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

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Date:   Tue, 5 Mar 2019 08:21:17 +0800
From:   Vincent Chen <vincentc@...estech.com>
To:     Palmer Dabbelt <palmer@...ive.com>
CC:     "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        Jim Wilson <jimw@...ive.com>, Arnd Bergmann <arnd@...db.de>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "deanbo422@...il.com" <deanbo422@...il.com>
Subject: Re: [PATCH 0/3] riscv: Fix debug instruction check and support
 trap-based WARN()

On Tue, Mar 05, 2019 at 04:35:08AM +0800, Palmer Dabbelt wrote:
> 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?


OK, I will improve it and submit a v2 patch.