On Wed, Aug 16, 2023 at 03:10:23PM -0400, David Marchevsky wrote: > On 8/16/23 1:44 PM, David Vernet wrote: > > On Wed, Aug 16, 2023 at 09:58:13AM -0700, Dave Marchevsky wrote: > >> This patch adds selftests that exercise kfunc flavor relocation > >> functionality added in the previous patch. The actual kfunc defined in > >> kernel/bpf/helpers.c is > >> > >> struct task_struct *bpf_task_acquire(struct task_struct *p) > >> > >> The following relocation behaviors are checked: > >> > >> struct task_struct *bpf_task_acquire___one(struct task_struct *name) > >> * Should succeed despite differing param name > >> > >> struct task_struct *bpf_task_acquire___two(struct task_struct *p, void *ctx) > >> * Should fail because there is no two-param bpf_task_acquire > >> > >> struct task_struct *bpf_task_acquire___three(void *ctx) > >> * Should fail because, despite vmlinux's bpf_task_acquire having one param, > >> the types don't match > >> > >> Changelog: > >> v1 -> v2: https://lore.kernel.org/bpf/20230811201346.3240403-2-davemarchevsky@xxxxxx/ > >> * Change comment on bpf_task_acquire___two to more accurately reflect > >> that it fails in same codepath as bpf_task_acquire___three, and to > >> not mention dead code elimination as thats an implementation detail > >> (Yonghong) > >> > >> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx> > >> --- > >> .../selftests/bpf/prog_tests/task_kfunc.c | 1 + > >> .../selftests/bpf/progs/task_kfunc_success.c | 37 +++++++++++++++++++ > >> 2 files changed, 38 insertions(+) > >> > >> diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c > >> index 740d5f644b40..99abb0350154 100644 > >> --- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c > >> +++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c > >> @@ -79,6 +79,7 @@ static const char * const success_tests[] = { > >> "test_task_from_pid_current", > >> "test_task_from_pid_invalid", > >> "task_kfunc_acquire_trusted_walked", > >> + "test_task_kfunc_flavor_relo", > >> }; > >> > >> void test_task_kfunc(void) > >> diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c > >> index b09371bba204..ffbe3ff72639 100644 > >> --- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c > >> +++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c > > > > Do you think it's worth it to also add a failure case for if there's no > > correct bpf_taks_acquire___one(), to verify e.g. that we can't resolve > > bpf_task_acquire___three(void *ctx) __ksym __weak? > > > > IIUC you're asking about whether it's possible to fail loading the program > entirely if _none_ of the three variants resolve successfully? If so, I > sent out a response to another email in this round of your comments that should > address it. Sorry, that was unclear in the way I worded it. I understand that the program will still load if none of the variants resolve succesfully. I was asking whether we should add a test that verifies that the wrong variant won't be resolved if a correct one isn't present. Maybe that's overkill? Seems prudent to add just in case, though. Something like this: SEC("tp_btf/task_newtask") int BPF_PROG(test_task_kfunc_flavor_relo_not_found, struct task_struct *task, u64 clone_flags) { /* Neither symbol should resolve successfully. */ if (bpf_ksym_exists(bpf_task_acquire___two)) err = 1; else if (bpf_ksym_exists(bpf_task_acquire___three)) err = 2; return 0; } > > >> @@ -18,6 +18,13 @@ int err, pid; > >> */ > >> > >> struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak; > >> + > >> +struct task_struct *bpf_task_acquire___one(struct task_struct *task) __ksym __weak; > >> +/* The two-param bpf_task_acquire doesn't exist */ > >> +struct task_struct *bpf_task_acquire___two(struct task_struct *p, void *ctx) __ksym __weak; > >> +/* Incorrect type for first param */ > >> +struct task_struct *bpf_task_acquire___three(void *ctx) __ksym __weak; > >> + > >> void invalid_kfunc(void) __ksym __weak; > >> void bpf_testmod_test_mod_kfunc(int i) __ksym __weak; > >> > >> @@ -55,6 +62,36 @@ static int test_acquire_release(struct task_struct *task) > >> return 0; > >> } > >> > >> +SEC("tp_btf/task_newtask") > >> +int BPF_PROG(test_task_kfunc_flavor_relo, struct task_struct *task, u64 clone_flags) > >> +{ > >> + struct task_struct *acquired = NULL; > >> + int fake_ctx = 42; > >> + > >> + if (bpf_ksym_exists(bpf_task_acquire___one)) { > >> + acquired = bpf_task_acquire___one(task); > >> + } else if (bpf_ksym_exists(bpf_task_acquire___two)) { > >> + /* Here, bpf_object__resolve_ksym_func_btf_id's find_ksym_btf_id > >> + * call will find vmlinux's bpf_task_acquire, but subsequent > >> + * bpf_core_types_are_compat will fail > >> + */ > >> + acquired = bpf_task_acquire___two(task, &fake_ctx); > >> + err = 3; > >> + return 0; > >> + } else if (bpf_ksym_exists(bpf_task_acquire___three)) { > >> + /* bpf_core_types_are_compat will fail similarly to above case */ > >> + acquired = bpf_task_acquire___three(&fake_ctx); > >> + err = 4; > >> + return 0; > >> + } > >> + > >> + if (acquired) > >> + bpf_task_release(acquired); > > > > Might be slightly simpler to do the release + return immediately in the > > bpf_task_acquire___one branch, and then to just do the following here > > without the if / else: > > > > err = 5; > > return 0; > > > > What do you think? > > > > Eh, I like this form more because it's easier to visually distinguish that the > bpf_task_acquire___one case above is not a 'failure' case and should > successfully resolve, whereas the other two bail out early. > > >> + else > >> + err = 5; > >> + return 0; > >> +} > >> + > >> SEC("tp_btf/task_newtask") > >> int BPF_PROG(test_task_acquire_release_argument, struct task_struct *task, u64 clone_flags) > >> { > >> -- > >> 2.34.1 > >> > >>
