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| author | Eduard Zingerman <eddyz87@gmail.com> | 2025-06-11 23:08:27 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-06-13 02:52:42 +0300 |
| commit | 96c6aa4c63af0bb0675c41b3e61a2fc7f6fed998 (patch) | |
| tree | b7d02b1816f5f21bacb69071d2421e9137ddf007 /include | |
| parent | baaebe0928bf321a1cd980d569e308dec66be94c (diff) | |
| download | linux-96c6aa4c63af0bb0675c41b3e61a2fc7f6fed998.tar.xz | |
bpf: compute SCCs in program control flow graph
Compute strongly connected components in the program CFG.
Assign an SCC number to each instruction, recorded in
env->insn_aux[*].scc. Use Tarjan's algorithm for SCC computation
adapted to run non-recursively.
For debug purposes print out computed SCCs as a part of full program
dump in compute_live_registers() at log level 2, e.g.:
func#0 @0
Live regs before insn:
0: .......... (b4) w6 = 10
2 1: ......6... (18) r1 = 0xffff88810bbb5565
2 3: .1....6... (b4) w2 = 2
2 4: .12...6... (85) call bpf_trace_printk#6
2 5: ......6... (04) w6 += -1
2 6: ......6... (56) if w6 != 0x0 goto pc-6
7: .......... (b4) w6 = 5
1 8: ......6... (18) r1 = 0xffff88810bbb5567
1 10: .1....6... (b4) w2 = 2
1 11: .12...6... (85) call bpf_trace_printk#6
1 12: ......6... (04) w6 += -1
1 13: ......6... (56) if w6 != 0x0 goto pc-6
14: .......... (b4) w0 = 0
15: 0......... (95) exit
^^^
SCC number for the instruction
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250611200836.4135542-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/bpf_verifier.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 3e77befdbc4b..95f5211610f4 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -609,6 +609,11 @@ struct bpf_insn_aux_data { * accepts callback function as a parameter. */ bool calls_callback; + /* + * CFG strongly connected component this instruction belongs to, + * zero if it is a singleton SCC. + */ + u32 scc; /* registers alive before this instruction. */ u16 live_regs_before; }; |