e-3f2f-e87f-042f-842c96308626@fb.com>
[not found] ` <20180410175015.GA6762@rdna-mbp.dhcp.thefacebook.com>
2018-04-10 14:41 ` [RFC bpf-next v2 8/8] bpf: add documentation for eBPF helpers (58-64) Quentin Monnet
7 siblings, 2 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast
Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man,
Lawrence Brakmo, Yonghong Song, Josef Bacik, Andrey Ignatov
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions:
Helpers from Lawrence:
- bpf_setsockopt()
- bpf_getsockopt()
- bpf_sock_ops_cb_flags_set()
Helpers from Yonghong:
- bpf_perf_event_read_value()
- bpf_perf_prog_read_value()
Helper from Josef:
- bpf_override_return()
Helper from Andrey:
- bpf_bind()
Cc: Lawrence Brakmo <brakmo@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 184 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 184 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 15d9ccafebbe..7343af4196c8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1208,6 +1208,28 @@ union bpf_attr {
* Return
* 0
*
+ * int bpf_setsockopt(struct bpf_sock_ops_kern *bpf_socket, int level, int optname, char *optval, int optlen)
+ * Description
+ * Emulate a call to **setsockopt()** on the socket associated to
+ * *bpf_socket*, which must be a full socket. The *level* at
+ * which the option resides and the name *optname* of the option
+ * must be specified, see **setsockopt(2)** for more information.
+ * The option value of length *optlen* is pointed by *optval*.
+ *
+ * This helper actually implements a subset of **setsockopt()**.
+ * It supports the following *level*\ s:
+ *
+ * * **SOL_SOCKET**, which supports the following *optname*\ s:
+ * **SO_RCVBUF**, **SO_SNDBUF**, **SO_MAX_PACING_RATE**,
+ * **SO_PRIORITY**, **SO_RCVLOWAT**, **SO_MARK**.
+ * * **IPPROTO_TCP**, which supports the following *optname*\ s:
+ * **TCP_CONGESTION**, **TCP_BPF_IW**,
+ * **TCP_BPF_SNDCWND_CLAMP**.
+ * * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
+ * * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
* int bpf_skb_adjust_room(struct sk_buff *skb, u32 len_diff, u32 mode, u64 flags)
* Description
* Grow or shrink the room for data in the packet associated to
@@ -1255,6 +1277,168 @@ union bpf_attr {
* performed again.
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_perf_event_read_value(struct bpf_map *map, u64 flags, struct bpf_perf_event_value *buf, u32 buf_size)
+ * Description
+ * Read the value of a perf event counter, and store it into *buf*
+ * of size *buf_size*. This helper relies on a *map* of type
+ * **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of the perf
+ * event counter is selected at the creation of the *map*. The
+ * *map* is an array whose size is the number of available CPU
+ * cores, and each cell contains a value relative to one core. The
+ * value to retrieve is indicated by *flags*, that contains the
+ * index of the core to look up, masked with
+ * **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
+ * **BPF_F_CURRENT_CPU** to indicate that the value for the
+ * current CPU core should be retrieved.
+ *
+ * This helper behaves in a way close to
+ * **bpf_perf_event_read**\ () helper, save that instead of
+ * just returning the value observed, it fills the *buf*
+ * structure. This allows for additional data to be retrieved: in
+ * particular, the enabled and running times (in *buf*\
+ * **->enabled** and *buf*\ **->running**, respectively) are
+ * copied.
+ *
+ * These values are interesting, because hardware PMU (Performance
+ * Monitoring Unit) counters are limited resources. When there are
+ * more PMU based perf events opened than available counters,
+ * kernel will multiplex these events so each event gets certain
+ * percentage (but not all) of the PMU time. In case that
+ * multiplexing happens, the number of samples or counter value
+ * will not reflect the case compared to when no multiplexing
+ * occurs. This makes comparison between different runs difficult.
+ * Typically, the counter value should be normalized before
+ * comparing to other experiments. The usual normalization is done
+ * as follows.
+ *
+ * ::
+ *
+ * normalized_counter = counter * t_enabled / t_running
+ *
+ * Where t_enabled is the time enabled for event and t_running is
+ * the time running for event since last normalization. The
+ * enabled and running times are accumulated since the perf event
+ * open. To achieve scaling factor between two invocations of an
+ * eBPF program, users can can use CPU id as the key (which is
+ * typical for perf array usage model) to remember the previous
+ * value and do the calculation inside the eBPF program.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_perf_prog_read_value(struct bpf_perf_event_data_kern *ctx, struct bpf_perf_event_value *buf, u32 buf_size)
+ * Description
+ * For en eBPF program attached to a perf event, retrieve the
+ * value of the event counter associated to *ctx* and store it in
+ * the structure pointed by *buf* and of size *buf_size*. Enabled
+ * and running times are also stored in the structure (see
+ * description of helper **bpf_perf_event_read_value**\ () for
+ * more details).
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_getsockopt(struct bpf_sock_ops_kern *bpf_socket, int level, int optname, char *optval, int optlen)
+ * Description
+ * Emulate a call to **getsockopt()** on the socket associated to
+ * *bpf_socket*, which must be a full socket. The *level* at
+ * which the option resides and the name *optname* of the option
+ * must be specified, see **getsockopt(2)** for more information.
+ * The retrieved value is stored in the structure pointed by
+ * *opval* and of length *optlen*.
+ *
+ * This helper actually implements a subset of **getsockopt()**.
+ * It supports the following *level*\ s:
+ *
+ * * **IPPROTO_TCP**, which supports *optname*
+ * **TCP_CONGESTION**.
+ * * **IPPROTO_IP**, which supports *optname* **IP_TOS**.
+ * * **IPPROTO_IPV6**, which supports *optname* **IPV6_TCLASS**.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
+ * int bpf_override_return(struct pt_reg *regs, u64 rc)
+ * Description
+ * Used for error injection, this helper uses kprobes to override
+ * the return value of the probed function, and to set it to *rc*.
+ * The first argument is the context *regs* on which the kprobe
+ * works.
+ *
+ * This helper works by setting setting the PC (program counter)
+ * to an override function which is run in place of the original
+ * probed function. This means the probed function is not run at
+ * all. The replacement function just returns with the required
+ * value.
+ *
+ * This helper has security implications, and thus is subject to
+ * restrictions. It is only available if the kernel was compiled
+ * with the **CONFIG_BPF_KPROBE_OVERRIDE** configuration
+ * option, and in this case it only works on functions tagged with
+ * **ALLOW_ERROR_INJECTION** in the kernel code.
+ *
+ * Also, the helper is only available for the architectures having
+ * the CONFIG_FUNCTION_ERROR_INJECTION option. As of this writing,
+ * x86 architecture is the only one to support this feature.
+ * Return
+ * 0
+ *
+ * int bpf_sock_ops_cb_flags_set(struct bpf_sock_ops_kern *bpf_sock, int argval)
+ * Description
+ * Attempt to set the value of the **bpf_sock_ops_cb_flags** field
+ * for the full TCP socket associated to *bpf_sock_ops* to
+ * *argval*.
+ *
+ * The primary use of this field is to determine if there should
+ * be calls to eBPF programs of type
+ * **BPF_PROG_TYPE_SOCK_OPS** at various points in the TCP
+ * code. A program of the same type can change its value, per
+ * connection and as necessary, when the connection is
+ * established. This field is directly accessible for reading, but
+ * this helper must be used for updates in order to return an
+ * error if an eBPF program tries to set a callback that is not
+ * supported in the current kernel.
+ *
+ * The supported callback values that *argval* can combine are:
+ *
+ * * **BPF_SOCK_OPS_RTO_CB_FLAG** (retransmission time out)
+ * * **BPF_SOCK_OPS_RETRANS_CB_FLAG** (retransmission)
+ * * **BPF_SOCK_OPS_STATE_CB_FLAG** (TCP state change)
+ *
+ * Here are some examples of where one could call such eBPF
+ * program:
+ *
+ * * When RTO fires.
+ * * When a packet is retransmitted.
+ * * When the connection terminates.
+ * * When a packet is sent.
+ * * When a packet is received.
+ * Return
+ * Code **-EINVAL** if the socket is not a full TCP socket;
+ * otherwise, a positive number containing the bits that could not
+ * be set is returned (which comes down to 0 if all bits were set
+ * as required).
+ *
+ * int bpf_bind(struct bpf_sock_addr_kern *ctx, struct sockaddr *addr, int addr_len)
+ * Description
+ * Bind the socket associated to *ctx* to the address pointed by
+ * *addr*, of length *addr_len*. This allows for making outgoing
+ * connection from the desired IP address, which can be useful for
+ * example when all processes inside a cgroup should use one
+ * single IP address on a host that has multiple IP configured.
+ *
+ * This helper works for IPv4 and IPv6, TCP and UDP sockets. The
+ * domain (*addr*\ **->sa_family**) must be **AF_INET** (or
+ * **AF_INET6**). Looking for a free port to bind to can be
+ * expensive, therefore binding to port is not permitted by the
+ * helper: *addr*\ **->sin_port** (or **sin6_port**, respectively)
+ * must be set to zero.
+ *
+ * As for the remote end, both parts of it can be overridden,
+ * remote IP and remote port. This can be useful if an application
+ * inside a cgroup wants to connect to another application inside
+ * the same cgroup or to itself, but knows nothing about the IP
+ * address assigned to the cgroup.
+ * Return
+ * 0 on success, or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 8/8] bpf: add documentation for eBPF helpers (58-64)
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
` (6 preceding siblings ...)
2018-04-10 14:41 ` [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57) Quentin Monnet
@ 2018-04-10 14:41 ` Quentin Monnet
[not found] ` <20180411121759.4191e267@redhat.com>
7 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-10 14:41 UTC (permalink / raw)
To: daniel, ast
Cc: netdev, oss-drivers, quentin.monnet, linux-doc, linux-man,
John Fastabend
Add documentation for eBPF helper functions to bpf.h user header file.
This documentation can be parsed with the Python script provided in
another commit of the patch series, in order to provide a RST document
that can later be converted into a man page.
The objective is to make the documentation easily understandable and
accessible to all eBPF developers, including beginners.
This patch contains descriptions for the following helper functions, all
written by John:
- bpf_redirect_map()
- bpf_sk_redirect_map()
- bpf_sock_map_update()
- bpf_msg_redirect_map()
- bpf_msg_apply_bytes()
- bpf_msg_cork_bytes()
- bpf_msg_pull_data()
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
---
include/uapi/linux/bpf.h | 140 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 140 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7343af4196c8..db090ad03626 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1250,6 +1250,51 @@ union bpf_attr {
* Return
* 0 on success, or a negative error in case of failure.
*
+ * int bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
+ * Description
+ * Redirect the packet to the endpoint referenced by *map* at
+ * index *key*. Depending on its type, his *map* can contain
+ * references to net devices (for forwarding packets through other
+ * ports), or to CPUs (for redirecting XDP frames to another CPU;
+ * but this is not fully implemented as of this writing).
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ * Return
+ * **XDP_REDIRECT** on success, or **XDP_ABORT** on error.
+ *
+ * int bpf_sk_redirect_map(struct bpf_map *map, u32 key, u64 flags)
+ * Description
+ * Redirect the packet to the socket referenced by *map* (of type
+ * **BPF_MAP_TYPE_SOCKMAP**) at index *key*. The only flag
+ * supported for now is **BPF_F_INGRESS**, which indicates the
+ * packet is to be redirected to the ingress side of the socket
+ * instead of (by default) egress.
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ * Return
+ * **SK_PASS** on success, or **SK_DROP** on error.
+ *
+ * int bpf_sock_map_update(struct bpf_sock_ops_kern *skops, struct bpf_map *map, void *key, u64 flags)
+ * Description
+ * Add an entry to, or update a *map* referencing sockets. The
+ * *skops* is used as a new value for the entry associated to
+ * *key*. *flags* is one of:
+ *
+ * **BPF_NOEXIST**
+ * The entry for *key* must not exist in the map.
+ * **BPF_EXIST**
+ * The entry for *key* must already exist in the map.
+ * **BPF_ANY**
+ * No condition on the existence of the entry for *key*.
+ *
+ * If the *map* has eBPF programs (parser and verdict), those will
+ * be inherited by the socket being added. If the socket is
+ * already attached to eBPF programs, this results in an error.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
* int bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
* Description
* Adjust the address pointed by *xdp_md*\ **->data_meta** by
@@ -1417,6 +1462,101 @@ union bpf_attr {
* be set is returned (which comes down to 0 if all bits were set
* as required).
*
+ * int bpf_msg_redirect_map(struct sk_msg_buff *msg, struct bpf_map *map, u32 key, u64 flags)
+ * Description
+ * This helper is used in programs implementing policies at the
+ * socket level. If the message *msg* is allowed to pass (i.e. if
+ * the verdict eBPF program returns **SK_PASS**), redirect it to
+ * the socket referenced by *map* (of type
+ * **BPF_MAP_TYPE_SOCKMAP**) at index *key*. The only flag
+ * supported for now is **BPF_F_INGRESS**, which indicates the
+ * packet is to be redirected to the ingress side of the socket
+ * instead of (by default) egress.
+ * Return
+ * **SK_PASS** on success, or **SK_DROP** on error.
+ *
+ * int bpf_msg_apply_bytes(struct sk_msg_buff *msg, u32 bytes)
+ * Description
+ * For socket policies, apply the verdict of the eBPF program to
+ * the next *bytes* (number of bytes) of message *msg*.
+ *
+ * For example, this helper can be used in the following cases:
+ *
+ * * A single **sendmsg**\ () or **sendfile**\ () system call
+ * contains multiple logical messages that the eBPF program is
+ * supposed to read and for which it should apply a verdict.
+ * * An eBPF program only cares to read the first *bytes* of a
+ * *msg*. If the message has a large payload, then setting up
+ * and calling the eBPF program repeatedly for all bytes, even
+ * though the verdict is already known, would create unnecessary
+ * overhead.
