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Date:   Tue, 7 Apr 2020 11:57:58 +0200
From:   Michal =?iso-8859-1?Q?Such=E1nek?= <msuchanek@suse.de>
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     linuxppc-dev@lists.ozlabs.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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        Ingo Molnar <mingo@redhat.com>,
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        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
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        Namhyung Kim <namhyung@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
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Subject: Re: [PATCH v12 5/8] powerpc/64: make buildable without CONFIG_COMPAT
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On Tue, Apr 07, 2020 at 07:50:30AM +0200, Christophe Leroy wrote:
> 
> 
> Le 20/03/2020 ? 11:20, Michal Suchanek a ?crit?:
> > There are numerous references to 32bit functions in generic and 64bit
> > code so ifdef them out.
> > 
> > Signed-off-by: Michal Suchanek <msuchanek@suse.de>
> > ---
> > v2:
> > - fix 32bit ifdef condition in signal.c
> > - simplify the compat ifdef condition in vdso.c - 64bit is redundant
> > - simplify the compat ifdef condition in callchain.c - 64bit is redundant
> > v3:
> > - use IS_ENABLED and maybe_unused where possible
> > - do not ifdef declarations
> > - clean up Makefile
> > v4:
> > - further makefile cleanup
> > - simplify is_32bit_task conditions
> > - avoid ifdef in condition by using return
> > v5:
> > - avoid unreachable code on 32bit
> > - make is_current_64bit constant on !COMPAT
> > - add stub perf_callchain_user_32 to avoid some ifdefs
> > v6:
> > - consolidate current_is_64bit
> > v7:
> > - remove leftover perf_callchain_user_32 stub from previous series version
> > v8:
> > - fix build again - too trigger-happy with stub removal
> > - remove a vdso.c hunk that causes warning according to kbuild test robot
> > v9:
> > - removed current_is_64bit in previous patch
> > v10:
> > - rebase on top of 70ed86f4de5bd
> > ---
> >   arch/powerpc/include/asm/thread_info.h | 4 ++--
> >   arch/powerpc/kernel/Makefile           | 6 +++---
> >   arch/powerpc/kernel/entry_64.S         | 2 ++
> >   arch/powerpc/kernel/signal.c           | 3 +--
> >   arch/powerpc/kernel/syscall_64.c       | 6 ++----
> >   arch/powerpc/kernel/vdso.c             | 3 ++-
> >   arch/powerpc/perf/callchain.c          | 8 +++++++-
> >   7 files changed, 19 insertions(+), 13 deletions(-)
> > 
> 
> [...]
> 
> > 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())) {
> 
> is_compat() should be used here instead, because we dont want to use
is_compat_task()
> compat_sys_call_table() on PPC32.
> 
> >   		f = (void *)compat_sys_call_table[r0];
> >   		r3 &= 0x00000000ffffffffULL;
> 
That only applies once you use this for 32bit as well. Right now it's
64bit only so the two are the same.

Thanks

Michal