Re: [RFC PATCH v2 06/13] powerpc/syscall: Make syscall_64.c buildable on PPC32

[Christophe Leroy]

Le 06/04/2020 Ã 03:52, Nicholas Piggin a ÃcritÂ:
> Christophe Leroy's on April 6, 2020 3:44 am:
> > ifdef out specific PPC64 stuff to allow building
> > syscall_64.c on PPC32.
> >
> > Modify Makefile to always build syscall.o
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> >   arch/powerpc/kernel/Makefile  |  5 ++---
> >   arch/powerpc/kernel/syscall.c | 10 ++++++++++
> >   2 files changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> > index 8cc3c831dccd..e4be425b7718 100644
> > --- a/arch/powerpc/kernel/Makefile
> > +++ b/arch/powerpc/kernel/Makefile
> > @@ -45,11 +45,10 @@ obj-y				:= cputable.o syscalls.o \
> >   				   signal.o sysfs.o cacheinfo.o time.o \
> >   				   prom.o traps.o setup-common.o \
> >   				   udbg.o misc.o io.o misc_$(BITS).o \
> > -				   of_platform.o prom_parse.o
> > +				   of_platform.o prom_parse.o syscall.o
> >   obj-y				+= ptrace/
> >   obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o signal_64.o \
> > -				   paca.o nvram_64.o firmware.o note.o \
> > -				   syscall.o
> > +				   paca.o nvram_64.o firmware.o note.o
> >   obj-$(CONFIG_VDSO32)		+= vdso32/
> >   obj-$(CONFIG_PPC_WATCHDOG)	+= watchdog.o
> >   obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
> > diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
> > index 72f3d2f0a823..28bd43db8755 100644
> > --- a/arch/powerpc/kernel/syscall.c
> > +++ b/arch/powerpc/kernel/syscall.c
> > @@ -25,8 +25,10 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >   	unsigned long ti_flags;
> >   	syscall_fn f;
> >   
> > +#ifdef CONFIG_PPC64
> >   	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
> >   		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
> > +#endif
> >   
> >   	trace_hardirqs_off(); /* finish reconciling */
> >   
> > @@ -34,7 +36,9 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >   		BUG_ON(!(regs->msr & MSR_RI));
> >   	BUG_ON(!(regs->msr & MSR_PR));
> >   	BUG_ON(!FULL_REGS(regs));
> > +#ifdef CONFIG_PPC64
> >   	BUG_ON(regs->softe != IRQS_ENABLED);
> > +#endif
> >   
> >   	account_cpu_user_entry();
> >   
> > @@ -56,7 +60,9 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >   	 * frame, or if the unwinder was taught the first stack frame always
> >   	 * returns to user with IRQS_ENABLED, this store could be avoided!
> >   	 */
> > +#ifdef CONFIG_PPC64
> >   	regs->softe = IRQS_ENABLED;
> > +#endif
> >   
> >   	local_irq_enable();
> >   
> > @@ -148,7 +154,9 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
> >   		ret |= _TIF_RESTOREALL;
> >   	}
> >   
> > +#ifdef CONFIG_PPC64
> >   again:
> > +#endif
> >   	local_irq_disable();
> >   	ti_flags = READ_ONCE(*ti_flagsp);
> >   	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
> > @@ -191,6 +199,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
> >   
> >   	/* This pattern matches prep_irq_for_idle */
> >   	__hard_EE_RI_disable();
> > +#ifdef CONFIG_PPC64
> >   	if (unlikely(lazy_irq_pending())) {
> >   		__hard_RI_enable();
> >   		trace_hardirqs_off();
> > @@ -201,6 +210,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
> >   	}
> >   	local_paca->irq_happened = 0;
> >   	irq_soft_mask_set(IRQS_ENABLED);
> > +#endif
> >   
> >   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> >   	local_paca->tm_scratch = regs->msr;
> > --
> > 2.25.0
>
> The #ifdefs disappoint me!

They disappoint me as well. I tried to removed most of them in v3, I 
also took your patch up front the series.

> Here is (unested) something that should help 32-bit avoid several ifdefs
> in the main part of the function. I should have done this as part of the
> merged series, but that's okay I'll submit as a cleanup.
>
> The rest looks okay for now. Maybe we grow some helpers to manage the
> soft-mask state, though I'm not really sure it would make sense for
> 32-bit code to ever call them. Maybe just confined to this file would be
> okay but for now the ifdefs are okay.

Thanks
Christophe