Skip to content

Commit

Permalink
bpf: Minor fixes to BPF helpers documentation
Browse files Browse the repository at this point in the history 
Minor improvements to the documentation for BPF helpers:

* Fix formatting for the description of "bpf_socket" for
  bpf_getsockopt() and bpf_setsockopt(), thus suppressing two warnings
  from rst2man about "Unexpected indentation".
* Fix formatting for return values for bpf_sk_assign() and seq_file
  helpers.
* Fix and harmonise formatting, in particular for function/struct names.
* Remove blank lines before "Return:" sections.
* Replace tabs found in the middle of text lines.
* Fix typos.
* Add a note to the footer (in Python script) about "bpftool feature
  probe", including for listing features available to unprivileged
  users, and add a reference to bpftool man page.

Thanks to Florian for reporting two typos (duplicated words).

Signed-off-by: Quentin Monnet <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
  • Loading branch information
@qmonnet @borkmann
qmonnet authored and borkmann committed May 11, 2020
1 parent c8caa0b commit ab8d780
Show file tree
Hide file tree
Showing 2 changed files with 65 additions and 50 deletions.
109 changes: 59 additions & 50 deletions include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -675,16 +675,16 @@ union bpf_attr {
* For tracing programs, safely attempt to read *size* bytes from
* kernel space address *unsafe_ptr* and store the data in *dst*.
*
* Generally, use bpf_probe_read_user() or bpf_probe_read_kernel()
* instead.
* Generally, use **bpf_probe_read_user**\ () or
* **bpf_probe_read_kernel**\ () instead.
* 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.
* Does not include time the system was suspended.
* See: clock_gettime(CLOCK_MONOTONIC)
* See: **clock_gettime**\ (**CLOCK_MONOTONIC**)
* Return
* Current *ktime*.
*
Expand Down Expand Up @@ -1543,11 +1543,11 @@ union bpf_attr {
* int bpf_probe_read_str(void *dst, u32 size, const void *unsafe_ptr)
* Description
* Copy a NUL terminated string from an unsafe kernel address
* *unsafe_ptr* to *dst*. See bpf_probe_read_kernel_str() for
* *unsafe_ptr* to *dst*. See **bpf_probe_read_kernel_str**\ () for
* more details.
*
* Generally, use bpf_probe_read_user_str() or bpf_probe_read_kernel_str()
* instead.
* Generally, use **bpf_probe_read_user_str**\ () or
* **bpf_probe_read_kernel_str**\ () instead.
* Return
* On success, the strictly positive length of the string,
* including the trailing NUL character. On error, a negative
Expand Down Expand Up @@ -1575,7 +1575,7 @@ union bpf_attr {
*
* u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)
* Description
* Equivalent to bpf_get_socket_cookie() helper that accepts
* Equivalent to **bpf_get_socket_cookie**\ () helper that accepts
* *skb*, but gets socket from **struct bpf_sock_ops** context.
* Return
* A 8-byte long non-decreasing number.
Expand Down Expand Up @@ -1604,6 +1604,7 @@ union bpf_attr {
* The option value of length *optlen* is pointed by *optval*.
*
* *bpf_socket* should be one of the following:
*
* * **struct bpf_sock_ops** for **BPF_PROG_TYPE_SOCK_OPS**.
* * **struct bpf_sock_addr** for **BPF_CGROUP_INET4_CONNECT**
* and **BPF_CGROUP_INET6_CONNECT**.
Expand Down Expand Up @@ -1672,12 +1673,12 @@ union bpf_attr {
*
* The lower two bits of *flags* are used as the return code if
* the map lookup fails. This is so that the return value can be
* one of the XDP program return codes up to XDP_TX, as chosen by
* the caller. Any higher bits in the *flags* argument must be
* one of the XDP program return codes up to **XDP_TX**, as chosen
* by the caller. Any higher bits in the *flags* argument must be
* unset.
*
* See also bpf_redirect(), which only supports redirecting to an
* ifindex, but doesn't require a map to do so.
* See also **bpf_redirect**\ (), which only supports redirecting
* to an ifindex, but doesn't require a map to do so.
* Return
* **XDP_REDIRECT** on success, or the value of the two lower bits
* of the *flags* argument on error.
Expand Down Expand Up @@ -1785,7 +1786,7 @@ union bpf_attr {
* 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
* eBPF program, users 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
Expand All @@ -1812,6 +1813,7 @@ union bpf_attr {
* *opval* and of length *optlen*.
*
* *bpf_socket* should be one of the following:
*
* * **struct bpf_sock_ops** for **BPF_PROG_TYPE_SOCK_OPS**.
* * **struct bpf_sock_addr** for **BPF_CGROUP_INET4_CONNECT**
* and **BPF_CGROUP_INET6_CONNECT**.
Expand All @@ -1833,7 +1835,7 @@ union bpf_attr {
