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Subject[PATCH v3 net-next 11/12] selftests/bpf: add tests for subtraction & negative numbers
Date
Signed-off-by: Edward Cree <ecree@solarflare.com>
---
tools/testing/selftests/bpf/test_align.c | 104 +++++++++++++++++++++++++++++++
1 file changed, 104 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_align.c b/tools/testing/selftests/bpf/test_align.c
index dfd96c6..6bc2ceb 100644
--- a/tools/testing/selftests/bpf/test_align.c
+++ b/tools/testing/selftests/bpf/test_align.c
@@ -497,6 +497,110 @@ static struct bpf_align_test tests[] = {
{16, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,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.
+ */
+ {7, "R2=pkt(id=0,off=0,r=8,imm=0)"},
+ {9, "R6=inv(id=0,umax_value=1020,var_off=(0x0; 0x3fc))"},
+ /* Adding 14 makes R6 be (4n+2) */
+ {10, "R6=inv(id=0,umin_value=14,umax_value=1034,var_off=(0x2; 0x7fc))"},
+ /* New unknown value in R7 is (4n) */
+ {11, "R7=inv(id=0,umax_value=1020,var_off=(0x0; 0x3fc))"},
+ /* Subtracting it from R6 blows our unsigned bounds */
+ {12, "R6=inv(id=0,smin_value=-1006,smax_value=1034,var_off=(0x2; 0xfffffffffffffffc))"},
+ /* Checked s>= 0 */
+ {14, "R6=inv(id=0,umin_value=2,umax_value=1034,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=pkt(id=1,off=0,r=4,umin_value=2,umax_value=1034,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.
+ */
+ {7, "R2=pkt(id=0,off=0,r=8,imm=0)"},
+ {10, "R6=inv(id=0,umax_value=60,var_off=(0x0; 0x3c))"},
+ /* Adding 14 makes R6 be (4n+2) */
+ {11, "R6=inv(id=0,umin_value=14,umax_value=74,var_off=(0x2; 0x7c))"},
+ /* Subtracting from packet pointer overflows ubounds */
+ {13, "R5=pkt(id=1,off=0,r=8,umin_value=18446744073709551542,umax_value=18446744073709551602,var_off=(0xffffffffffffff82; 0x7c))"},
+ /* New unknown value in R7 is (4n), >= 76 */
+ {15, "R7=inv(id=0,umin_value=76,umax_value=1096,var_off=(0x0; 0x7fc))"},
+ /* Adding it to packet pointer gives nice bounds again */
+ {16, "R5=pkt(id=2,off=0,r=0,umin_value=2,umax_value=1082,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=pkt(id=2,off=0,r=4,umin_value=2,umax_value=1082,var_off=(0x2; 0x7fc))"},
+ },
+ },
};

static int probe_filter_length(const struct bpf_insn *fp)
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