bpf: Add minimal bpf() command documentation
Introduce high-level descriptions of the intent and return codes of the bpf() syscall commands. Subsequent patches may further flesh out the content to provide a more useful programming reference. Signed-off-by: Joe Stringer <joe@cilium.io> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Quentin Monnet <quentin@isovalent.com> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20210302171947.2268128-3-joe@cilium.io
This commit is contained in:
Joe Stringer
Alexei Starovoitov
parent
7799e4d9d8
commit
f67c9cbf6c
|
|
@ -204,6 +204,374 @@ union bpf_iter_link_info {
|
|||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_OBJ_PIN
|
||||
* Description
|
||||
* Pin an eBPF program or map referred by the specified *bpf_fd*
|
||||
* to the provided *pathname* on the filesystem.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_OBJ_GET
|
||||
* Description
|
||||
* Open a file descriptor for the eBPF object pinned to the
|
||||
* specified *pathname*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_PROG_ATTACH
|
||||
* Description
|
||||
* Attach an eBPF program to a *target_fd* at the specified
|
||||
* *attach_type* hook.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_DETACH
|
||||
* Description
|
||||
* Detach the eBPF program associated with the *target_fd* at the
|
||||
* hook specified by *attach_type*. The program must have been
|
||||
* previously attached using **BPF_PROG_ATTACH**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_TEST_RUN
|
||||
* Description
|
||||
* Run an eBPF program a number of times against a provided
|
||||
* program context and return the modified program context and
|
||||
* duration of the test run.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_GET_NEXT_ID
|
||||
* Description
|
||||
* Fetch the next eBPF program currently loaded into the kernel.
|
||||
*
|
||||
* Looks for the eBPF program with an id greater than *start_id*
|
||||
* and updates *next_id* on success. If no other eBPF programs
|
||||
* remain with ids higher than *start_id*, returns -1 and sets
|
||||
* *errno* to **ENOENT**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, or when no id remains, -1
|
||||
* is returned and *errno* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_GET_NEXT_ID
|
||||
* Description
|
||||
* Fetch the next eBPF map currently loaded into the kernel.
|
||||
*
|
||||
* Looks for the eBPF map with an id greater than *start_id*
|
||||
* and updates *next_id* on success. If no other eBPF maps
|
||||
* remain with ids higher than *start_id*, returns -1 and sets
|
||||
* *errno* to **ENOENT**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, or when no id remains, -1
|
||||
* is returned and *errno* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_GET_FD_BY_ID
|
||||
* Description
|
||||
* Open a file descriptor for the eBPF program corresponding to
|
||||
* *prog_id*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_MAP_GET_FD_BY_ID
|
||||
* Description
|
||||
* Open a file descriptor for the eBPF map corresponding to
|
||||
* *map_id*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_OBJ_GET_INFO_BY_FD
|
||||
* Description
|
||||
* Obtain information about the eBPF object corresponding to
|
||||
* *bpf_fd*.
|
||||
*
|
||||
* Populates up to *info_len* bytes of *info*, which will be in
|
||||
* one of the following formats depending on the eBPF object type
|
||||
* of *bpf_fd*:
|
||||
*
|
||||
* * **struct bpf_prog_info**
|
||||
* * **struct bpf_map_info**
|
||||
* * **struct bpf_btf_info**
|
||||
* * **struct bpf_link_info**
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_QUERY
|
||||
* Description
|
||||
* Obtain information about eBPF programs associated with the
|
||||
* specified *attach_type* hook.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_RAW_TRACEPOINT_OPEN
|
||||
* Description
|
||||
* Attach an eBPF program to a tracepoint *name* to access kernel
|
||||
* internal arguments of the tracepoint in their raw form.
|
||||
*
|
||||
* The *prog_fd* must be a valid file descriptor associated with
|
||||
* a loaded eBPF program of type **BPF_PROG_TYPE_RAW_TRACEPOINT**.
|
||||
*
|
||||
* No ABI guarantees are made about the content of tracepoint
|
||||
* arguments exposed to the corresponding eBPF program.
