linux-kernel - Re: [PATCH] mm/kprobes: Add generic kprobe_fault

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Date:   Thu, 11 Jul 2019 15:28:07 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vineet Gupta <vgupta@...opsys.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Allison Randal <allison@...utok.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Enrico Weigelt <info@...ux.net>,
        Richard Fontana <rfontana@...hat.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>, x86@...nel.org,
        linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org
Subject: Re: [PATCH] mm/kprobes: Add generic kprobe_fault_handler() fallback
 definition



On 07/05/2019 11:00 AM, Anshuman Khandual wrote:
> Architectures like parisc enable CONFIG_KROBES without having a definition
> for kprobe_fault_handler() which results in a build failure. Arch needs to
> provide kprobe_fault_handler() as it is platform specific and cannot have
> a generic working alternative. But in the event when platform lacks such a
> definition there needs to be a fallback.
> 
> This adds a stub kprobe_fault_handler() definition which not only prevents
> a build failure but also makes sure that kprobe_page_fault() if called will
> always return negative in absence of a sane platform specific alternative.
> 
> While here wrap kprobe_page_fault() in CONFIG_KPROBES. This enables stud
> definitions for generic kporbe_fault_handler() and kprobes_built_in() can
> just be dropped. Only on x86 it needs to be added back locally as it gets
> used in a !CONFIG_KPROBES function do_general_protection().
> 
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Paul Burton <paul.burton@...s.com>
> Cc: James Hogan <jhogan@...nel.org>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> Cc: Rich Felker <dalias@...c.org>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Allison Randal <allison@...utok.net>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Enrico Weigelt <info@...ux.net>
> Cc: Richard Fontana <rfontana@...hat.com>
> Cc: Kate Stewart <kstewart@...uxfoundation.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: x86@...nel.org
> Cc: linux-snps-arc@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-ia64@...r.kernel.org
> Cc: linux-mips@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-s390@...r.kernel.org
> Cc: linux-sh@...r.kernel.org
> Cc: sparclinux@...r.kernel.org
> 
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---

Any updates or suggestions on this patch ? Currently there is a build failure on
parisc architecture due to the lack of a kprobe_fault_handler() definition when
CONFIG_KPROBES is enabled and this build failure needs to be fixed.

This patch solves the build problem. But otherwise I am also happy to just define
a stub definition for kprobe_fault_handler() on parisc arch when CONFIG_KPROBES
is enabled, which will avoid the build failure. Please suggest.