bpf/tests: Add exhaustive test of LD_IMM64 immediate magnitudes

This patch adds a test for the 64-bit immediate load, a two-instruction
operation, to verify correctness for all possible magnitudes of the
immediate operand. Mainly intended for JIT testing.
Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-8-johan.almbladh@anyfinetworks.com

lib/test_bpf.c

@@ -1104,6 +1104,60 @@ static int bpf_fill_alu32_mod_reg(struct bpf_test *self)
 	return __bpf_fill_alu32_reg(self, BPF_MOD);
 }
 
+/*
+ * Test the two-instruction 64-bit immediate load operation for all
+ * power-of-two magnitudes of the immediate operand. For each MSB, a block
+ * of immediate values centered around the power-of-two MSB are tested,
+ * both for positive and negative values. The test is designed to verify
+ * the operation for JITs that emit different code depending on the magnitude
+ * of the immediate value. This is often the case if the native instruction
+ * immediate field width is narrower than 32 bits.
+ */
+static int bpf_fill_ld_imm64(struct bpf_test *self)
+{
+	int block = 64; /* Increase for more tests per MSB position */
+	int len = 3 + 8 * 63 * block * 2;
+	struct bpf_insn *insn;
+	int bit, adj, sign;
+	int i = 0;
+
+	insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL);
+	if (!insn)
+		return -ENOMEM;
+
+	insn[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 0);
+
+	for (bit = 0; bit <= 62; bit++) {
+		for (adj = -block / 2; adj < block / 2; adj++) {
+			for (sign = -1; sign <= 1; sign += 2) {
+				s64 imm = sign * ((1LL << bit) + adj);
+
+				/* Perform operation */
+				i += __bpf_ld_imm64(&insn[i], R1, imm);
+
+				/* Load reference */
+				insn[i++] = BPF_ALU32_IMM(BPF_MOV, R2, imm);
+				insn[i++] = BPF_ALU32_IMM(BPF_MOV, R3,
+							  (u32)(imm >> 32));
+				insn[i++] = BPF_ALU64_IMM(BPF_LSH, R3, 32);
+				insn[i++] = BPF_ALU64_REG(BPF_OR, R2, R3);
+
+				/* Check result */
+				insn[i++] = BPF_JMP_REG(BPF_JEQ, R1, R2, 1);
+				insn[i++] = BPF_EXIT_INSN();
+			}
+		}
+	}
+
+	insn[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 1);
+	insn[i++] = BPF_EXIT_INSN();
+
+	self->u.ptr.insns = insn;
+	self->u.ptr.len = len;
+	BUG_ON(i != len);
+
+	return 0;
+}
 
 /*
  * Exhaustive tests of JMP operations for all combinations of power-of-two
@@ -10245,6 +10299,15 @@ static struct bpf_test tests[] = {
 		.fill_helper = bpf_fill_alu32_mod_reg,
 		.nr_testruns = NR_PATTERN_RUNS,
 	},
+	/* LD_IMM64 immediate magnitudes */
+	{
+		"LD_IMM64: all immediate value magnitudes",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_ld_imm64,
+	},
 	/* JMP immediate magnitudes */
 	{
 		"JMP_JSET_K: all immediate value magnitudes",