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Date: Sat, 09 Feb 2002 11:34:51 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: Linus Torvalds <torvalds@transmeta.com>
CC: Hugh Dickins <hugh@veritas.com>,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] BUG preserve registers
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Linus Torvalds wrote:
> 
> On Sat, 9 Feb 2002, Hugh Dickins wrote:
> >
> > It's frustrating that when Verbose BUG() reporting is configured,
> > info gets lost: fix for i386 below.  This is your area, Andrew:
> > please confirm to Marcelo if you'd like him to apply this.
> >
> > Example: in hpa's recent prune_dcache crash, %eax showed the length of
> > the kernel BUG printk, when we'd have liked to see the invalid d_count:
> > off-by-one or obviously corrupted?
> 
> Don't do it this way.
> 
> Instead, put the string printout in the _trap_ handler, and make the
> format of BUG() be something like this:
> 
>         #ifdef CONFIG_DEBUG_BUGVERBOSE
>         #define BUGSTR "\"" __FILE__ "\""
>         #else
>         #define BUGSTR ""
>         #endif
> 
>         #define BUG() \
>                 asm("ud2\n\t.word __LINE__\n\t.asciiz " BUGSTR)
> 

Is better, except the filename gets expanded multipe times into
the object file.  How about:

#define BUG()                   \
        asm(    "ud2\n"         \
                "\t.word %0\n"  \
                "\t.long %1\n"  \
                 : : "i" (__LINE__), "i" (__FILE__))

void erp(void)
{
        if (c())
                BUG();
        if (d())
                BUG();
}

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