On 8/28/24 11:16 PM, Eduard Zingerman wrote:
On Tue, 2024-08-27 at 12:48 -0700, Martin KaFai Lau wrote:From: Martin KaFai Lau <martin.lau@xxxxxxxxxx> This patch adds a gen_epilogue test to test a main prog using a bpf_tail_call. A non test_loader test is used. The tailcall target program, "test_epilogue_subprog", needs to be used in a struct_ops map before it can be loaded. Another struct_ops map is also needed to host the actual "test_epilogue_tailcall" struct_ops program that does the bpf_tail_call. The earlier test_loader patch will attach all struct_ops maps but the bpf_testmod.c does not support >1 attached struct_ops. The earlier patch used the test_loader which has already covered checking for the patched pro/epilogue instructions. This is done by the __xlated tag. This patch goes for the regular skel load and syscall test to do the tailcall test that can also allow to directly pass the the "struct st_ops_args *args" as ctx_in to the SEC("syscall") program. Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx> ---Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx> [...]+static void test_tailcall(void) +{ + LIBBPF_OPTS(bpf_test_run_opts, topts); + struct epilogue_tailcall *skel; + struct st_ops_args args; + int err, prog_fd; + + skel = epilogue_tailcall__open_and_load(); + if (!ASSERT_OK_PTR(skel, "epilogue_tailcall__open_and_load")) + return; + + topts.ctx_in = &args; + topts.ctx_size_in = sizeof(args); + + skel->links.epilogue_tailcall = + bpf_map__attach_struct_ops(skel->maps.epilogue_tailcall); + if (!ASSERT_OK_PTR(skel->links.epilogue_tailcall, "attach_struct_ops")) + goto done; +Nitpick: Both test_epilogue_tailcall and test_epilogue_subprog would be augmented with epilogue, and we know that tail call run as expected because only test_epilogue_subprog does +1, right?
Yes. and also the epilogue of the test_epilogue_subprog is executed.
If above is true, could you please update the comment a bit, e.g.: /* Both test_epilogue_tailcall and test_epilogue_subprog are * augmented with epilogue. When syscall_epilogue_tailcall() * is run test_epilogue_tailcall() is triggered, * it executes a tail call and control is transferred to * test_epilogue_subprog(). Only test_epilogue_subprog() * does args->a += 1, thus final args.a value of 10001 * guarantees that tail call was executed as expected. */
Added. I massaged the wordings a little.
