linux-kernel - Re: [PATCH v2] arm64: rename dump_instr as dump_kernel

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Message-ID: <20190624132129.4c772nkjbrilxtcy@willie-the-truck>
Date:   Mon, 24 Jun 2019 14:21:29 +0100
From:   Will Deacon <will@...nel.org>
To:     jinho lim <jordan.lim@...sung.com>
Cc:     will.deacon@....com, mark.rutland@....com,
        anshuman.khandual@....com, marc.zyngier@....com,
        andreyknvl@...gle.com, linux-kernel@...r.kernel.org,
        seroto7@...il.com, ebiederm@...ssion.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] arm64: rename dump_instr as dump_kernel_instr

On Thu, Jun 20, 2019 at 03:52:49PM +0900, jinho lim wrote:
> [v2]

The version information is not usually part of the commit message. Please
drop that...

> dump_kernel_instr does not work for user mode.
> rename dump_instr function and remove __dump_instr.

... and rewrite this so it explains the problem that you're solving.

> Signed-off-by: jinho lim <jordan.lim@...sung.com>
> ---
> 
> Thanks for review, I rename dump_instr function and merge __dump_instr in it.
> 
>  arch/arm64/kernel/traps.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index ccc13b45d9b1..7053165cb31a 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -66,11 +66,20 @@ static void dump_backtrace_entry(unsigned long where)
>  	printk(" %pS\n", (void *)where);
>  }
>  
> -static void __dump_instr(const char *lvl, struct pt_regs *regs)
> +static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
>  {
> -	unsigned long addr = instruction_pointer(regs);
> +	unsigned long addr;
>  	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
>  	int i;
> +	mm_segment_t fs;
> +
> +	if (user_mode(regs))
> +		return;
> +
> +	addr = instruction_pointer(regs);
> +
> +	fs = get_fs();
> +	set_fs(KERNEL_DS);

Actually, if we use aarch64_insn_read() instead of get_user() then we can
avoid having to mess directly with the fs and we'll also get endianness
correction for free when running a big-endian kernel.

Will