linux-kernel - Re: [PATCH 2.6.27-rc1 2/25] mdb: Merkey's Kernel Debugger 2.6.27-rc1

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Message-ID: <48970E07.60804@s5r6.in-berlin.de>
Date:	Mon, 04 Aug 2008 16:11:19 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	jmerkey@...fmountaingroup.com
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.27-rc1 2/25] mdb:  Merkey's Kernel Debugger 2.6.27-rc1

jmerkey@...fmountaingroup.com wrote:
> Netware style debugger for Linux written by Jeffrey Vernon Merkey
> 
> --- a/arch/x86/kernel/traps_32.c	2008-08-03 16:09:54.000000000 -0600
> +++ b/arch/x86/kernel/traps_32.c	2008-08-03 17:33:06.000000000 -0600
...
> @@ -865,6 +896,16 @@
>  }
>  #endif
> 
> +#if defined(CONFIG_MDB) && !defined(CONFIG_KPROBES)
> +fastcall void do_int3(struct pt_regs * regs, long error_code)
> +{
> +#ifdef	CONFIG_MDB
> +        if (mdb(BREAKPOINT_EXCEPTION, error_code, regs))
> +           return;
> +#endif
> +	do_trap(3, SIGTRAP, "int3", 1, regs, error_code, NULL);
> +}
> +#endif	/* CONFIG_KDB && !CONFIG_KPROBES */

The inner #ifdef is always true.


>  /*
>   * Our handling of the processor debug registers is non-trivial.
>   * We do not clear them on entry and exit from the kernel. Therefore
> @@ -895,6 +936,10 @@
>  	trace_hardirqs_fixup();
> 
>  	get_debugreg(condition, 6);
> +#ifdef	CONFIG_MDB
> +        if (mdb(DEBUGGER_EXCEPTION, error_code, regs))
> +           return;
> +#endif
> 
>  	/*
>  	 * The processor cleared BTF, so don't mark that we need it set.

I wonder if it would be beneficial to
 - include an mdb header file in source files like this one,
 - in the mdb header, define mdb() as a static inline function which
   does nothing but return false if CONFIG_MDB is not defined.

Would get rid of the visual clutter introduced by #ifdef/#endif and
catch potential syntax errors when people later modify this code.  I
assume that a compiler is used which eliminates code properly when mdb()
is nothing but constant false...
-- 
Stefan Richter
-=====-==--- =--- --=--
http://arcgraph.de/sr/
--
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