diff options
| -rw-r--r-- | lib/test_bpf.c | 125 |
1 files changed, 91 insertions, 34 deletions
diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 2aa1d0d3c685..dd6bb0044097 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -463,47 +463,79 @@ static int bpf_fill_stxdw(struct bpf_test *self) return __bpf_fill_stxdw(self, BPF_DW); } -static int bpf_fill_long_jmp(struct bpf_test *self) +static int __bpf_ld_imm64(struct bpf_insn insns[2], u8 reg, s64 imm64) { - unsigned int len = BPF_MAXINSNS; - struct bpf_insn *insn; + struct bpf_insn tmp[] = {BPF_LD_IMM64(reg, imm64)}; + + memcpy(insns, tmp, sizeof(tmp)); + return 2; +} + +/* + * Branch conversion tests. Complex operations can expand to a lot + * of instructions when JITed. This in turn may cause jump offsets + * to overflow the field size of the native instruction, triggering + * a branch conversion mechanism in some JITs. + */ +static int __bpf_fill_max_jmp(struct bpf_test *self, int jmp, int imm) +{ + struct bpf_insn *insns; + int len = S16_MAX + 5; int i; - insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL); - if (!insn) + insns = kmalloc_array(len, sizeof(*insns), GFP_KERNEL); + if (!insns) return -ENOMEM; - insn[0] = BPF_ALU64_IMM(BPF_MOV, R0, 1); - insn[1] = BPF_JMP_IMM(BPF_JEQ, R0, 1, len - 2 - 1); + i = __bpf_ld_imm64(insns, R1, 0x0123456789abcdefULL); + insns[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 1); + insns[i++] = BPF_JMP_IMM(jmp, R0, imm, S16_MAX); + insns[i++] = BPF_ALU64_IMM(BPF_MOV, R0, 2); + insns[i++] = BPF_EXIT_INSN(); - /* - * Fill with a complex 64-bit operation that expands to a lot of - * instructions on 32-bit JITs. The large jump offset can then - * overflow the conditional branch field size, triggering a branch - * conversion mechanism in some JITs. - * - * Note: BPF_MAXINSNS of ALU64 MUL is enough to trigger such branch - * conversion on the 32-bit MIPS JIT. For other JITs, the instruction - * count and/or operation may need to be modified to trigger the - * branch conversion. - */ - for (i = 2; i < len - 1; i++) - insn[i] = BPF_ALU64_IMM(BPF_MUL, R0, (i << 16) + i); + while (i < len - 1) { + static const int ops[] = { + BPF_LSH, BPF_RSH, BPF_ARSH, BPF_ADD, + BPF_SUB, BPF_MUL, BPF_DIV, BPF_MOD, + }; + int op = ops[(i >> 1) % ARRAY_SIZE(ops)]; - insn[len - 1] = BPF_EXIT_INSN(); + if (i & 1) + insns[i++] = BPF_ALU32_REG(op, R0, R1); + else + insns[i++] = BPF_ALU64_REG(op, R0, R1); + } - self->u.ptr.insns = insn; + insns[i++] = BPF_EXIT_INSN(); + self->u.ptr.insns = insns; self->u.ptr.len = len; + BUG_ON(i != len); return 0; } -static int __bpf_ld_imm64(struct bpf_insn insns[2], u8 reg, s64 imm64) +/* Branch taken by runtime decision */ +static int bpf_fill_max_jmp_taken(struct bpf_test *self) { - struct bpf_insn tmp[] = {BPF_LD_IMM64(reg, imm64)}; + return __bpf_fill_max_jmp(self, BPF_JEQ, 1); +} - memcpy(insns, tmp, sizeof(tmp)); - return 2; +/* Branch not taken by runtime decision */ +static int bpf_fill_max_jmp_not_taken(struct bpf_test *self) +{ + return __bpf_fill_max_jmp(self, BPF_JEQ, 0); +} + +/* Branch always taken, known at JIT time */ +static int bpf_fill_max_jmp_always_taken(struct bpf_test *self) +{ + return __bpf_fill_max_jmp(self, BPF_JGE, 0); +} + +/* Branch never taken, known at JIT time */ +static int bpf_fill_max_jmp_never_taken(struct bpf_test *self) +{ + return __bpf_fill_max_jmp(self, BPF_JLT, 0); } /* Test an ALU shift operation for all valid shift values */ @@ -8653,14 +8685,6 @@ static struct bpf_test tests[] = { { }, { { 0, 1 } }, }, - { /* Mainly checking JIT here. */ - "BPF_MAXINSNS: Very long conditional jump", - { }, - INTERNAL | FLAG_NO_DATA, - { }, - { { 0, 1 } }, - .fill_helper = bpf_fill_long_jmp, - }, { "JMP_JA: Jump, gap, jump, ...", { }, @@ -11009,6 +11033,39 @@ static struct bpf_test tests[] = { { }, { { 0, 0 } }, }, + /* Conditional branch conversions */ + { + "Long conditional jump: taken at runtime", + { }, + INTERNAL | FLAG_NO_DATA, + { }, + { { 0, 1 } }, + .fill_helper = bpf_fill_max_jmp_taken, + }, + { + "Long conditional jump: not taken at runtime", + { }, + INTERNAL | FLAG_NO_DATA, + { }, + { { 0, 2 } }, + .fill_helper = bpf_fill_max_jmp_not_taken, + }, + { + "Long conditional jump: always taken, known at JIT time", + { }, + INTERNAL | FLAG_NO_DATA, + { }, + { { 0, 1 } }, + .fill_helper = bpf_fill_max_jmp_always_taken, + }, + { + "Long conditional jump: never taken, known at JIT time", + { }, + INTERNAL | FLAG_NO_DATA, + { }, + { { 0, 2 } }, + .fill_helper = bpf_fill_max_jmp_never_taken, + }, /* Staggered jump sequences, immediate */ { "Staggered jumps: JMP_JA", |