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.. contents::
.. sectnum::
===================================================
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``.
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