On 3/2/21 9:19 AM, Joe Stringer wrote:
These descriptions are present in the man-pages project from the
original submissions around 2015-2016. Import them so that they can be
kept up to date as developers extend the bpf syscall commands.
These descriptions follow the pattern used by scripts/bpf_helpers_doc.py
so that we can take advantage of the parser to generate more up-to-date
man page writing based upon these headers.
Some minor wording adjustments were made to make the descriptions
more consistent for the description / return format.
Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Co-authored-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Co-authored-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Joe Stringer <joe@xxxxxxxxx>
Ack with one nit below.
Acked-by: Yonghong Song <yhs@xxxxxx>
---
include/uapi/linux/bpf.h | 122 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 121 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index b89af20cfa19..fb16c590e6d9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -93,7 +93,127 @@ union bpf_iter_link_info {
} map;
};
-/* BPF syscall commands, see bpf(2) man-page for details. */
+/* BPF syscall commands, see bpf(2) man-page for more details. */
+/**
+ * DOC: eBPF Syscall Preamble
+ *
+ * The operation to be performed by the **bpf**\ () system call is determined
+ * by the *cmd* argument. Each operation takes an accompanying argument,
+ * provided via *attr*, which is a pointer to a union of type *bpf_attr* (see
+ * below). The size argument is the size of the union pointed to by *attr*.
+ */
+/**
+ * DOC: eBPF Syscall Commands
+ *
+ * BPF_MAP_CREATE
+ * Description
+ * Create a map and return a file descriptor that refers to the
+ * map. The close-on-exec file descriptor flag (see **fcntl**\ (2))
+ * is automatically enabled for the new file descriptor.
+ *
+ * Applying **close**\ (2) to the file descriptor returned by
+ * **BPF_MAP_CREATE** will delete the map (but see NOTES).
+ *
+ * Return
+ * A new file descriptor (a nonnegative integer), or -1 if an
+ * error occurred (in which case, *errno* is set appropriately).
+ *
[...]
+ * BPF_PROG_LOAD
+ * Description
+ * Verify and load an eBPF program, returning a new file
+ * descriptor associated with the program.
+ *
+ * Applying **close**\ (2) to the file descriptor returned by
+ * **BPF_PROG_LOAD** will unload the eBPF program (but see NOTES).
+ *
+ * The close-on-exec file descriptor flag (see **fcntl**\ (2)) is
+ * automatically enabled for the new file descriptor.
+ *
+ * Return
+ * A new file descriptor (a nonnegative integer), or -1 if an
+ * error occurred (in which case, *errno* is set appropriately).
+ *
+ * NOTES
+ * eBPF objects (maps and programs) can be shared between processes.
+ * For example, after **fork**\ (2), the child inherits file descriptors
+ * referring to the same eBPF objects. In addition, file descriptors
+ * referring to eBPF objects can be transferred over UNIX domain sockets.
+ * File descriptors referring to eBPF objects can be duplicated in the
+ * usual way, using **dup**\ (2) and similar calls. An eBPF object is
+ * deallocated only after all file descriptors referring to the object
+ * have been closed.
if the object is pinned, the object will be live if the pinned file is
not removed. The file description can refer to a link file descriptor or
an iterator file descriptor which will (indirectly) hold a reference
count to the program as well. It will be good we can clarify a little
more in Patch #2 at NOTES section after other bpf syscall commands are
introduced.
+ */
enum bpf_cmd {
BPF_MAP_CREATE,
BPF_MAP_LOOKUP_ELEM,
