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From: "Michal Suchánek" <msuchanek@suse.de>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "open list:LINUX FOR POWERPC PA SEMI PWRFICIENT" 
	<linuxppc-dev@lists.ozlabs.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Rob Herring <robh@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Christophe Leroy <christophe.leroy@c-s.fr>,
	Thomas Gleixner <tglx@linutronix.de>,
	Arnd Bergmann <arnd@arndb.de>, Nayna Jain <nayna@linux.ibm.com>,
	Eric Richter <erichte@linux.ibm.com>,
	Claudio Carvalho <cclaudio@linux.ibm.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Hari Bathini <hbathini@linux.ibm.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Jordan Niethe <jniethe5@gmail.com>,
	Michael Neuling <mikey@neuling.org>,
	Gustavo Luiz Duarte <gustavold@linux.ibm.com>,
	Allison Randal <allison@lohutok.net>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-fsdevel @ vger . kernel . org --in-reply-to=" 
	<20200225173541.1549955-1-npiggin@gmail.com>
Subject: Re: [PATCH v11 4/8] powerpc/perf: consolidate valid_user_sp
Date: Thu, 19 Mar 2020 15:04:16 +0100	[thread overview]
Message-ID: <20200319140416.GK25468@kitsune.suse.cz> (raw)
In-Reply-To: <CAHp75VcMkPeJ6exroipnxvf-7g-C8QbVm0bAnp=rk505_nxySw@mail.gmail.com>

On Thu, Mar 19, 2020 at 03:35:03PM +0200, Andy Shevchenko wrote:
> On Thu, Mar 19, 2020 at 1:54 PM Michal Suchanek <msuchanek@suse.de> wrote:
> >
> > Merge the 32bit and 64bit version.
> >
> > Halve the check constants on 32bit.
> >
> > Use STACK_TOP since it is defined.
> >
> > Passing is_64 is now redundant since is_32bit_task() is used to
> > determine which callchain variant should be used. Use STACK_TOP and
> > is_32bit_task() directly.
> >
> > This removes a page from the valid 32bit area on 64bit:
> >  #define TASK_SIZE_USER32 (0x0000000100000000UL - (1 * PAGE_SIZE))
> >  #define STACK_TOP_USER32 TASK_SIZE_USER32
> 
> ...
> 
> > +static inline int valid_user_sp(unsigned long sp)
> > +{
> > +       bool is_64 = !is_32bit_task();
> > +
> > +       if (!sp || (sp & (is_64 ? 7 : 3)) || sp > STACK_TOP - (is_64 ? 32 : 16))
> > +               return 0;
> > +       return 1;
> > +}
> 
> Perhaps better to read
> 
>   if (!sp)
>     return 0;
> 
>   if (is_32bit_task()) {
>     if (sp & 0x03)
>       return 0;
>     if (sp > STACK_TOP - 16)
>       return 0;
>   } else {
>     ...
>   }
> 
>   return 1;
> 
> Other possibility:
> 
>   unsigned long align = is_32bit_task() ? 3 : 7;
>   unsigned long top = STACK_TOP - (is_32bit_task() ? 16 : 32);
> 
>   return !(!sp || (sp & align) || sp > top);
Sounds reasonale.

Thanks

Michal
> 
> -- 
> With Best Regards,
> Andy Shevchenko

  reply	other threads:[~2020-03-19 14:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19 11:52 [PATCH v11 0/8] Disable compat cruft on ppc64le v11 Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 1/8] powerpc: Add back __ARCH_WANT_SYS_LLSEEK macro Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 2/8] powerpc: move common register copy functions from signal_32.c to signal.c Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 3/8] powerpc/perf: consolidate read_user_stack_32 Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 4/8] powerpc/perf: consolidate valid_user_sp Michal Suchanek
2020-03-19 13:35   ` Andy Shevchenko
2020-03-19 14:04     ` Michal Suchánek [this message]
2020-03-19 14:16     ` Christophe Leroy
2020-03-19 14:46       ` Michal Suchánek
2020-03-19 11:52 ` [PATCH v11 5/8] powerpc/64: make buildable without CONFIG_COMPAT Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 6/8] powerpc/64: Make COMPAT user-selectable disabled on littleendian by default Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 7/8] powerpc/perf: split callchain.c by bitness Michal Suchanek
2020-03-19 11:52 ` [PATCH v11 8/8] MAINTAINERS: perf: Add pattern that matches ppc perf to the perf entry Michal Suchanek
     [not found] <20200225173541.1549955-1-npiggin@gmail.com>
2020-03-19 12:19 ` [PATCH v11 0/8] Disable compat cruft on ppc64le v11 Michal Suchanek
2020-03-19 12:19   ` [PATCH v11 4/8] powerpc/perf: consolidate valid_user_sp Michal Suchanek

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