[PATCH bpf v2 2/2] selftests/bpf: Test r0 bounds after BPF to BPF call with abnormal return

[Arthur Fabre <afabre@xxxxxxxxxxxxxx>]

Test the bounds of r0 aren't known by the verifier in all three cases
where a callee can abnormally return.

Signed-off-by: Arthur Fabre <afabre@xxxxxxxxxxxxxx>
---
 .../selftests/bpf/prog_tests/verifier.c       |  2 +
 .../bpf/progs/verifier_abnormal_ret.c         | 88 +++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_abnormal_ret.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 3ee40ee9413a..6bed606544e3 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -3,6 +3,7 @@
 #include <test_progs.h>
 
 #include "cap_helpers.h"
+#include "verifier_abnormal_ret.skel.h"
 #include "verifier_and.skel.h"
 #include "verifier_arena.skel.h"
 #include "verifier_arena_large.skel.h"
@@ -133,6 +134,7 @@ static void run_tests_aux(const char *skel_name,
 
 #define RUN(skel) run_tests_aux(#skel, skel##__elf_bytes, NULL)
 
+void test_verifier_abnormal_ret(void)         { RUN(verifier_abnormal_ret); }
 void test_verifier_and(void)                  { RUN(verifier_and); }
 void test_verifier_arena(void)                { RUN(verifier_arena); }
 void test_verifier_arena_large(void)          { RUN(verifier_arena_large); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_abnormal_ret.c b/tools/testing/selftests/bpf/progs/verifier_abnormal_ret.c
new file mode 100644
index 000000000000..5e246986945f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_abnormal_ret.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "../../../include/linux/filter.h"
+#include "bpf_misc.h"
+
+#define TEST(NAME, CALLEE) \
+	SEC("socket")					\
+	__description("abnormal_ret: " #NAME)		\
+	__failure __msg("math between ctx pointer and register with unbounded min value") \
+	__naked void check_abnormal_ret_##NAME(void)	\
+	{						\
+		asm volatile("				\
+		r6 = r1;				\
+		call " #CALLEE ";			\
+		r6 += r0;				\
+		r0 = 0;					\
+		exit;					\
+	"	:					\
+		:					\
+		: __clobber_all);			\
+	}
+
+TEST(ld_abs, callee_ld_abs);
+TEST(ld_ind, callee_ld_ind);
+TEST(tail_call, callee_tail_call);
+
+static __naked __noinline __used
+int callee_ld_abs(void)
+{
+	asm volatile("					\
+	r6 = r1;					\
+	.8byte %[ld_abs];				\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm_insn(ld_abs, BPF_LD_ABS(BPF_W, 0))
+	: __clobber_all);
+}
+
+static __naked __noinline __used
+int callee_ld_ind(void)
+{
+	asm volatile("					\
+	r6 = r1;					\
+	r7 = 1;						\
+	.8byte %[ld_ind];				\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm_insn(ld_ind, BPF_LD_IND(BPF_W, BPF_REG_7, 0))
+	: __clobber_all);
+}
+
+SEC("socket")
+__auxiliary __naked
+void dummy_prog(void)
+{
+	asm volatile("r0 = 1; exit;");
+}
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(int));
+	__array(values, void(void));
+} map_prog SEC(".maps") = {
+	.values = {
+		[0] = (void *)&dummy_prog,
+	},
+};
+
+static __naked __noinline __used
+int callee_tail_call(void)
+{
+	asm volatile("					\
+	r2 = %[map_prog] ll;				\
+	r3 = 0;						\
+	call %[bpf_tail_call];				\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_tail_call), __imm_addr(map_prog)
+	: __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.34.1