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4 ============================================== 4 ===================================================
5 BPF ABI Recommended Conventions and Guidelines 5 BPF ABI Recommended Conventions and Guidelines v1.0
6 ============================================== 6 ===================================================
7 7
8 This is version 1.0 of an informational docume 8 This is version 1.0 of an informational document containing recommended
9 conventions and guidelines for producing porta 9 conventions and guidelines for producing portable BPF program binaries.
10 10
11 Registers and calling convention 11 Registers and calling convention
12 ================================ 12 ================================
13 13
14 BPF has 10 general purpose registers and a rea 14 BPF has 10 general purpose registers and a read-only frame pointer register,
15 all of which are 64-bits wide. 15 all of which are 64-bits wide.
16 16
17 The BPF calling convention is defined as: 17 The BPF calling convention is defined as:
18 18
19 * R0: return value from function calls, and ex 19 * R0: return value from function calls, and exit value for BPF programs
20 * R1 - R5: arguments for function calls 20 * R1 - R5: arguments for function calls
21 * R6 - R9: callee saved registers that functio 21 * R6 - R9: callee saved registers that function calls will preserve
22 * R10: read-only frame pointer to access stack 22 * R10: read-only frame pointer to access stack
23 23
24 R0 - R5 are scratch registers and BPF programs 24 R0 - R5 are scratch registers and BPF programs needs to spill/fill them if
25 necessary across calls. 25 necessary across calls.
26 <<
27 The BPF program needs to store the return valu <<
28 ``EXIT``. <<
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