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2018-04-23bpf: Document sockmap '-target bpf' requirement for PROG_TYPE_SK_MSGJohn Fastabend1-1/+9
BPF_PROG_TYPE_SK_MSG programs use a 'void *' for both data and the data_end pointers. Additionally, the verifier ensures that every accesses into the values is a __u64 read. This correctly maps on to the BPF 64-bit architecture. However, to ensure that when building on 32bit architectures that clang uses correct types the '-target bpf' option _must_ be specified. To make this clear add a note to the Documentation. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-03-20bpf, doc: add description wrt native/bpf clang target and pointer sizeDaniel Borkmann1-0/+12
As this recently came up on netdev [0], lets add it to the BPF devel doc. [0] https://www.spinics.net/lists/netdev/msg489612.html Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2018-02-02bpf: add documentation to compare clang "-target bpf" and default targetYonghong Song1-0/+31
The added documentation explains how generated codes may differ between clang bpf target and default target, and when to use each target. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2017-12-06bpf, doc: add faq about bpf development processDaniel Borkmann1-0/+519
In the same spirit of netdev FAQ, start a BPF FAQ as a collection of expectations and/or workflow details in the context of BPF patch processing. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2017-11-01bpf: document answers to common questions about BPFAlexei Starovoitov1-0/+156
to address common misconceptions about what BPF is and what it's not add short BPF Q&A that clarifies core BPF design principles and answers some common questions. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net>