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selftests/bpf: check if verifier tracks constants spilled by BPF_ST_MEM 

Check that verifier tracks the value of 'imm' spilled to stack by
BPF_ST_MEM instruction. Cover the following cases:
- write of non-zero constant to stack;
- write of a zero constant to stack.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20230214232030.1502829-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2023-02-15 01:20:28 +02:00 committed by Alexei Starovoitov
parent ecdf985d76
commit 1a24af65bb
1 changed files with 37 additions and 0 deletions
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37
tools/testing/selftests/bpf/verifier/bpf_st_mem.c Normal file
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{
"BPF_ST_MEM stack imm non-zero",
.insns = {
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 42),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, -42),
/* if value is tracked correctly R0 is zero */
BPF_EXIT_INSN(),
},
.result = ACCEPT,
/* Use prog type that requires return value in range [0, 1] */
.prog_type = BPF_PROG_TYPE_SK_LOOKUP,
.expected_attach_type = BPF_SK_LOOKUP,
.runs = -1,
},
{
"BPF_ST_MEM stack imm zero",
.insns = {
/* mark stack 0000 0000 */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
/* read and sum a few bytes */
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_10, -8),
BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_10, -4),
BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_10, -1),
BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
/* if value is tracked correctly R0 is zero */
BPF_EXIT_INSN(),
},
.result = ACCEPT,
/* Use prog type that requires return value in range [0, 1] */
.prog_type = BPF_PROG_TYPE_SK_LOOKUP,
.expected_attach_type = BPF_SK_LOOKUP,
.runs = -1,
},