linux-kernel - bpf: test_verifier: sanitation: alu with different scalars

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Date:   Tue, 25 Jun 2019 11:29:40 +0300
From:   Yauheni Kaliuta <yauheni.kaliuta@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
        Jiri Benc <jbenc@...hat.com>
Subject: bpf: test_verifier: sanitation: alu with different scalars

Hi!

I'm wondering, how the sanitaion tests (#903 5.2-rc6 for example)
are supposed to work on BE arches:

{
	"sanitation: alu with different scalars 1",
	.insns = {
	BPF_MOV64_IMM(BPF_REG_0, 1),
	BPF_LD_MAP_FD(BPF_REG_ARG1, 0),
	BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_FP),
	BPF_ALU64_IMM(BPF_ADD, BPF_REG_ARG2, -16),
	BPF_ST_MEM(BPF_DW, BPF_REG_FP, -16, 0),
	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
	BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
	BPF_EXIT_INSN(),
	BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, 0),

reads one byte 0 on BE and 28 on LE (from ->index) since

	struct test_val {
		unsigned int index;
		int foo[MAX_ENTRIES];
	};

        struct test_val value = {
		.index = (6 + 1) * sizeof(int),
		.foo[6] = 0xabcdef12,
	};

	BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 3),

So different branches are taken depending of the endianness.

	BPF_MOV64_IMM(BPF_REG_2, 0),
	BPF_MOV64_IMM(BPF_REG_3, 0x100000),
	BPF_JMP_A(2),
	BPF_MOV64_IMM(BPF_REG_2, 42),
	BPF_MOV64_IMM(BPF_REG_3, 0x100001),
	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_3),
	BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
	BPF_EXIT_INSN(),
	},
	.fixup_map_array_48b = { 1 },
	.result = ACCEPT,
	.retval = 0x100000,
},



-- 
WBR,
Yauheni Kaliuta