Re: [PATCH RFC v4 net-next 03/26] bpf: introduce syscall(BPF, ...) and BPF maps
From: Brendan Gregg <hidden>
Date: 2014-08-14 22:28:38
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lkml, netdev
On Wed, Aug 13, 2014 at 12:57 AM, Alexei Starovoitov [off-list ref] wrote: [...]
maps can have different types: hash, bloom filter, radix-tree, etc. The map is defined by: . type . max number of elements . key size in bytes . value size in bytes
Can values be strings or byte arrays? How would user-level bpf read them? The two types of uses I'm thinking are: A. Constructing a custom string in kernel-context, and using that as the value. Eg, a truncated filename, or a dotted quad IP address, or the raw contents of a packet. B. I have a pointer to an existing buffer or string, eg a filename, that will likely be around for some time (>1s). Instead of the value storing the string, it could just be a ptr, so long as user-level bpf has a way to read it. Also, can keys be strings? I'd ask about multiple keys, but if they can be a string, I can delimit in the key (eg, "PID:filename"). Thanks, Brendan -- http://www.brendangregg.com