+ *
+ * When called from within an eBPF program, the helper sets a
+ * counter internal to the BPF infrastructure, that is used to
+ * apply the last verdict to the next *bytes*. If *bytes* is
+ * smaller than the current data being processed from a
+ * **sendmsg**\ () or **sendfile**\ () system call, the first
+ * *bytes* will be sent and the eBPF program will be re-run with
+ * the pointer for start of data pointing to byte number *bytes*
+ * **+ 1**. If *bytes* is larger than the current data being
+ * processed, then the eBPF verdict will be applied to multiple
+ * **sendmsg**\ () or **sendfile**\ () calls until *bytes* are
+ * consumed.
+ *
+ * Note that if a socket closes with the internal counter holding
+ * a non-zero value, this is not a problem because data is not
+ * being buffered for *bytes* and is sent as it is received.
+ * Return
+ * 0
+ *
+ * int bpf_msg_cork_bytes(struct sk_msg_buff *msg, u32 bytes)
+ * Description
+ * For socket policies, prevent the execution of the verdict eBPF
+ * program for message *msg* until *bytes* (byte number) have been
+ * accumulated.
+ *
+ * This can be used when one needs a specific number of bytes
+ * before a verdict can be assigned, even if the data spans
+ * multiple **sendmsg**\ () or **sendfile**\ () calls. The extreme
+ * case would be a user calling **sendmsg**\ () repeatedly with
+ * 1-byte long message segments. Obviously, this is bad for
+ * performance, but it is still valid. If the eBPF program needs
+ * *bytes* bytes to validate a header, this helper can be used to
+ * prevent the eBPF program to be called again until *bytes* have
+ * been accumulated.
+ * Return
+ * 0
+ *
+ * int bpf_msg_pull_data(struct sk_msg_buff *msg, u32 start, u32 end, u64 flags)
+ * Description
+ * For socket policies, pull in non-linear data from user space
+ * for *msg* and set pointers *msg*\ **->data** and *msg*\
+ * **->data_end** to *start* and *end* bytes offsets into *msg*,
+ * respectively.
+ *
+ * If a program of type **BPF_PROG_TYPE_SK_MSG** is run on a
+ * *msg* it can only parse data that the (**data**, **data_end**)
+ * pointers have already consumed. For **sendmsg**\ () hooks this
+ * is likely the first scatterlist element. But for calls relying
+ * on the **sendpage** handler (e.g. **sendfile**\ ()) this will
+ * be the range (**0**, **0**) because the data is shared with
+ * user space and by default the objective is to avoid allowing
+ * user space to modify data while (or after) eBPF verdict is
+ * being decided. This helper can be used to pull in data and to
+ * set the start and end pointer to given values. Data will be
+ * copied if necessary (i.e. if data was not linear and if start
+ * and end pointers do not point to the same chunk).
+ *
+ * A call to this helper is susceptible to change data from the
+ * packet. Therefore, at load time, all checks on pointers
+ * previously done by the verifier are invalidated and must be
+ * performed again.
+ *
+ * All values for *flags* are reserved for future usage, and must
+ * be left at zero.
+ * Return
+ * 0 on success, or a negative error in case of failure.
+ *
* int bpf_bind(struct bpf_sock_addr_kern *ctx, struct sockaddr *addr, int addr_len)
* Description
* Bind the socket associated to *ctx* to the address pointed by
--
2.14.1
^ permalink raw reply related [flat|nested] 20+ messages in thread
* Re: [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation
2018-04-10 14:41 ` [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation Quentin Monnet
@ 2018-04-10 18:16 ` Alexei Starovoitov
2018-04-11 15:41 ` Quentin Monnet
0 siblings, 1 reply; 20+ messages in thread
From: Alexei Starovoitov @ 2018-04-10 18:16 UTC (permalink / raw)
To: Quentin Monnet; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
On Tue, Apr 10, 2018 at 03:41:50PM +0100, Quentin Monnet wrote:
> Remove previous "overview" of eBPF helpers from user bpf.h header.
> Replace it by a comment explaining how to process the new documentation
> (to come in following patches) with a Python script to produce RST, then
> man page documentation.
>
> Also add the aforementioned Python script under scripts/. It is used to
> process include/uapi/linux/bpf.h and to extract helper descriptions, to
> turn it into a RST document that can further be processed with rst2man
> to produce a man page. The script takes one "--filename <path/to/file>"
> option. If the script is launched from scripts/ in the kernel root
> directory, it should be able to find the location of the header to
> parse, and "--filename <path/to/file>" is then optional. If it cannot
> find the file, then the option becomes mandatory. RST-formatted
> documentation is printed to standard output.
>
> Typical workflow for producing the final man page would be:
>
> $ ./scripts/bpf_helpers_doc.py \
> --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
> $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
> $ man /tmp/bpf-helpers.7
>
> Note that the tool kernel-doc cannot be used to document eBPF helpers,
> whose signatures are not available directly in the header files
> (pre-processor directives are used to produce them at the beginning of
> the compilation process).
>
> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
> ---
> include/uapi/linux/bpf.h | 406 ++------------------------------------------
> scripts/bpf_helpers_doc.py | 414 +++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 430 insertions(+), 390 deletions(-)
> create mode 100755 scripts/bpf_helpers_doc.py
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c5ec89732a8d..45f77f01e672 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -365,396 +365,22 @@ union bpf_attr {
> } raw_tracepoint;
> } __attribute__((aligned(8)));
>
> -/* BPF helper function descriptions:
> - *
> - * void *bpf_map_lookup_elem(&map, &key)
> - * Return: Map value or NULL
> - *
> - * int bpf_map_update_elem(&map, &key, &value, flags)
> - * Return: 0 on success or negative error
> - *
> - * int bpf_map_delete_elem(&map, &key)
> - * Return: 0 on success or negative error
> - *
> - * int bpf_probe_read(void *dst, int size, void *src)
> - * Return: 0 on success or negative error
> - *
> - * u64 bpf_ktime_get_ns(void)
> - * Return: current ktime
> - *
> - * int bpf_trace_printk(const char *fmt, int fmt_size, ...)
> - * Return: length of buffer written or negative error
> - *
> - * u32 bpf_prandom_u32(void)
> - * Return: random value
> - *
> - * u32 bpf_raw_smp_processor_id(void)
> - * Return: SMP processor ID
> - *
> - * int bpf_skb_store_bytes(skb, offset, from, len, flags)
> - * store bytes into packet
> - * @skb: pointer to skb
> - * @offset: offset within packet from skb->mac_header
> - * @from: pointer where to copy bytes from
> - * @len: number of bytes to store into packet
> - * @flags: bit 0 - if true, recompute skb->csum
> - * other bits - reserved
> - * Return: 0 on success or negative error
> - *
> - * int bpf_l3_csum_replace(skb, offset, from, to, flags)
> - * recompute IP checksum
> - * @skb: pointer to skb
> - * @offset: offset within packet where IP checksum is located
> - * @from: old value of header field
> - * @to: new value of header field
> - * @flags: bits 0-3 - size of header field
> - * other bits - reserved
> - * Return: 0 on success or negative error
> - *
> - * int bpf_l4_csum_replace(skb, offset, from, to, flags)
> - * recompute TCP/UDP checksum
> - * @skb: pointer to skb
> - * @offset: offset within packet where TCP/UDP checksum is located
> - * @from: old value of header field
> - * @to: new value of header field
> - * @flags: bits 0-3 - size of header field
> - * bit 4 - is pseudo header
> - * other bits - reserved
> - * Return: 0 on success or negative error
> - *
> - * int bpf_tail_call(ctx, prog_array_map, index)
> - * jump into another BPF program
> - * @ctx: context pointer passed to next program
> - * @prog_array_map: pointer to map which type is BPF_MAP_TYPE_PROG_ARRAY
> - * @index: 32-bit index inside array that selects specific program to run
> - * Return: 0 on success or negative error
> - *
> - * int bpf_clone_redirect(skb, ifindex, flags)
> - * redirect to another netdev
> - * @skb: pointer to skb
> - * @ifindex: ifindex of the net device
> - * @flags: bit 0 - if set, redirect to ingress instead of egress
> - * other bits - reserved
> - * Return: 0 on success or negative error
> - *
> - * u64 bpf_get_current_pid_tgid(void)
> - * Return: current->tgid << 32 | current->pid
> - *
> - * u64 bpf_get_current_uid_gid(void)
> - * Return: current_gid << 32 | current_uid
> - *
> - * int bpf_get_current_comm(char *buf, int size_of_buf)
> - * stores current->comm into buf
> - * Return: 0 on success or negative error
> - *
> - * u32 bpf_get_cgroup_classid(skb)
> - * retrieve a proc's classid
> - * @skb: pointer to skb
> - * Return: classid if != 0
> - *
> - * int bpf_skb_vlan_push(skb, vlan_proto, vlan_tci)
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_vlan_pop(skb)
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_get_tunnel_key(skb, key, size, flags)
> - * int bpf_skb_set_tunnel_key(skb, key, size, flags)
> - * retrieve or populate tunnel metadata
> - * @skb: pointer to skb
> - * @key: pointer to 'struct bpf_tunnel_key'
> - * @size: size of 'struct bpf_tunnel_key'
> - * @flags: room for future extensions
> - * Return: 0 on success or negative error
> - *
> - * u64 bpf_perf_event_read(map, flags)
> - * read perf event counter value
> - * @map: pointer to perf_event_array map
> - * @flags: index of event in the map or bitmask flags
> - * Return: value of perf event counter read or error code
> - *
> - * int bpf_redirect(ifindex, flags)
> - * redirect to another netdev
> - * @ifindex: ifindex of the net device
> - * @flags:
> - * cls_bpf:
> - * bit 0 - if set, redirect to ingress instead of egress
> - * other bits - reserved
> - * xdp_bpf:
> - * all bits - reserved
> - * Return: cls_bpf: TC_ACT_REDIRECT on success or TC_ACT_SHOT on error
> - * xdp_bfp: XDP_REDIRECT on success or XDP_ABORT on error
> - * int bpf_redirect_map(map, key, flags)
> - * redirect to endpoint in map
> - * @map: pointer to dev map
> - * @key: index in map to lookup
> - * @flags: --
> - * Return: XDP_REDIRECT on success or XDP_ABORT on error
> - *
> - * u32 bpf_get_route_realm(skb)
> - * retrieve a dst's tclassid
> - * @skb: pointer to skb
> - * Return: realm if != 0
> - *
> - * int bpf_perf_event_output(ctx, map, flags, data, size)
> - * output perf raw sample
> - * @ctx: struct pt_regs*
> - * @map: pointer to perf_event_array map
> - * @flags: index of event in the map or bitmask flags
> - * @data: data on stack to be output as raw data
> - * @size: size of data
> - * Return: 0 on success or negative error
> - *
> - * int bpf_get_stackid(ctx, map, flags)
> - * walk user or kernel stack and return id
> - * @ctx: struct pt_regs*
> - * @map: pointer to stack_trace map
> - * @flags: bits 0-7 - numer of stack frames to skip
> - * bit 8 - collect user stack instead of kernel
> - * bit 9 - compare stacks by hash only
> - * bit 10 - if two different stacks hash into the same stackid
> - * discard old
> - * other bits - reserved
> - * Return: >= 0 stackid on success or negative error
> - *
> - * s64 bpf_csum_diff(from, from_size, to, to_size, seed)
> - * calculate csum diff
> - * @from: raw from buffer
> - * @from_size: length of from buffer
> - * @to: raw to buffer
> - * @to_size: length of to buffer
> - * @seed: optional seed
> - * Return: csum result or negative error code
> - *
> - * int bpf_skb_get_tunnel_opt(skb, opt, size)
> - * retrieve tunnel options metadata
> - * @skb: pointer to skb
> - * @opt: pointer to raw tunnel option data
> - * @size: size of @opt
> - * Return: option size
> - *
> - * int bpf_skb_set_tunnel_opt(skb, opt, size)
> - * populate tunnel options metadata
> - * @skb: pointer to skb
> - * @opt: pointer to raw tunnel option data
> - * @size: size of @opt
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_change_proto(skb, proto, flags)
> - * Change protocol of the skb. Currently supported is v4 -> v6,
> - * v6 -> v4 transitions. The helper will also resize the skb. eBPF
> - * program is expected to fill the new headers via skb_store_bytes
> - * and lX_csum_replace.
> - * @skb: pointer to skb
> - * @proto: new skb->protocol type
> - * @flags: reserved
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_change_type(skb, type)
> - * Change packet type of skb.
> - * @skb: pointer to skb
> - * @type: new skb->pkt_type type
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_under_cgroup(skb, map, index)
> - * Check cgroup2 membership of skb
> - * @skb: pointer to skb
> - * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
> - * @index: index of the cgroup in the bpf_map
> - * Return:
> - * == 0 skb failed the cgroup2 descendant test
> - * == 1 skb succeeded the cgroup2 descendant test
> - * < 0 error
> - *
> - * u32 bpf_get_hash_recalc(skb)
> - * Retrieve and possibly recalculate skb->hash.
> - * @skb: pointer to skb
> - * Return: hash
> - *
> - * u64 bpf_get_current_task(void)
> - * Returns current task_struct
> - * Return: current
> - *
> - * int bpf_probe_write_user(void *dst, void *src, int len)
> - * safely attempt to write to a location
> - * @dst: destination address in userspace
> - * @src: source address on stack
> - * @len: number of bytes to copy
> - * Return: 0 on success or negative error
> - *
> - * int bpf_current_task_under_cgroup(map, index)
> - * Check cgroup2 membership of current task
> - * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
> - * @index: index of the cgroup in the bpf_map
> - * Return:
> - * == 0 current failed the cgroup2 descendant test
> - * == 1 current succeeded the cgroup2 descendant test
> - * < 0 error
> - *
> - * int bpf_skb_change_tail(skb, len, flags)
> - * The helper will resize the skb to the given new size, to be used f.e.
> - * with control messages.
> - * @skb: pointer to skb
> - * @len: new skb length
> - * @flags: reserved
> - * Return: 0 on success or negative error
> - *
> - * int bpf_skb_pull_data(skb, len)
> - * The helper will pull in non-linear data in case the skb is non-linear
> - * and not all of len are part of the linear section. Only needed for
> - * read/write with direct packet access.
> - * @skb: pointer to skb
> - * @len: len to make read/writeable
> - * Return: 0 on success or negative error
> - *
> - * s64 bpf_csum_update(skb, csum)
> - * Adds csum into skb->csum in case of CHECKSUM_COMPLETE.
