linux-kernel - Re: [RFC PATCH] kernel/kallsyms.c: only show legal kernel symbol

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Message-ID: <20131024084559.GD16735@n2100.arm.linux.org.uk>
Date:	Thu, 24 Oct 2013 09:45:59 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Ming Lei <tom.leiming@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Chen Gang <gang.chen@...anux.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH] kernel/kallsyms.c: only show legal kernel symbol

On Thu, Oct 24, 2013 at 11:51:18AM +1030, Rusty Russell wrote:
> Ming Lei <tom.leiming@...il.com> writes:
> > Address of non-module kernel symbol should always be located
> > from CONFIG_PAGE_OFFSET on, so only show these legal kernel
> > symbols in /proc/kallsyms.
> >
> > On ARM, some symbols(see below) may drop in relocatable code, so
> > perf can't parse kernel symbols any more from /proc/kallsyms, this
> > patch fixes the problem.
> >
> > 	00000000 t __vectors_start
> > 	00000020 A cpu_v7_suspend_size
> > 	00001000 t __stubs_start
> > 	00001004 t vector_rst
> > 	00001020 t vector_irq
> > 	000010a0 t vector_dabt
> > 	00001120 t vector_pabt
> > 	000011a0 t vector_und
> > 	00001220 t vector_addrexcptn
> > 	00001224 t vector_fiq
> > 	00001224 T vector_fiq_offset
> >
> > The issue can be fixed in scripts/kallsyms.c too, but looks this
> > approach is easier.
> 
> This fix looks hacky; if these symbols are not available, don't just
> remove them from /proc/kallsyms, but don't put them in the kernel at
> all.

How do you "don't put them in the kernel at all" when they're used by
the kernel internally as offsets?

If you mean, just get rid of them, shall I just add these as magic
numbers instead based on the values in this email?  Is that really a
sane solution?

No, we have to keep these symbols IMHO.
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