|
||||
*
|
||||
* Applying **close**\ (2) to the file descriptor returned by
|
||||
* **BPF_RAW_TRACEPOINT_OPEN** 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_BTF_LOAD
|
||||
* Description
|
||||
* Verify and load BPF Type Format (BTF) metadata into the kernel,
|
||||
* returning a new file descriptor associated with the metadata.
|
||||
* BTF is described in more detail at
|
||||
* https://www.kernel.org/doc/html/latest/bpf/btf.html.
|
||||
*
|
||||
* The *btf* parameter must point to valid memory providing
|
||||
* *btf_size* bytes of BTF binary metadata.
|
||||
*
|
||||
* The returned file descriptor can be passed to other **bpf**\ ()
|
||||
* subcommands such as **BPF_PROG_LOAD** or **BPF_MAP_CREATE** to
|
||||
* associate the BTF with those objects.
|
||||
*
|
||||
* Similar to **BPF_PROG_LOAD**, **BPF_BTF_LOAD** has optional
|
||||
* parameters to specify a *btf_log_buf*, *btf_log_size* and
|
||||
* *btf_log_level* which allow the kernel to return freeform log
|
||||
* output regarding the BTF verification process.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_BTF_GET_FD_BY_ID
|
||||
* Description
|
||||
* Open a file descriptor for the BPF Type Format (BTF)
|
||||
* corresponding to *btf_id*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_TASK_FD_QUERY
|
||||
* Description
|
||||
* Obtain information about eBPF programs associated with the
|
||||
* target process identified by *pid* and *fd*.
|
||||
*
|
||||
* If the *pid* and *fd* are associated with a tracepoint, kprobe
|
||||
* or uprobe perf event, then the *prog_id* and *fd_type* will
|
||||
* be populated with the eBPF program id and file descriptor type
|
||||
* of type **bpf_task_fd_type**. If associated with a kprobe or
|
||||
* uprobe, the *probe_offset* and *probe_addr* will also be
|
||||
* populated. Optionally, if *buf* is provided, then up to
|
||||
* *buf_len* bytes of *buf* will be populated with the name of
|
||||
* the tracepoint, kprobe or uprobe.
|
||||
*
|
||||
* The resulting *prog_id* may be introspected in deeper detail
|
||||
* using **BPF_PROG_GET_FD_BY_ID** and **BPF_OBJ_GET_INFO_BY_FD**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_LOOKUP_AND_DELETE_ELEM
|
||||
* Description
|
||||
* Look up an element with the given *key* in the map referred to
|
||||
* by the file descriptor *fd*, and if found, delete the element.
|
||||
*
|
||||
* The **BPF_MAP_TYPE_QUEUE** and **BPF_MAP_TYPE_STACK** map types
|
||||
* implement this command as a "pop" operation, deleting the top
|
||||
* element rather than one corresponding to *key*.
|
||||
* The *key* and *key_len* parameters should be zeroed when
|
||||
* issuing this operation for these map types.
|
||||
*
|
||||
* This command is only valid for the following map types:
|
||||
* * **BPF_MAP_TYPE_QUEUE**
|
||||
* * **BPF_MAP_TYPE_STACK**
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_FREEZE
|
||||
* Description
|
||||
* Freeze the permissions of the specified map.
|
||||
*
|
||||
* Write permissions may be frozen by passing zero *flags*.
|
||||
* Upon success, no future syscall invocations may alter the
|
||||
* map state of *map_fd*. Write operations from eBPF programs
|
||||
* are still possible for a frozen map.
|
||||
*
|
||||
* Not supported for maps of type **BPF_MAP_TYPE_STRUCT_OPS**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_BTF_GET_NEXT_ID
|
||||
* Description
|
||||
* Fetch the next BPF Type Format (BTF) object currently loaded
|
||||
* into the kernel.
