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libbpf: Add version script for DSO 

More and more projects use libbpf and one day it'll likely be packaged
and distributed as DSO and that requires ABI versioning so that both
compatible and incompatible changes to ABI can be introduced in a safe
way in the future without breaking executables dynamically linked with a
previous version of the library.

Usual way to do ABI versioning is version script for the linker. Add
such a script for libbpf. All global symbols currently exported via
LIBBPF_API macro are added to the version script libbpf.map.

The version name LIBBPF_0.0.1 is constructed from the name of the
library + version specified by $(LIBBPF_VERSION) in Makefile.

Version script does not duplicate the work done by LIBBPF_API macro, it
rather complements it. The macro is used at compile time and can be used
by compiler to do optimization that can't be done at link time, it is
purely about global symbol visibility. The version script, in turn, is
used at link time and takes care of ABI versioning. Both techniques are
described in details in [1].

Whenever ABI is changed in the future, version script should be changed
appropriately.

[1] https://www.akkadia.org/drepper/dsohowto.pdf

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrey Ignatov 2018-11-23 16:44:33 -08:00 committed by Alexei Starovoitov
parent 1d2f44ca34
commit 16192a771d
2 changed files with 124 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
tools/lib/bpf/Makefile
View File

@ -145,6 +145,7 @@ include $(srctree)/tools/build/Makefile.include
BPF_IN := $(OUTPUT)libbpf-in.o
LIB_FILE := $(addprefix $(OUTPUT),$(LIB_FILE))
VERSION_SCRIPT := libbpf.map
CMD_TARGETS = $(LIB_FILE)
@ -176,7 +177,8 @@ $(BPF_IN): force elfdep bpfdep
$(Q)$(MAKE) $(build)=libbpf
$(OUTPUT)libbpf.so: $(BPF_IN)
$(QUIET_LINK)$(CC) --shared $^ -o $@
$(QUIET_LINK)$(CC) --shared -Wl,--version-script=$(VERSION_SCRIPT) \
$^ -o $@
$(OUTPUT)libbpf.a: $(BPF_IN)
$(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^

121
tools/lib/bpf/libbpf.map Normal file
View File

@ -0,0 +1,121 @@
LIBBPF_0.0.1 {
global:
bpf_btf_get_fd_by_id;
bpf_create_map;
bpf_create_map_in_map;
bpf_create_map_in_map_node;
bpf_create_map_name;
bpf_create_map_node;
bpf_create_map_xattr;
bpf_load_btf;
bpf_load_program;
bpf_load_program_xattr;
bpf_map__btf_key_type_id;
bpf_map__btf_value_type_id;
bpf_map__def;
bpf_map__fd;
bpf_map__is_offload_neutral;
bpf_map__name;
bpf_map__next;
bpf_map__pin;
bpf_map__prev;
bpf_map__priv;
bpf_map__reuse_fd;
bpf_map__set_ifindex;
bpf_map__set_inner_map_fd;
bpf_map__set_priv;
bpf_map__unpin;
bpf_map_delete_elem;
bpf_map_get_fd_by_id;
bpf_map_get_next_id;
bpf_map_get_next_key;
bpf_map_lookup_and_delete_elem;
bpf_map_lookup_elem;
bpf_map_update_elem;
bpf_obj_get;
bpf_obj_get_info_by_fd;
bpf_obj_pin;
bpf_object__btf_fd;
bpf_object__close;
bpf_object__find_map_by_name;
bpf_object__find_map_by_offset;
bpf_object__find_program_by_title;
bpf_object__kversion;
bpf_object__load;
bpf_object__name;
bpf_object__next;
bpf_object__open;
bpf_object__open_buffer;
bpf_object__open_xattr;
bpf_object__pin;
bpf_object__pin_maps;
bpf_object__pin_programs;
bpf_object__priv;
bpf_object__set_priv;
bpf_object__unload;
bpf_object__unpin_maps;
bpf_object__unpin_programs;
bpf_perf_event_read_simple;
bpf_prog_attach;
bpf_prog_detach;
bpf_prog_detach2;
bpf_prog_get_fd_by_id;
bpf_prog_get_next_id;
bpf_prog_load;
bpf_prog_load_xattr;
bpf_prog_query;
bpf_prog_test_run;
bpf_program__fd;
bpf_program__is_kprobe;
bpf_program__is_perf_event;
bpf_program__is_raw_tracepoint;
bpf_program__is_sched_act;
bpf_program__is_sched_cls;
bpf_program__is_socket_filter;
bpf_program__is_tracepoint;
bpf_program__is_xdp;
bpf_program__load;
bpf_program__next;
bpf_program__nth_fd;
bpf_program__pin;
bpf_program__pin_instance;
bpf_program__prev;
bpf_program__priv;
bpf_program__set_expected_attach_type;
bpf_program__set_ifindex;
bpf_program__set_kprobe;
bpf_program__set_perf_event;
bpf_program__set_prep;
bpf_program__set_priv;
bpf_program__set_raw_tracepoint;
bpf_program__set_sched_act;
bpf_program__set_sched_cls;
bpf_program__set_socket_filter;
bpf_program__set_tracepoint;
bpf_program__set_type;
bpf_program__set_xdp;
bpf_program__title;
bpf_program__unload;
bpf_program__unpin;
bpf_program__unpin_instance;
bpf_raw_tracepoint_open;
bpf_set_link_xdp_fd;
bpf_task_fd_query;
bpf_verify_program;
btf__fd;
btf__find_by_name;
btf__free;
btf__get_from_id;
btf__name_by_offset;
btf__new;
btf__resolve_size;
btf__resolve_type;
btf__type_by_id;
libbpf_attach_type_by_name;
libbpf_get_error;
libbpf_prog_type_by_name;
libbpf_set_print;
libbpf_strerror;
local:
*;
};