* The first argument is the context *regs* on which the kprobe
* works.
*
* This helper works by setting setting the PC (program counter)
* This helper works by 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
Expand Down Expand Up @@ -2300,7 +2302,7 @@ union bpf_attr {
* **bpf_rc_keydown**\ () again with the same values, or calling
* **bpf_rc_repeat**\ ().
*
* Some protocols include a toggle bit, in case the button was
* Some protocols include a toggle bit, in case the button was
* released and pressed again between consecutive scancodes.
*
* The *ctx* should point to the lirc sample as passed into
Expand Down Expand Up @@ -2646,7 +2648,6 @@ union bpf_attr {
*
* *th* points to the start of the TCP header, while *th_len*
* contains **sizeof**\ (**struct tcphdr**).
*
* Return
* 0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
* error otherwise.
Expand Down Expand Up @@ -2829,7 +2830,6 @@ union bpf_attr {
*
* *th* points to the start of the TCP header, while *th_len*
* contains the length of the TCP header.
*
* Return
* On success, lower 32 bits hold the generated SYN cookie in
* followed by 16 bits which hold the MSS value for that cookie,
Expand Down Expand Up @@ -2912,7 +2912,7 @@ union bpf_attr {
* // size, after checking its boundaries.
* }
*
* In comparison, using **bpf_probe_read_user()** helper here
* In comparison, using **bpf_probe_read_user**\ () 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.
Expand All @@ -2930,14 +2930,14 @@ union bpf_attr {
* int bpf_probe_read_kernel_str(void *dst, u32 size, const void *unsafe_ptr)
* Description
* Copy a NUL terminated string from an unsafe kernel address *unsafe_ptr*
* to *dst*. Same semantics as with bpf_probe_read_user_str() apply.
* to *dst*. Same semantics as with **bpf_probe_read_user_str**\ () apply.
* Return
* On success, the strictly positive length of the string, including
* On success, the strictly positive length of the string, including
* the trailing NUL character. On error, a negative value.
*
* int bpf_tcp_send_ack(void *tp, u32 rcv_nxt)
* Description
* Send out a tcp-ack. *tp* is the in-kernel struct tcp_sock.
* Send out a tcp-ack. *tp* is the in-kernel struct **tcp_sock**.
* *rcv_nxt* is the ack_seq to be sent out.
* Return
* 0 on success, or a negative error in case of failure.
Expand Down Expand Up @@ -2965,28 +2965,28 @@ union bpf_attr {
* int bpf_read_branch_records(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 flags)
* Description
* For an eBPF program attached to a perf event, retrieve the
* branch records (struct perf_branch_entry) associated to *ctx*
* and store it in the buffer pointed by *buf* up to size
* branch records (**struct perf_branch_entry**) associated to *ctx*
* and store it in the buffer pointed by *buf* up to size
* *size* bytes.
* Return
* On success, number of bytes written to *buf*. On error, a
* negative value.
*
* The *flags* can be set to **BPF_F_GET_BRANCH_RECORDS_SIZE** to
* instead return the number of bytes required to store all the
* instead return the number of bytes required to store all the
* branch entries. If this flag is set, *buf* may be NULL.
*
* **-EINVAL** if arguments invalid or **size** not a multiple
* of sizeof(struct perf_branch_entry).
* of **sizeof**\ (**struct perf_branch_entry**\ ).
*
* **-ENOENT** if architecture does not support branch records.
*
* int bpf_get_ns_current_pid_tgid(u64 dev, u64 ino, struct bpf_pidns_info *nsdata, u32 size)
* Description
* Returns 0 on success, values for *pid* and *tgid* as seen from the current
* *namespace* will be returned in *nsdata*.
*
* On failure, the returned value is one of the following:
* Return
* 0 on success, or one of the following in case of failure:
*
* **-EINVAL** if dev and inum supplied don't match dev_t and inode number
* with nsfs of current task, or if dev conversion to dev_t lost high bits.
Expand Down Expand Up @@ -3025,8 +3025,8 @@ union bpf_attr {
* a global identifier that can be assumed unique. If *ctx* is
* NULL, then the helper returns the cookie for the initial
* network namespace. The cookie itself is very similar to that
* of bpf_get_socket_cookie() helper, but for network namespaces
* instead of sockets.
* of **bpf_get_socket_cookie**\ () helper, but for network
* namespaces instead of sockets.
* Return
* A 8-byte long opaque number.
*
Expand Down Expand Up @@ -3061,57 +3061,66 @@ union bpf_attr {
*
* The *flags* argument must be zero.
* Return
* 0 on success, or a negative errno in case of failure.
* 0 on success, or a negative error in case of failure:
*
