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bpf: Remove bpf_kfunc_call_test_kptr_get() test kfunc
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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.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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David Vernet authored and Alexei Starovoitov committed Apr 16, 2023
1 parent 7a0788f commit 09b501d
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Showing 4 changed files with 5 additions and 152 deletions.
12 changes: 0 additions & 12 deletions net/bpf/test_run.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down Expand Up @@ -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)
Expand Down
40 changes: 5 additions & 35 deletions tools/testing/selftests/bpf/progs/map_kptr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down Expand Up @@ -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")
Expand Down Expand Up @@ -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;
Expand Down
78 changes: 0 additions & 78 deletions tools/testing/selftests/bpf/progs/map_kptr_fail.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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")
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down
27 changes: 0 additions & 27 deletions tools/testing/selftests/bpf/verifier/map_kptr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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",
Expand Down

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