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bpf, selftests: Add test for BPF_STX BPF_B storing R10

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This patch adds a test to test_verifier that writes the lower 8 bits of
R10 (aka FP) using BPF_B to an array map and reads the result back. The
expected behavior is that the result should be the same as first copying
R10 to R9, and then storing / loading the lower 8 bits of R9.

This test catches a bug that was present in the x86-64 JIT that caused
an incorrect encoding for BPF_STX BPF_B when the source operand is R10.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200418232655.23870-2-luke.r.nels@gmail.com
This commit is contained in:
Luke Nelson 2020-04-18 16:26:54 -07:00 committed by Alexei Starovoitov
parent aee194b14d
commit d2b6c3ab70
1 changed files with 40 additions and 0 deletions
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40
tools/testing/selftests/bpf/verifier/stack_ptr.c
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@ -315,3 +315,43 @@
},
.result = ACCEPT,
},
{
"store PTR_TO_STACK in R10 to array map using BPF_B",
.insns = {
/* Load pointer to map. */
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
BPF_MOV64_IMM(BPF_REG_0, 2),
BPF_EXIT_INSN(),
BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
/* Copy R10 to R9. */
BPF_MOV64_REG(BPF_REG_9, BPF_REG_10),
/* Pollute other registers with unaligned values. */
BPF_MOV64_IMM(BPF_REG_2, -1),
BPF_MOV64_IMM(BPF_REG_3, -1),
BPF_MOV64_IMM(BPF_REG_4, -1),
BPF_MOV64_IMM(BPF_REG_5, -1),
BPF_MOV64_IMM(BPF_REG_6, -1),
BPF_MOV64_IMM(BPF_REG_7, -1),
BPF_MOV64_IMM(BPF_REG_8, -1),
/* Store both R9 and R10 with BPF_B and read back. */
BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_10, 0),
BPF_LDX_MEM(BPF_B, BPF_REG_2, BPF_REG_1, 0),
BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_9, 0),
BPF_LDX_MEM(BPF_B, BPF_REG_3, BPF_REG_1, 0),
/* Should read back as same value. */
BPF_JMP_REG(BPF_JEQ, BPF_REG_2, BPF_REG_3, 2),
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_EXIT_INSN(),
BPF_MOV64_IMM(BPF_REG_0, 42),
BPF_EXIT_INSN(),
},
.fixup_map_array_48b = { 3 },
.result = ACCEPT,
.retval = 42,
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
},