1 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.
1.1 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.