path: root/tools/testing/selftests/bpf/prog_tests/align.c

// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>

#define MAX_INSNS	512
#define MAX_MATCHES	24

struct bpf_reg_match {
	unsigned int line;
	const char *reg;
	const char *match;
};

struct bpf_align_test {
	const char *descr;
	struct bpf_insn	insns[MAX_INSNS];
	enum {
		UNDEF,
		ACCEPT,
		REJECT
	} result;
	enum bpf_prog_type prog_type;
	/* Matches must be in order of increasing line */
	struct bpf_reg_match matches[MAX_MATCHES];
};

static struct bpf_align_test tests[] = {
	/* Four tests of known constants.  These aren't staggeringly
	 * interesting since we track exact values now.
	 */
	{
		.descr = "mov",
		.insns = {
			BPF_MOV64_IMM(BPF_REG_3, 2),
			BPF_MOV64_IMM(BPF_REG_3, 4),
			BPF_MOV64_IMM(BPF_REG_3, 8),
			BPF_MOV64_IMM(BPF_REG_3, 16),
			BPF_MOV64_IMM(BPF_REG_3, 32),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{0, "R1", "ctx()"},
			{0, "R10", "fp0"},
			{0, "R3_w", "2"},
			{1, "R3_w", "4"},
			{2, "R3_w", "8"},
			{3, "R3_w", "16"},
			{4, "R3_w", "32"},
		},
	},
	{
		.descr = "shift",
		.insns = {
			BPF_MOV64_IMM(BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_3, 4),
			BPF_MOV64_IMM(BPF_REG_4, 32),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{0, "R1", "ctx()"},
			{0, "R10", "fp0"},
			{0, "R3_w", "1"},
			{1, "R3_w", "2"},
			{2, "R3_w", "4"},
			{3, "R3_w", "8"},
			{4, "R3_w", "16"},
			{5, "R3_w", "1"},
			{6, "R4_w", "32"},
			{7, "R4_w", "16"},
			{8, "R4_w", "8"},
			{9, "R4_w", "4"},
			{10, "R4_w", "2"},
		},
	},
	{
		.descr = "addsub",
		.insns = {
			BPF_MOV64_IMM(BPF_REG_3, 4),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 4),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 2),
			BPF_MOV64_IMM(BPF_REG_4, 8),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 2),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{0, "R1", "ctx()"},
			{0, "R10", "fp0"},
			{0, "R3_w", "4"},
			{1, "R3_w", "8"},
			{2, "R3_w", "10"},
			{3, "R4_w", "8"},
			{4, "R4_w", "12"},
			{5, "R4_w", "14"},
		},
	},
	{
		.descr = "mul",
		.insns = {
			BPF_MOV64_IMM(BPF_REG_3, 7),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_3, 2),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_3, 4),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{0, "R1", "ctx()"},
			{0, "R10", "fp0"},
			{0, "R3_w", "7"},
			{1, "R3_w", "7"},
			{2, "R3_w", "14"},
			{3, "R3_w", "56"},
		},
	},

	/* Tests using unknown values */
#define PREP_PKT_POINTERS \
	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, \
		    offsetof(struct __sk_buff, data)), \
	BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, \
		    offsetof(struct __sk_buff, data_end))

#define LOAD_UNKNOWN(DST_REG) \
	PREP_PKT_POINTERS, \
	BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), \
	BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8), \
	BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_0, 1), \
	BPF_EXIT_INSN(), \
	BPF_LDX_MEM(BPF_B, DST_REG, BPF_REG_2, 0)