> - * @skb: pointer to skb
> - * @csum: csum to add
> - * Return: csum on success or negative error
> - *
> - * void bpf_set_hash_invalid(skb)
> - * Invalidate current skb->hash.
> - * @skb: pointer to skb
> - *
> - * int bpf_get_numa_node_id()
> - * Return: Id of current NUMA node.
> - *
> - * int bpf_skb_change_head()
> - * Grows headroom of skb and adjusts MAC header offset accordingly.
> - * Will extends/reallocae as required automatically.
> - * May change skb data pointer and will thus invalidate any check
> - * performed for direct packet access.
> - * @skb: pointer to skb
> - * @len: length of header to be pushed in front
> - * @flags: Flags (unused for now)
> - * Return: 0 on success or negative error
> - *
> - * int bpf_xdp_adjust_head(xdp_md, delta)
> - * Adjust the xdp_md.data by delta
> - * @xdp_md: pointer to xdp_md
> - * @delta: An positive/negative integer to be added to xdp_md.data
> - * Return: 0 on success or negative on error
> - *
> - * int bpf_probe_read_str(void *dst, int size, const void *unsafe_ptr)
> - * Copy a NUL terminated string from unsafe address. In case the string
> - * length is smaller than size, the target is not padded with further NUL
> - * bytes. In case the string length is larger than size, just count-1
> - * bytes are copied and the last byte is set to NUL.
> - * @dst: destination address
> - * @size: maximum number of bytes to copy, including the trailing NUL
> - * @unsafe_ptr: unsafe address
> - * Return:
> - * > 0 length of the string including the trailing NUL on success
> - * < 0 error
> - *
> - * u64 bpf_get_socket_cookie(skb)
> - * Get the cookie for the socket stored inside sk_buff.
> - * @skb: pointer to skb
> - * Return: 8 Bytes non-decreasing number on success or 0 if the socket
> - * field is missing inside sk_buff
> - *
> - * u32 bpf_get_socket_uid(skb)
> - * Get the owner uid of the socket stored inside sk_buff.
> - * @skb: pointer to skb
> - * Return: uid of the socket owner on success or overflowuid if failed.
> - *
> - * u32 bpf_set_hash(skb, hash)
> - * Set full skb->hash.
> - * @skb: pointer to skb
> - * @hash: hash to set
> - *
> - * int bpf_setsockopt(bpf_socket, level, optname, optval, optlen)
> - * Calls setsockopt. Not all opts are available, only those with
> - * integer optvals plus TCP_CONGESTION.
> - * Supported levels: SOL_SOCKET and IPPROTO_TCP
> - * @bpf_socket: pointer to bpf_socket
> - * @level: SOL_SOCKET or IPPROTO_TCP
> - * @optname: option name
> - * @optval: pointer to option value
> - * @optlen: length of optval in bytes
> - * Return: 0 or negative error
> - *
> - * int bpf_getsockopt(bpf_socket, level, optname, optval, optlen)
> - * Calls getsockopt. Not all opts are available.
> - * Supported levels: IPPROTO_TCP
> - * @bpf_socket: pointer to bpf_socket
> - * @level: IPPROTO_TCP
> - * @optname: option name
> - * @optval: pointer to option value
> - * @optlen: length of optval in bytes
> - * Return: 0 or negative error
> - *
> - * int bpf_sock_ops_cb_flags_set(bpf_sock_ops, flags)
> - * Set callback flags for sock_ops
> - * @bpf_sock_ops: pointer to bpf_sock_ops_kern struct
> - * @flags: flags value
> - * Return: 0 for no error
> - * -EINVAL if there is no full tcp socket
> - * bits in flags that are not supported by current kernel
> - *
> - * int bpf_skb_adjust_room(skb, len_diff, mode, flags)
> - * Grow or shrink room in sk_buff.
> - * @skb: pointer to skb
> - * @len_diff: (signed) amount of room to grow/shrink
> - * @mode: operation mode (enum bpf_adj_room_mode)
> - * @flags: reserved for future use
> - * Return: 0 on success or negative error code
> - *
> - * int bpf_sk_redirect_map(map, key, flags)
> - * Redirect skb to a sock in map using key as a lookup key for the
> - * sock in map.
> - * @map: pointer to sockmap
> - * @key: key to lookup sock in map
> - * @flags: reserved for future use
> - * Return: SK_PASS
> - *
> - * int bpf_sock_map_update(skops, map, key, flags)
> - * @skops: pointer to bpf_sock_ops
> - * @map: pointer to sockmap to update
> - * @key: key to insert/update sock in map
> - * @flags: same flags as map update elem
> - *
> - * int bpf_xdp_adjust_meta(xdp_md, delta)
> - * Adjust the xdp_md.data_meta by delta
> - * @xdp_md: pointer to xdp_md
> - * @delta: An positive/negative integer to be added to xdp_md.data_meta
> - * Return: 0 on success or negative on error
> - *
> - * int bpf_perf_event_read_value(map, flags, buf, buf_size)
> - * read perf event counter value and perf event enabled/running time
> - * @map: pointer to perf_event_array map
> - * @flags: index of event in the map or bitmask flags
> - * @buf: buf to fill
> - * @buf_size: size of the buf
> - * Return: 0 on success or negative error code
> - *
> - * int bpf_perf_prog_read_value(ctx, buf, buf_size)
> - * read perf prog attached perf event counter and enabled/running time
> - * @ctx: pointer to ctx
> - * @buf: buf to fill
> - * @buf_size: size of the buf
> - * Return : 0 on success or negative error code
> - *
> - * int bpf_override_return(pt_regs, rc)
> - * @pt_regs: pointer to struct pt_regs
> - * @rc: the return value to set
> - *
> - * int bpf_msg_redirect_map(map, key, flags)
> - * Redirect msg to a sock in map using key as a lookup key for the
> - * sock in map.
> - * @map: pointer to sockmap
> - * @key: key to lookup sock in map
> - * @flags: reserved for future use
> - * Return: SK_PASS
> - *
> - * int bpf_bind(ctx, addr, addr_len)
> - * Bind socket to address. Only binding to IP is supported, no port can be
> - * set in addr.
> - * @ctx: pointer to context of type bpf_sock_addr
> - * @addr: pointer to struct sockaddr to bind socket to
> - * @addr_len: length of sockaddr structure
> - * Return: 0 on success or negative error code
> +/* The description below is an attempt at providing documentation to eBPF
> + * developers about the multiple available eBPF helper functions. It can be
> + * parsed and used to produce a manual page. The workflow is the following,
> + * and requires the rst2man utility:
> + *
> + * $ ./scripts/bpf_helpers_doc.py \
> + * --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
> + * $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
> + * $ man /tmp/bpf-helpers.7
> + *
> + * Note that in order to produce this external documentation, some RST
> + * formatting is used in the descriptions to get "bold" and "italics" in
> + * manual pages. Also note that the few trailing white spaces are
> + * intentional, removing them would break paragraphs for rst2man.
> + *
> + * Start of BPF helper function descriptions:
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
> new file mode 100755
> index 000000000000..3a15ba3f0a83
> --- /dev/null
> +++ b/scripts/bpf_helpers_doc.py
> @@ -0,0 +1,414 @@
> +#!/usr/bin/python3
> +#
> +# Copyright (C) 2018 Netronome Systems, Inc.
> +#
> +# This software is licensed under the GNU General License Version 2,
> +# June 1991 as shown in the file COPYING in the top-level directory of this
> +# source tree.
please use SPDX instead.
> +#
> +# THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
> +# WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
> +# BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
> +# FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
> +# OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
> +# THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
> +
> +# In case user attempts to run with Python 2.
> +from __future__ import print_function
> +
> +import argparse
> +import re
> +import sys, os
> +
> +class NoHelperFound(BaseException):
> + pass
> +
> +class ParsingError(BaseException):
> + def __init__(self, line='<line not provided>', reader=None):
> + if reader:
> + BaseException.__init__(self,
> + 'Error at file offset %d, parsing line: %s' %
> + (reader.tell(), line))
> + else:
> + BaseException.__init__(self, 'Error parsing line: %s' % line)
> +
> +class Helper(object):
> + """
> + An object representing the description of an eBPF helper function.
> + @proto: function prototype of the helper function
> + @desc: textual description of the helper function
> + @ret: description of the return value of the helper function
> + """
> + def __init__(self, proto='', desc='', ret=''):
> + self.proto = proto
> + self.desc = desc
> + self.ret = ret
> +
> + def proto_break_down(self):
> + """
> + Break down helper function protocol into smaller chunks: return type,
> + name, distincts arguments.
> + """
> + arg_re = re.compile('^((const )?(struct )?(\w+|...))( (\**)(\w+))?$')
> + res = {}
> + proto_re = re.compile('^(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
> +
> + capture = proto_re.match(self.proto)
> + res['ret_type'] = capture.group(1)
> + res['ret_star'] = capture.group(2)
> + res['name'] = capture.group(3)
> + res['args'] = []
> +
> + args = capture.group(4).split(', ')
> + for a in args:
> + capture = arg_re.match(a)
> + res['args'].append({
> + 'type' : capture.group(1),
> + 'star' : capture.group(6),
> + 'name' : capture.group(7)
> + })
> +
> + return res
> +
> +class HeaderParser(object):
> + """
> + An object used to parse a file in order to extract the documentation of a
> + list of eBPF helper functions. All the helpers that can be retrieved are
> + stored as Helper object, in the self.helpers() array.
> + @filename: name of file to parse, usually include/uapi/linux/bpf.h in the
> + kernel tree
> + """
> + def __init__(self, filename):
> + self.reader = open(filename, 'r')
> + self.line = ''
> + self.helpers = []
> +
> + def parse_helper(self):
> + proto = self.parse_proto()
> + desc = self.parse_desc()
> + ret = self.parse_ret()
> + return Helper(proto=proto, desc=desc, ret=ret)
> +
> + def parse_proto(self):
> + # Argument can be of shape:
> + # - "void"
> + # - "type name"
> + # - "type *name"
> + # - Same as above, with "const" and/or "struct" in front of type
> + # - "..." (undefined number of arguments, for bpf_trace_printk())
> + # There is at least one term ("void"), and at most five arguments.
> + p = re.compile('^ \* ((.+) \**\w+\((((const )?(struct )?(\w+|\.\.\.)( \**\w+)?)(, )?){1,5}\))$')
> + capture = p.match(self.line)
> + if not capture:
> + raise NoHelperFound
> + self.line = self.reader.readline()
> + return capture.group(1)
> +
> + def parse_desc(self):
> + p = re.compile('^ \* \tDescription$')
> + capture = p.match(self.line)
> + if not capture:
> + # Helper can have empty description and we might be parsing another
> + # attribute: return but do not consume.
> + return ''
> + # Description can be several lines, some of them possibly empty, and it
> + # stops when another subsection title is met.
> + desc = ''
> + while True:
> + self.line = self.reader.readline()
> + if self.line == ' *\n':
> + desc += '\n'
> + else:
> + p = re.compile('^ \* \t\t(.*)')
> + capture = p.match(self.line)
> + if capture:
> + desc += capture.group(1) + '\n'
> + else:
> + break
> + return desc
> +
> + def parse_ret(self):
> + p = re.compile('^ \* \tReturn$')
> + capture = p.match(self.line)
> + if not capture:
> + # Helper can have empty retval and we might be parsing another
> + # attribute: return but do not consume.
> + return ''
> + # Return value description can be several lines, some of them possibly
> + # empty, and it stops when another subsection title is met.
> + ret = ''
> + while True:
> + self.line = self.reader.readline()
> + if self.line == ' *\n':
> + ret += '\n'
> + else:
> + p = re.compile('^ \* \t\t(.*)')
> + capture = p.match(self.line)
> + if capture:
> + ret += capture.group(1) + '\n'
> + else:
> + break
> + return ret
> +
> + def run(self):
> + # Advance to start of helper function descriptions.
> + offset = self.reader.read().find('* Start of BPF helper function descriptions:')
> + if offset == -1:
> + raise Exception('Could not find start of eBPF helper descriptions list')
> + self.reader.seek(offset)
> + self.reader.readline()
> + self.reader.readline()
> + self.line = self.reader.readline()
> +
> + while True:
> + try:
> + helper = self.parse_helper()
> + self.helpers.append(helper)
> + except NoHelperFound:
> + break
> +
> + self.reader.close()
> + print('Parsed description of %d helper function(s)' % len(self.helpers),
> + file=sys.stderr)
> +
> +###############################################################################
> +
> +class Printer(object):
> + """
> + A generic class for printers. Printers should be created with an array of
> + Helper objects, and implement a way to print them in the desired fashion.
> + @helpers: array of Helper objects to print to standard output
> + """
> + def __init__(self, helpers):
> + self.helpers = helpers
> +
> + def print_header(self):
> + pass
> +
> + def print_footer(self):
> + pass
> +
> + def print_one(self, helper):
> + pass
> +
> + def print_all(self):
> + self.print_header()
> + for helper in self.helpers:
> + self.print_one(helper)
> + self.print_footer()
> +
> +class PrinterRST(Printer):
> + """
> + A printer for dumping collected information about helpers as a ReStructured
> + Text page compatible with the rst2man program, which can be used to
> + generate a manual page for the helpers.
> + @helpers: array of Helper objects to print to standard output
> + """
> + def print_header(self):
> + header = '''\
> +.. Copyright (C) 2018 Netronome Systems, Inc.
I think would be good to capture copyrights of all authors that added
the helpers being documented. Since a lot of text was copied from commit
logs it's only fair to preserve the copyrights.
Such man page file is automatically generated by the python script
and script itself is copyrighted by Netronome. That's fine, but the text
of man page is not netronome only.
I'm not sure what would be the solution. May be something like:
"
Copyright (C) All BPF authors and contributors from 2011 to present
See git log include/uapi/linux/bpf.h for details
"
?
> +..
> +.. %%%LICENSE_START(VERBATIM)
> +.. Permission is granted to make and distribute verbatim copies of this
> +.. manual provided the copyright notice and this permission notice are
> +.. preserved on all copies.
> +..
> +.. Permission is granted to copy and distribute modified versions of this
> +.. manual under the conditions for verbatim copying, provided that the
> +.. entire resulting derived work is distributed under the terms of a
> +.. permission notice identical to this one.
