linux-kernel - Re: [RFC] [patch 1/2] add non_init_kernel_text

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Message-Id: <200712181557.35712.rusty@rustcorp.com.au>
Date:	Tue, 18 Dec 2007 15:57:35 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	ananth@...ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Srinivasa Ds <srinivasa@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>
Subject: Re: [RFC] [patch 1/2] add non_init_kernel_text_address

On Friday 14 December 2007 18:51:06 Ananth N Mavinakayanahalli wrote:
> On Thu, Dec 13, 2007 at 11:09:16PM -0800, Andrew Morton wrote:
> > regular_kernel_text_address()?  Dunno.
>
> Sounds better :-)

The better answer was to invert it and use "discarded_kernel_text_address()",
which is what you actually care about (rather than the details of whether it
was init or not).

However, you have, in fact, located a potential bug.  If someone were to
kmalloc module text, then symbol_put() could fail.

How's this?
---
Don't report discarded init pages as kernel text.

In theory this could cause a bug in symbol_put() if an arch used for
a module: we might think the symbol belongs to the core kernel.

The downside is that this might make backtraces through (discarded)
init functions harder to read on some archs.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r 0eabf082c13a kernel/extable.c
--- a/kernel/extable.c	Tue Dec 18 13:51:13 2007 +1100
+++ b/kernel/extable.c	Tue Dec 18 15:53:01 2007 +1100
@@ -46,7 +46,8 @@ int core_kernel_text(unsigned long addr)
 	    addr <= (unsigned long)_etext)
 		return 1;
 
-	if (addr >= (unsigned long)_sinittext &&
+	if (system_state == SYSTEM_BOOTING &&
+	    addr >= (unsigned long)_sinittext &&
 	    addr <= (unsigned long)_einittext)
 		return 1;
 	return 0;
--
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