	{
		.descr = "unknown shift",
		.insns = {
			LOAD_UNKNOWN(BPF_REG_3),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_3, 1),
			LOAD_UNKNOWN(BPF_REG_4),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_4, 5),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 1),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{6, "R0_w", "pkt(off=8,r=8)"},
			{6, "R3_w", "var_off=(0x0; 0xff)"},
			{7, "R3_w", "var_off=(0x0; 0x1fe)"},
			{8, "R3_w", "var_off=(0x0; 0x3fc)"},
			{9, "R3_w", "var_off=(0x0; 0x7f8)"},
			{10, "R3_w", "var_off=(0x0; 0xff0)"},
			{12, "R3_w", "pkt_end()"},
			{17, "R4_w", "var_off=(0x0; 0xff)"},
			{18, "R4_w", "var_off=(0x0; 0x1fe0)"},
			{19, "R4_w", "var_off=(0x0; 0xff0)"},
			{20, "R4_w", "var_off=(0x0; 0x7f8)"},
			{21, "R4_w", "var_off=(0x0; 0x3fc)"},
			{22, "R4_w", "var_off=(0x0; 0x1fe)"},
		},
	},
	{
		.descr = "unknown mul",
		.insns = {
			LOAD_UNKNOWN(BPF_REG_3),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_3),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_4, 1),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_3),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_4, 2),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_3),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_4, 4),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_3),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_4, 8),
			BPF_ALU64_IMM(BPF_MUL, BPF_REG_4, 2),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{6, "R3_w", "var_off=(0x0; 0xff)"},
			{7, "R4_w", "var_off=(0x0; 0xff)"},
			{8, "R4_w", "var_off=(0x0; 0xff)"},
			{9, "R4_w", "var_off=(0x0; 0xff)"},
			{10, "R4_w", "var_off=(0x0; 0x1fe)"},
			{11, "R4_w", "var_off=(0x0; 0xff)"},
			{12, "R4_w", "var_off=(0x0; 0x3fc)"},
			{13, "R4_w", "var_off=(0x0; 0xff)"},
			{14, "R4_w", "var_off=(0x0; 0x7f8)"},
			{15, "R4_w", "var_off=(0x0; 0xff0)"},
		},
	},
	{
		.descr = "packet const offset",
		.insns = {
			PREP_PKT_POINTERS,
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),

			BPF_MOV64_IMM(BPF_REG_0, 0),

			/* Skip over ethernet header.  */
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),

			BPF_LDX_MEM(BPF_B, BPF_REG_4, BPF_REG_5, 0),
			BPF_LDX_MEM(BPF_B, BPF_REG_4, BPF_REG_5, 1),
			BPF_LDX_MEM(BPF_B, BPF_REG_4, BPF_REG_5, 2),
			BPF_LDX_MEM(BPF_B, BPF_REG_4, BPF_REG_5, 3),
			BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_5, 0),
			BPF_LDX_MEM(BPF_H, BPF_REG_4, BPF_REG_5, 2),
			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),

			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			{2, "R5_w", "pkt(r=0)"},
			{4, "R5_w", "pkt(off=14,r=0)"},
			{5, "R4_w", "pkt(off=14,r=0)"},
			{9, "R2", "pkt(r=18)"},
			{10, "R5", "pkt(off=14,r=18)"},
			{10, "R4_w", "var_off=(0x0; 0xff)"},
			{13, "R4_w", "var_off=(0x0; 0xffff)"},
			{14, "R4_w", "var_off=(0x0; 0xffff)"},
		},
	},
	{
		.descr = "packet variable offset",
		.insns = {
			LOAD_UNKNOWN(BPF_REG_6),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_6, 2),

			/* First, add a constant to the R5 packet pointer,
			 * then a variable with a known alignment.
			 */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),

			/* Now, test in the other direction.  Adding first
			 * the variable offset to R5, then the constant.
			 */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),

			/* Test multiple accumulations of unknown values
			 * into a packet pointer.
			 */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 4),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_5, 0),

