BPF Syscall BPF_OBJ_GET command
The BPF_OBJ_GET command is used get a file descriptor to a BPF object from a pin.
Return value
This command will return a file descriptor to the pinned BTF object on success (positive integer) or an error number (negative integer) if something went wrong.
Usage
A common use case for opening such a pin is to transfer a reference to a BPF object from one process to another. The BPF_OBJ_PIN syscall command can be used to pin a BPF object to the BPF file system so another process can get a reference to it with this syscall command.
Please the pinning concept page for more details.
Attributes
filename
This field indicates the filename of the pin we wish to open. It should be a pointer to a null terminated string.
The filename must indicate a existing file in a directory that is within the "BPF file system" (typically mounted at /sys/fs/bpf).
The filename must be an absolute path, so not relative paths (paths including a . or ..).
bpf_fd
This field is unused for this command.
file_flags
This field indicates flags that apply to the file descriptor opened with this syscall command.
BPF_F_RDONLY
Setting this flag is only applicable when opening a pin for a BPF map.
Setting this flag will make it so the process is only allowed to read from the map.
This flag is is mutually exclusive with the BPF_F_WRONLY flag. By default (if no flags are set) the map is opened in read and write mode.
BPF_F_WRONLY
Setting this flag is only applicable when opening a pin for a BPF map.
Setting this flag will make it so the process is only allowed to write to the map.
This flag is is mutually exclusive with the BPF_F_RDONLY flag. By default (if no flags are set) the map is opened in read and write mode.