Re: [PATCH v2 5/5] powerpc/signal: Use unsafe_copy_siginfo_to_user()

[Christophe Leroy]

Le 02/09/2021 à 20:38, Eric W. Biederman a écrit :
> Christophe Leroy <christophe.leroy@xxxxxxxxxx> writes:
>
> > Use unsafe_copy_siginfo_to_user() in order to do the copy
> > within the user access block.
> >
> > On an mpc 8321 (book3s/32) the improvment is about 5% on a process
> > sending a signal to itself.
>
> Nacked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>
> copy_siginfo_to_user is not the same as copy_siginfo_to_user32.
>
> As in this patch breaks 32bit userspace on powerpc.

I don't understand your comment. As you can see below, copy_siginfo_to_user32() is used in the 
compat case (ie 32 bit userspace on PPC64) and unsafe_copy_siginfo_to_user() is used on the 
non-compat case (ie 32 bit userspace on PPC32).

So what's the issue really ?

> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   arch/powerpc/kernel/signal_32.c | 13 ++++++-------
> >   arch/powerpc/kernel/signal_64.c |  5 +----
> >   2 files changed, 7 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> > index ff101e2b3bab..f9e16d108bc8 100644
> > --- a/arch/powerpc/kernel/signal_32.c
> > +++ b/arch/powerpc/kernel/signal_32.c
> > @@ -710,12 +710,6 @@ static long restore_tm_user_regs(struct pt_regs *regs, struct mcontext __user *s
> >   }
> >   #endif
> >   
> > -#ifdef CONFIG_PPC64
> > -
> > -#define copy_siginfo_to_user	copy_siginfo_to_user32
> > -
> > -#endif /* CONFIG_PPC64 */
> > -
> >   /*
> >    * Set up a signal frame for a "real-time" signal handler
> >    * (one which gets siginfo).
> > @@ -779,14 +773,19 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
> >   		asm("dcbst %y0; sync; icbi %y0; sync" :: "Z" (mctx->mc_pad[0]));
> >   	}
> >   	unsafe_put_sigset_t(&frame->uc.uc_sigmask, oldset, failed);
> > +#ifndef CONFIG_COMPAT
> > +	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, failed);
> > +#endif
> >   
> >   	/* create a stack frame for the caller of the handler */
> >   	unsafe_put_user(regs->gpr[1], newsp, failed);
> >   
> >   	user_access_end();
> >   
> > -	if (copy_siginfo_to_user(&frame->info, &ksig->info))
> > +#ifdef CONFIG_COMPAT
> > +	if (copy_siginfo_to_user32(&frame->info, &ksig->info))
> >   		goto badframe;
> > +#endif
> >   
> >   	regs->link = tramp;
> >   
> > diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> > index 2cca6c8febe1..82b73fbd937d 100644
> > --- a/arch/powerpc/kernel/signal_64.c
> > +++ b/arch/powerpc/kernel/signal_64.c
> > @@ -901,15 +901,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
> >   	}
> >   
> >   	unsafe_copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set), badframe_block);
> > +	unsafe_copy_siginfo_to_user(&frame->info, &ksig->info, badframe_block);
> >   	/* Allocate a dummy caller frame for the signal handler. */
> >   	unsafe_put_user(regs->gpr[1], newsp, badframe_block);
> >   
> >   	user_write_access_end();
> >   
> > -	/* Save the siginfo outside of the unsafe block. */
> > -	if (copy_siginfo_to_user(&frame->info, &ksig->info))
> > -		goto badframe;
> > -
> >   	/* Make sure signal handler doesn't get spurious FP exceptions */
> >   	tsk->thread.fp_state.fpscr = 0;