			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			/* Calculated offset in R6 has unknown value, but known
			 * alignment of 4.
			 */
			{6, "R2_w", "pkt(r=8)"},
			{7, "R6_w", "var_off=(0x0; 0x3fc)"},
			/* Offset is added to packet pointer R5, resulting in
			 * known fixed offset, and variable offset from R6.
			 */
			{11, "R5_w", "pkt(id=1,off=14,"},
			/* At the time the word size load is performed from R5,
			 * it's total offset is NET_IP_ALIGN + reg->off (0) +
			 * reg->aux_off (14) which is 16.  Then the variable
			 * offset is considered using reg->aux_off_align which
			 * is 4 and meets the load's requirements.
			 */
			{15, "R4", "var_off=(0x0; 0x3fc)"},
			{15, "R5", "var_off=(0x0; 0x3fc)"},
			/* Variable offset is added to R5 packet pointer,
			 * resulting in auxiliary alignment of 4. To avoid BPF
			 * verifier's precision backtracking logging
			 * interfering we also have a no-op R4 = R5
			 * instruction to validate R5 state. We also check
			 * that R4 is what it should be in such case.
			 */
			{18, "R4_w", "var_off=(0x0; 0x3fc)"},
			{18, "R5_w", "var_off=(0x0; 0x3fc)"},
			/* Constant offset is added to R5, resulting in
			 * reg->off of 14.
			 */
			{19, "R5_w", "pkt(id=2,off=14,"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off
			 * (14) which is 16.  Then the variable offset is 4-byte
			 * aligned, so the total offset is 4-byte aligned and
			 * meets the load's requirements.
			 */
			{24, "R4", "var_off=(0x0; 0x3fc)"},
			{24, "R5", "var_off=(0x0; 0x3fc)"},
			/* Constant offset is added to R5 packet pointer,
			 * resulting in reg->off value of 14.
			 */
			{26, "R5_w", "pkt(off=14,r=8)"},
			/* Variable offset is added to R5, resulting in a
			 * variable offset of (4n). See comment for insn #18
			 * for R4 = R5 trick.
			 */
			{28, "R4_w", "var_off=(0x0; 0x3fc)"},
			{28, "R5_w", "var_off=(0x0; 0x3fc)"},
			/* Constant is added to R5 again, setting reg->off to 18. */
			{29, "R5_w", "pkt(id=3,off=18,"},
			/* And once more we add a variable; resulting var_off
			 * is still (4n), fixed offset is not changed.
			 * Also, we create a new reg->id.
			 */
			{31, "R4_w", "var_off=(0x0; 0x7fc)"},
			{31, "R5_w", "var_off=(0x0; 0x7fc)"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off (18)
			 * which is 20.  Then the variable offset is (4n), so
			 * the total offset is 4-byte aligned and meets the
			 * load's requirements.
			 */
			{35, "R4", "var_off=(0x0; 0x7fc)"},
			{35, "R5", "var_off=(0x0; 0x7fc)"},
		},
	},
	{
		.descr = "packet variable offset 2",
		.insns = {
			/* Create an unknown offset, (4n+2)-aligned */
			LOAD_UNKNOWN(BPF_REG_6),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_6, 2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 14),
			/* Add it to the packet pointer */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			/* Check bounds and perform a read */
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_5, 0),
			/* Make a (4n) offset from the value we just read */
			BPF_ALU64_IMM(BPF_AND, BPF_REG_6, 0xff),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_6, 2),
			/* Add it to the packet pointer */
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			/* Check bounds and perform a read */
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_5, 0),
			BPF_MOV64_IMM(BPF_REG_0, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			/* Calculated offset in R6 has unknown value, but known
			 * alignment of 4.
			 */
			{6, "R2_w", "pkt(r=8)"},
			{7, "R6_w", "var_off=(0x0; 0x3fc)"},
			/* Adding 14 makes R6 be (4n+2) */
			{8, "R6_w", "var_off=(0x2; 0x7fc)"},
			/* Packet pointer has (4n+2) offset */
			{11, "R5_w", "var_off=(0x2; 0x7fc)"},
			{12, "R4", "var_off=(0x2; 0x7fc)"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off (0)
			 * which is 2.  Then the variable offset is (4n+2), so
			 * the total offset is 4-byte aligned and meets the
			 * load's requirements.
			 */
			{15, "R5", "var_off=(0x2; 0x7fc)"},
			/* Newly read value in R6 was shifted left by 2, so has
			 * known alignment of 4.
			 */
			{17, "R6_w", "var_off=(0x0; 0x3fc)"},
			/* Added (4n) to packet pointer's (4n+2) var_off, giving
			 * another (4n+2).
			 */
			{19, "R5_w", "var_off=(0x2; 0xffc)"},
			{20, "R4", "var_off=(0x2; 0xffc)"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off (0)
			 * which is 2.  Then the variable offset is (4n+2), so
			 * the total offset is 4-byte aligned and meets the
			 * load's requirements.
			 */
			{23, "R5", "var_off=(0x2; 0xffc)"},
		},
	},
	{
		.descr = "dubious pointer arithmetic",
		.insns = {
			PREP_PKT_POINTERS,
			BPF_MOV64_IMM(BPF_REG_0, 0),
			/* (ptr - ptr) << 2 */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_3),
			BPF_ALU64_REG(BPF_SUB, BPF_REG_5, BPF_REG_2),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_5, 2),
			/* We have a (4n) value.  Let's make a packet offset
			 * out of it.  First add 14, to make it a (4n+2)
			 */