> +..
> +.. Since the Linux kernel and libraries are constantly changing, this
> +.. manual page may be incorrect or out-of-date. The author(s) assume no
> +.. responsibility for errors or omissions, or for damages resulting from
> +.. the use of the information contained herein. The author(s) may not
> +.. have taken the same level of care in the production of this manual,
> +.. which is licensed free of charge, as they might when working
> +.. professionally.
> +..
> +.. Formatted or processed versions of this manual, if unaccompanied by
> +.. the source, must acknowledge the copyright and authors of this work.
> +.. %%%LICENSE_END
> +..
> +.. Please do not edit this file. It was generated from the documentation
> +.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
> +.. (helpers description), and from scripts/bpf_helpers_doc.py in the same
> +.. repository (header and footer).
> +
> +===========
> +BPF-HELPERS
> +===========
> +-------------------------------------------------------------------------------
> +list of eBPF helper functions
> +-------------------------------------------------------------------------------
> +
> +:Manual section: 7
> +
> +DESCRIPTION
> +===========
> +
> +The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
> +written in a pseudo-assembly language, then attached to one of the several
> +kernel hooks and run in reaction of specific events. This framework differs
> +from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
> +the ability to call special functions (or "helpers") from within a program. For
> +security reasons, these functions are restricted to a white-list of helpers
> +defined in the kernel.
'for security reasons' sounds a bit odd. May be 'for safety reasons' ?
Or drop that part.
> +
> +These helpers are used by eBPF programs to interact with the system, or with
> +the context in which they work. For instance, they can be used to print
> +debugging messages, to get the time since the system was booted, to interact
> +with eBPF maps, or to manipulate network packets metadata. Since there are
s/packets metadata/packets/
> +several eBPF program types, and that they do not run in the same context, each
> +program type can only call a subset of those helpers.
> +
> +Due to eBPF conventions, a helper can not have more than five arguments.
> +
> +This document is an attempt to list and document the helpers available to eBPF
> +developers. They are sorted by chronological order (the oldest helpers in the
> +kernel at the top).
> +
> +HELPERS
> +=======
> +'''
> + print(header)
> +
> + def print_footer(self):
> + footer = '''
> +NOTES
> +=====
> +
> +On the performance side, eBPF programs move to the stack all arguments to pass
> +to the helpers, and call directly into the compiled helper functions without
"move to the stack all arguments" ?! I'm not sure what you're trying to say.
The arguments stay in registers for the call.
> +requiring any foreign-function interface. As a result, calling helpers
> +introduce very little overhead.
not true. it's zero overhead. Literally. Very little is not the same as zero.
> +
> +EXAMPLES
> +========
> +
> +Example usage for most of the eBPF helpers listed in this manual page are
> +available within the Linux kernel sources, at the following locations:
> +
> +* *samples/bpf/*
> +* *tools/testing/selftests/bpf/*
> +
> +IMPLEMENTATION
> +==============
> +
> +This manual page is an effort to document the existing eBPF helper functions.
> +But as of this writing, the BPF sub-system is under heavy development. New eBPF
> +program or map types are added, along with new helper functions. Some helpers
> +are occasionally made available for additional program types. So in spite of
> +the efforts of the community, this page might not be up-to-date. If you want to
> +check by yourself what helper functions exist in your kernel, or what types of
> +programs they can support, here are some files among the kernel tree that you
> +may be interested in:
> +
> +* *include/uapi/linux/bpf.h* contains the full list of all helper functions.
> +* *net/core/filter.c* contains the definition of most network-related helper
> + functions, and the list of program types from which they can be used.
> +* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
> + helpers.
> +* *kernel/bpf/verifier.c* contains the functions used to check that valid types
> + of eBPF maps are used with a given helper function.
> +* *kernel/bpf/* directory contains other files in which additional helpers are
> + defined (for cgroups, sockmaps, etc.).
> +
> +Compatibility between helper functions and program types can generally be found
> +in the files where helper functions are defined. Look for the **struct
> +bpf_func_proto** objects and for functions returning them: these functions
> +contain a list of helpers that a given program type can call. Note that the
> +**default:** label of the **switch ... case** used to filter helpers can call
> +other functions, themselves allowing access to additional helpers. The
> +requirement for GPL license is also in those **struct bpf_func_proto**.
I think here would be good to add that most networking helpers are non-GPL
because they operate on packets which are abstract bytes on the wire,
whereas most tracing helpers are GPL, since they inspect the guts of
the linux kernel which is GPL itself.
That's the main reason why adding extra 'gpl=yes/no' for each helper
description is redundant.
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22)
2018-04-10 14:41 ` [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22) Quentin Monnet
@ 2018-04-10 22:43 ` Alexei Starovoitov
2018-04-11 15:43 ` Quentin Monnet
0 siblings, 1 reply; 20+ messages in thread
From: Alexei Starovoitov @ 2018-04-10 22:43 UTC (permalink / raw)
To: Quentin Monnet; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
On Tue, Apr 10, 2018 at 03:41:52PM +0100, Quentin Monnet wrote:
> Add documentation for eBPF helper functions to bpf.h user header file.
> This documentation can be parsed with the Python script provided in
> another commit of the patch series, in order to provide a RST document
> that can later be converted into a man page.
>
> The objective is to make the documentation easily understandable and
> accessible to all eBPF developers, including beginners.
>
> This patch contains descriptions for the following helper functions, all
> writter by Alexei:
>
> - bpf_get_current_pid_tgid()
> - bpf_get_current_uid_gid()
> - bpf_get_current_comm()
> - bpf_skb_vlan_push()
> - bpf_skb_vlan_pop()
> - bpf_skb_get_tunnel_key()
> - bpf_skb_set_tunnel_key()
> - bpf_redirect()
> - bpf_perf_event_output()
> - bpf_get_stackid()
> - bpf_get_current_task()
>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
> ---
> include/uapi/linux/bpf.h | 237 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 237 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 2bc653a3a20f..f3ea8824efbc 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -580,6 +580,243 @@ union bpf_attr {
> * performed again.
> * Return
> * 0 on success, or a negative error in case of failure.
> + *
> + * u64 bpf_get_current_pid_tgid(void)
> + * Return
> + * A 64-bit integer containing the current tgid and pid, and
> + * created as such:
> + * *current_task*\ **->tgid << 32 \|**
> + * *current_task*\ **->pid**.
> + *
> + * u64 bpf_get_current_uid_gid(void)
> + * Return
> + * A 64-bit integer containing the current GID and UID, and
> + * created as such: *current_gid* **<< 32 \|** *current_uid*.
> + *
> + * int bpf_get_current_comm(char *buf, u32 size_of_buf)
> + * Description
> + * Copy the **comm** attribute of the current task into *buf* of
> + * *size_of_buf*. The **comm** attribute contains the name of
> + * the executable (excluding the path) for the current task. The
> + * *size_of_buf* must be strictly positive. On success, the
that reminds me that we probably should relax it to ARG_CONST_SIZE_OR_ZERO.
The programs won't be passing an actual zero into it, but it helps
a lot to tell verifier that zero is also valid, since programs
become much simpler.
> + * helper makes sure that the *buf* is NUL-terminated. On failure,
> + * it is filled with zeroes.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
> + * Description
> + * Push a *vlan_tci* (VLAN tag control information) of protocol
> + * *vlan_proto* to the packet associated to *skb*, then update
> + * the checksum. Note that if *vlan_proto* is different from
> + * **ETH_P_8021Q** and **ETH_P_8021AD**, it is considered to
> + * be **ETH_P_8021Q**.
> + *
> + * A call to this helper is susceptible to change data from the
> + * packet. Therefore, at load time, all checks on pointers
> + * previously done by the verifier are invalidated and must be
> + * performed again.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_vlan_pop(struct sk_buff *skb)
> + * Description
> + * Pop a VLAN header from the packet associated to *skb*.
> + *
> + * A call to this helper is susceptible to change data from the
> + * packet. Therefore, at load time, all checks on pointers
> + * previously done by the verifier are invalidated and must be
> + * performed again.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_get_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
> + * Description
> + * Get tunnel metadata. This helper takes a pointer *key* to an
> + * empty **struct bpf_tunnel_key** of **size**, that will be
> + * filled with tunnel metadata for the packet associated to *skb*.
> + * The *flags* can be set to **BPF_F_TUNINFO_IPV6**, which
> + * indicates that the tunnel is based on IPv6 protocol instead of
> + * IPv4.
> + *
> + * This is typically used on the receive path to perform a lookup
> + * or a packet redirection based on the value of *key*:
above is correct, but feels a bit cryptic.
May be give more concrete example for particular tunneling protocol like gre
and say that tunnel_key.remote_ip[46] is essential part of the encap and
bpf prog will make decisions based on the contents of the encap header
where bpf_tunnel_key is a single structure that generalizes parameters of
various tunneling protocols into one struct.
> + *
> + * ::
> + *
> + * struct bpf_tunnel_key key = {};
> + * bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
> + * lookup or redirect based on key ...
> + *
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_set_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
> + * Description
> + * Populate tunnel metadata for packet associated to *skb.* The
> + * tunnel metadata is set to the contents of *key*, of *size*. The
> + * *flags* can be set to a combination of the following values:
> + *
> + * **BPF_F_TUNINFO_IPV6**
> + * Indicate that the tunnel is based on IPv6 protocol
> + * instead of IPv4.
> + * **BPF_F_ZERO_CSUM_TX**
> + * For IPv4 packets, add a flag to tunnel metadata
> + * indicating that checksum computation should be skipped
> + * and checksum set to zeroes.
> + * **BPF_F_DONT_FRAGMENT**
> + * Add a flag to tunnel metadata indicating that the
> + * packet should not be fragmented.
> + * **BPF_F_SEQ_NUMBER**
> + * Add a flag to tunnel metadata indicating that a
> + * sequence number should be added to tunnel header before
> + * sending the packet. This flag was added for GRE
> + * encapsulation, but might be used with other protocols
> + * as well in the future.
> + *
> + * Here is a typical usage on the transmit path:
> + *
> + * ::
> + *
> + * struct bpf_tunnel_key key;
> + * populate key ...
> + * bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
> + * bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
> + *
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_redirect(u32 ifindex, u64 flags)
> + * Description
> + * Redirect the packet to another net device of index *ifindex*.
> + * This helper is somewhat similar to **bpf_clone_redirect**\
> + * (), except that the packet is not cloned, which provides
> + * increased performance.
> + *
> + * For hooks other than XDP, *flags* can be set to
> + * **BPF_F_INGRESS**, which indicates the packet is to be
> + * redirected to the ingress interface instead of (by default)
> + * egress. Currently, XDP does not support any flag.
> + * Return
> + * For XDP, the helper returns **XDP_REDIRECT** on success or
> + * **XDP_ABORT** on error. For other program types, the values
> + * are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
> + * error.
> + *
> + * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
> + * Description
> + * Write perf raw sample into a perf event held by *map* of type
I'd say:
Write raw *data* blob into special bpf perf event held by ...
> + * **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf event must
> + * have the following attributes: **PERF_SAMPLE_RAW** as
> + * **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
> + * **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
> + *
> + * The *flags* are used to indicate the index in *map* for which
> + * the value must be put, masked with **BPF_F_INDEX_MASK**.
> + * Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
> + * to indicate that the index of the current CPU core should be
> + * used.
> + *
> + * The value to write, of *size*, is passed through eBPF stack and
> + * pointed by *data*.
> + *
> + * The context of the program *ctx* needs also be passed to the
> + * helper, and will get interpreted as a pointer to a **struct
> + * pt_reg**.
Not quite correct.
Initially bpf_perf_event_output() was only used with 'struct pt_reg *ctx',
but then later it was generalized for all other tracing prog types,
for clsact and even for XDP.
So 'ctx' can be any of the context used by these program types.
> + *
> + * On user space, a program willing to read the values needs to
> + * call **perf_event_open**\ () on the perf event (either for
> + * one or for all CPUs) and to store the file descriptor into the
> + * *map*. This must be done before the eBPF program can send data
> + * into it. An example is available in file
> + * *samples/bpf/trace_output_user.c* in the Linux kernel source
> + * tree (the eBPF program counterpart is in
> + * *samples/bpf/trace_output_kern.c*). It looks like the
> + * following snippet:
> + *
> + * ::
> + *
> + * volatile struct perf_event_mmap_page *header;
> + * struct perf_event_attr attr = {
> + * .sample_type = PERF_SAMPLE_RAW,
> + * .type = PERF_TYPE_SOFTWARE,
> + * .config = PERF_COUNT_SW_BPF_OUTPUT,
> + * };
> + * int page_size;
> + * int mmap_size;
> + * int key = 0;
> + * int pmu_fd;
> + * void *base;
> + *
> + * if (load_bpf_file(filename))
> + * return -1;
> + *
> + * pmu_fd = sys_perf_event_open(&attr,
> + * -1, // pid
> + * 0, // cpu
> + * -1, // group_fd
> + * 0);
> + *
> + * assert(pmu_fd >= 0);
> + * assert(bpf_map_update_elem(map_fd[0], &key,
> + * &pmu_fd, BPF_ANY) == 0);
> + * assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0) == 0);
> + *
> + * page_size = getpagesize();
> + * mmap_size = page_size * (page_cnt + 1);
> + *
> + * base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
> + * MAP_SHARED, fd, 0);
> + * if (base == MAP_FAILED)
> + * return -1;
> + *
> + * header = base;
I think that is too much for the man page, especially above is far from
complete example.
> + *
> + * **bpf_perf_event_output**\ () achieves better performance
> + * than **bpf_trace_printk**\ () for sharing data with user
> + * space, and is much better suitable for streaming data from eBPF
> + * programs.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
> + * Description
> + * Walk a user or a kernel stack and return its id. To achieve
> + * this, the helper needs *ctx*, which is a pointer to the context
> + * on which the tracing program is executed, and a pointer to a
> + * *map* of type **BPF_MAP_TYPE_STACK_TRACE**.
> + *
> + * The last argument, *flags*, holds the number of stack frames to
> + * skip (from 0 to 255), masked with
> + * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
> + * a combination of the following flags:
> + *
> + * **BPF_F_USER_STACK**
> + * Collect a user space stack instead of a kernel stack.
