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

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Date:	Thu, 17 Mar 2016 12:22:30 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'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)

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??

Thank you,

>
> int __init arch_init_kprobes(void)
>--
>2.5.0
>
>
>_______________________________________________
>linux-arm-kernel mailing list
>linux-arm-kernel@...ts.infradead.org
>http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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