* * **-EINVAL** Unsupported flags specified.
* * **-ENOENT** Socket is unavailable for assignment.
* * **-ENETUNREACH** Socket is unreachable (wrong netns).
* * **-EOPNOTSUPP** Unsupported operation, for example a
* call from outside of TC ingress.
* * **-ESOCKTNOSUPPORT** Socket type not supported (reuseport).
* **-EINVAL** if specified *flags* are not supported.
*
* **-ENOENT** if the socket is unavailable for assignment.
*
* **-ENETUNREACH** if the socket is unreachable (wrong netns).
*
* **-EOPNOTSUPP** if the operation is not supported, for example
* a call from outside of TC ingress.
*
* **-ESOCKTNOSUPPORT** if the socket type is not supported
* (reuseport).
*
* u64 bpf_ktime_get_boot_ns(void)
* Description
* Return the time elapsed since system boot, in nanoseconds.
* Does include the time the system was suspended.
* See: clock_gettime(CLOCK_BOOTTIME)
* See: **clock_gettime**\ (**CLOCK_BOOTTIME**)
* Return
* Current *ktime*.
*
* int bpf_seq_printf(struct seq_file *m, const char *fmt, u32 fmt_size, const void *data, u32 data_len)
* Description
* seq_printf uses seq_file seq_printf() to print out the format string.
* **bpf_seq_printf**\ () uses seq_file **seq_printf**\ () to print
* out the format string.
* The *m* represents the seq_file. The *fmt* and *fmt_size* are for
* the format string itself. The *data* and *data_len* are format string
* arguments. The *data* are a u64 array and corresponding format string
* arguments. The *data* are a **u64** array and corresponding format string
* values are stored in the array. For strings and pointers where pointees
* are accessed, only the pointer values are stored in the *data* array.
* The *data_len* is the *data* size in term of bytes.
* The *data_len* is the size of *data* in bytes.
*
* Formats **%s**, **%p{i,I}{4,6}** requires to read kernel memory.
* Reading kernel memory may fail due to either invalid address or
* valid address but requiring a major memory fault. If reading kernel memory
* fails, the string for **%s** will be an empty string, and the ip
* address for **%p{i,I}{4,6}** will be 0. Not returning error to
* bpf program is consistent with what bpf_trace_printk() does for now.
* bpf program is consistent with what **bpf_trace_printk**\ () does for now.
* Return
* 0 on success, or a negative errno in case of failure.
* 0 on success, or a negative error in case of failure:
*
* **-EBUSY** if per-CPU memory copy buffer is busy, can try again
* by returning 1 from bpf program.
*
* **-EINVAL** if arguments are invalid, or if *fmt* is invalid/unsupported.
*
* **-E2BIG** if *fmt* contains too many format specifiers.
*
* * **-EBUSY** Percpu memory copy buffer is busy, can try again
* by returning 1 from bpf program.
* * **-EINVAL** Invalid arguments, or invalid/unsupported formats.
* * **-E2BIG** Too many format specifiers.
* * **-EOVERFLOW** Overflow happens, the same object will be tried again.
* **-EOVERFLOW** if an overflow happened: The same object will be tried again.
*
* int bpf_seq_write(struct seq_file *m, const void *data, u32 len)
* Description
* seq_write uses seq_file seq_write() to write the data.
* **bpf_seq_write**\ () uses seq_file **seq_write**\ () to write the data.
* The *m* represents the seq_file. The *data* and *len* represent the
* data to write in bytes.
* data to write in bytes.
* Return
* 0 on success, or a negative errno in case of failure.
* 0 on success, or a negative error in case of failure:
*
* * **-EOVERFLOW** Overflow happens, the same object will be tried again.
* **-EOVERFLOW** if an overflow happened: The same object will be tried again.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
Expand Down
6 changes: 6 additions & 0 deletions scripts/bpf_helpers_doc.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -318,6 +318,11 @@ def print_footer(self):
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.).
* The bpftool utility can be used to probe the availability of helper functions
on the system (as well as supported program and map types, and a number of
other parameters). To do so, run **bpftool feature probe** (see
**bpftool-feature**\ (8) for details). Add the **unprivileged** keyword to
list features available to unprivileged users.
Compatibility between helper functions and program types can generally be found
in the files where helper functions are defined. Look for the **struct
Expand All @@ -338,6 +343,7 @@ def print_footer(self):
========
**bpf**\ (2),
**bpftool**\ (8),
**cgroups**\ (7),
**ip**\ (8),
**perf_event_open**\ (2),
Expand Down

0 comments on commit ab8d780

Please sign in to comment.