selftests/bpf: Negative test case for ref_obj_id in args

This patch adds a test case, as shown below, for the verifier error
"more than one arg with ref_obj_id".

    0: (b7) r2 = 20
    1: (b7) r3 = 0
    2: (18) r1 = 0xffff92cee3cbc600
    4: (85) call bpf_ringbuf_reserve#131
    5: (55) if r0 == 0x0 goto pc+3
    6: (bf) r1 = r0
    7: (bf) r2 = r0
    8: (85) call bpf_tcp_raw_gen_syncookie_ipv4#204
    9: (95) exit

This error is currently incorrectly reported as a verifier bug, with a
warning. The next patch in this series will address that.

Signed-off-by: Paul Chaignon <[email protected]>
Link: https://lore.kernel.org/r/3ba78e6cda47ccafd6ea70dadbc718d020154664.1751463262.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>

Author: pchaigno

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

@@ -2409,3 +2409,27 @@
 	.errstr_unpriv = "",
 	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
 },
+{
+	"calls: several args with ref_obj_id",
+	.insns = {
+	/* Reserve at least sizeof(struct iphdr) bytes in the ring buffer.
+	 * With a smaller size, the verifier would reject the call to
+	 * bpf_tcp_raw_gen_syncookie_ipv4 before we can reach the
+	 * ref_obj_id error.
+	 */
+	BPF_MOV64_IMM(BPF_REG_2, 20),
+	BPF_MOV64_IMM(BPF_REG_3, 0),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),
+	/* if r0 == 0 goto <exit> */
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_tcp_raw_gen_syncookie_ipv4),
+	BPF_EXIT_INSN(),
+	},
+	.fixup_map_ringbuf = { 2 },
+	.result = REJECT,
+	.errstr = "more than one arg with ref_obj_id",
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+},