linux-kernel - RE: [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes)

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Date:	Thu, 17 Mar 2016 12:58:20 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'ltc-kernel@...yrl.intra.hitachi.co.jp'" 
	<ltc-kernel@...yrl.intra.hitachi.co.jp>,
	"'David Long'" <dave.long@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	William Cohen <wcohen@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	Steve Capper <steve.capper@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Marc Zyngier <marc.zyngier@....com>
CC:	Mark Rutland <mark.rutland@....com>,
	Petr Mladek <pmladek@...e.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	John Blackwood <john.blackwood@...r.com>,
	Feng Kan <fkan@....com>, Zi Shen Lim <zlim.lnx@...il.com>,
	Dave P Martin <Dave.Martin@....com>,
	Yang Shi <yang.shi@...aro.org>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Kees Cook <keescook@...omium.org>,
	"Suzuki K. Poulose" <suzuki.poulose@....com>,
	"Mark Brown" <broonie@...nel.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	Mark Salyzyn <salyzyn@...roid.com>,
	James Morse <james.morse@....com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Murphy <Robin.Murphy@....com>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Balamurugan Shanmugam <bshanmugam@....com>,
	sysp-manager <cti.systems-productivity-manager.ts@...achi.com>
Subject: RE: [PATCH v11 8/9] arm64: Add kernel return probes support
 (kretprobes)

>From: 平松雅巳 / HIRAMATU，MASAMI [mailto:masami.hiramatsu.pt@...achi.com]
>
>Hi,
>
>>From: Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>
>>
>>The pre-handler of this special 'trampoline' kprobe executes the return
>>probe handler functions and restores original return address in ELR_EL1.
>>This way the saved pt_regs still hold the original register context to be
>>carried back to the probed kernel function.
>
>This patch seems not well separated.
>
>>diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
>>index bd3f233..13d3333 100644
>>--- a/arch/arm64/kernel/kprobes.c
>>+++ b/arch/arm64/kernel/kprobes.c
>
>[snip]
>
>>+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
>>+				      struct pt_regs *regs)
>>+{
>>+	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
>>+
>>+	/* replace return addr (x30) with trampoline */
>>+	regs->regs[30] = (long)&kretprobe_trampoline;
>
>So, where is the kretprobe_trampoline? It seems that function is
>defined in other patch.
>
>>+}
>>+
>>+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
>>+{
>>+	return 0;
>> }
>
>And what this function is for??

Ah, sorry, this was my fault. Yes, this function is required.
But this implementation also means there is an asm-based trampoline
function which should be included in this patch.

David, could you tell me the repository which I can get the latest
version of this series? I'd like to see the whole code of kprobes/arm64.

Thank you,