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
			/* Then make sure it's nonnegative */
			BPF_JMP_IMM(BPF_JSGE, BPF_REG_5, 0, 1),
			BPF_EXIT_INSN(),
			/* Add it to packet pointer */
			BPF_MOV64_REG(BPF_REG_6, BPF_REG_2),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_5),
			/* Check bounds and perform a read */
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_6),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_6, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.result = REJECT,
		.matches = {
			{3, "R5_w", "pkt_end()"},
			/* (ptr - ptr) << 2 == unknown, (4n) */
			{5, "R5_w", "var_off=(0x0; 0xfffffffffffffffc)"},
			/* (4n) + 14 == (4n+2).  We blow our bounds, because
			 * the add could overflow.
			 */
			{6, "R5_w", "var_off=(0x2; 0xfffffffffffffffc)"},
			/* Checked s>=0 */
			{9, "R5", "var_off=(0x2; 0x7ffffffffffffffc)"},
			/* packet pointer + nonnegative (4n+2) */
			{11, "R6_w", "var_off=(0x2; 0x7ffffffffffffffc)"},
			{12, "R4_w", "var_off=(0x2; 0x7ffffffffffffffc)"},
			/* NET_IP_ALIGN + (4n+2) == (4n), alignment is fine.
			 * We checked the bounds, but it might have been able
			 * to overflow if the packet pointer started in the
			 * upper half of the address space.
			 * So we did not get a 'range' on R6, and the access
			 * attempt will fail.
			 */
			{15, "R6_w", "var_off=(0x2; 0x7ffffffffffffffc)"},
		}
	},
	{
		.descr = "variable subtraction",
		.insns = {
			/* Create an unknown offset, (4n+2)-aligned */
			LOAD_UNKNOWN(BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_7, BPF_REG_6),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_6, 2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 14),
			/* Create another unknown, (4n)-aligned, and subtract
			 * it from the first one
			 */
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_7, 2),
			BPF_ALU64_REG(BPF_SUB, BPF_REG_6, BPF_REG_7),
			/* Bounds-check the result */
			BPF_JMP_IMM(BPF_JSGE, BPF_REG_6, 0, 1),
			BPF_EXIT_INSN(),
			/* Add it to the packet pointer */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_6),
			/* Check bounds and perform a read */
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_5, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			/* Calculated offset in R6 has unknown value, but known
			 * alignment of 4.
			 */
			{6, "R2_w", "pkt(r=8)"},
			{8, "R6_w", "var_off=(0x0; 0x3fc)"},
			/* Adding 14 makes R6 be (4n+2) */
			{9, "R6_w", "var_off=(0x2; 0x7fc)"},
			/* New unknown value in R7 is (4n) */
			{10, "R7_w", "var_off=(0x0; 0x3fc)"},
			/* Subtracting it from R6 blows our unsigned bounds */
			{11, "R6", "var_off=(0x2; 0xfffffffffffffffc)"},
			/* Checked s>= 0 */
			{14, "R6", "var_off=(0x2; 0x7fc)"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off (0)
			 * which is 2.  Then the variable offset is (4n+2), so
			 * the total offset is 4-byte aligned and meets the
			 * load's requirements.
			 */
			{20, "R5", "var_off=(0x2; 0x7fc)"},
		},
	},
	{
		.descr = "pointer variable subtraction",
		.insns = {
			/* Create an unknown offset, (4n+2)-aligned and bounded
			 * to [14,74]
			 */
			LOAD_UNKNOWN(BPF_REG_6),
			BPF_MOV64_REG(BPF_REG_7, BPF_REG_6),
			BPF_ALU64_IMM(BPF_AND, BPF_REG_6, 0xf),
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_6, 2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 14),
			/* Subtract it from the packet pointer */
			BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
			BPF_ALU64_REG(BPF_SUB, BPF_REG_5, BPF_REG_6),
			/* Create another unknown, (4n)-aligned and >= 74.
			 * That in fact means >= 76, since 74 % 4 == 2
			 */
			BPF_ALU64_IMM(BPF_LSH, BPF_REG_7, 2),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 76),
			/* Add it to the packet pointer */
			BPF_ALU64_REG(BPF_ADD, BPF_REG_5, BPF_REG_7),
			/* Check bounds and perform a read */
			BPF_MOV64_REG(BPF_REG_4, BPF_REG_5),
			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
			BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
			BPF_EXIT_INSN(),
			BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_5, 0),
			BPF_EXIT_INSN(),
		},
		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
		.matches = {
			/* Calculated offset in R6 has unknown value, but known
			 * alignment of 4.
			 */
			{6, "R2_w", "pkt(r=8)"},
			{9, "R6_w", "var_off=(0x0; 0x3c)"},
			/* Adding 14 makes R6 be (4n+2) */
			{10, "R6_w", "var_off=(0x2; 0x7c)"},
			/* Subtracting from packet pointer overflows ubounds */
			{13, "R5_w", "var_off=(0xffffffffffffff82; 0x7c)"},
			/* New unknown value in R7 is (4n), >= 76 */
			{14, "R7_w", "var_off=(0x0; 0x7fc)"},
			/* Adding it to packet pointer gives nice bounds again */
			{16, "R5_w", "var_off=(0x2; 0x7fc)"},
			/* At the time the word size load is performed from R5,
			 * its total fixed offset is NET_IP_ALIGN + reg->off (0)
			 * which is 2.  Then the variable offset is (4n+2), so
			 * the total offset is 4-byte aligned and meets the
			 * load's requirements.
			 */
			{20, "R5", "var_off=(0x2; 0x7fc)"},
		},
	},
};

