linux-kernel - Re: [RFT PATCH -next ] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64

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Date:	Thu, 08 May 2014 14:40:00 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	ananth@...ibm.com
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Tony Luck <tony.luck@...il.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-ia64@...r.kernel.org, sparse@...isli.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-tip-commits@...r.kernel.org, anil.s.keshavamurthy@...el.com,
	Ingo Molnar <mingo@...nel.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Arnd Bergmann <arnd@...db.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Chris Wright <chrisw@...s-sol.org>,
	yrl.pp-manager.tt@...achi.com, akataria@...are.com,
	Tony Luck <tony.luck@...el.com>,
	Kevin Hao <haokexin@...il.com>, linuxppc-dev@...ts.ozlabs.org,
	rdunlap@...radead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dl9pf@....de, Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFT PATCH -next ] [BUGFIX] kprobes: Fix "Failed to find blacklist"
 error on ia64 and ppc64

(2014/05/08 13:47), Ananth N Mavinakayanahalli wrote:
> On Wed, May 07, 2014 at 08:55:51PM +0900, Masami Hiramatsu wrote:
> 
> ...
> 
>> +#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
>> +/*
>> + * On PPC64 ABIv1 the function pointer actually points to the
>> + * function's descriptor. The first entry in the descriptor is the
>> + * address of the function text.
>> + */
>> +#define constant_function_entry(fn)	(((func_descr_t *)(fn))->entry)
>> +#else
>> +#define constant_function_entry(fn)	((unsigned long)(fn))
>> +#endif
>> +
>>  #endif /* __ASSEMBLY__ */
> 
> Hi Masami,
> 
> You could just use ppc_function_entry() instead.

No, I think ppc_function_entry() has two problems (on the latest -next kernel)

At first, that is an inlined functions which is not applied in build time.
Since the NOKPROBE_SYMBOL() is used outside of any functions as like as
EXPORT_SYMBOL(), we can only use preprocessed macros.
Next, on PPC64 ABI*v2*, ppc_function_entry() returns local function entry,
which seems global function entry + 2 insns. I'm not sure about implementation
of the kallsyms on PPC64 ABIv2, but I guess we need global function entry
for kallsyms.

BTW, could you test this patch on the latest -next tree on PPC64 if possible?

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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