bpf: Remove bpf_kfunc_call_test_kptr_get() test kfunc

We've managed to improve the UX for kptrs significantly over the last 9
months. All of the prior main use cases, struct bpf_cpumask *, struct
task_struct *, and struct cgroup *, have all been updated to be
synchronized mainly using RCU. In other words, their KF_ACQUIRE kfunc
calls are all KF_RCU, and the pointers themselves are MEM_RCU and can be
accessed in an RCU read region in BPF.

In a follow-on change, we'll be removing the KF_KPTR_GET kfunc flag.
This patch prepares for that by removing the
bpf_kfunc_call_test_kptr_get() kfunc, and all associated selftests.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230416084928.326135-2-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

net/bpf/test_run.c

@@ -679,17 +679,6 @@ __bpf_kfunc void bpf_kfunc_call_int_mem_release(int *p)
 {
 }
 
-__bpf_kfunc struct prog_test_ref_kfunc *
-bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **pp, int a, int b)
-{
-	struct prog_test_ref_kfunc *p = READ_ONCE(*pp);
-
-	if (!p)
-		return NULL;
-	refcount_inc(&p->cnt);
-	return p;
-}
-
 struct prog_test_pass1 {
 	int x0;
 	struct {
@@ -804,7 +793,6 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_get_rdwr_mem, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_get_rdonly_mem, KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_acq_rdonly_mem, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_kfunc_call_int_mem_release, KF_RELEASE)
-BTF_ID_FLAGS(func, bpf_kfunc_call_test_kptr_get, KF_ACQUIRE | KF_RET_NULL | KF_KPTR_GET)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_pass_ctx)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_pass1)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_pass2)

tools/testing/selftests/bpf/progs/map_kptr.c

@@ -115,8 +115,6 @@ DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, hash_malloc_map, hash_of_hash_mallo
 DEFINE_MAP_OF_MAP(BPF_MAP_TYPE_HASH_OF_MAPS, lru_hash_map, hash_of_lru_hash_maps);
 
 extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
-extern struct prog_test_ref_kfunc *
-bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
 extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
 void bpf_kfunc_call_test_ref(struct prog_test_ref_kfunc *p) __ksym;
 
@@ -187,25 +185,10 @@ static void test_kptr_ref(struct map_value *v)
 	bpf_kfunc_call_test_release(p);
 }
 
-static void test_kptr_get(struct map_value *v)
-{
-	struct prog_test_ref_kfunc *p;
-
-	p = bpf_kfunc_call_test_kptr_get(&v->ref_ptr, 0, 0);
-	if (!p)
-		return;
-	if (p->a + p->b > 100) {
-		bpf_kfunc_call_test_release(p);
-		return;
-	}
-	bpf_kfunc_call_test_release(p);
-}
-
 static void test_kptr(struct map_value *v)
 {
 	test_kptr_unref(v);
 	test_kptr_ref(v);
-	test_kptr_get(v);
 }
 
 SEC("tc")
@@ -338,38 +321,25 @@ int test_map_kptr_ref_pre(struct map_value *v)
 	if (p_st->cnt.refs.counter != ref)
 		return 4;
 
-	p = bpf_kfunc_call_test_kptr_get(&v->ref_ptr, 0, 0);
-	if (!p)
-		return 5;
-	ref++;
-	if (p_st->cnt.refs.counter != ref) {
-		ret = 6;
-		goto end;
-	}
-	bpf_kfunc_call_test_release(p);
-	ref--;
-	if (p_st->cnt.refs.counter != ref)
-		return 7;
-
 	p = bpf_kptr_xchg(&v->ref_ptr, NULL);
 	if (!p)
-		return 8;
+		return 5;
 	bpf_kfunc_call_test_release(p);
 	ref--;
 	if (p_st->cnt.refs.counter != ref)
-		return 9;
+		return 6;
 
 	p = bpf_kfunc_call_test_acquire(&arg);
 	if (!p)
-		return 10;
+		return 7;
 	ref++;
 	p = bpf_kptr_xchg(&v->ref_ptr, p);
 	if (p) {
-		ret = 11;
+		ret = 8;
 		goto end;
 	}
 	if (p_st->cnt.refs.counter != ref)
-		return 12;
+		return 9;
 	/* Leave in map */
 
 	return 0;

tools/testing/selftests/bpf/progs/map_kptr_fail.c

@@ -21,8 +21,6 @@ struct array_map {
 
 extern struct prog_test_ref_kfunc *bpf_kfunc_call_test_acquire(unsigned long *sp) __ksym;
 extern void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
-extern struct prog_test_ref_kfunc *
-bpf_kfunc_call_test_kptr_get(struct prog_test_ref_kfunc **p, int a, int b) __ksym;
 
