abi.rst

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 5BPF ABI Recommended Conventions and Guidelines v1.0
 6===================================================
 7
 8This is version 1.0 of an informational document containing recommended
 9conventions and guidelines for producing portable BPF program binaries.
10
11Registers and calling convention
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13
14BPF has 10 general purpose registers and a read-only frame pointer register,
15all of which are 64-bits wide.
16
17The BPF calling convention is defined as:
18
19* R0: return value from function calls, and exit value for BPF programs
20* R1 - R5: arguments for function calls
21* R6 - R9: callee saved registers that function calls will preserve
22* R10: read-only frame pointer to access stack
23
24R0 - R5 are scratch registers and BPF programs needs to spill/fill them if
25necessary across calls.
26
27The BPF program needs to store the return value into register R0 before doing an
28``EXIT``.