Re: [PATCH v11 5/8] powerpc/64: make buildable without CONFIG_COMPAT

From: "Michal Suchánek" <msuchanek@suse.de>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Gustavo Luiz Duarte <gustavold@linux.ibm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jordan Niethe <jniethe5@gmail.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Claudio Carvalho <cclaudio@linux.ibm.com>,
	Paul Mackerras <paulus@samba.org>, Jiri Olsa <jolsa@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Michael Neuling <mikey@neuling.org>,
	Eric Richter <erichte@linux.ibm.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nayna Jain <nayna@linux.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Allison Randal <allison@lohutok.net>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Hari Bathini <hbathini@linux.ibm.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	"David S. Miller" <davem@davemloft.net>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>
Subject: Re: [PATCH v11 5/8] powerpc/64: make buildable without CONFIG_COMPAT
Date: Tue, 24 Mar 2020 20:30:55 +0100	[thread overview]
Message-ID: <20200324193055.GG25468@kitsune.suse.cz> (raw)
In-Reply-To: <1585039733.dm1rivvych.astroid@bobo.none>

On Tue, Mar 24, 2020 at 06:54:20PM +1000, Nicholas Piggin wrote:
> Michal Suchanek's on March 19, 2020 10:19 pm:
> > diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
> > index 4b0152108f61..a264989626fd 100644
> > --- a/arch/powerpc/kernel/signal.c
> > +++ b/arch/powerpc/kernel/signal.c
> > @@ -247,7 +247,6 @@ static void do_signal(struct task_struct *tsk)
> >  	sigset_t *oldset = sigmask_to_save();
> >  	struct ksignal ksig = { .sig = 0 };
> >  	int ret;
> > -	int is32 = is_32bit_task();
> >  
> >  	BUG_ON(tsk != current);
> >  
> > @@ -277,7 +276,7 @@ static void do_signal(struct task_struct *tsk)
> >  
> >  	rseq_signal_deliver(&ksig, tsk->thread.regs);
> >  
> > -	if (is32) {
> > +	if (is_32bit_task()) {
> >          	if (ksig.ka.sa.sa_flags & SA_SIGINFO)
> >  			ret = handle_rt_signal32(&ksig, oldset, tsk);
> >  		else
> 
> Unnecessary?
> 
> > diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
> > index 87d95b455b83..2dcbfe38f5ac 100644
> > --- a/arch/powerpc/kernel/syscall_64.c
> > +++ b/arch/powerpc/kernel/syscall_64.c
> > @@ -24,7 +24,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >  				   long r6, long r7, long r8,
> >  				   unsigned long r0, struct pt_regs *regs)
> >  {
> > -	unsigned long ti_flags;
> >  	syscall_fn f;
> >  
> >  	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
> > @@ -68,8 +67,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >  
> >  	local_irq_enable();
> >  
> > -	ti_flags = current_thread_info()->flags;
> > -	if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
> > +	if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
> >  		/*
> >  		 * We use the return value of do_syscall_trace_enter() as the
> >  		 * syscall number. If the syscall was rejected for any reason
> > @@ -94,7 +92,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >  	/* May be faster to do array_index_nospec? */
> >  	barrier_nospec();
> >  
> > -	if (unlikely(ti_flags & _TIF_32BIT)) {
> > +	if (unlikely(is_32bit_task())) {
> 
> Problem is, does this allow the load of ti_flags to be used for both
> tests, or does test_bit make it re-load?
> 
> This could maybe be fixed by testing if(IS_ENABLED(CONFIG_COMPAT) &&
Both points already discussed here:

https://lore.kernel.org/linuxppc-dev/13fa324dc879a7f325290bf2e131b87eb491cd7b.1573576649.git.msuchanek@suse.de/

Thanks

Michal