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    SubjectRe: [PATCH v2 3/4] powerpc/64: make buildable without CONFIG_COMPAT
    On Wed, 28 Aug 2019 14:49:16 +0200
    Christophe Leroy <christophe.leroy@c-s.fr> wrote:

    > Le 28/08/2019 à 12:30, Michal Suchanek a écrit :
    > > There are numerous references to 32bit functions in generic and 64bit
    > > code so ifdef them out.
    >
    > As far as possible, avoid opting things out with ifdefs. Ref
    > https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation
    >
    > See comment below.
    >
    > >
    > > 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
    > > ---
    > > arch/powerpc/include/asm/syscall.h | 2 ++
    > > arch/powerpc/kernel/Makefile | 15 ++++++++++++---
    > > arch/powerpc/kernel/entry_64.S | 2 ++
    > > arch/powerpc/kernel/signal.c | 5 +++--
    > > arch/powerpc/kernel/syscall_64.c | 5 +++--
    > > arch/powerpc/kernel/vdso.c | 4 +++-
    > > arch/powerpc/perf/callchain.c | 14 ++++++++++----
    > > 7 files changed, 35 insertions(+), 12 deletions(-)
    > >
    > > diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
    > > index 38d62acfdce7..3ed3b75541a1 100644
    > > --- a/arch/powerpc/include/asm/syscall.h
    > > +++ b/arch/powerpc/include/asm/syscall.h
    > > @@ -16,7 +16,9 @@
    > >
    > > /* ftrace syscalls requires exporting the sys_call_table */
    > > extern const unsigned long sys_call_table[];
    > > +#ifdef CONFIG_COMPAT
    > > extern const unsigned long compat_sys_call_table[];
    > > +#endif
    >
    > Leaving the declaration should be harmless.

    Yes, it only allows earlier check that the type is not used.

    >
    > >
    > > static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
    > > {
    > > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
    > > index 1d646a94d96c..b0db365b83d8 100644
    > > --- a/arch/powerpc/kernel/Makefile
    > > +++ b/arch/powerpc/kernel/Makefile
    > > @@ -44,16 +44,25 @@ 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 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 \
    > > +ifndef CONFIG_PPC64
    > > +obj-y += signal_32.o
    > > +else
    > > +ifdef CONFIG_COMPAT
    > > +obj-y += signal_32.o
    > > +endif
    > > +endif
    > > +obj-$(CONFIG_PPC64) += setup_64.o signal_64.o \
    > > paca.o nvram_64.o firmware.o \
    > > syscall_64.o
    >
    > That's still a bit messy. You could have:
    >
    > obj-y = +=signal_$(BITS).o
    > obj-$(CONFIG_COMPAT) += signal_32.o
    >
    > > +ifdef CONFIG_COMPAT
    > > +obj-$(CONFIG_PPC64) += sys_ppc32.o ptrace32.o
    > > +endif
    >
    > AFAIK, CONFIG_COMPAT is only defined when CONFIG_PP64 is defined, so
    > could be:
    >
    > obj-$(CONFIG_COMPAT) += sys_ppc32.o ptrace32.o
    >
    > And could be grouped with the above signal_32.o
    >

    Looks better.

    >
    > > 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 2ec825a85f5b..a2dbf216f607 100644
    > > --- a/arch/powerpc/kernel/entry_64.S
    > > +++ b/arch/powerpc/kernel/entry_64.S
    > > @@ -51,8 +51,10 @@
    > > 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
    >
    > Can we avoid this ifdef ?

    AFAICT it creates reference to non-existent table otherwise.

    >
    > >
    > > /* 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..ffd045e9fb57 100644
    > > --- a/arch/powerpc/kernel/signal.c
    > > +++ b/arch/powerpc/kernel/signal.c
    > > @@ -277,14 +277,15 @@ static void do_signal(struct task_struct *tsk)
    > >
    > > rseq_signal_deliver(&ksig, tsk->thread.regs);
    > >
    > > +#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
    > > if (is32) {
    > > if (ksig.ka.sa.sa_flags & SA_SIGINFO)
    > > ret = handle_rt_signal32(&ksig, oldset, tsk);
    > > else
    > > ret = handle_signal32(&ksig, oldset, tsk);
    > > - } else {
    > > + } else
    >
    > " if only one branch of a conditional statement is a single statement
    > [...] use braces in both branches"
    >
    > Ref
    > https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces
    >
    > > +#endif /* 32bit */
    >
    > Having an #ifdef in a middle of a if/else is gross.
    >
    > Check what are the possible values for is32. It will be always true
    > which CONFIG_PPC32.
    > If you can make sure it is always false without CONFIG_COMPAT, you are
    > done. If not, then combine the if(is32) with something involving
    > IS_ENABLED(CONFIG_COMPAT).

    The value of is32 is not a problem. References to non-existent
    functions could be.

    ...

    > > diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
    > > index c84bbd4298a0..b3dacc8bc98d 100644
    > > --- a/arch/powerpc/perf/callchain.c
    > > +++ b/arch/powerpc/perf/callchain.c
    > > @@ -15,7 +15,7 @@
    > > #include <asm/sigcontext.h>
    > > #include <asm/ucontext.h>
    > > #include <asm/vdso.h>
    > > -#ifdef CONFIG_PPC64
    > > +#ifdef CONFIG_COMPAT
    > > #include "../kernel/ppc32.h"

    /srv/kernel/arch/powerpc/perf/../kernel/ppc32.h:50:2: error: unknown type name ‘compat_stack_t’

    When required declarations are ifdefed in compat.h

    > >
    > > static inline int valid_user_sp(unsigned long sp, int is_64)
    > > {
    > > @@ -341,6 +343,7 @@ static inline int valid_user_sp(unsigned long sp, int is_64)
    > >
    > > #endif /* CONFIG_PPC64 */
    > >
    > > +#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
    >
    > You don't need to opt that out.

    You need to opt out here:

    /srv/kernel/arch/powerpc/perf/callchain.c:349:22: error: field ‘sctx’ has incomplete type
    struct sigcontext32 sctx;
    /srv/kernel/arch/powerpc/perf/callchain.c:359:2: error: unknown type name ‘compat_siginfo_t’
    compat_siginfo_t info;
    ...
    >
    > > /*
    > > * Layout for non-RT signal frames
    > > */
    > > @@ -482,12 +485,15 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
    > > sp = next_sp;
    > > }
    > > }
    > > +#endif /* 32bit */
    > >
    > > void
    > > perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
    > > {
    > > - if (current_is_64bit())
    > > - perf_callchain_user_64(entry, regs);
    > > - else
    > > +#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
    > > + if (!current_is_64bit())
    > > perf_callchain_user_32(entry, regs);
    > > + else
    > > +#endif
    > > + perf_callchain_user_64(entry, regs);
    >
    > Please rewrite using IS_ENABLED() instead of #ifdefs.

    And ifdef here.

    The ifdefs could be potentially reduced in some places, though.

    Thanks

    Michal

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