libbpf: Wire up spec management and other arch-independent USDT logic
Last part of architecture-agnostic user-space USDT handling logic is to set up BPF spec and, optionally, IP-to-ID maps from user-space. usdt_manager performs a compact spec ID allocation to utilize fixed-sized BPF maps as efficiently as possible. We also use hashmap to deduplicate USDT arg spec strings and map identical strings to single USDT spec, minimizing the necessary BPF map size. usdt_manager supports arbitrary sequences of attachment and detachment, both of the same USDT and multiple different USDTs and internally maintains a free list of unused spec IDs. bpf_link_usdt's logic is extended with proper setup and teardown of this spec ID free list and supporting BPF maps. Signed-off-by:Andrii Nakryiko <andrii@kernel.org> Signed-off-by:
Alexei Starovoitov <ast@kernel.org> Reviewed-by:
Alan Maguire <alan.maguire@oracle.com> Reviewed-by:
Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/bpf/20220404234202.331384-5-andrii@kernel.org
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