On Fri, 2025-04-11 at 22:32 +0200, Alexis Lothoré (eBPF Foundation) wrote:
When dealing with large types (>8 bytes), ARM64 trampolines need to take extra care about the arguments alignment to respect the calling convention set by AAPCS64.
Add two tests ensuring that the BPF trampoline arranges arguments with the relevant layout. The two new tests involve almost the same arguments, except that the second one requires a more specific alignment to be set by the trampoline when preparing arguments before calling the the target function.
Signed-off-by: Alexis Lothoré (eBPF Foundation) alexis.lothore@bootlin.com
[...]
+SEC("fentry/bpf_testmod_test_struct_arg_11") +int BPF_PROG2(test_struct_many_args_9, struct bpf_testmod_struct_arg_5, a,
struct bpf_testmod_struct_arg_5, b,struct bpf_testmod_struct_arg_5, c,struct bpf_testmod_struct_arg_5, d, int, e,struct bpf_testmod_struct_arg_5, f)
Hello Alexis,
I'm trying to double check the error you've seen for x86. I see that tracing_struct/struct_many_args fails with assertion: "test_struct_many_args:FAIL:t11:f unexpected t11:f: actual 35 != expected 43". Could you please help me understand this test? The function listened to is defined as accepting 'struct bpf_testmod_struct_arg_7', at the same time this function uses 'struct bpf_testmod_struct_arg_5'. Nevertheless, the assertion persists even with correct types.
+{
- t11_a = a.a;
- t11_b = b.a;
- t11_c = c.a;
- t11_d = d.a;
- t11_e = e;
- t11_f = f.a;
- return 0;
+}
[...]