static int probe_filter_length(const struct bpf_insn *fp)
{
	int len;

	for (len = MAX_INSNS - 1; len > 0; --len)
		if (fp[len].code != 0 || fp[len].imm != 0)
			break;
	return len + 1;
}

static char bpf_vlog[32768];

static int do_test_single(struct bpf_align_test *test)
{
	struct bpf_insn *prog = test->insns;
	int prog_type = test->prog_type;
	char bpf_vlog_copy[32768];
	LIBBPF_OPTS(bpf_prog_load_opts, opts,
		.prog_flags = BPF_F_STRICT_ALIGNMENT,
		.log_buf = bpf_vlog,
		.log_size = sizeof(bpf_vlog),
		.log_level = 2,
	);
	const char *line_ptr;
	int cur_line = -1;
	int prog_len, i;
	int fd_prog;
	int ret;

	prog_len = probe_filter_length(prog);
	fd_prog = bpf_prog_load(prog_type ? : BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL",
				prog, prog_len, &opts);
	if (fd_prog < 0 && test->result != REJECT) {
		printf("Failed to load program.\n");
		printf("%s", bpf_vlog);
		ret = 1;
	} else if (fd_prog >= 0 && test->result == REJECT) {
		printf("Unexpected success to load!\n");
		printf("%s", bpf_vlog);
		ret = 1;
		close(fd_prog);
	} else {
		ret = 0;
		/* We make a local copy so that we can strtok() it */
		strncpy(bpf_vlog_copy, bpf_vlog, sizeof(bpf_vlog_copy));
		line_ptr = strtok(bpf_vlog_copy, "\n");
		for (i = 0; i < MAX_MATCHES; i++) {
			struct bpf_reg_match m = test->matches[i];
			const char *p;
			int tmp;

			if (!m.match)
				break;
			while (line_ptr) {
				cur_line = -1;
				sscanf(line_ptr, "%u: ", &cur_line);
				if (cur_line == -1)
					sscanf(line_ptr, "from %u to %u: ", &tmp, &cur_line);
				if (cur_line == m.line)
					break;
				line_ptr = strtok(NULL, "\n");
			}
			if (!line_ptr) {
				printf("Failed to find line %u for match: %s=%s\n",
				       m.line, m.reg, m.match);
				ret = 1;
				printf("%s", bpf_vlog);
				break;
			}
			/* Check the next line as well in case the previous line
			 * did not have a corresponding bpf insn. Example:
			 * func#0 @0
			 * 0: R1=ctx() R10=fp0
			 * 0: (b7) r3 = 2                 ; R3_w=2
			 *
			 * Sometimes it's actually two lines below, e.g. when
			 * searching for "6: R3_w=scalar(umax=255,var_off=(0x0; 0xff))":
			 *   from 4 to 6: R0_w=pkt(off=8,r=8) R1=ctx() R2_w=pkt(r=8) R3_w=pkt_end() R10=fp0
			 *   6: R0_w=pkt(off=8,r=8) R1=ctx() R2_w=pkt(r=8) R3_w=pkt_end() R10=fp0
			 *   6: (71) r3 = *(u8 *)(r2 +0)           ; R2_w=pkt(r=8) R3_w=scalar(umax=255,var_off=(0x0; 0xff))
			 */
			while (!(p = strstr(line_ptr, m.reg)) || !strstr(p, m.match)) {
				cur_line = -1;
				line_ptr = strtok(NULL, "\n");
				sscanf(line_ptr ?: "", "%u: ", &cur_line);
				if (!line_ptr || cur_line != m.line)
					break;
			}
			if (cur_line != m.line || !line_ptr || !(p = strstr(line_ptr, m.reg)) || !strstr(p, m.match)) {
				printf("Failed to find match %u: %s=%s\n", m.line, m.reg, m.match);
				ret = 1;
				printf("%s", bpf_vlog);
				break;
			}
		}
		if (fd_prog >= 0)
			close(fd_prog);
	}
	return ret;
}

void test_align(void)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(tests); i++) {
		struct bpf_align_test *test = &tests[i];

		if (!test__start_subtest(test->descr))
			continue;

		ASSERT_OK(do_test_single(test), test->descr);
	}
}