|
||||
*
|
||||
* Looks for the BTF object with an id greater than *start_id*
|
||||
* and updates *next_id* on success. If no other BTF objects
|
||||
* remain with ids higher than *start_id*, returns -1 and sets
|
||||
* *errno* to **ENOENT**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, or when no id remains, -1
|
||||
* is returned and *errno* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_LOOKUP_BATCH
|
||||
* Description
|
||||
* Iterate and fetch multiple elements in a map.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_LOOKUP_AND_DELETE_BATCH
|
||||
* Description
|
||||
* Iterate and delete multiple elements in a map.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_UPDATE_BATCH
|
||||
* Description
|
||||
* Iterate and update multiple elements in a map.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_MAP_DELETE_BATCH
|
||||
* Description
|
||||
* Iterate and delete multiple elements in a map.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_LINK_CREATE
|
||||
* Description
|
||||
* Attach an eBPF program to a *target_fd* at the specified
|
||||
* *attach_type* hook and return a file descriptor handle for
|
||||
* managing the link.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_LINK_UPDATE
|
||||
* Description
|
||||
* Update the eBPF program in the specified *link_fd* to
|
||||
* *new_prog_fd*.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_LINK_GET_FD_BY_ID
|
||||
* Description
|
||||
* Open a file descriptor for the eBPF Link corresponding to
|
||||
* *link_id*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_LINK_GET_NEXT_ID
|
||||
* Description
|
||||
* Fetch the next eBPF link currently loaded into the kernel.
|
||||
*
|
||||
* Looks for the eBPF link with an id greater than *start_id*
|
||||
* and updates *next_id* on success. If no other eBPF links
|
||||
* remain with ids higher than *start_id*, returns -1 and sets
|
||||
* *errno* to **ENOENT**.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, or when no id remains, -1
|
||||
* is returned and *errno* is set appropriately.
|
||||
*
|
||||
* BPF_ENABLE_STATS
|
||||
* Description
|
||||
* Enable eBPF runtime statistics gathering.
|
||||
*
|
||||
* Runtime statistics gathering for the eBPF runtime is disabled
|
||||
* by default to minimize the corresponding performance overhead.
|
||||
* This command enables statistics globally.
|
||||
*
|
||||
* Multiple programs may independently enable statistics.
|
||||
* After gathering the desired statistics, eBPF runtime statistics
|
||||
* may be disabled again by calling **close**\ (2) for the file
|
||||
* descriptor returned by this function. Statistics will only be
|
||||
* disabled system-wide when all outstanding file descriptors
|
||||
* returned by prior calls for this subcommand are closed.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_ITER_CREATE
|
||||
* Description
|
||||
* Create an iterator on top of the specified *link_fd* (as
|
||||
* previously created using **BPF_LINK_CREATE**) and return a
|
||||
* file descriptor that can be used to trigger the iteration.
|
||||
*
|
||||
* If the resulting file descriptor is pinned to the filesystem
|
||||
* using **BPF_OBJ_PIN**, then subsequent **read**\ (2) syscalls
|
||||
* for that path will trigger the iterator to read kernel state
|
||||
* using the eBPF program attached to *link_fd*.
|
||||
*
|
||||
* Return
|
||||
* A new file descriptor (a nonnegative integer), or -1 if an
|
||||
* error occurred (in which case, *errno* is set appropriately).
|
||||
*
|
||||
* BPF_LINK_DETACH
|
||||
* Description
|
||||
* Forcefully detach the specified *link_fd* from its
|
||||
* corresponding attachment point.
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *errno*
|
||||
* is set appropriately.
|
||||
*
|
||||
* BPF_PROG_BIND_MAP
|
||||
* Description
|
||||
* Bind a map to the lifetime of an eBPF program.
|
||||
*
|
||||
* The map identified by *map_fd* is bound to the program
|
||||
* identified by *prog_fd* and only released when *prog_fd* is
|
||||
* released. This may be used in cases where metadata should be
|
||||
* associated with a program which otherwise does not contain any
|
||||
* references to the map (for example, embedded in the eBPF
|
||||
* program instructions).
|
||||
*
|
||||
* Return
|
||||
* Returns zero on success. On error, -1 is returned and *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
|
||||
|
|
|
|||
Loading…
Reference in New Issue