linux-kernel - Re: [PATCH] mm: Generalize and rename notify_page_fault() as kprobe_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190613130408.3091869d8e50d0524157523f@linux-foundation.org>
Date:   Thu, 13 Jun 2019 13:04:08 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH] mm: Generalize and rename notify_page_fault() as
 kprobe_page_fault()

On Thu, 13 Jun 2019 15:37:24 +0530 Anshuman Khandual <anshuman.khandual@....com> wrote:

> Architectures which support kprobes have very similar boilerplate around
> calling kprobe_fault_handler(). Use a helper function in kprobes.h to unify
> them, based on the x86 code.
> 
> This changes the behaviour for other architectures when preemption is
> enabled. Previously, they would have disabled preemption while calling the
> kprobe handler. However, preemption would be disabled if this fault was
> due to a kprobe, so we know the fault was not due to a kprobe handler and
> can simply return failure.
> 
> This behaviour was introduced in the commit a980c0ef9f6d ("x86/kprobes:
> Refactor kprobes_fault() like kprobe_exceptions_notify()")
> 
> ...
>
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -30,28 +30,6 @@
>  
>  #ifdef CONFIG_MMU
>  
> -#ifdef CONFIG_KPROBES
> -static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)

Some architectures make this `static inline'.  Others make it
`nokprobes_inline', others make it `static inline __kprobes'.  The
latter seems weird - why try to put an inline function into
.kprobes.text?

So..  what's the best thing to do here?  You chose `static
nokprobe_inline' - is that the best approach, if so why?  Does
kprobe_page_fault() actually need to be inlined?

Also, some architectures had notify_page_fault returning int, others
bool.  You chose bool and that seems appropriate and all callers are OK
with that.