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    SubjectRe: [PATCH 31/33] powerpc/64: make buildable without CONFIG_COMPAT
    On Wed, Nov 13, 2019 at 01:02:34PM +1000, Nicholas Piggin wrote:
    > Michal Suchanek's on November 13, 2019 2:52 am:
    > > There are numerous references to 32bit functions in generic and 64bit
    > > code so ifdef them out.
    > >
    > > Signed-off-by: Michal Suchanek <msuchanek@suse.de>
    >
    > For the most part these seem okay to me.
    >
    > > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
    > > index 45f1d5e54671..35874119b398 100644
    > > --- a/arch/powerpc/kernel/Makefile
    > > +++ b/arch/powerpc/kernel/Makefile
    > > @@ -44,16 +44,16 @@ CFLAGS_btext.o += -DDISABLE_BRANCH_PROFILING
    > > endif
    > >
    > > obj-y := cputable.o ptrace.o syscalls.o \
    > > - irq.o align.o signal_32.o pmc.o vdso.o \
    > > + irq.o align.o signal_$(BITS).o pmc.o vdso.o \
    > > process.o systbl.o idle.o \
    > > signal.o sysfs.o cacheinfo.o time.o \
    > > prom.o traps.o setup-common.o \
    > > udbg.o misc.o io.o misc_$(BITS).o \
    > > of_platform.o prom_parse.o
    > > -obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
    > > - signal_64.o ptrace32.o \
    > > +obj-$(CONFIG_PPC64) += setup_64.o \
    > > paca.o nvram_64.o firmware.o note.o \
    > > syscall_64.o
    > > +obj-$(CONFIG_COMPAT) += sys_ppc32.o ptrace32.o signal_32.o
    > > obj-$(CONFIG_VDSO32) += vdso32/
    > > obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o
    > > obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
    > > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
    > > index 00173cc904ef..c339a984958f 100644
    > > --- a/arch/powerpc/kernel/entry_64.S
    > > +++ b/arch/powerpc/kernel/entry_64.S
    > > @@ -52,8 +52,10 @@
    > > SYS_CALL_TABLE:
    > > .tc sys_call_table[TC],sys_call_table
    > >
    > > +#ifdef CONFIG_COMPAT
    > > COMPAT_SYS_CALL_TABLE:
    > > .tc compat_sys_call_table[TC],compat_sys_call_table
    > > +#endif
    > >
    > > /* This value is used to mark exception frames on the stack. */
    > > exception_marker:
    > > diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
    > > index 60436432399f..61678cb0e6a1 100644
    > > --- a/arch/powerpc/kernel/signal.c
    > > +++ b/arch/powerpc/kernel/signal.c
    > > @@ -247,7 +247,6 @@ static void do_signal(struct task_struct *tsk)
    > > sigset_t *oldset = sigmask_to_save();
    > > struct ksignal ksig = { .sig = 0 };
    > > int ret;
    > > - int is32 = is_32bit_task();
    > >
    > > BUG_ON(tsk != current);
    > >
    > > @@ -277,7 +276,7 @@ static void do_signal(struct task_struct *tsk)
    > >
    > > rseq_signal_deliver(&ksig, tsk->thread.regs);
    > >
    > > - if (is32) {
    > > + if (is_32bit_task()) {
    > > if (ksig.ka.sa.sa_flags & SA_SIGINFO)
    > > ret = handle_rt_signal32(&ksig, oldset, tsk);
    > > else
    >
    > This is just a clean up I guess.

    It also expands directly to if(0) or if(1) for the !COMPAT cases. I am
    not sure how it would work with the intermediate variable.

    There was more complex change initially but after some additional
    cleanups removing the variable is the only part left.

    >
    > > diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
    > > index d00cfc4a39a9..319ebd4f494d 100644
    > > --- a/arch/powerpc/kernel/syscall_64.c
    > > +++ b/arch/powerpc/kernel/syscall_64.c
    > > @@ -17,7 +17,6 @@ typedef long (*syscall_fn)(long, long, long, long, long, long);
    > >
    > > 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_BOOK3S))
    > > @@ -64,8 +63,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
    > >
    > > __hard_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
    > > @@ -81,7 +79,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
    > > /* May be faster to do array_index_nospec? */
    > > barrier_nospec();
    > >
    > > - if (unlikely(ti_flags & _TIF_32BIT)) {
    > > + if (unlikely(is_32bit_task())) {
    > > f = (void *)compat_sys_call_table[r0];
    > >
    > > r3 &= 0x00000000ffffffffULL;
    >
    > I guess this is okay, I did want to be careful about where ti_flags
    > was loaded exactly, but I think DOTRACE and 32BIT are not volatile.
    > Is it possible to define _TIF_32BIT to zero for 64-bit !compat case
    > and have the original branch eliminated, or does that cause other
    > problems?

    is_32bit_task() expands to 0 or 1 constant unless CONFIG_COMPAT is set.
    That's why the test needs replacing here.

    Unsetting _TIF_32BIT might also be feasible but it is not necessary.

    Thanks

    Michal

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