Re: [PATCH v2 36/43] powerpc/32: Set current->thread.regs in C interrupt entry

[Christophe Leroy]

Le 10/03/2021 à 02:33, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of March 9, 2021 10:10 pm:
> > No need to do that is assembly, do it in C.
>
> Hmm. No issues with the patch as such, but why does ppc32 need this but
> not 64? AFAIKS 64 sets this when a thread is created.

Looks like ppc64 was doing the same in function save_remaining_regs() in arch/ppc64/kernel/head.S 
until commit https://github.com/mpe/linux-fullhistory/commit/e5bb080d

But I can't find what happend to it in that commit.

Where is it done now ? Maybe that's also already done for ppc32.

Thanks
Christophe


> Thanks,
> Nick
>
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   arch/powerpc/include/asm/interrupt.h | 4 +++-
> >   arch/powerpc/kernel/entry_32.S       | 3 +--
> >   2 files changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
> > index 861e6eadc98c..e6d71c2e3aa2 100644
> > --- a/arch/powerpc/include/asm/interrupt.h
> > +++ b/arch/powerpc/include/asm/interrupt.h
> > @@ -33,8 +33,10 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
> >   	if (!arch_irq_disabled_regs(regs))
> >   		trace_hardirqs_off();
> >   
> > -	if (user_mode(regs))
> > +	if (user_mode(regs)) {
> > +		current->thread.regs = regs;
> >   		account_cpu_user_entry();
> > +	}
> >   #endif
> >   	/*
> >   	 * Book3E reconciles irq soft mask in asm
> > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> > index 8fe1c3fdfa6e..815a4ff1ba76 100644
> > --- a/arch/powerpc/kernel/entry_32.S
> > +++ b/arch/powerpc/kernel/entry_32.S
> > @@ -52,8 +52,7 @@
> >   prepare_transfer_to_handler:
> >   	andi.	r0,r9,MSR_PR
> >   	addi	r12, r2, THREAD
> > -	beq	2f			/* if from user, fix up THREAD.regs */
> > -	stw	r3,PT_REGS(r12)
> > +	beq	2f
> >   #ifdef CONFIG_PPC_BOOK3S_32
> >   	kuep_lock r11, r12
> >   #endif
> > --
> > 2.25.0