From f999d64c346c0154e7ed4beb0eba7d2eed422a34 Mon Sep 17 00:00:00 2001 From: Edward Cree Date: Mon, 7 Aug 2017 15:29:34 +0100 Subject: [PATCH] selftests/bpf: add tests for subtraction & negative numbers Signed-off-by: Edward Cree Signed-off-by: David S. Miller --- 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 b0816830a937..8591c89c0828 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) -- 2.20.1