On 8/11/23 1:13 PM, 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
Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
.../selftests/bpf/prog_tests/task_kfunc.c | 1 +
.../selftests/bpf/progs/task_kfunc_success.c | 41 +++++++++++++++++++
2 files changed, 42 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..33e1eb88874f 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
@@ -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 +62,40 @@ 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)) {
+ /* if verifier's dead code elimination doesn't remove this,
+ * verification should fail due to return w/o bpf_task_release
+ */
+ acquired = bpf_task_acquire___two(task, &fake_ctx);
+ err = 3;
+ return 0;
+ } else if (bpf_ksym_exists(bpf_task_acquire___three)) {
+ /* 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
+ *
+ * Should be removed by dead code elimination similar to ___two
+ */
+ acquired = bpf_task_acquire___three(&fake_ctx);
+ err = 4;
+ return 0;
+ }
The comments for the above 'bpf_task_acquire___two' and
'bpf_task_acquire___three' a little confusing. For example, for
'bpf_task_acquire___two', libbpf incorrectly made
'bpf_ksym_exists(bpf_task_acquire___two)' non-NULL, hence
dead code elimination cannot happen and verification will
fail due to missing bpf_task_release. But if libbpf correctly
made ''bpf_ksym_exists(bpf_task_acquire___two)' NULL, but
verifier didn't remove dead code, we should be fine.
I think both 'bpf_task_acquire___two' and 'bpf_task_acquire___three'
can use the same comment as in 'bpf_task_acquire___three'.
There is no need to mention dead code elimination which is
not important for this patch set.
+
+ if (acquired)
+ bpf_task_release(acquired);
+ 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)
{
