linux-kernel - Re: [PATCH RESEND 0/2] ARM: v7m: handle faults and enable debugging

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Date:   Sun, 18 Sep 2022 16:59:45 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Ben Wolsieffer <benwolsieffer@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Vladimir Murzin <vladimir.murzin@....com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 0/2] ARM: v7m: handle faults and enable debugging

On Sat, Sep 17, 2022 at 6:14 AM Ben Wolsieffer <benwolsieffer@...il.com> wrote:

> This series enables real exception handlers on no-MMU systems,
> increasing robustness in the face of buggy user- or kernel-space
> software. Previously, any fault would trigger the invalid exception
> handler, which would hang the system. With this series, faults only
> kill the offending process and allow the rest of the system to
> continue operating.
>
> The second patch in this series adds support for undefined instruction
> hooks, enabling software breakpoints through ptrace. Using this
> functionality currently requires a patch to gdb.
>
> This series has been tested on an STM32F746 (Cortex-M7).
>
> I would appreciate feedback in particular on the following questions:
> * Is the fault table formatting acceptable? Or should the lines be
>   wrapped/shortened?
> * Does my chosen mapping between faults and signals make sense?

Very few people use NOMMU so I would seek review from the
STM32 community.

The kernel looks better after than before the patches so:
Acked-by: Linus Walleij <linus.walleij@...aro.org>
but I do not fully understand this code, so my review is
a bit superficial.

Yours,
Linus Walleij