 SEC("?tc")
 __failure __msg("kptr access size must be BPF_DW")
@@ -220,67 +218,6 @@ int reject_kptr_xchg_on_unref(struct __sk_buff *ctx)
 	return 0;
 }
 
-SEC("?tc")
-__failure __msg("arg#0 expected pointer to map value")
-int reject_kptr_get_no_map_val(struct __sk_buff *ctx)
-{
-	bpf_kfunc_call_test_kptr_get((void *)&ctx, 0, 0);
-	return 0;
-}
-
-SEC("?tc")
-__failure __msg("arg#0 expected pointer to map value")
-int reject_kptr_get_no_null_map_val(struct __sk_buff *ctx)
-{
-	bpf_kfunc_call_test_kptr_get(bpf_map_lookup_elem(&array_map, &(int){0}), 0, 0);
-	return 0;
-}
-
-SEC("?tc")
-__failure __msg("arg#0 no referenced kptr at map value offset=0")
-int reject_kptr_get_no_kptr(struct __sk_buff *ctx)
-{
-	struct map_value *v;
-	int key = 0;
-
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v)
-		return 0;
-
-	bpf_kfunc_call_test_kptr_get((void *)v, 0, 0);
-	return 0;
-}
-
-SEC("?tc")
-__failure __msg("arg#0 no referenced kptr at map value offset=8")
-int reject_kptr_get_on_unref(struct __sk_buff *ctx)
-{
-	struct map_value *v;
-	int key = 0;
-
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v)
-		return 0;
-
-	bpf_kfunc_call_test_kptr_get(&v->unref_ptr, 0, 0);
-	return 0;
-}
-
-SEC("?tc")
-__failure __msg("kernel function bpf_kfunc_call_test_kptr_get args#0")
-int reject_kptr_get_bad_type_match(struct __sk_buff *ctx)
-{
-	struct map_value *v;
-	int key = 0;
-
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v)
-		return 0;
-
-	bpf_kfunc_call_test_kptr_get((void *)&v->ref_memb_ptr, 0, 0);
-	return 0;
-}
-
 SEC("?tc")
 __failure __msg("R1 type=rcu_ptr_or_null_ expected=percpu_ptr_")
 int mark_ref_as_untrusted_or_null(struct __sk_buff *ctx)
@@ -428,21 +365,6 @@ int kptr_xchg_ref_state(struct __sk_buff *ctx)
 	return 0;
 }
 
-SEC("?tc")
-__failure __msg("Unreleased reference id=3 alloc_insn=")
-int kptr_get_ref_state(struct __sk_buff *ctx)
-{
-	struct map_value *v;
-	int key = 0;
-
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v)
-		return 0;
-
-	bpf_kfunc_call_test_kptr_get(&v->ref_ptr, 0, 0);
-	return 0;
-}
-
 SEC("?tc")
 __failure __msg("Possibly NULL pointer passed to helper arg2")
 int kptr_xchg_possibly_null(struct __sk_buff *ctx)

tools/testing/selftests/bpf/verifier/map_kptr.c

@@ -288,33 +288,6 @@
 	.result = REJECT,
 	.errstr = "off=0 kptr isn't referenced kptr",
 },
-{
-	"map_kptr: unref: bpf_kfunc_call_test_kptr_get rejected",
-	.insns = {
-	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
-	BPF_LD_MAP_FD(BPF_REG_6, 0),
-	BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
-	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
-	BPF_MOV64_IMM(BPF_REG_0, 0),
-	BPF_ST_MEM(BPF_W, BPF_REG_2, 0, 0),
-	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
-	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
-	BPF_EXIT_INSN(),
-	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
-	BPF_MOV64_IMM(BPF_REG_2, 0),
-	BPF_MOV64_IMM(BPF_REG_3, 0),
-	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
-	BPF_MOV64_IMM(BPF_REG_0, 0),
-	BPF_EXIT_INSN(),
-	},
-	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
-	.fixup_map_kptr = { 1 },
-	.result = REJECT,
-	.errstr = "arg#0 no referenced kptr at map value offset=0",
-	.fixup_kfunc_btf_id = {
-		{ "bpf_kfunc_call_test_kptr_get", 13 },
-	}
-},
 /* Tests for referenced PTR_TO_BTF_ID */
 {
 	"map_kptr: ref: loaded pointer marked as untrusted",