linux-kernel - Re: [PATCH v1 1/4] LoongArch: Move three functions from kprobes.c to inst.h

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Date:   Wed, 12 Apr 2023 18:39:04 +0800
From:   Xi Ruoyao <xry111@...111.site>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v1 1/4] LoongArch: Move three functions from kprobes.c
 to inst.h

On Wed, 2023-04-12 at 18:04 +0800, Tiezhu Yang wrote:
> +static inline bool insns_not_supported(union loongarch_instruction insn)

This function seems long enough (to me) not to use "static inline". 
Note that most part of this function belongs to a cold path, and IMO
it's bad to inline a cold path into every caller.

> +{
> +       switch (insn.reg2i14_format.opcode) {
> +       case llw_op:
> +       case lld_op:
> +       case scw_op:
> +       case scd_op:
> +               pr_notice("kprobe: ll and sc instructions are not supported\n");
> +               return true;
> +       }
> +
> +       switch (insn.reg1i21_format.opcode) {
> +       case bceqz_op:
> +               pr_notice("kprobe: bceqz and bcnez instructions are not supported\n");
> +               return true;
> +       }
> +
> +       return false;
> +}
> +
> +static inline bool insns_need_simulation(union loongarch_instruction insn)
> +{
> +       if (is_pc_ins(&insn))
> +               return true;
> +
> +       if (is_branch_ins(&insn))
> +               return true;
> +
> +       return false;

I'd write "return is_pc_ins(&insn) || is_branch_ins(&insn);" here, but
there is no behavioral difference anyway.

> +}

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University