Re: [PATCH v5 6/9] riscv/kprobe: Add code to check if kprobe can be optimized

liaochang (A)
2023-01-04T08:38:21Z

在 2023/1/3 2:04, Björn Töpel 写道:
> Chen Guokai <chenguokai17@mails.ucas.ac.cn> writes:
>
>> From: Liao Chang <liaochang1@huawei.com>
>
>> diff --git a/arch/riscv/kernel/probes/opt.c b/arch/riscv/kernel/probes/opt.c
>> index a0d2ab39e3fa..258a283c906d 100644
>> --- a/arch/riscv/kernel/probes/opt.c
>> +++ b/arch/riscv/kernel/probes/opt.c
>> @@ -271,15 +271,103 @@ static void find_free_registers(struct kprobe *kp, struct optimized_kprobe *op,
>> *ra = (kw == 1UL) ? 0 : __builtin_ctzl(kw & ~1UL);
>> }
>>
>> +static bool insn_jump_into_range(unsigned long addr, unsigned long start,
>> + unsigned long end)
>> +{
>> + kprobe_opcode_t insn = *(kprobe_opcode_t *)addr;
>> + unsigned long target, offset = GET_INSN_LENGTH(insn);
>> +
>> +#ifdef CONFIG_RISCV_ISA_C
>> + if (offset == RVC_INSN_LEN) {
>> + if (riscv_insn_is_c_beqz(insn) || riscv_insn_is_c_bnez(insn))
>> + target = addr + rvc_branch_imme(insn);
>> + else if (riscv_insn_is_c_jal(insn) || riscv_insn_is_c_j(insn))
>> + target = addr + rvc_jal_imme(insn);
>> + else
>> + target = 0;
>> + return (target >= start) && (target < end);
>> + }
>> +#endif
>> +
>> + if (riscv_insn_is_branch(insn))
>> + target = addr + rvi_branch_imme(insn);
>> + else if (riscv_insn_is_jal(insn))
>> + target = addr + rvi_jal_imme(insn);
>> + else
>> + target = 0;
>> + return (target >= start) && (target < end);
>> +}
>> +
>> +static int search_copied_insn(unsigned long paddr, struct optimized_kprobe *op)
>> +{
>> + int i = 1;
>> + unsigned long offset = GET_INSN_LENGTH(*(kprobe_opcode_t *)paddr);
>> +
>> + while ((i++ < MAX_COPIED_INSN) && (offset < 2 * RVI_INSN_LEN)) {
>> + if (riscv_probe_decode_insn((probe_opcode_t *)paddr + offset,
>> + NULL) != INSN_GOOD)
>
> If the second argument is NULL, and the insn is auipc, we'll splat with
> NULL-ptr exception.

Good catch, it is my fault to ignore the access to second argument in macro RISCV_INSN_SET_SIMULATE.

>
> Hmm, probe_opcode_t is u32, right? And GET_INSN_LENGTH() returns 4 or 2
> ...then the pointer arithmetic will be a mess?

Hmm, This pointer arithemtic does make no sense here, i had debugged this function on QEMU step by step,
and it work well. Anyway, i will go through this function again, thanks.

>
>
> Björn

--
BR,
Liao, Chang