On 04/26/2018 12:12 PM, Wang YanQing wrote:
[...]
> +/* encode 'dst_reg' and 'src_reg' registers into x86_32 opcode 'byte' */
> +static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg)
> +{
> + return byte + dst_reg + (src_reg << 3);
> +}
> +
> +static void jit_fill_hole(void *area, unsigned int size)
> +{
> + /* fill whole space with int3 instructions */
> + memset(area, 0xcc, size);
> +}
> +
> +/* Checks whether BPF register is on scratch stack space or not. */
> +static inline bool is_on_stack(u8 bpf_reg)
> +{
> + static u8 stack_regs[] = {BPF_REG_AX};
Nit: you call this stack_regs here ...
> + int i, reg_len = sizeof(stack_regs);
> +
> + for (i = 0 ; i < reg_len ; i++) {
> + if (bpf_reg == stack_regs[i])
> + return false;
... but [BPF_REG_AX] = {IA32_ESI, IA32_EDI} is the only one
that is not on stack?
> + }
> + return true;
> +}
> +
> +static inline void emit_ia32_mov_i(const u8 dst, const u32 val, bool dstk,
> + u8 **pprog)
> +{
> + u8 *prog = *pprog;
> + int cnt = 0;
> +
> + if (dstk) {
> + if (val == 0) {
> + /* xor eax,eax */
> + EMIT2(0x33, add_2reg(0xC0, IA32_EAX, IA32_EAX));
> + /* mov dword ptr [ebp+off],eax */
> + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EAX),
> + STACK_VAR(dst));
> + } else {
> + EMIT3_off32(0xC7, add_1reg(0x40, IA32_EBP),
> + STACK_VAR(dst), val);
> + }
> + } else {
> + if (val == 0)
> + EMIT2(0x33, add_2reg(0xC0, dst, dst));
> + else
> + EMIT2_off32(0xC7, add_1reg(0xC0, dst),
> + val);
> + }
> + *pprog = prog;
> +}
> +
[...]
> + if (is_imm8(jmp_offset)) {
> + EMIT2(jmp_cond, jmp_offset);
> + } else if (is_simm32(jmp_offset)) {
> + EMIT2_off32(0x0F, jmp_cond + 0x10, jmp_offset);
> + } else {
> + pr_err("cond_jmp gen bug %llx\n", jmp_offset);
> + return -EFAULT;
> + }
> +
> + break;
> + }
> + case BPF_JMP | BPF_JA:
> + jmp_offset = addrs[i + insn->off] - addrs[i];
> + if (!jmp_offset)
> + /* optimize out nop jumps */
> + break;
Needs same fix as in x86-64 JIT in 1612a981b766 ("bpf, x64: fix JIT emission
for dead code").
> +emit_jmp:
> + if (is_imm8(jmp_offset)) {
> + EMIT2(0xEB, jmp_offset);
> + } else if (is_simm32(jmp_offset)) {
> + EMIT1_off32(0xE9, jmp_offset);
> + } else {
> + pr_err("jmp gen bug %llx\n", jmp_offset);
> + return -EFAULT;
> + }
> + break;