> + * **BPF_F_FAST_STACK_CMP**
> + * Compare stacks by hash only.
> + * **BPF_F_REUSE_STACKID**
> + * If two different stacks hash into the same *stackid*,
> + * discard the old one.
we have an annoying bug here that we will be sending a patch to fix soon,
since right now there is no way for the program to know that stackid
got replaced.
> + *
> + * The stack id retrieved is a 32 bit long integer handle which
> + * can be further combined with other data (including other stack
> + * ids) and used as a key into maps. This can be useful for
> + * generating a variety of graphs (such as flame graphs or off-cpu
> + * graphs).
> + *
> + * For walking a stack, this helper is an improvement over
> + * **bpf_probe_read**\ (), which can be used with unrolled loops
> + * but is not efficient and consumes a lot of eBPF instructions.
> + * Instead, **bpf_get_stackid**\ () can collect up to
> + * **PERF_MAX_STACK_DEPTH** both kernel and user frames.
PERF_MAX_STACK_DEPTH is now controlled by sysctl knob.
Would be good to mention that this limit can and should be increased
for profiling long user stacks like java.
> + * Return
> + * The positive or null stack id on success, or a negative error
> + * in case of failure.
> + *
> + * u64 bpf_get_current_task(void)
> + * Return
> + * A pointer to the current task struct.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> --
> 2.14.1
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation
2018-04-10 18:16 ` Alexei Starovoitov
@ 2018-04-11 15:41 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:41 UTC (permalink / raw)
To: Alexei Starovoitov; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
2018-04-10 11:16 UTC-0700 ~ Alexei Starovoitov
<alexei.starovoitov@gmail.com>
> On Tue, Apr 10, 2018 at 03:41:50PM +0100, Quentin Monnet wrote:
>> Remove previous "overview" of eBPF helpers from user bpf.h header.
>> Replace it by a comment explaining how to process the new documentation
>> (to come in following patches) with a Python script to produce RST, then
>> man page documentation.
>>
>> Also add the aforementioned Python script under scripts/. It is used to
>> process include/uapi/linux/bpf.h and to extract helper descriptions, to
>> turn it into a RST document that can further be processed with rst2man
>> to produce a man page. The script takes one "--filename <path/to/file>"
>> option. If the script is launched from scripts/ in the kernel root
>> directory, it should be able to find the location of the header to
>> parse, and "--filename <path/to/file>" is then optional. If it cannot
>> find the file, then the option becomes mandatory. RST-formatted
>> documentation is printed to standard output.
>>
>> Typical workflow for producing the final man page would be:
>>
>> $ ./scripts/bpf_helpers_doc.py \
>> --filename include/uapi/linux/bpf.h > /tmp/bpf-helpers.rst
>> $ rst2man /tmp/bpf-helpers.rst > /tmp/bpf-helpers.7
>> $ man /tmp/bpf-helpers.7
>>
>> Note that the tool kernel-doc cannot be used to document eBPF helpers,
>> whose signatures are not available directly in the header files
>> (pre-processor directives are used to produce them at the beginning of
>> the compilation process).
>>
>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>> ---
>> include/uapi/linux/bpf.h | 406 ++------------------------------------------
>> scripts/bpf_helpers_doc.py | 414 +++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 430 insertions(+), 390 deletions(-)
>> create mode 100755 scripts/bpf_helpers_doc.py
>>
[...]
>> diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
>> new file mode 100755
>> index 000000000000..3a15ba3f0a83
>> --- /dev/null
>> +++ b/scripts/bpf_helpers_doc.py
>> @@ -0,0 +1,414 @@
>> +#!/usr/bin/python3
>> +#
>> +# Copyright (C) 2018 Netronome Systems, Inc.
>> +#
>> +# This software is licensed under the GNU General License Version 2,
>> +# June 1991 as shown in the file COPYING in the top-level directory of this
>> +# source tree.
>
> please use SPDX instead.
>
Same as for bpftool, our layers remain a bit cautious about it. I'd be
happy to change it for SPDX as a follow-up when I get the green light.
>> +#
>> +# THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
>> +# WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING,
>> +# BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
>> +# FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
>> +# OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
>> +# THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
>> +
[...]
>> +class PrinterRST(Printer):
>> + """
>> + A printer for dumping collected information about helpers as a ReStructured
>> + Text page compatible with the rst2man program, which can be used to
>> + generate a manual page for the helpers.
>> + @helpers: array of Helper objects to print to standard output
>> + """
>> + def print_header(self):
>> + header = '''\
>> +.. Copyright (C) 2018 Netronome Systems, Inc.
>
> I think would be good to capture copyrights of all authors that added
> the helpers being documented. Since a lot of text was copied from commit
> logs it's only fair to preserve the copyrights.
> Such man page file is automatically generated by the python script
> and script itself is copyrighted by Netronome. That's fine, but the text
> of man page is not netronome only.
> I'm not sure what would be the solution. May be something like:
> "
> Copyright (C) All BPF authors and contributors from 2011 to present
> See git log include/uapi/linux/bpf.h for details
> "
> ?
Seems fair indeed. I do not have a better suggestion myself, so I will
stick to yours.
Out of curiosity, why 2011 for the year? I thought you introduced eBPF
in the kernel in 2014 (bd4cf0ed331a), and I do not believe helpers have
any link with cBPF?
>> +..
>> +.. %%%LICENSE_START(VERBATIM)
>> +.. Permission is granted to make and distribute verbatim copies of this
>> +.. manual provided the copyright notice and this permission notice are
>> +.. preserved on all copies.
>> +..
>> +.. Permission is granted to copy and distribute modified versions of this
>> +.. manual under the conditions for verbatim copying, provided that the
>> +.. entire resulting derived work is distributed under the terms of a
>> +.. permission notice identical to this one.
>> +..
>> +.. Since the Linux kernel and libraries are constantly changing, this
>> +.. manual page may be incorrect or out-of-date. The author(s) assume no
>> +.. responsibility for errors or omissions, or for damages resulting from
>> +.. the use of the information contained herein. The author(s) may not
>> +.. have taken the same level of care in the production of this manual,
>> +.. which is licensed free of charge, as they might when working
>> +.. professionally.
>> +..
>> +.. Formatted or processed versions of this manual, if unaccompanied by
>> +.. the source, must acknowledge the copyright and authors of this work.
>> +.. %%%LICENSE_END
>> +..
>> +.. Please do not edit this file. It was generated from the documentation
>> +.. located in file include/uapi/linux/bpf.h of the Linux kernel sources
>> +.. (helpers description), and from scripts/bpf_helpers_doc.py in the same
>> +.. repository (header and footer).
>> +
>> +===========
>> +BPF-HELPERS
>> +===========
>> +-------------------------------------------------------------------------------
>> +list of eBPF helper functions
>> +-------------------------------------------------------------------------------
>> +
>> +:Manual section: 7
>> +
>> +DESCRIPTION
>> +===========
>> +
>> +The extended Berkeley Packet Filter (eBPF) subsystem consists in programs
>> +written in a pseudo-assembly language, then attached to one of the several
>> +kernel hooks and run in reaction of specific events. This framework differs
>> +from the older, "classic" BPF (or "cBPF") in several aspects, one of them being
>> +the ability to call special functions (or "helpers") from within a program. For
>> +security reasons, these functions are restricted to a white-list of helpers
>> +defined in the kernel.
>
> 'for security reasons' sounds a bit odd. May be 'for safety reasons' ?
> Or drop that part.
I'll drop it and keep "These functions are restricted to a white-list of
helpers defined in the kernel."
>> +
>> +These helpers are used by eBPF programs to interact with the system, or with
>> +the context in which they work. For instance, they can be used to print
>> +debugging messages, to get the time since the system was booted, to interact
>> +with eBPF maps, or to manipulate network packets metadata. Since there are
>
> s/packets metadata/packets/
Ok.
>> +several eBPF program types, and that they do not run in the same context, each
>> +program type can only call a subset of those helpers.
>> +
>> +Due to eBPF conventions, a helper can not have more than five arguments.
>> +
>> +This document is an attempt to list and document the helpers available to eBPF
>> +developers. They are sorted by chronological order (the oldest helpers in the
>> +kernel at the top).
>> +
>> +HELPERS
>> +=======
>> +'''
>> + print(header)
>> +
>> + def print_footer(self):
>> + footer = '''
>> +NOTES
>> +=====
>> +
>> +On the performance side, eBPF programs move to the stack all arguments to pass
>> +to the helpers, and call directly into the compiled helper functions without
>
> "move to the stack all arguments" ?! I'm not sure what you're trying to say.
> The arguments stay in registers for the call.
>
>> +requiring any foreign-function interface. As a result, calling helpers
>> +introduce very little overhead.
>
> not true. it's zero overhead. Literally. Very little is not the same as zero.
Not the same indeed :). I will fix with "no overhead".
I'm not too sure either what I meant when I wrote the thing about moving
arguments to the stack... In fact this "NOTES" section is short and not
really relevant. I will probably delete it and add a line in page header
about helpers being called with no overhead.
>> +
>> +EXAMPLES
>> +========
>> +
>> +Example usage for most of the eBPF helpers listed in this manual page are
>> +available within the Linux kernel sources, at the following locations:
>> +
>> +* *samples/bpf/*
>> +* *tools/testing/selftests/bpf/*
>> +
>> +IMPLEMENTATION
>> +==============
>> +
>> +This manual page is an effort to document the existing eBPF helper functions.
>> +But as of this writing, the BPF sub-system is under heavy development. New eBPF
>> +program or map types are added, along with new helper functions. Some helpers
>> +are occasionally made available for additional program types. So in spite of
>> +the efforts of the community, this page might not be up-to-date. If you want to
>> +check by yourself what helper functions exist in your kernel, or what types of
>> +programs they can support, here are some files among the kernel tree that you
>> +may be interested in:
>> +
>> +* *include/uapi/linux/bpf.h* contains the full list of all helper functions.
>> +* *net/core/filter.c* contains the definition of most network-related helper
>> + functions, and the list of program types from which they can be used.
>> +* *kernel/trace/bpf_trace.c* is the equivalent for most tracing program-related
>> + helpers.
>> +* *kernel/bpf/verifier.c* contains the functions used to check that valid types
>> + of eBPF maps are used with a given helper function.
>> +* *kernel/bpf/* directory contains other files in which additional helpers are
>> + defined (for cgroups, sockmaps, etc.).
>> +
>> +Compatibility between helper functions and program types can generally be found
>> +in the files where helper functions are defined. Look for the **struct
>> +bpf_func_proto** objects and for functions returning them: these functions
>> +contain a list of helpers that a given program type can call. Note that the
>> +**default:** label of the **switch ... case** used to filter helpers can call
>> +other functions, themselves allowing access to additional helpers. The
>> +requirement for GPL license is also in those **struct bpf_func_proto**.
>
> I think here would be good to add that most networking helpers are non-GPL
> because they operate on packets which are abstract bytes on the wire,
> whereas most tracing helpers are GPL, since they inspect the guts of
> the linux kernel which is GPL itself.
> That's the main reason why adding extra 'gpl=yes/no' for each helper
> description is redundant.
>
I removed information from the page header about licensing since v1, I
may reintroduce some of it and tell about the difference between
networking and tracing programs, as you suggest.
I understand this difference and I see that specifying GPL requirement
for each individual helper is redundant. And yet I still believe that
for newcomers, it remains easier to have the indication for the specific
helper they are reading about in the man page rather than to take a
guess ("Is this helper for networking only?"). But I do not intend to
add it back to this set anyway, so let's keep this for future
discussions :).
Thanks for the review!
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 2/8] bpf: add documentation for eBPF helpers (01-11)
[not found] ` <20180410175605.2wqhaqx34a4o3gdi@ast-mbp.dhcp.thefacebook.com>
@ 2018-04-11 15:42 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:42 UTC (permalink / raw)
To: Alexei Starovoitov; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
2018-04-10 10:56 UTC-0700 ~ Alexei Starovoitov
<alexei.starovoitov@gmail.com>
> On Tue, Apr 10, 2018 at 03:41:51PM +0100, Quentin Monnet wrote:
>> Add documentation for eBPF helper functions to bpf.h user header file.
>> This documentation can be parsed with the Python script provided in
>> another commit of the patch series, in order to provide a RST document
>> that can later be converted into a man page.
>>
>> The objective is to make the documentation easily understandable and
>> accessible to all eBPF developers, including beginners.
>>
>> This patch contains descriptions for the following helper functions, all
>> written by Alexei:
>>
>> - bpf_map_lookup_elem()
>> - bpf_map_update_elem()
>> - bpf_map_delete_elem()
>> - bpf_probe_read()
>> - bpf_ktime_get_ns()
>> - bpf_trace_printk()
>> - bpf_skb_store_bytes()
>> - bpf_l3_csum_replace()
>> - bpf_l4_csum_replace()
>> - bpf_tail_call()
>> - bpf_clone_redirect()
>>
>> Cc: Alexei Starovoitov <ast@kernel.org>
>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>> ---
>> include/uapi/linux/bpf.h | 199 +++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 199 insertions(+)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 45f77f01e672..2bc653a3a20f 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -381,6 +381,205 @@ union bpf_attr {
>> * intentional, removing them would break paragraphs for rst2man.
>> *
>> * Start of BPF helper function descriptions:
>> + *
>> + * void *bpf_map_lookup_elem(struct bpf_map *map, void *key)
>> + * Description
>> + * Perform a lookup in *map* for an entry associated to *key*.
>> + * Return
>> + * Map value associated to *key*, or **NULL** if no entry was
>> + * found.
>> + *
>> + * int bpf_map_update_elem(struct bpf_map *map, void *key, void *value, u64 flags)
>> + * Description
>> + * Add or update the value of the entry associated to *key* in
>> + * *map* with *value*. *flags* is one of:
>> + *
>> + * **BPF_NOEXIST**
>> + * The entry for *key* must not exist in the map.
>> + * **BPF_EXIST**
>> + * The entry for *key* must already exist in the map.
>> + * **BPF_ANY**
>> + * No condition on the existence of the entry for *key*.
>> + *
>> + * These flags are only useful for maps of type
>> + * **BPF_MAP_TYPE_HASH**. For all other map types, **BPF_ANY**
>> + * should be used.
>
> I think that's not entirely accurate.
