Re: [PATCH v3 bpf-next 17/18] selftests/bpf: Extend test_pkt_access test
From: Song Liu <hidden>
Date: 2019-11-08 19:16:07
Also in:
bpf
On Nov 7, 2019, at 10:40 PM, Alexei Starovoitov [off-list ref] wrote: The test_pkt_access.o is used by multiple tests. Fix its section name so that program type can be automatically detected by libbpf and make it call other subprograms with skb argument. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <redacted>
quoted hunk ↗ jump to hunk
--- .../selftests/bpf/progs/test_pkt_access.c | 38 ++++++++++++++++++- 1 file changed, 36 insertions(+), 2 deletions(-)diff --git a/tools/testing/selftests/bpf/progs/test_pkt_access.c b/tools/testing/selftests/bpf/progs/test_pkt_access.c index 7cf42d14103f..3a7b4b607ed3 100644 --- a/tools/testing/selftests/bpf/progs/test_pkt_access.c +++ b/tools/testing/selftests/bpf/progs/test_pkt_access.c@@ -17,8 +17,38 @@#define barrier() __asm__ __volatile__("": : :"memory") int _version SEC("version") = 1; -SEC("test1") -int process(struct __sk_buff *skb) +/* llvm will optimize both subprograms into exactly the same BPF assembly + * + * Disassembly of section .text: + * + * 0000000000000000 test_pkt_access_subprog1: + * ; return skb->len * 2; + * 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) + * 1: 64 00 00 00 01 00 00 00 w0 <<= 1 + * 2: 95 00 00 00 00 00 00 00 exit + * + * 0000000000000018 test_pkt_access_subprog2: + * ; return skb->len * val; + * 3: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) + * 4: 64 00 00 00 01 00 00 00 w0 <<= 1 + * 5: 95 00 00 00 00 00 00 00 exit + * + * Which makes it an interesting test for BTF-enabled verifier.
This is interesting!