Messages in this thread | | | Date | Mon, 25 May 2015 17:23:54 +0800 | From | "Wangnan (F)" <> | Subject | Re: [RFC PATCH v3 21/37] bpf tools: Create eBPF maps defined in an object file |
| |
On 2015/5/19 2:48, Alexei Starovoitov wrote: > On 5/17/15 3:56 AM, Wang Nan wrote: >> This patch creates maps based on 'map' section in object file using >> bpf_create_map(), and store the fds into an array in >> 'struct bpf_object'. Since the byte order of the object may differ >> from the host, swap map definition before processing. >> >> This is the first patch in 'loading' phase. Previous patches parse ELF >> object file and create needed data structure, but doesnnt play with >> kernel. They belong to 'opening' phase. >> >> Signed-off-by: Wang Nan <wangnan0@huawei.com> > ... >> + for (j = 0; j < i; j++) { >> + close(obj->maps_fds[j]); >> + obj->maps_fds[j] = -1; > > this line is unnecessary, since you're freeing the whole array > at the line below: > >> + } >> + free(obj->maps_fds); >> + obj->maps_fds = NULL; > > ... > >> void bpf_close_object(struct bpf_object *obj) >> { >> if (!obj) >> return; >> >> bpf_obj_clear_elf(obj); >> + bpf_unload_object(obj); > > just realized that this API keeps elf file open for the whole > life time. I think that should be split up. > bpf_open_object() can do elf parsing, creation of maps and > bpf loading. > bpf_close_object() can unload programs, maps. That's fine, > but closing of elf file and freeing memory associated > with parsing sections should be a separate call. >
Looks like I didn't describe the API of libbpf very clearly in patch 0/37.
There are two phases of the API: opening and loading. Opening phase does ELF parsing, and records all related information info 'struct bpf_object'. After that, ELF file itself is closed by bpf_obj_elf_finish(). See patch 19/37. After that, caller will have a chance to adjust programs and maps (currently not implemented). Caller should call bpf_load_object() to do real useful things with kernel. bpf_unload_object() remove map and programs in the object from kernel. It also calls bpf_obj_elf_finish(). However, if it has been called once, the 2nd call doesn't take effect at all. Just in case.
Thank you.
| |