> The flags work as expected for all other map types as well
> and for lru map, sockmap, map in map the flags have practical use cases.
>
Ok, I missed that. I have to go back and check how the flags are used
for those maps. I will cook up something cleaner for the next version of
the set.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
[...]
>> + *
>> + * int bpf_trace_printk(const char *fmt, u32 fmt_size, ...)
>> + * Description
>> + * This helper is a "printk()-like" facility for debugging. It
>> + * prints a message defined by format *fmt* (of size *fmt_size*)
>> + * to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
>> + * available. It can take up to three additional **u64**
>> + * arguments (as an eBPF helpers, the total number of arguments is
>> + * limited to five). Each time the helper is called, it appends a
>> + * line that looks like the following:
>> + *
>> + * ::
>> + *
>> + * telnet-470 [001] .N.. 419421.045894: 0x00000001: BPF command: 2
>> + *
>> + * In the above:
>> + *
>> + * * ``telnet`` is the name of the current task.
>> + * * ``470`` is the PID of the current task.
>> + * * ``001`` is the CPU number on which the task is
>> + * running.
>> + * * In ``.N..``, each character refers to a set of
>> + * options (whether irqs are enabled, scheduling
>> + * options, whether hard/softirqs are running, level of
>> + * preempt_disabled respectively). **N** means that
>> + * **TIF_NEED_RESCHED** and **PREEMPT_NEED_RESCHED**
>> + * are set.
>> + * * ``419421.045894`` is a timestamp.
>> + * * ``0x00000001`` is a fake value used by BPF for the
>> + * instruction pointer register.
>> + * * ``BPF command: 2`` is the message formatted with
>> + * *fmt*.
>
> the above depends on how trace_pipe was configured. It's a default
> configuration for many, but would be good to explain this a bit better.
>
I did not know about that. Would you have a pointer about how to
configure trace_pipe, please?
>> + *
>> + * The conversion specifiers supported by *fmt* are similar, but
>> + * more limited than for printk(). They are **%d**, **%i**,
>> + * **%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
>> + * **%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
>> + * of field, padding with zeroes, etc.) is available, and the
>> + * helper will silently fail if it encounters an unknown
>> + * specifier.
>
> This is not true. bpf_trace_printk will return -EINVAL for unknown specifier.
>
Correct, sorry about that. I never check the return value of
bpf_trace_printk(), and it's hard to realise it failed without resorting
to another bpf_trace_printk() :). I'll fix it, what about:
"No modifier (size of field, padding with zeroes, etc.) is available,
and the helper will return **-EINVAL** (but print nothing) if it
encounters an unknown specifier."
(I would like to keep the "print nothing" idea, at the beginning I spent
some time myself trying to figure out why my bpf_trace_prink() seemed to
be never called--I was simply trying to print with "%#x".)
>> + *
>> + * Also, note that **bpf_trace_printk**\ () is slow, and should
>> + * only be used for debugging purposes. For passing values to user
>> + * space, perf events should be preferred.
>
> please mention the giant dmesg warning that people will definitely
> notice when they try to use this helper.
This is a good idea, I will mention it.
>> + * Return
>> + * The number of bytes written to the buffer, or a negative error
>> + * in case of failure.
>> + *
[...]
>> + * int bpf_tail_call(void *ctx, struct bpf_map *prog_array_map, u32 index)
>> + * Description
>> + * This special helper is used to trigger a "tail call", or in
>> + * other words, to jump into another eBPF program. The contents of
>> + * eBPF registers and stack are not modified, the new program
>> + * "inherits" them from the caller. This mechanism allows for
>
> "inherits" is a technically correct, but misleading statement,
> since callee program cannot access caller's registers and stack.
>
I can replace this sentence by:
"The same stack frame is used (but values on stack and in registers for
the caller are not accessible to the callee)."
>> + * program chaining, either for raising the maximum number of
>> + * available eBPF instructions, or to execute given programs in
>> + * conditional blocks. For security reasons, there is an upper
>> + * limit to the number of successive tail calls that can be
>> + * performed.
>> + *
>> + * Upon call of this helper, the program attempts to jump into a
>> + * program referenced at index *index* in *prog_array_map*, a
>> + * special map of type **BPF_MAP_TYPE_PROG_ARRAY**, and passes
>> + * *ctx*, a pointer to the context.
>> + *
>> + * If the call succeeds, the kernel immediately runs the first
>> + * instruction of the new program. This is not a function call,
>> + * and it never goes back to the previous program. If the call
>> + * fails, then the helper has no effect, and the caller continues
>> + * to run its own instructions. A call can fail if the destination
>> + * program for the jump does not exist (i.e. *index* is superior
>> + * to the number of entries in *prog_array_map*), or if the
>> + * maximum number of tail calls has been reached for this chain of
>> + * programs. This limit is defined in the kernel by the macro
>> + * **MAX_TAIL_CALL_CNT** (not accessible to user space), which
>> + * is currently set to 32.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_clone_redirect(struct sk_buff *skb, u32 ifindex, u64 flags)
>> + * Description
>> + * Clone and redirect the packet associated to *skb* to another
>> + * net device of index *ifindex*. The only flag supported for now
>> + * is **BPF_F_INGRESS**, which indicates the packet is to be
>> + * redirected to the ingress interface instead of (by default)
>> + * egress.
>
> imo the above sentence is prone to misinterpretation.
> Can you rephrase it to say that both redirect to ingress and redirect to egress
> are supported and flag is used to indicate which path to take ?
>
I could replace with the following:
"Clone and redirect the packet associated to *skb* to another net device
of index *ifindex*. Both ingress and egress interfaces can be used for
redirection. The **BPF_F_INGRESS** value in *flags* is used to make the
distinction (ingress path is selected if the flag is present, egress
path otherwise). This is the only flag supported for now."
I think I wrote similar things about other helpers using BPF_F_INGRESS
flag, I will also update them accordingly.
>> + *
>> + * A call to this helper is susceptible to change data from the
>> + * packet. Therefore, at load time, all checks on pointers
>> + * previously done by the verifier are invalidated and must be
>> + * performed again.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> */
>> #define __BPF_FUNC_MAPPER(FN) \
>> FN(unspec), \
>> --
>> 2.14.1
>>
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22)
2018-04-10 22:43 ` Alexei Starovoitov
@ 2018-04-11 15:43 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:43 UTC (permalink / raw)
To: Alexei Starovoitov; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
2018-04-10 15:43 UTC-0700 ~ Alexei Starovoitov
<alexei.starovoitov@gmail.com>
> On Tue, Apr 10, 2018 at 03:41:52PM +0100, Quentin Monnet wrote:
>> Add documentation for eBPF helper functions to bpf.h user header file.
>> This documentation can be parsed with the Python script provided in
>> another commit of the patch series, in order to provide a RST document
>> that can later be converted into a man page.
>>
>> The objective is to make the documentation easily understandable and
>> accessible to all eBPF developers, including beginners.
>>
>> This patch contains descriptions for the following helper functions, all
>> writter by Alexei:
>>
>> - bpf_get_current_pid_tgid()
>> - bpf_get_current_uid_gid()
>> - bpf_get_current_comm()
>> - bpf_skb_vlan_push()
>> - bpf_skb_vlan_pop()
>> - bpf_skb_get_tunnel_key()
>> - bpf_skb_set_tunnel_key()
>> - bpf_redirect()
>> - bpf_perf_event_output()
>> - bpf_get_stackid()
>> - bpf_get_current_task()
>>
>> Cc: Alexei Starovoitov <ast@kernel.org>
>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>> ---
>> include/uapi/linux/bpf.h | 237 +++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 237 insertions(+)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 2bc653a3a20f..f3ea8824efbc 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -580,6 +580,243 @@ union bpf_attr {
>> * performed again.
>> * Return
>> * 0 on success, or a negative error in case of failure.
>> + *
>> + * u64 bpf_get_current_pid_tgid(void)
>> + * Return
>> + * A 64-bit integer containing the current tgid and pid, and
>> + * created as such:
>> + * *current_task*\ **->tgid << 32 \|**
>> + * *current_task*\ **->pid**.
>> + *
>> + * u64 bpf_get_current_uid_gid(void)
>> + * Return
>> + * A 64-bit integer containing the current GID and UID, and
>> + * created as such: *current_gid* **<< 32 \|** *current_uid*.
>> + *
>> + * int bpf_get_current_comm(char *buf, u32 size_of_buf)
>> + * Description
>> + * Copy the **comm** attribute of the current task into *buf* of
>> + * *size_of_buf*. The **comm** attribute contains the name of
>> + * the executable (excluding the path) for the current task. The
>> + * *size_of_buf* must be strictly positive. On success, the
>
> that reminds me that we probably should relax it to ARG_CONST_SIZE_OR_ZERO.
> The programs won't be passing an actual zero into it, but it helps
> a lot to tell verifier that zero is also valid, since programs
> become much simpler.
>
Ok. No change to helper description for now, we will update here when
your patch lands.
>> + * helper makes sure that the *buf* is NUL-terminated. On failure,
>> + * it is filled with zeroes.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
>> + * Description
>> + * Push a *vlan_tci* (VLAN tag control information) of protocol
>> + * *vlan_proto* to the packet associated to *skb*, then update
>> + * the checksum. Note that if *vlan_proto* is different from
>> + * **ETH_P_8021Q** and **ETH_P_8021AD**, it is considered to
>> + * be **ETH_P_8021Q**.
>> + *
>> + * A call to this helper is susceptible to change data from the
>> + * packet. Therefore, at load time, all checks on pointers
>> + * previously done by the verifier are invalidated and must be
>> + * performed again.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_skb_vlan_pop(struct sk_buff *skb)
>> + * Description
>> + * Pop a VLAN header from the packet associated to *skb*.
>> + *
>> + * A call to this helper is susceptible to change data from the
>> + * packet. Therefore, at load time, all checks on pointers
>> + * previously done by the verifier are invalidated and must be
>> + * performed again.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_skb_get_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
>> + * Description
>> + * Get tunnel metadata. This helper takes a pointer *key* to an
>> + * empty **struct bpf_tunnel_key** of **size**, that will be
>> + * filled with tunnel metadata for the packet associated to *skb*.
>> + * The *flags* can be set to **BPF_F_TUNINFO_IPV6**, which
>> + * indicates that the tunnel is based on IPv6 protocol instead of
>> + * IPv4.
>> + *
>> + * This is typically used on the receive path to perform a lookup
>> + * or a packet redirection based on the value of *key*:
>
> above is correct, but feels a bit cryptic.
> May be give more concrete example for particular tunneling protocol like gre
> and say that tunnel_key.remote_ip[46] is essential part of the encap and
> bpf prog will make decisions based on the contents of the encap header
> where bpf_tunnel_key is a single structure that generalizes parameters of
> various tunneling protocols into one struct.
>
I will try to do this.
>> + *
>> + * ::
>> + *
>> + * struct bpf_tunnel_key key = {};
>> + * bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
>> + * lookup or redirect based on key ...
>> + *
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_skb_set_tunnel_key(struct sk_buff *skb, struct bpf_tunnel_key *key, u32 size, u64 flags)
>> + * Description
>> + * Populate tunnel metadata for packet associated to *skb.* The
>> + * tunnel metadata is set to the contents of *key*, of *size*. The
>> + * *flags* can be set to a combination of the following values:
>> + *
>> + * **BPF_F_TUNINFO_IPV6**
>> + * Indicate that the tunnel is based on IPv6 protocol
>> + * instead of IPv4.
>> + * **BPF_F_ZERO_CSUM_TX**
>> + * For IPv4 packets, add a flag to tunnel metadata
>> + * indicating that checksum computation should be skipped
>> + * and checksum set to zeroes.
>> + * **BPF_F_DONT_FRAGMENT**
>> + * Add a flag to tunnel metadata indicating that the
>> + * packet should not be fragmented.
>> + * **BPF_F_SEQ_NUMBER**
>> + * Add a flag to tunnel metadata indicating that a
>> + * sequence number should be added to tunnel header before
>> + * sending the packet. This flag was added for GRE
>> + * encapsulation, but might be used with other protocols
>> + * as well in the future.
>> + *
>> + * Here is a typical usage on the transmit path:
>> + *
>> + * ::
>> + *
>> + * struct bpf_tunnel_key key;
>> + * populate key ...
>> + * bpf_skb_set_tunnel_key(skb, &key, sizeof(key), 0);
>> + * bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);
>> + *
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_redirect(u32 ifindex, u64 flags)
>> + * Description
>> + * Redirect the packet to another net device of index *ifindex*.
>> + * This helper is somewhat similar to **bpf_clone_redirect**\
>> + * (), except that the packet is not cloned, which provides
>> + * increased performance.
>> + *
>> + * For hooks other than XDP, *flags* can be set to
>> + * **BPF_F_INGRESS**, which indicates the packet is to be
>> + * redirected to the ingress interface instead of (by default)
>> + * egress. Currently, XDP does not support any flag.
>> + * Return
>> + * For XDP, the helper returns **XDP_REDIRECT** on success or
>> + * **XDP_ABORT** on error. For other program types, the values
>> + * are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
>> + * error.
>> + *
>> + * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
>> + * Description
>> + * Write perf raw sample into a perf event held by *map* of type
>
> I'd say:
> Write raw *data* blob into special bpf perf event held by ...
>
Yes it sounds better, I will follow the suggestion.
>> + * **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. This perf event must
>> + * have the following attributes: **PERF_SAMPLE_RAW** as
>> + * **sample_type**, **PERF_TYPE_SOFTWARE** as **type**, and
>> + * **PERF_COUNT_SW_BPF_OUTPUT** as **config**.
>> + *
>> + * The *flags* are used to indicate the index in *map* for which
>> + * the value must be put, masked with **BPF_F_INDEX_MASK**.
>> + * Alternatively, *flags* can be set to **BPF_F_CURRENT_CPU**
>> + * to indicate that the index of the current CPU core should be
>> + * used.
>> + *
>> + * The value to write, of *size*, is passed through eBPF stack and
>> + * pointed by *data*.
>> + *
>> + * The context of the program *ctx* needs also be passed to the
>> + * helper, and will get interpreted as a pointer to a **struct
>> + * pt_reg**.
>
> Not quite correct.
