linux-kernel - Re: [PATCH v5 5/5] powerpc/perf: split callchain.c by bitness

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Date:   Fri, 30 Aug 2019 09:12:12 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     David Hildenbrand <david@...hat.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        David Howells <dhowells@...hat.com>,
        Paul Mackerras <paulus@...ba.org>,
        Breno Leitao <leitao@...ian.org>,
        Michael Neuling <mikey@...ling.org>,
        Nicolai Stange <nstange@...e.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Allison Randal <allison@...utok.net>,
        Firoz Khan <firoz.khan@...aro.org>,
        Joel Stanley <joel@....id.au>, Arnd Bergmann <arnd@...db.de>,
        Nicholas Piggin <npiggin@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christian Brauner <christian@...uner.io>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v5 5/5] powerpc/perf: split callchain.c by bitness

On Fri, 30 Aug 2019 08:42:25 +0200
Michal Suchánek <msuchanek@...e.de> wrote:

> On Fri, 30 Aug 2019 06:35:11 +0000 (UTC)
> Christophe Leroy <christophe.leroy@....fr> wrote:
> 
> > On 08/29/2019 10:28 PM, Michal Suchanek wrote:  

> >  obj-$(CONFIG_PPC_PERF_CTRS)	+= core-book3s.o bhrb.o
> > diff --git a/arch/powerpc/perf/callchain_32.c b/arch/powerpc/perf/callchain_32.c
> > index 0bd4484eddaa..17c43ae03084 100644
> > --- a/arch/powerpc/perf/callchain_32.c
> > +++ b/arch/powerpc/perf/callchain_32.c
> > @@ -15,50 +15,13 @@
> >  #include <asm/sigcontext.h>
> >  #include <asm/ucontext.h>
> >  #include <asm/vdso.h>
> > -#ifdef CONFIG_PPC64
> > -#include "../kernel/ppc32.h"
> > -#endif
> >  #include <asm/pte-walk.h>
> >  
> >  #include "callchain.h"
> >  
> >  #ifdef CONFIG_PPC64
> > -static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> > -{
> > -	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> > -	    ((unsigned long)ptr & 3))
> > -		return -EFAULT;
> > -
> > -	pagefault_disable();
> > -	if (!__get_user_inatomic(*ret, ptr)) {
> > -		pagefault_enable();
> > -		return 0;
> > -	}
> > -	pagefault_enable();
> > -
> > -	return read_user_stack_slow(ptr, ret, 4);
> > -}
> > -#else /* CONFIG_PPC64 */
> > -/*
> > - * On 32-bit we just access the address and let hash_page create a
> > - * HPTE if necessary, so there is no need to fall back to reading
> > - * the page tables.  Since this is called at interrupt level,
> > - * do_page_fault() won't treat a DSI as a page fault.
> > - */
> > -static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> > -{
> > -	int rc;
> > -
> > -	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> > -	    ((unsigned long)ptr & 3))
> > -		return -EFAULT;
> > -
> > -	pagefault_disable();
> > -	rc = __get_user_inatomic(*ret, ptr);
> > -	pagefault_enable();
> > -
> > -	return rc;
> > -}
> > +#include "../kernel/ppc32.h"
> > +#else
> >  
> >  #define __SIGNAL_FRAMESIZE32	__SIGNAL_FRAMESIZE
> >  #define sigcontext32		sigcontext
> > @@ -95,6 +58,30 @@ struct rt_signal_frame_32 {
> >  	int			abigap[56];
> >  };
> >  
> > +/*
> > + * On 32-bit we just access the address and let hash_page create a
> > + * HPTE if necessary, so there is no need to fall back to reading
> > + * the page tables.  Since this is called at interrupt level,
> > + * do_page_fault() won't treat a DSI as a page fault.
> > + */
> > +static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> > +{
> > +	int rc;
> > +
> > +	if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> > +	    ((unsigned long)ptr & 3))
> > +		return -EFAULT;
> > +
> > +	pagefault_disable();
> > +	rc = __get_user_inatomic(*ret, ptr);
> > +	pagefault_enable();
> > +
> > +	if (IS_ENABLED(CONFIG_PPC32) || !rc)
> > +		return rc;
> > +
> > +	return read_user_stack_slow(ptr, ret, 4);
> > +}
> > +
> >  static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
> >  {
> >  	if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))  
> 
> I will leave consolidating this function to somebody who knows what the
> desired semantic is. With a short ifdef section at the top of the file
> it is a low-hanging fruit.

It looks ok if done as a separate patch.

Thanks

Michal