bpf/tests: Add exhaustive tests of ALU shift values

This patch adds a set of tests for ALU64 and ALU32 shift operations to
verify correctness for all possible values of the shift value. 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/20210914091842.4186267-4-johan.almbladh@anyfinetworks.com

lib/test_bpf.c

@@ -497,6 +497,168 @@ static int bpf_fill_long_jmp(struct bpf_test *self)
 	return 0;
 }
 
+static int __bpf_ld_imm64(struct bpf_insn insns[2], u8 reg, s64 imm64)
+{
+	struct bpf_insn tmp[] = {BPF_LD_IMM64(reg, imm64)};
+
+	memcpy(insns, tmp, sizeof(tmp));
+	return 2;
+}
+
+/* Test an ALU shift operation for all valid shift values */
+static int __bpf_fill_alu_shift(struct bpf_test *self, u8 op,
+				u8 mode, bool alu32)
+{
+	static const s64 regs[] = {
+		0x0123456789abcdefLL, /* dword > 0, word < 0 */
+		0xfedcba9876543210LL, /* dowrd < 0, word > 0 */
+		0xfedcba0198765432LL, /* dowrd < 0, word < 0 */
+		0x0123458967abcdefLL, /* dword > 0, word > 0 */
+	};
+	int bits = alu32 ? 32 : 64;
+	int len = (2 + 7 * bits) * ARRAY_SIZE(regs) + 3;
+	struct bpf_insn *insn;
+	int imm, k;
+	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 (k = 0; k < ARRAY_SIZE(regs); k++) {
+		s64 reg = regs[k];
+
+		i += __bpf_ld_imm64(&insn[i], R3, reg);
+
+		for (imm = 0; imm < bits; imm++) {
+			u64 val;
+
+			/* Perform operation */
+			insn[i++] = BPF_ALU64_REG(BPF_MOV, R1, R3);
+			insn[i++] = BPF_ALU64_IMM(BPF_MOV, R2, imm);
+			if (alu32) {
+				if (mode == BPF_K)
+					insn[i++] = BPF_ALU32_IMM(op, R1, imm);
+				else
+					insn[i++] = BPF_ALU32_REG(op, R1, R2);
+				switch (op) {
+				case BPF_LSH:
+					val = (u32)reg << imm;
+					break;
+				case BPF_RSH:
+					val = (u32)reg >> imm;
+					break;
+				case BPF_ARSH:
+					val = (u32)reg >> imm;
+					if (imm > 0 && (reg & 0x80000000))
+						val |= ~(u32)0 << (32 - imm);
+					break;
+				}
+			} else {
+				if (mode == BPF_K)
+					insn[i++] = BPF_ALU64_IMM(op, R1, imm);
+				else
+					insn[i++] = BPF_ALU64_REG(op, R1, R2);
+				switch (op) {
+				case BPF_LSH:
+					val = (u64)reg << imm;
+					break;
+				case BPF_RSH:
+					val = (u64)reg >> imm;
+					break;
+				case BPF_ARSH:
+					val = (u64)reg >> imm;
+					if (imm > 0 && reg < 0)
+						val |= ~(u64)0 << (64 - imm);
+					break;
+				}
+			}
+
+			/*
+			 * When debugging a JIT that fails this test, one
+			 * can write the immediate value to R0 here to find
+			 * out which operand values that fail.
+			 */
+
+			/* Load reference and check the result */
+			i += __bpf_ld_imm64(&insn[i], R4, val);
+			insn[i++] = BPF_JMP_REG(BPF_JEQ, R1, R4, 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;
+}
+
+static int bpf_fill_alu_lsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_LSH, BPF_K, false);
+}
+
+static int bpf_fill_alu_rsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_RSH, BPF_K, false);
+}
+
+static int bpf_fill_alu_arsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_K, false);
+}
+
+static int bpf_fill_alu_lsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_LSH, BPF_X, false);
+}
+
+static int bpf_fill_alu_rsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_RSH, BPF_X, false);
+}
+
+static int bpf_fill_alu_arsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_X, false);
+}
+
+static int bpf_fill_alu32_lsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_LSH, BPF_K, true);
+}
+
+static int bpf_fill_alu32_rsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_RSH, BPF_K, true);
+}
+
+static int bpf_fill_alu32_arsh_imm(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_K, true);
+}
+
+static int bpf_fill_alu32_lsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_LSH, BPF_X, true);
+}
+
+static int bpf_fill_alu32_rsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_RSH, BPF_X, true);
+}
+
+static int bpf_fill_alu32_arsh_reg(struct bpf_test *self)
+{
+	return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_X, true);
+}
+
 static struct bpf_test tests[] = {
 	{
 		"TAX",
@@ -8414,6 +8576,104 @@ static struct bpf_test tests[] = {
 		{},
 		{ { 0, 2 } },
 	},
+	/* Exhaustive test of ALU64 shift operations */
+	{
+		"ALU64_LSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_lsh_imm,
+	},
+	{
+		"ALU64_RSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_rsh_imm,
+	},
+	{
+		"ALU64_ARSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_arsh_imm,
+	},
+	{
+		"ALU64_LSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_lsh_reg,
+	},
+	{
+		"ALU64_RSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_rsh_reg,
+	},
+	{
+		"ALU64_ARSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu_arsh_reg,
+	},
+	/* Exhaustive test of ALU32 shift operations */
+	{
+		"ALU32_LSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_lsh_imm,
+	},
+	{
+		"ALU32_RSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_rsh_imm,
+	},
+	{
+		"ALU32_ARSH_K: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_arsh_imm,
+	},
+	{
+		"ALU32_LSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_lsh_reg,
+	},
+	{
+		"ALU32_RSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_rsh_reg,
+	},
+	{
+		"ALU32_ARSH_X: all shift values",
+		{ },
+		INTERNAL | FLAG_NO_DATA,
+		{ },
+		{ { 0, 1 } },
+		.fill_helper = bpf_fill_alu32_arsh_reg,
+	},
 };
 
 static struct net_device dev;