> Initially bpf_perf_event_output() was only used with 'struct pt_reg *ctx',
> but then later it was generalized for all other tracing prog types,
> for clsact and even for XDP.
> So 'ctx' can be any of the context used by these program types.
>
Right, I suppose I only looked at bpf_perf_event_output_tp() for this
one :(. I can simply trim it to:
"The context of the program *ctx* needs also be passed to the helper."
>> + *
>> + * On user space, a program willing to read the values needs to
>> + * call **perf_event_open**\ () on the perf event (either for
>> + * one or for all CPUs) and to store the file descriptor into the
>> + * *map*. This must be done before the eBPF program can send data
>> + * into it. An example is available in file
>> + * *samples/bpf/trace_output_user.c* in the Linux kernel source
>> + * tree (the eBPF program counterpart is in
>> + * *samples/bpf/trace_output_kern.c*). It looks like the
>> + * following snippet:
>> + *
>> + * ::
>> + *
>> + * volatile struct perf_event_mmap_page *header;
>> + * struct perf_event_attr attr = {
>> + * .sample_type = PERF_SAMPLE_RAW,
>> + * .type = PERF_TYPE_SOFTWARE,
>> + * .config = PERF_COUNT_SW_BPF_OUTPUT,
>> + * };
>> + * int page_size;
>> + * int mmap_size;
>> + * int key = 0;
>> + * int pmu_fd;
>> + * void *base;
>> + *
>> + * if (load_bpf_file(filename))
>> + * return -1;
>> + *
>> + * pmu_fd = sys_perf_event_open(&attr,
>> + * -1, // pid
>> + * 0, // cpu
>> + * -1, // group_fd
>> + * 0);
>> + *
>> + * assert(pmu_fd >= 0);
>> + * assert(bpf_map_update_elem(map_fd[0], &key,
>> + * &pmu_fd, BPF_ANY) == 0);
>> + * assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0) == 0);
>> + *
>> + * page_size = getpagesize();
>> + * mmap_size = page_size * (page_cnt + 1);
>> + *
>> + * base = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
>> + * MAP_SHARED, fd, 0);
>> + * if (base == MAP_FAILED)
>> + * return -1;
>> + *
>> + * header = base;
>
> I think that is too much for the man page, especially above is far from
> complete example.
>
Yeah, I was unsure about keeping it. I will remove the snippet.
>> + *
>> + * **bpf_perf_event_output**\ () achieves better performance
>> + * than **bpf_trace_printk**\ () for sharing data with user
>> + * space, and is much better suitable for streaming data from eBPF
>> + * programs.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
>> + * Description
>> + * Walk a user or a kernel stack and return its id. To achieve
>> + * this, the helper needs *ctx*, which is a pointer to the context
>> + * on which the tracing program is executed, and a pointer to a
>> + * *map* of type **BPF_MAP_TYPE_STACK_TRACE**.
>> + *
>> + * The last argument, *flags*, holds the number of stack frames to
>> + * skip (from 0 to 255), masked with
>> + * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
>> + * a combination of the following flags:
>> + *
>> + * **BPF_F_USER_STACK**
>> + * Collect a user space stack instead of a kernel stack.
>> + * **BPF_F_FAST_STACK_CMP**
>> + * Compare stacks by hash only.
>> + * **BPF_F_REUSE_STACKID**
>> + * If two different stacks hash into the same *stackid*,
>> + * discard the old one.
>
> we have an annoying bug here that we will be sending a patch to fix soon,
> since right now there is no way for the program to know that stackid
> got replaced.
>
Understood. Same as for bpf_get_current_comm(), I will leave the
description untouched until the patch lands.
>> + *
>> + * The stack id retrieved is a 32 bit long integer handle which
>> + * can be further combined with other data (including other stack
>> + * ids) and used as a key into maps. This can be useful for
>> + * generating a variety of graphs (such as flame graphs or off-cpu
>> + * graphs).
>> + *
>> + * For walking a stack, this helper is an improvement over
>> + * **bpf_probe_read**\ (), which can be used with unrolled loops
>> + * but is not efficient and consumes a lot of eBPF instructions.
>> + * Instead, **bpf_get_stackid**\ () can collect up to
>> + * **PERF_MAX_STACK_DEPTH** both kernel and user frames.
>
> PERF_MAX_STACK_DEPTH is now controlled by sysctl knob.
> Would be good to mention that this limit can and should be increased
> for profiling long user stacks like java.
>
Good idea, I will add it.
Thanks a lot Alexei for the thorough reviews!
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57)
[not found] ` <cc54b41e-3f2f-e87f-042f-842c96308626@fb.com>
@ 2018-04-11 15:44 ` Quentin Monnet
2018-04-11 18:01 ` Quentin Monnet
0 siblings, 1 reply; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:44 UTC (permalink / raw)
To: Yonghong Song, daniel, ast
Cc: netdev, oss-drivers, linux-doc, linux-man, Lawrence Brakmo,
Josef Bacik, Andrey Ignatov
2018-04-10 09:58 UTC-0700 ~ Yonghong Song <yhs@fb.com>
> On 4/10/18 7:41 AM, Quentin Monnet wrote:
>> Add documentation for eBPF helper functions to bpf.h user header file.
>> This documentation can be parsed with the Python script provided in
>> another commit of the patch series, in order to provide a RST document
>> that can later be converted into a man page.
>>
>> The objective is to make the documentation easily understandable and
>> accessible to all eBPF developers, including beginners.
>>
>> This patch contains descriptions for the following helper functions:
>>
>> Helpers from Lawrence:
>> - bpf_setsockopt()
>> - bpf_getsockopt()
>> - bpf_sock_ops_cb_flags_set()
>>
>> Helpers from Yonghong:
>> - bpf_perf_event_read_value()
>> - bpf_perf_prog_read_value()
>>
>> Helper from Josef:
>> - bpf_override_return()
>>
>> Helper from Andrey:
>> - bpf_bind()
>>
>> Cc: Lawrence Brakmo <brakmo@fb.com>
>> Cc: Yonghong Song <yhs@fb.com>
>> Cc: Josef Bacik <jbacik@fb.com>
>> Cc: Andrey Ignatov <rdna@fb.com>
>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>> ---
>> include/uapi/linux/bpf.h | 184
>> +++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 184 insertions(+)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 15d9ccafebbe..7343af4196c8 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
[...]
>> @@ -1255,6 +1277,168 @@ union bpf_attr {
>> * performed again.
>> * Return
>> * 0 on success, or a negative error in case of failure.
>> + *
>> + * int bpf_perf_event_read_value(struct bpf_map *map, u64 flags,
>> struct bpf_perf_event_value *buf, u32 buf_size)
>> + * Description
>> + * Read the value of a perf event counter, and store it into
>> *buf*
>> + * of size *buf_size*. This helper relies on a *map* of type
>> + * **BPF_MAP_TYPE_PERF_EVENT_ARRAY**. The nature of the perf
>> + * event counter is selected at the creation of the *map*. The
>
> The nature of the perf event counter is selected when *map* is updated
> with perf_event fd's.
>
Thanks, I will fix it.
>> + * *map* is an array whose size is the number of available CPU
>> + * cores, and each cell contains a value relative to one
>> core. The
>
> It is confusing to mix core/cpu here. Maybe just use perf_event
> convention, always using cpu?
>
Right, I'll remove occurrences of "core".
>> + * value to retrieve is indicated by *flags*, that contains the
>> + * index of the core to look up, masked with
>> + * **BPF_F_INDEX_MASK**. Alternatively, *flags* can be set to
>> + * **BPF_F_CURRENT_CPU** to indicate that the value for the
>> + * current CPU core should be retrieved.
>> + *
>> + * This helper behaves in a way close to
>> + * **bpf_perf_event_read**\ () helper, save that instead of
>> + * just returning the value observed, it fills the *buf*
>> + * structure. This allows for additional data to be
>> retrieved: in
>> + * particular, the enabled and running times (in *buf*\
>> + * **->enabled** and *buf*\ **->running**, respectively) are
>> + * copied.
>> + *
>> + * These values are interesting, because hardware PMU
>> (Performance
>> + * Monitoring Unit) counters are limited resources. When
>> there are
>> + * more PMU based perf events opened than available counters,
>> + * kernel will multiplex these events so each event gets certain
>> + * percentage (but not all) of the PMU time. In case that
>> + * multiplexing happens, the number of samples or counter value
>> + * will not reflect the case compared to when no multiplexing
>> + * occurs. This makes comparison between different runs
>> difficult.
>> + * Typically, the counter value should be normalized before
>> + * comparing to other experiments. The usual normalization is
>> done
>> + * as follows.
>> + *
>> + * ::
>> + *
>> + * normalized_counter = counter * t_enabled / t_running
>> + *
>> + * Where t_enabled is the time enabled for event and
>> t_running is
>> + * the time running for event since last normalization. The
>> + * enabled and running times are accumulated since the perf
>> event
>> + * open. To achieve scaling factor between two invocations of an
>> + * eBPF program, users can can use CPU id as the key (which is
>> + * typical for perf array usage model) to remember the previous
>> + * value and do the calculation inside the eBPF program.
>> + * Return
>> + * 0 on success, or a negative error in case of failure.
>> + *
[...]
Thanks Yonghong for the review!
I have a favor to ask of you. I got a bounce for Kaixu Xia's email
address, and I don't know what alternative email address I could use. I
CC-ed to have a review for helper bpf_perf_event_read() (in patch 6 of
this series), which is rather close to bpf_perf_event_read_value().
Would you mind having a look at that one too, please? The description is
not long.
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57)
[not found] ` <20180410175015.GA6762@rdna-mbp.dhcp.thefacebook.com>
@ 2018-04-11 15:45 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:45 UTC (permalink / raw)
To: Andrey Ignatov
Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man,
Lawrence Brakmo, Yonghong Song, Josef Bacik
2018-04-10 10:50 UTC-0700 ~ Andrey Ignatov <rdna@fb.com>
> Quentin Monnet <quentin.monnet@netronome.com> [Tue, 2018-04-10 07:43 -0700]:
>> + * int bpf_bind(struct bpf_sock_addr_kern *ctx, struct sockaddr *addr, int addr_len)
>> + * Description
>> + * Bind the socket associated to *ctx* to the address pointed by
>> + * *addr*, of length *addr_len*. This allows for making outgoing
>> + * connection from the desired IP address, which can be useful for
>> + * example when all processes inside a cgroup should use one
>> + * single IP address on a host that has multiple IP configured.
>> + *
>> + * This helper works for IPv4 and IPv6, TCP and UDP sockets. The
>> + * domain (*addr*\ **->sa_family**) must be **AF_INET** (or
>> + * **AF_INET6**). Looking for a free port to bind to can be
>> + * expensive, therefore binding to port is not permitted by the
>> + * helper: *addr*\ **->sin_port** (or **sin6_port**, respectively)
>> + * must be set to zero.
>> + *
>> + * As for the remote end, both parts of it can be overridden,
>> + * remote IP and remote port. This can be useful if an application
>> + * inside a cgroup wants to connect to another application inside
>> + * the same cgroup or to itself, but knows nothing about the IP
>> + * address assigned to the cgroup.
>
> The last paragraph ("As for the remote end ...") is not relevant to
> bpf_bind() and should be removed. It's about sys_connect hook itself
> that can call to bpf_bind() but also has other functionality (and that
> other functionality is described by this paragraph).
Thanks Andrey, I will remove this paragraph.
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* [RFC bpf-next v2 8/8] bpf: add documentation for eBPF helpers (58-64)
[not found] ` <20180411121759.4191e267@redhat.com>
@ 2018-04-11 15:45 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 15:45 UTC (permalink / raw)
To: Jesper Dangaard Brouer
Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man, John Fastabend
2018-04-11 12:17 UTC+0200 ~ Jesper Dangaard Brouer <brouer@redhat.com>
> On Tue, 10 Apr 2018 15:41:57 +0100
> Quentin Monnet <quentin.monnet@netronome.com> wrote:
>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 7343af4196c8..db090ad03626 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -1250,6 +1250,51 @@ union bpf_attr {
>> * Return
>> * 0 on success, or a negative error in case of failure.
>> *
>> + * int bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
>> + * Description
>> + * Redirect the packet to the endpoint referenced by *map* at
>> + * index *key*. Depending on its type, his *map* can contain
>> + * references to net devices (for forwarding packets through other
>> + * ports), or to CPUs (for redirecting XDP frames to another CPU;
>> + * but this is not fully implemented as of this writing).
>
> Stating that CPUMAP redirect "is not fully implemented" is confusing.
> The issue is that CPUMAP only works for "native" XDP.
>
> What about saying:
>
> "[...] or to CPUs (for redirecting XDP frames to another CPU;
> but this is only implemented for native XDP as of this writing)"
>
Fine by me, I will change it. Thank you Jesper for the review!
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57)
2018-04-11 15:44 ` Quentin Monnet
@ 2018-04-11 18:01 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-11 18:01 UTC (permalink / raw)
To: Yonghong Song, daniel, ast
Cc: netdev, oss-drivers, linux-doc, linux-man, Lawrence Brakmo,
Josef Bacik, Andrey Ignatov
2018-04-11 16:44 UTC+0100 ~ Quentin Monnet <quentin.monnet@netronome.com>
> 2018-04-10 09:58 UTC-0700 ~ Yonghong Song <yhs@fb.com>
>> On 4/10/18 7:41 AM, Quentin Monnet wrote:
>>> Add documentation for eBPF helper functions to bpf.h user header file.
>>> This documentation can be parsed with the Python script provided in
>>> another commit of the patch series, in order to provide a RST document
>>> that can later be converted into a man page.
>>>
>>> The objective is to make the documentation easily understandable and
>>> accessible to all eBPF developers, including beginners.
>>>
>>> This patch contains descriptions for the following helper functions:
>>>
>>> Helpers from Lawrence:
>>> - bpf_setsockopt()
>>> - bpf_getsockopt()
>>> - bpf_sock_ops_cb_flags_set()
>>>
>>> Helpers from Yonghong:
>>> - bpf_perf_event_read_value()
>>> - bpf_perf_prog_read_value()
>>>
>>> Helper from Josef:
>>> - bpf_override_return()
>>>
>>> Helper from Andrey:
>>> - bpf_bind()
>>>
>>> Cc: Lawrence Brakmo <brakmo@fb.com>
>>> Cc: Yonghong Song <yhs@fb.com>
>>> Cc: Josef Bacik <jbacik@fb.com>
>>> Cc: Andrey Ignatov <rdna@fb.com>
>>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>>> ---
> [...]
