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| =================================================== | |
| BPF ABI Recommended Conventions and Guidelines v1.0 | |
| =================================================== | |
| This is version 1.0 of an informational document containing recommended | |
| conventions and guidelines for producing portable BPF program binaries. | |
| Registers and calling convention | |
| ================================ | |
| BPF has 10 general purpose registers and a read-only frame pointer register, | |
| all of which are 64-bits wide. | |
| The BPF calling convention is defined as: | |
| * R0: return value from function calls, and exit value for BPF programs | |
| * R1 - R5: arguments for function calls | |
| * R6 - R9: callee saved registers that function calls will preserve | |
| * R10: read-only frame pointer to access stack | |
| R0 - R5 are scratch registers and BPF programs needs to spill/fill them if | |
| necessary across calls. | |
| The BPF program needs to store the return value into register R0 before doing an | |
| ``EXIT``. |