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-rw-r--r--Documentation/bpf/bpf_devel_QA.txt10
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/bpf/bpf_devel_QA.txt b/Documentation/bpf/bpf_devel_QA.txt
index 1a0b704e1a38..da57601153a0 100644
--- a/Documentation/bpf/bpf_devel_QA.txt
+++ b/Documentation/bpf/bpf_devel_QA.txt
@@ -557,6 +557,14 @@ A: Although LLVM IR generation and optimization try to stay architecture
pulls in some header files containing file scope host assembly codes.
- You can add "-fno-jump-tables" to work around the switch table issue.
- Otherwise, you can use bpf target.
+ Otherwise, you can use bpf target. Additionally, you _must_ use bpf target
+ when:
+
+ - Your program uses data structures with pointer or long / unsigned long
+ types that interface with BPF helpers or context data structures. Access
+ into these structures is verified by the BPF verifier and may result
+ in verification failures if the native architecture is not aligned with
+ the BPF architecture, e.g. 64-bit. An example of this is
+ BPF_PROG_TYPE_SK_MSG require '-target bpf'
Happy BPF hacking!