>
> Thanks Yonghong for the review!
>
> I have a favor to ask of you. I got a bounce for Kaixu Xia's email
> address, and I don't know what alternative email address I could use. I
> CC-ed to have a review for helper bpf_perf_event_read() (in patch 6 of
> this series), which is rather close to bpf_perf_event_read_value().
> Would you mind having a look at that one too, please? The description is
> not long.
Well I read again the description I wrote, and actually the one for
bpf_perf_evnet_read() is nearly a subset of the one for
perf_event_read_value(). So the same comments that you raised earlier
apply, there's probably nothing more to review. But if you notice that
some important info is missing for bpf_perf_event_read(), I'm interested
too!
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32)
2018-04-10 14:41 ` [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32) Quentin Monnet
@ 2018-04-13 0:28 ` Alexei Starovoitov
2018-04-13 18:18 ` Quentin Monnet
0 siblings, 1 reply; 20+ messages in thread
From: Alexei Starovoitov @ 2018-04-13 0:28 UTC (permalink / raw)
To: Quentin Monnet; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
On Tue, Apr 10, 2018 at 03:41:53PM +0100, Quentin Monnet wrote:
> Add documentation for eBPF helper functions to bpf.h user header file.
> This documentation can be parsed with the Python script provided in
> another commit of the patch series, in order to provide a RST document
> that can later be converted into a man page.
>
> The objective is to make the documentation easily understandable and
> accessible to all eBPF developers, including beginners.
>
> This patch contains descriptions for the following helper functions, all
> written by Daniel:
>
> - bpf_get_prandom_u32()
> - bpf_get_smp_processor_id()
> - bpf_get_cgroup_classid()
> - bpf_get_route_realm()
> - bpf_skb_load_bytes()
> - bpf_csum_diff()
> - bpf_skb_get_tunnel_opt()
> - bpf_skb_set_tunnel_opt()
> - bpf_skb_change_proto()
> - bpf_skb_change_type()
>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
> ---
> include/uapi/linux/bpf.h | 125 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 125 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index f3ea8824efbc..d147d9dd6a83 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -473,6 +473,14 @@ union bpf_attr {
> * The number of bytes written to the buffer, or a negative error
> * in case of failure.
> *
> + * u32 bpf_prandom_u32(void)
> + * Return
> + * A random 32-bit unsigned value.
there is no such helper.
It's called bpf_get_prandom_u32().
I'd also add a note that it's using its own random state and cannot be
used to infer seed of other random functions in the kernel.
> + *
> + * u32 bpf_get_smp_processor_id(void)
> + * Return
> + * The SMP (Symmetric multiprocessing) processor id.
probably worth adding a note to explain that all bpf programs run
with preemption disabled, so processor id is stable for the run of the program.
> + *
> * int bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len, u64 flags)
> * Description
> * Store *len* bytes from address *from* into the packet
> @@ -604,6 +612,13 @@ union bpf_attr {
> * Return
> * 0 on success, or a negative error in case of failure.
> *
> + * u32 bpf_get_cgroup_classid(struct sk_buff *skb)
> + * Description
> + * Retrieve the classid for the current task, i.e. for the
> + * net_cls (network classifier) cgroup to which *skb* belongs.
please add that kernel should be configured with CONFIG_NET_CLS_CGROUP=y|m
and mention Documentation/cgroup-v1/net_cls.txt
Otherwise 'network classifier' is way too generic.
I'd also mention that placing a task into net_cls controller
disables all of cgroup-bpf.
> + * Return
> + * The classid, or 0 for the default unconfigured classid.
> + *
> * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
> * Description
> * Push a *vlan_tci* (VLAN tag control information) of protocol
> @@ -703,6 +718,14 @@ union bpf_attr {
> * are **TC_ACT_REDIRECT** on success or **TC_ACT_SHOT** on
> * error.
> *
> + * u32 bpf_get_route_realm(struct sk_buff *skb)
> + * Description
> + * Retrieve the realm or the route, that is to say the
> + * **tclassid** field of the destination for the *skb*.
Similarly this only works if CONFIG_IP_ROUTE_CLASSID is on.
> + * Return
> + * The realm of the route for the packet associated to *sdb*, or 0
> + * if none was found.
> + *
> * int bpf_perf_event_output(struct pt_reg *ctx, struct bpf_map *map, u64 flags, void *data, u64 size)
> * Description
> * Write perf raw sample into a perf event held by *map* of type
> @@ -779,6 +802,21 @@ union bpf_attr {
> * Return
> * 0 on success, or a negative error in case of failure.
> *
> + * int bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void *to, u32 len)
> + * Description
> + * This helper was provided as an easy way to load data from a
> + * packet. It can be used to load *len* bytes from *offset* from
> + * the packet associated to *skb*, into the buffer pointed by
> + * *to*.
> + *
> + * Since Linux 4.7, this helper is deprecated in favor of
> + * "direct packet access", enabling packet data to be manipulated
> + * with *skb*\ **->data** and *skb*\ **->data_end** pointing
> + * respectively to the first byte of packet data and to the byte
> + * after the last byte of packet data.
I wouldn't call it deprecated.
It's still useful when programmer wants to read large quantities of
data from the packet
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> * int bpf_get_stackid(struct pt_reg *ctx, struct bpf_map *map, u64 flags)
> * Description
> * Walk a user or a kernel stack and return its id. To achieve
> @@ -814,6 +852,93 @@ union bpf_attr {
> * The positive or null stack id on success, or a negative error
> * in case of failure.
> *
> + * s64 bpf_csum_diff(__be32 *from, u32 from_size, __be32 *to, u32 to_size, __wsum seed)
> + * Description
> + * Compute a checksum difference, from the raw buffer pointed by
> + * *from*, of length *from_size* (that must be a multiple of 4),
> + * towards the raw buffer pointed by *to*, of size *to_size*
> + * (same remark). An optional *seed* can be added to the value.
> + *
> + * This is flexible enough to be used in several ways:
> + *
> + * * With *from_size* == 0, *to_size* > 0 and *seed* set to
> + * checksum, it can be used when pushing new data.
> + * * With *from_size* > 0, *to_size* == 0 and *seed* set to
> + * checksum, it can be used when removing data from a packet.
> + * * With *from_size* > 0, *to_size* > 0 and *seed* set to 0, it
> + * can be used to compute a diff. Note that *from_size* and
> + * *to_size* do not need to be equal.
> + * Return
> + * The checksum result, or a negative error code in case of
> + * failure.
> + *
> + * int bpf_skb_get_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
> + * Description
> + * Retrieve tunnel options metadata for the packet associated to
> + * *skb*, and store the raw tunnel option data to the buffer *opt*
> + * of *size*.
> + * Return
> + * The size of the option data retrieved.
> + *
> + * int bpf_skb_set_tunnel_opt(struct sk_buff *skb, u8 *opt, u32 size)
> + * Description
> + * Set tunnel options metadata for the packet associated to *skb*
> + * to the option data contained in the raw buffer *opt* of *size*.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_change_proto(struct sk_buff *skb, __be16 proto, u64 flags)
> + * Description
> + * Change the protocol of the *skb* to *proto*. Currently
> + * supported are transition from IPv4 to IPv6, and from IPv6 to
> + * IPv4. The helper takes care of the groundwork for the
> + * transition, including resizing the socket buffer. The eBPF
> + * program is expected to fill the new headers, if any, via
> + * **skb_store_bytes**\ () and to recompute the checksums with
> + * **bpf_l3_csum_replace**\ () and **bpf_l4_csum_replace**\
> + * ().
> + *
> + * Internally, the GSO type is marked as dodgy so that headers are
> + * checked and segments are recalculated by the GSO/GRO engine.
> + * The size for GSO target is adapted as well.
> + *
> + * All values for *flags* are reserved for future usage, and must
> + * be left at zero.
> + *
> + * A call to this helper is susceptible to change data from the
> + * packet. Therefore, at load time, all checks on pointers
> + * previously done by the verifier are invalidated and must be
> + * performed again.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_skb_change_type(struct sk_buff *skb, u32 type)
> + * Description
> + * Change the packet type for the packet associated to *skb*. This
> + * comes down to setting *skb*\ **->pkt_type** to *type*, except
> + * the eBPF program does not have a write access to *skb*\
> + * **->pkt_type** beside this helper. Using a helper here allows
> + * for graceful handling of errors.
> + *
> + * The major use case is to change incoming *skb*s to
> + * **PACKET_HOST** in a programmatic way instead of having to
> + * recirculate via **redirect**\ (..., **BPF_F_INGRESS**), for
> + * example.
> + *
> + * Note that *type* only allows certain values. At this time, they
> + * are:
> + *
> + * **PACKET_HOST**
> + * Packet is for us.
> + * **PACKET_BROADCAST**
> + * Send packet to all.
> + * **PACKET_MULTICAST**
> + * Send packet to group.
> + * **PACKET_OTHERHOST**
> + * Send packet to someone else.
> + * Return
> + * 0 on success, or a negative error in case of failure.
> + *
> * u64 bpf_get_current_task(void)
> * Return
> * A pointer to the current task struct.
> --
> 2.14.1
>
^ permalink raw reply [flat|nested] 20+ messages in thread
* Re: [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32)
2018-04-13 0:28 ` Alexei Starovoitov
@ 2018-04-13 18:18 ` Quentin Monnet
0 siblings, 0 replies; 20+ messages in thread
From: Quentin Monnet @ 2018-04-13 18:18 UTC (permalink / raw)
To: Alexei Starovoitov; +Cc: daniel, ast, netdev, oss-drivers, linux-doc, linux-man
2018-04-12 17:28 UTC-0700 ~ Alexei Starovoitov
<alexei.starovoitov@gmail.com>
> On Tue, Apr 10, 2018 at 03:41:53PM +0100, Quentin Monnet wrote:
>> Add documentation for eBPF helper functions to bpf.h user header file.
>> This documentation can be parsed with the Python script provided in
>> another commit of the patch series, in order to provide a RST document
>> that can later be converted into a man page.
>>
>> The objective is to make the documentation easily understandable and
>> accessible to all eBPF developers, including beginners.
>>
>> This patch contains descriptions for the following helper functions, all
>> written by Daniel:
>>
>> - bpf_get_prandom_u32()
>> - bpf_get_smp_processor_id()
>> - bpf_get_cgroup_classid()
>> - bpf_get_route_realm()
>> - bpf_skb_load_bytes()
>> - bpf_csum_diff()
>> - bpf_skb_get_tunnel_opt()
>> - bpf_skb_set_tunnel_opt()
>> - bpf_skb_change_proto()
>> - bpf_skb_change_type()
>>
>> Cc: Daniel Borkmann <daniel@iogearbox.net>
>> Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
>> ---
>> include/uapi/linux/bpf.h | 125 +++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 125 insertions(+)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index f3ea8824efbc..d147d9dd6a83 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
[...]
>> @@ -604,6 +612,13 @@ union bpf_attr {
>> * Return
>> * 0 on success, or a negative error in case of failure.
>> *
>> + * u32 bpf_get_cgroup_classid(struct sk_buff *skb)
>> + * Description
>> + * Retrieve the classid for the current task, i.e. for the
>> + * net_cls (network classifier) cgroup to which *skb* belongs.
>
> please add that kernel should be configured with CONFIG_NET_CLS_CGROUP=y|m
> and mention Documentation/cgroup-v1/net_cls.txt
Ok.
> Otherwise 'network classifier' is way too generic.
I am not so familiar with cgroups. What would you suggest instead?
> I'd also mention that placing a task into net_cls controller
> disables all of cgroup-bpf.
Could you please explain a bit more? Placing a task into the controller
is using:
echo <task_pid> > /sys/fs/cgroup/<my_cgroup_name>/tasks
correct? Then if I do this, it disables all of cgroup-bpf. Does this
mean that I loose the possibility to use or add BPF programs to all
cgroup-related attach points for this cgroup? I think I missed something
here.
>> + * Return
>> + * The classid, or 0 for the default unconfigured classid.
>> + *
>> * int bpf_skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
>> * Description
>> * Push a *vlan_tci* (VLAN tag control information) of protocol
I have no particular comments on the other items you reported on this
patch, I will fix them. Thanks!
Quentin
^ permalink raw reply [flat|nested] 20+ messages in thread
end of thread, other threads:[~2018-04-13 18:18 UTC | newest]
Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-04-10 14:41 [RFC bpf-next v2 0/8] bpf: document eBPF helpers and add a script to generate man page Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 1/8] bpf: add script and prepare bpf.h for new helpers documentation Quentin Monnet
2018-04-10 18:16 ` Alexei Starovoitov
2018-04-11 15:41 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 2/8] bpf: add documentation for eBPF helpers (01-11) Quentin Monnet
[not found] ` <20180410175605.2wqhaqx34a4o3gdi@ast-mbp.dhcp.thefacebook.com>
2018-04-11 15:42 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 3/8] bpf: add documentation for eBPF helpers (12-22) Quentin Monnet
2018-04-10 22:43 ` Alexei Starovoitov
2018-04-11 15:43 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 4/8] bpf: add documentation for eBPF helpers (23-32) Quentin Monnet
2018-04-13 0:28 ` Alexei Starovoitov
2018-04-13 18:18 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 5/8] bpf: add documentation for eBPF helpers (33-41) Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 6/8] bpf: add documentation for eBPF helpers (42-50) Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 7/8] bpf: add documentation for eBPF helpers (51-57) Quentin Monnet
[not found] ` <cc54b41e-3f2f-e87f-042f-842c96308626@fb.com>
2018-04-11 15:44 ` Quentin Monnet
2018-04-11 18:01 ` Quentin Monnet
[not found] ` <20180410175015.GA6762@rdna-mbp.dhcp.thefacebook.com>
2018-04-11 15:45 ` Quentin Monnet
2018-04-10 14:41 ` [RFC bpf-next v2 8/8] bpf: add documentation for eBPF helpers (58-64) Quentin Monnet
[not found] ` <20180411121759.4191e267@redhat.com>
2018-04-11 15:45 ` Quentin Monnet
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