Re: [PATCH v4 20/23] powerpc/syscall: Do not check unsupported scv vector on PPC32

[Christophe Leroy]

Le 26/01/2021 à 11:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of January 26, 2021 12:48 am:
> > Only PPC64 has scv. No need to check the 0x7ff0 trap on PPC32.
> >
> > And ignore the scv parameter in syscall_exit_prepare (Save 14 cycles
> > 346 => 332 cycles)
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   arch/powerpc/kernel/entry_32.S | 1 -
> >   arch/powerpc/kernel/syscall.c  | 7 +++++--
> >   2 files changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> > index 9922a04650f7..6ae9c7bcb06c 100644
> > --- a/arch/powerpc/kernel/entry_32.S
> > +++ b/arch/powerpc/kernel/entry_32.S
> > @@ -343,7 +343,6 @@ transfer_to_syscall:
> >   
> >   ret_from_syscall:
> >   	addi    r4,r1,STACK_FRAME_OVERHEAD
> > -	li	r5,0
> >   	bl	syscall_exit_prepare
> >   #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
> >   	/* If the process has its own DBCR0 value, load it up.  The internal
> > diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
> > index 476909b11051..30f8a397a522 100644
> > --- a/arch/powerpc/kernel/syscall.c
> > +++ b/arch/powerpc/kernel/syscall.c
> > @@ -86,7 +86,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >   	local_irq_enable();
> >   
> >   	if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
> > -		if (unlikely(regs->trap == 0x7ff0)) {
> > +		if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap == 0x7ff0)) {
> >   			/* Unsupported scv vector */
> >   			_exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
> >   			return regs->gpr[3];
> > @@ -109,7 +109,7 @@ notrace long system_call_exception(long r3, long r4, long r5,
> >   		r8 = regs->gpr[8];
> >   
> >   	} else if (unlikely(r0 >= NR_syscalls)) {
> > -		if (unlikely(regs->trap == 0x7ff0)) {
> > +		if (IS_ENABLED(CONFIG_PPC64) && unlikely(regs->trap == 0x7ff0)) {
>
> Perhaps this could be hidden behind a function like trap_is_scv()?
>
> trap_is_unsupported_scv() ?

Ok, I did that in v5

Thanks
Christophe