path: root/arch
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authorDaniel Borkmann <daniel@iogearbox.net>2015-12-17 23:51:53 +0100
committerDavid S. Miller <davem@davemloft.net>2015-12-18 16:04:50 -0500
commit05c74e5e53f6cb07502c3e6a820f33e2777b6605 (patch)
treebb21567c453dc262c318bdfed152cb76b00ea7e4 /arch
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next (diff)
bpf: add bpf_skb_load_bytes helper
When hacking tc programs with eBPF, one of the issues that come up from time to time is to load addresses from headers. In eBPF as in classic BPF, we have BPF_LD | BPF_ABS | BPF_{B,H,W} instructions that extract a byte, half-word or word out of the skb data though helpers such as bpf_load_pointer() (interpreter case). F.e. extracting a whole IPv6 address could possibly look like ... union v6addr { struct { __u32 p1; __u32 p2; __u32 p3; __u32 p4; }; __u8 addr[16]; }; [...] a.p1 = htonl(load_word(skb, off)); a.p2 = htonl(load_word(skb, off + 4)); a.p3 = htonl(load_word(skb, off + 8)); a.p4 = htonl(load_word(skb, off + 12)); [...] /* access to a.addr[...] */ This work adds a complementary helper bpf_skb_load_bytes() (we also have bpf_skb_store_bytes()) as an alternative where the same call would look like from an eBPF program: ret = bpf_skb_load_bytes(skb, off, addr, sizeof(addr)); Same verifier restrictions apply as in ffeedafbf023 ("bpf: introduce current->pid, tgid, uid, gid, comm accessors") case, where stack memory access needs to be statically verified and thus guaranteed to be initialized in first use (otherwise verifier cannot tell whether a subsequent access to it is valid or not as it's runtime dependent). Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch')
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