Test that nullness elision works for common use cases. For example, we
want to check that both full and subreg stack slots are recognized. As
well as when there's both const and non-const values of R2 leading up to
a lookup. And obviously some bound checks.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 .../bpf/progs/verifier_array_access.c         | 166 ++++++++++++++++++
 1 file changed, 166 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_array_access.c b/tools/testing/selftests/bpf/progs/verifier_array_access.c
index 95d7ecc12963..2e74504ddbb5 100644
--- a/tools/testing/selftests/bpf/progs/verifier_array_access.c
+++ b/tools/testing/selftests/bpf/progs/verifier_array_access.c
@@ -28,6 +28,20 @@ struct {
 	__uint(map_flags, BPF_F_WRONLY_PROG);
 } map_array_wo SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, 2);
+	__type(key, int);
+	__type(value, struct test_val);
+} map_array_pcpu SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 2);
+	__type(key, int);
+	__type(value, struct test_val);
+} map_array SEC(".maps");
+
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__uint(max_entries, 1);
@@ -526,4 +540,156 @@ l0_%=:	exit;						\
 	: __clobber_all);
 }
 
+SEC("socket")
+__description("valid map access into an array using constant without nullness")
+__success __retval(4)
+__naked void an_array_with_a_constant_no_nullness(void)
+{
+	asm volatile ("					\
+	r1 = 1;						\
+	*(u64*)(r10 - 8) = r1;				\
+	r2 = r10;					\
+	r2 += -8;					\
+	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	r1 = %[test_val_foo];				\
+	*(u64*)(r0 + 0) = r1;				\
+	r0 = *(u64*)(r0 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array),
+	  __imm_const(test_val_foo, offsetof(struct test_val, foo))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("valid multiple map access into an array using constant without nullness")
+__success __retval(8)
+__naked void multiple_array_with_a_constant_no_nullness(void)
+{
+	asm volatile ("					\
+	r1 = 1;						\
+	*(u64*)(r10 - 8) = r1;				\
+	r2 = r10;					\
+	r2 += -8;					\
+	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	r6 = %[test_val_foo];				\
+	*(u64*)(r0 + 0) = r6;				\
+	r7 = *(u64*)(r0 + 0);				\
+	r1 = 0;						\
+	*(u64*)(r10 - 16) = r1;				\
+	r2 = r10;					\
+	r2 += -16;					\
+	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	*(u64*)(r0 + 0) = r6;				\
+	r1 = *(u64*)(r0 + 0);				\
+	r7 += r1;					\
+	r0 = r7;					\
+	exit;						\
+"	:
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array),
+	  __imm_const(test_val_foo, offsetof(struct test_val, foo))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("valid map access into an array using 32-bit constant without nullness")
+__success __retval(4)
+__naked void an_array_with_a_32bit_constant_no_nullness(void)
+{
+	asm volatile ("					\
+	r1 = 1;						\
+	*(u32*)(r10 - 4) = r1;				\
+	r2 = r10;					\
+	r2 += -4;					\
+	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	r1 = %[test_val_foo];				\
+	*(u64*)(r0 + 0) = r1;				\
+	r0 = *(u64*)(r0 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array),
+	  __imm_const(test_val_foo, offsetof(struct test_val, foo))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("valid map access into a pcpu array using constant without nullness")
+__success __retval(4)
+__naked void a_pcpu_array_with_a_constant_no_nullness(void)
+{
+	asm volatile ("					\
+	r1 = 1;						\
+	*(u64*)(r10 - 8) = r1;				\
+	r2 = r10;					\
+	r2 += -8;					\
+	r1 = %[map_array_pcpu] ll;			\
+	call %[bpf_map_lookup_elem];			\
+	r1 = %[test_val_foo];				\
+	*(u64*)(r0 + 0) = r1;				\
+	r0 = *(u64*)(r0 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array_pcpu),
+	  __imm_const(test_val_foo, offsetof(struct test_val, foo))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("invalid map access into an array using constant without nullness")
+__failure __msg("R0 invalid mem access 'map_value_or_null'")
+__naked void an_array_with_a_constant_no_nullness_out_of_bounds(void)
+{
+	asm volatile ("					\
+	r1 = 3;						\
+	*(u64*)(r10 - 8) = r1;				\
+	r2 = r10;					\
+	r2 += -8;					\
+	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	r1 = %[test_val_foo];				\
+	*(u64*)(r0 + 0) = r1;				\
+	r0 = *(u64*)(r0 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array),
+	  __imm_const(test_val_foo, offsetof(struct test_val, foo))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("invalid elided lookup using const and non-const key")
+__failure __msg("R0 invalid mem access 'map_value_or_null'")
+__naked void mixed_const_and_non_const_key_lookup(void)
+{
+	asm volatile ("					\
+	call %[bpf_get_prandom_u32];			\
+	if r0 > 42 goto l1_%=;				\
+	*(u64*)(r10 - 8) = r0;				\
+	r2 = r10;					\
+	r2 += -8;					\
+	goto l0_%=;					\
+l1_%=:	r1 = 1;						\
+	*(u64*)(r10 - 8) = r1;				\
+	r2 = r10;					\
+	r2 += -8;					\
+l0_%=:	r1 = %[map_array] ll;				\
+	call %[bpf_map_lookup_elem];			\
+	r0 = *(u64*)(r0 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32),
+	  __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_array)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.46.0

On Sun, 2024-09-15 at 21:45 -0600, Daniel Xu wrote:
> Test that nullness elision works for common use cases. For example, we
> want to check that both full and subreg stack slots are recognized. As
> well as when there's both const and non-const values of R2 leading up to
> a lookup. And obviously some bound checks.
> 
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

[...]