linux-kernel - Re: [tip:core/stacktrace] symbols, stacktrace: look up init symbols after module symbols

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Date:	Mon, 23 Mar 2009 16:01:50 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	peterz@...radead.org, tglx@...utronix.de, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/stacktrace] symbols, stacktrace: look up init symbols after module symbols

On Thursday 19 March 2009 22:24:35 Ingo Molnar wrote:
>   a2da405: module: Don't report discarded init pages as kernel text.
> 
> The reason is this check added to core_kernel_text():
> 
> -       if (addr >= (unsigned long)_sinittext &&
> +       if (system_state == SYSTEM_BOOTING &&
> +           addr >= (unsigned long)_sinittext &&
>             addr <= (unsigned long)_einittext)
>                 return 1;
> 
> This will discard inittext symbols even though their symbol table
> is still present and even though stacktraces done while the system
> was booting up might still be relevant.
> 
> To not reintroduce the (not well-specified) bug addressed in that
> commit, first do a module symbols lookup, then a final init-symbols
> lookup.
> 
> This will work fine on architectures that have separate address
> spaces for modules (such as x86) - and should not crash any other
> architectures either.

Returning "1" all the time won't crash them either, AFAICT, but it's still
misleading if kernel_text_address() isn't reliable.  It makes me
uncomfortable.

Does every kernel_text_address() caller want this behavior, or should we
have a was_ever_text_address()?

Rusty.
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