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bpf: Simplify __bpf_arch_text_poke poke type handling

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Given that we have BPF_MOD_NOP_TO_{CALL,JUMP}, BPF_MOD_{CALL,JUMP}_TO_NOP
and BPF_MOD_{CALL,JUMP}_TO_{CALL,JUMP} poke types and that we also pass in
old_addr as well as new_addr, it's a bit redundant and unnecessarily
complicates __bpf_arch_text_poke() itself since we can derive the same from
the *_addr that were passed in. Hence simplify and use BPF_MOD_{CALL,JUMP}
as types which also allows to clean up call-sites.

In addition to that, __bpf_arch_text_poke() currently verifies that text
matches expected old_insn before we invoke text_poke_bp(). Also add a check
on new_insn and skip rewrite if it already matches. Reason why this is rather
useful is that it avoids making any special casing in prog_array_map_poke_run()
when old and new prog were NULL and has the benefit that also for this case
we perform a check on text whether it really matches our expectations.

Suggested-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/fcb00a2b0b288d6c73de4ef58116a821c8fe8f2f.1574555798.git.daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann 2019-11-24 01:39:42 +01:00 • committed by Alexei Starovoitov
parent f9a7cf6eb1
commit b553a6ec57
4 changed files with 32 additions and 83 deletions
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10
include/linux/bpf.h
View file

@ -1324,14 +1324,8 @@ static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
#endif /* CONFIG_INET */
enum bpf_text_poke_type {
/* All call-related pokes. */
BPF_MOD_NOP_TO_CALL,
BPF_MOD_CALL_TO_CALL,
BPF_MOD_CALL_TO_NOP,
/* All jump-related pokes. */
BPF_MOD_NOP_TO_JUMP,
BPF_MOD_JUMP_TO_JUMP,
BPF_MOD_JUMP_TO_NOP,
BPF_MOD_CALL,
BPF_MOD_JUMP,
};
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,