linux-kernel - Re: [External] Re: [PATCH] riscv/fault: Dump user opcode bytes on fatal faults

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Date:   Wed, 29 Mar 2023 15:35:26 +0800
From:   运辉崔 <cuiyunhui@...edance.com>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     Conor Dooley <conor@...nel.org>, paul.walmsley@...ive.com,
        palmer@...belt.com, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH] riscv/fault: Dump user opcode bytes on
 fatal faults

Hi Conor,

On Wed, Mar 29, 2023 at 2:25 PM Conor Dooley <conor.dooley@...rochip.com> wrote:

>
> Right, I'm trying to figure out of this is another bug in the kernel -
> if you don't have "fd" in riscv,isa in your devicetree then, even if
> CONFIG_FPU is set, none of the FPU code is meant to run, right?

yeah, CONFIG_FPU is set.
In the problem I encountered, the init to be executed in user mode
contained floating-point instructions, which caused an exception.

> What would be nice to have is what the new show_opcodes() function will
> look like ;)

After printing the contents of __show_regs(), this line will continue
to be printed:
Opcode: 53 80 02 f0

It is not just the problem I encountered. When the process exits
unexpected, we all want to know what the instruction that caused the
process exception is.

Thanks,
Yunhui