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bpf/tests: Add exhaustive tests of ALU shift values
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This patch adds a set of tests for ALU64 and ALU32 shift operations to
verify correctness for all possible values of the shift value. Mainly
intended for JIT testing.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-4-johan.almbladh@anyfinetworks.com
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Johan Almbladh authored and Daniel Borkmann committed Sep 28, 2021
1 parent 4bc3541 commit 68c956f
Showing 1 changed file with 260 additions and 0 deletions.
260 changes: 260 additions & 0 deletions lib/test_bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -497,6 +497,168 @@ static int bpf_fill_long_jmp(struct bpf_test *self)
return 0;
}

static int __bpf_ld_imm64(struct bpf_insn insns[2], u8 reg, s64 imm64)
{
struct bpf_insn tmp[] = {BPF_LD_IMM64(reg, imm64)};

memcpy(insns, tmp, sizeof(tmp));
return 2;
}

/* Test an ALU shift operation for all valid shift values */
static int __bpf_fill_alu_shift(struct bpf_test *self, u8 op,
u8 mode, bool alu32)
{
static const s64 regs[] = {
0x0123456789abcdefLL, /* dword > 0, word < 0 */
0xfedcba9876543210LL, /* dowrd < 0, word > 0 */
0xfedcba0198765432LL, /* dowrd < 0, word < 0 */
0x0123458967abcdefLL, /* dword > 0, word > 0 */
};
int bits = alu32 ? 32 : 64;
int len = (2 + 7 * bits) * ARRAY_SIZE(regs) + 3;
struct bpf_insn *insn;
int imm, k;
int i = 0;

insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL);
if (!insn)
return -ENOMEM;

insn[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 0);

for (k = 0; k < ARRAY_SIZE(regs); k++) {
s64 reg = regs[k];

i += __bpf_ld_imm64(&insn[i], R3, reg);

for (imm = 0; imm < bits; imm++) {
u64 val;

/* Perform operation */
insn[i++] = BPF_ALU64_REG(BPF_MOV, R1, R3);
insn[i++] = BPF_ALU64_IMM(BPF_MOV, R2, imm);
if (alu32) {
if (mode == BPF_K)
insn[i++] = BPF_ALU32_IMM(op, R1, imm);
else
insn[i++] = BPF_ALU32_REG(op, R1, R2);
switch (op) {
case BPF_LSH:
val = (u32)reg << imm;
break;
case BPF_RSH:
val = (u32)reg >> imm;
break;
case BPF_ARSH:
val = (u32)reg >> imm;
if (imm > 0 && (reg & 0x80000000))
val |= ~(u32)0 << (32 - imm);
break;
}
} else {
if (mode == BPF_K)
insn[i++] = BPF_ALU64_IMM(op, R1, imm);
else
insn[i++] = BPF_ALU64_REG(op, R1, R2);
switch (op) {
case BPF_LSH:
val = (u64)reg << imm;
break;
case BPF_RSH:
val = (u64)reg >> imm;
break;
case BPF_ARSH:
val = (u64)reg >> imm;
if (imm > 0 && reg < 0)
val |= ~(u64)0 << (64 - imm);
break;
}
}

/*
* When debugging a JIT that fails this test, one
* can write the immediate value to R0 here to find
* out which operand values that fail.
*/

/* Load reference and check the result */
i += __bpf_ld_imm64(&insn[i], R4, val);
insn[i++] = BPF_JMP_REG(BPF_JEQ, R1, R4, 1);
insn[i++] = BPF_EXIT_INSN();
}
}

insn[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 1);
insn[i++] = BPF_EXIT_INSN();

self->u.ptr.insns = insn;
self->u.ptr.len = len;
BUG_ON(i > len);

return 0;
}

static int bpf_fill_alu_lsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_LSH, BPF_K, false);
}

static int bpf_fill_alu_rsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_RSH, BPF_K, false);
}

static int bpf_fill_alu_arsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_K, false);
}

static int bpf_fill_alu_lsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_LSH, BPF_X, false);
}

static int bpf_fill_alu_rsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_RSH, BPF_X, false);
}

static int bpf_fill_alu_arsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_X, false);
}

static int bpf_fill_alu32_lsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_LSH, BPF_K, true);
}

static int bpf_fill_alu32_rsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_RSH, BPF_K, true);
}

static int bpf_fill_alu32_arsh_imm(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_K, true);
}

static int bpf_fill_alu32_lsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_LSH, BPF_X, true);
}

static int bpf_fill_alu32_rsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_RSH, BPF_X, true);
}

static int bpf_fill_alu32_arsh_reg(struct bpf_test *self)
{
return __bpf_fill_alu_shift(self, BPF_ARSH, BPF_X, true);
}

static struct bpf_test tests[] = {
{
"TAX",
Expand Down Expand Up @@ -8414,6 +8576,104 @@ static struct bpf_test tests[] = {
{},
{ { 0, 2 } },
},
/* Exhaustive test of ALU64 shift operations */
{
"ALU64_LSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_lsh_imm,
},
{
"ALU64_RSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_rsh_imm,
},
{
"ALU64_ARSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_arsh_imm,
},
{
"ALU64_LSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_lsh_reg,
},
{
"ALU64_RSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_rsh_reg,
},
{
"ALU64_ARSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu_arsh_reg,
},
/* Exhaustive test of ALU32 shift operations */
{
"ALU32_LSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_lsh_imm,
},
{
"ALU32_RSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_rsh_imm,
},
{
"ALU32_ARSH_K: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_arsh_imm,
},
{
"ALU32_LSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_lsh_reg,
},
{
"ALU32_RSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_rsh_reg,
},
{
"ALU32_ARSH_X: all shift values",
{ },
INTERNAL | FLAG_NO_DATA,
{ },
{ { 0, 1 } },
.fill_helper = bpf_fill_alu32_arsh_reg,
},
};

static struct net_device dev;
Expand Down

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