From: Andrii Nakryiko andrii@kernel.org
[ Upstream commit 4f999b767769b76378c3616c624afd6f4bb0d99f ]
test_align selftest relies on BPF verifier log emitting register states for specific instructions in expected format. Unfortunately, BPF verifier precision backtracking log interferes with such expectations. And instruction on which precision propagation happens sometimes don't output full expected register states. This does indeed look like something to be improved in BPF verifier, but is beyond the scope of this patch set.
So to make test_align a bit more robust, inject few dummy R4 = R5 instructions which capture desired state of R5 and won't have precision tracking logs on them. This fixes tests until we can improve BPF verifier output in the presence of precision tracking.
Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/r/20221104163649.121784-7-andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Stable-dep-of: ecdf985d7615 ("bpf: track immediate values written to stack by BPF_ST instruction") Signed-off-by: Pu Lehui pulehui@huawei.com Tested-by: Luiz Capitulino luizcap@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/bpf/prog_tests/align.c | 36 +++++++++++++++---------- 1 file changed, 23 insertions(+), 13 deletions(-)
--- a/tools/testing/selftests/bpf/prog_tests/align.c +++ b/tools/testing/selftests/bpf/prog_tests/align.c @@ -2,7 +2,7 @@ #include <test_progs.h>
#define MAX_INSNS 512 -#define MAX_MATCHES 16 +#define MAX_MATCHES 24
struct bpf_reg_match { unsigned int line; @@ -267,6 +267,7 @@ static struct bpf_align_test tests[] = { */ 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), @@ -280,6 +281,7 @@ static struct bpf_align_test tests[] = { 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), @@ -311,44 +313,52 @@ static struct bpf_align_test tests[] = { {15, "R4=pkt(id=1,off=18,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, {15, "R5=pkt(id=1,off=14,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* Variable offset is added to R5 packet pointer, - * resulting in auxiliary alignment of 4. + * 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, "R5_w=pkt(id=2,off=0,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {19, "R4_w=pkt(id=2,off=0,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {19, "R5_w=pkt(id=2,off=0,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* Constant offset is added to R5, resulting in * reg->off of 14. */ - {19, "R5_w=pkt(id=2,off=14,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {20, "R5_w=pkt(id=2,off=14,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* 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. */ - {23, "R4=pkt(id=2,off=18,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, - {23, "R5=pkt(id=2,off=14,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {24, "R4=pkt(id=2,off=18,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {24, "R5=pkt(id=2,off=14,r=18,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* Constant offset is added to R5 packet pointer, * resulting in reg->off value of 14. */ - {26, "R5_w=pkt(id=0,off=14,r=8"}, + {27, "R5_w=pkt(id=0,off=14,r=8"}, /* Variable offset is added to R5, resulting in a - * variable offset of (4n). + * variable offset of (4n). See comment for insn #19 + * for R4 = R5 trick. */ - {27, "R5_w=pkt(id=3,off=14,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {29, "R4_w=pkt(id=3,off=14,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {29, "R5_w=pkt(id=3,off=14,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* Constant is added to R5 again, setting reg->off to 18. */ - {28, "R5_w=pkt(id=3,off=18,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, + {30, "R5_w=pkt(id=3,off=18,r=0,umax_value=1020,var_off=(0x0; 0x3fc))"}, /* 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. */ - {29, "R5_w=pkt(id=4,off=18,r=0,umax_value=2040,var_off=(0x0; 0x7fc)"}, + {32, "R4_w=pkt(id=4,off=18,r=0,umax_value=2040,var_off=(0x0; 0x7fc)"}, + {32, "R5_w=pkt(id=4,off=18,r=0,umax_value=2040,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. */ - {33, "R4=pkt(id=4,off=22,r=22,umax_value=2040,var_off=(0x0; 0x7fc)"}, - {33, "R5=pkt(id=4,off=18,r=22,umax_value=2040,var_off=(0x0; 0x7fc)"}, + {35, "R4=pkt(id=4,off=22,r=22,umax_value=2040,var_off=(0x0; 0x7fc)"}, + {35, "R5=pkt(id=4,off=18,r=22,umax_value=2040,var_off=(0x0; 0x7fc)"}, }, }, {