linux-kernel - Re: [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN()

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Date:   Mon, 04 Mar 2019 12:35:08 -0800 (PST)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     vincentc@...estech.com
CC:     aou@...s.berkeley.edu, ebiederm@...ssion.com,
        Jim Wilson <jimw@...ive.com>, Arnd Bergmann <arnd@...db.de>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        deanbo422@...il.com, vincentc@...estech.com
Subject:     Re: [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN()

On Thu, 28 Feb 2019 02:31:28 PST (-0800), vincentc@...estech.com wrote:
> The handler for the debug exception will call is_valid_bugaddr(bugaddr) to
> check if the instruction in bugaddr is a real debug instruction. However,
> the expected instruction, ebreak, is possibly translated to c.ebreak by
> assmebler when C extension is supported. This patchset will add c.ebreak
> into the check mechanism. In addition, BUG() is currently unable to work in
> the kernel module due to an inappropriated condition in is_valid_bugaddr().
> This issue will be fixed in this patchset. Finally, this patchset enables
> WARN() related functions to trap the code to help developers debug it.
>
>
>
>
>
> Vincent Chen (3):
>   riscv: Add the support for c.ebreak check in is_valid_bugaddr()
>   riscv: Support BUG() in kernel module
>   riscv: Make WARN() related functions able to trigger a trap exception

I'm finding this patch set a bit hard to follow, and I think it has more diff 
than is necessary.  For example, the first patch introduces a new die() only to 
have it removed by the third patch.  There's also some unnecessary 
non-functional diff, like

    @@ -149,12 +161,13 @@ int is_valid_bugaddr(unsigned long pc)
            if (probe_kernel_address((bug_insn_t *)pc, insn))
                    return 0;
            if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
    -               return insn == __BUG_INSN_32;
    +               return (insn == __BUG_INSN_32);
            else
    -               return (insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16;
    +               return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
     }
     #endif /* CONFIG_GENERIC_BUG */
    
    +
     void __init trap_init(void)
     {
            /*

I like the idea of the patch set, though.  Do you have time to clean it up and 
submit a v2?