Test st_ops assoc prog v3 #10026
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Test st_ops assoc prog v3 #10026
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Allow verifier to fixup kfuncs in kernel module to support kfuncs with __prog arguments. Currently, special kfuncs and kfuncs with __prog arguments are kernel kfuncs. Allowing kernel module kfuncs should not affect existing kfunc fixup as kernel module kfuncs have BTF IDs greater than kernel kfuncs' BTF IDs. Signed-off-by: Amery Hung <[email protected]>
Add a new BPF command BPF_PROG_ASSOC_STRUCT_OPS to allow associating a BPF program with a struct_ops map. This command takes a file descriptor of a struct_ops map and a BPF program and set prog->aux->st_ops_assoc to the kdata of the struct_ops map. The command does not accept a struct_ops program or a non-struct_ops map. Programs of a struct_ops map is automatically associated with the map during map update. If a program is shared between two struct_ops maps, prog->aux->st_ops_assoc will be poisoned to indicate that the associated struct_ops is ambiguous. The pointer, once poisoned, cannot be reset since we have lost track of associated struct_ops. For other program types, the associated struct_ops map, once set, cannot be changed later. This restriction may be lifted in the future if there is a use case. A kernel helper bpf_prog_get_assoc_struct_ops() can be used to retrieve the associated struct_ops pointer. The pointer returned, if not NULL, is guaranteed to be valid and point to a fully updated struct_ops struct. This is done by increasing the refcount of the map for every associated non-struct_ops programs. For struct_ops program reused in multiple struct_ops map, the return will be NULL. struct_ops implementers should note that the struct_ops returned may or may not be attached. The struct_ops implementer will be responsible for tracking and checking the state of the associated struct_ops map if the use case requires an attached struct_ops. Signed-off-by: Amery Hung <[email protected]>
Add low-level wrapper and libbpf API for BPF_PROG_ASSOC_STRUCT_OPS command in the bpf() syscall. Signed-off-by: Amery Hung <[email protected]>
Test BPF_PROG_ASSOC_STRUCT_OPS command that associates a BPF program with a struct_ops. The test follows the same logic in commit ba7000f ("selftests/bpf: Test multi_st_ops and calling kfuncs from different programs"), but instead of using map id to identify a specific struct_ops, this test uses the new BPF command to associate a struct_ops with a program. The test consists of two sets of almost identical struct_ops maps and BPF programs associated with the map. Their only difference is the unique value returned by bpf_testmod_multi_st_ops::test_1(). The test first loads the programs and associates them with struct_ops maps. Then, it exercises the BPF programs. They will in turn call kfunc bpf_kfunc_multi_st_ops_test_1_prog_arg() to trigger test_1() of the associated struct_ops map, and then check if the right unique value is returned. Signed-off-by: Amery Hung <[email protected]>
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